ORCID Profile
0000-0001-6012-9808
Current Organisation
University of Queensland
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Biomaterials | Colloid And Surface Chemistry | Nanoscale Characterisation | Manufacturing Processes and Technologies (excl. Textiles) | Biomechanical Engineering | Biomedical Engineering | Fluidization And Fluid Mechanics | Physical Chemistry (Incl. Structural) | Chemical Engineering | Chemical Engineering Not Elsewhere Classified | Manufacturing Engineering | Human Movement and Sports Science | Cell Development (Incl. Cell Division And Apoptosis) | Materials Engineering | Biomedical Engineering Not Elsewhere Classified | Biomechanics | Machining | Composite and Hybrid Materials |
ANZSRC Socio-Economic Objective (SEO)
Chemical sciences | Skeletal system and disorders (incl. arthritis) | Energy Conservation and Efficiency not elsewhere classified | Polymeric Materials (e.g. Paints) | Metals (e.g. Composites, Coatings, Bonding) | Manufacturing not elsewhere classified | Biological sciences | Cancer and related disorders | Expanding Knowledge in the Medical and Health Sciences | Polymeric materials (e.g. paints) | Clinical health not specific to particular organs, diseases and conditions | Manufactured products not elsewhere classified
Related Links
Publications
Evaluation of different methods for determination of the iron saturation level in bovine lactoferrin
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.FOODCHEM.2013.11.132
Abstract: Lactoferrin (Lf) s les with ca. 25%, 50%, 75%, 85% and 100% iron saturation were prepared for the purpose of evaluating Chromametry, Differential Scanning Calorimetry (DSC) and Circular Dichroism (CD) spectropolarimetry for their suitability in determining the iron saturation level. Numerical values for colour from Chromametry, enthalpy change of denaturation (ΔHcal) from DSC and molar ellipticities from CD were statistically analysed to evaluate their correlation with the level of iron saturation in Lf. Linear regression analysis of colour coordinates Chroma (C(∗)) and hue (h°) angle on percentage iron saturation level of Lf showed that the values can be used to estimate the iron saturation level. The ΔHcal for the iron saturated peak and the CD ellipticities in the 310-340 nm region provided reliable data for the estimation of iron saturation level of Lf up to 75%. Mono- and di-saturated Lf displayed the same thermal stability and very similar tertiary structures.
Copper(II) environments in some macrobicycle complexes at room and low temperatures: Some novel binuclear chloro-bridged systems
Publisher: Springer Science and Business Media LLC
Date: 27-04-2011
FT-IR spectroscopy of fluoro-substituted hydroxyapatite: Strengths and limitations
Publisher: Springer Science and Business Media LLC
Date: 05-05-2007
DOI: 10.1007/S10856-007-3052-3
Abstract: Fluoro substituted hydroxyapatite (FHAp) s les were prepared by a cyclic pH method. Both calcined and uncalcined s les were subjected to elemental analysis (F, Ca, P) and X-ray diffraction (XRD) analysis to verify composition and phase purity. Good correlation between a-axis parameters and fluoride ion content was found for calcined s les, however, for uncalcined s les the fluoride ion content was higher than estimated from the a-axis values. Fourier transform infra red (FT-IR) spectroscopy analysis of the calcined s les showed OH band shifts and splitting in accordance with F-HO interactions affecting the OH vibration. We conclude that the OH libration (620-780 cm(-1) range) is more suited for estimation of fluoride ion content than the OH stretching. In contrast, uncalcined s les all displayed FT-IR spectra similar to that of hydroxyapatite (HAp) despite the presence of fluoride ions (18-73%). FT-IR emission spectroscopy was used to probe the changes occurring in the FT-IR spectra of HAp and FHAp s les upon heating. Interpretation of the spectral changes occurring during heating to 1,000 degrees C and subsequent cooling is given. Room temperature spectra of s les heated to various temperatures was used to determine the temperature necessary to produce FT-IR spectra displaying the expected OH bands. A model accounting for the combined observations is proposed.
Challenges for the development of surface modified biodegradable polyester biomaterials: A chemistry perspective
Publisher: American Vacuum Society
Date: 26-09-2018
DOI: 10.1116/1.5045857
Abstract: The design of current implants produced from biodegradable polyesters is based on strength and rate of degradation and tailored by the choice of polyester used. However, detailed knowledge about the degradation mechanism of surface modified materials with applications in biomaterials science and tissue engineering is currently lacking. This perspective aims to outline the need for a greater focus on analyzing the degradation of modified polyesters to ensure they can fulfil their intended function and that degradation products can effectively be cleared from the body. The status of the literature regarding surface modified polyesters is summarized to illustrate the main aspects investigated in recent studies and specifically the number of studies investigating the fate of the materials upon degradation.
Replacement materials for facial reconstruction at the soft tissue-bone interface
Publisher: Elsevier
Date: 2010
Replacement materials for facial reconstruction at the soft tissue–bone interface
Publisher: Elsevier
Date: 2020
Evaluation of acrylic acid grafting on the loading and release of scopolamine butylbromide from polymeric matrices for future sialorrhea treatment
Publisher: Wiley
Date: 11-2020
DOI: 10.1002/APP.50117
Degradable alginate hydrogels crosslinked by the macromolecular crosslinker alginate dialdehyde
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM30564J
Surface modification and characterization of polycarbonate microdevices for capture of circulating biomarkers, both in vitro and in vivo
Publisher: American Chemical Society (ACS)
Date: 21-10-2013
DOI: 10.1021/AC402942X
Abstract: Herein, we report the fabrication, characterization, and testing of a polymer microprojection array, for the direct and selective capture of circulating biomarkers from the skin of live mice. First, we modified polycarbonate wafers using an electrophilic aromatic substitution reaction with nitric acid to insert aromatic nitro-groups into the benzene rings, followed by treatment with sodium borohydride to reduce the nitro-groups to primary amines. Initial characterization by ultraviolet-visible (UV-vis) spectroscopy suggested that increasing acid concentration led to increased depth of material modification and that this was associated with decreased surface hardness and slight changes in surface roughness. Chemical analysis with X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance fourier transform infrared (ATR-FT-IR) spectroscopy showed nitrogen species present at the surface for all acid concentrations used, but subsurface nitrogen species were only observed at acid concentrations >35%. The nitrogen species were identified as a mixture of nitro, imine, and amine groups, and following reduction, there was sufficient amounts of primary amine groups for covalent attachment of a polyethylene glycol antifouling layer and protein capture probes, as determined by colorimetric and radiometric assays. Finally, the modification scheme was applied to polycarbonate microprojection arrays, and we show that these devices achieve flank skin penetration depths and biomarker yields comparable with our previously reported gold-coated silicon arrays, with very low nonspecific binding even in 10% mouse serum (in vitro) or directly in mouse skin (in vivo). This study is the first demonstration showing the potential utility of polymer microprojections in immunodiagnostics applications.
Polymeric Grafting of Acrylic Acid onto Poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Surface Functionalization for Tissue Engineering Applications
Publisher: American Chemical Society (ACS)
Date: 10-06-2005
DOI: 10.1021/BM050127M
Abstract: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt processed disks and solvent cast films were modified by graft co-polymerization with acrylic acid (AAc) in methanol solution at ambient temperature using gamma irradiation (dose rate of 4.5 kGy/h). To assess the presence of carboxylic acid groups on the surface, reaction with pentafluorophenol was performed prior to X-ray photoelectron spectroscopy analysis. The grafting yield for all s les increased with monomer concentration (2-15%), and for the solvent cast films, it also increased with dose (2-9 kGy). However, the grafting yield of the melt processed disks was largely independent of the radiation dose (2-8 kGy). Toluidine blue was used to stain the modified materials facilitating visual information about the extent of carboxylic acid functionalization and depth penetration of the grafted copolymer. Covalent linking of glucosamine to the functionalized surface was achieved using carbodiimide chemistry verifying that the modified substrates are suitable for biomolecule attachment.
Interaction of zinc(II) with the cyclic octapeptides, cyclo[Ile(Oxn)-D-Val(Thz)]2 and ascidiacyclamide, a cyclic peptide from Lissoclinum patella
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A808836E
In vitro bioactivity of MOEP grafted ePTFE membranes for craniofacial applications
Publisher: Elsevier BV
Date: 09-2005
DOI: 10.1016/J.BIOMATERIALS.2005.01.061
Abstract: The bioactivity of three methacryloyloxyethyl phosphate (MOEP) grafted expanded polytetrafluoroethylene (ePTFE) membranes with varying surface coverage as well as unmodified ePTFE was investigated through a series of in vitro tests: calcium phosphate (CaP) growth in simulated body fluid (SBF), serum protein adsorption, and a morphology and attachment study of human osteoblast-like SaOS-2 cells. The graft copolymers were prepared by means of gamma irradiation induced grafting and displayed various surface morphologies and wettabilities depending on the grafting conditions used. Unmodified ePTFE did not induce nucleation of CaP minerals, whereas all the grafted membranes revealed the growth of CaP minerals after 7 days immersion in SBF. The s le with lowest surface grafting yield (24% coverage), a smooth graft morphology and relatively high hydrophobicity (theta(adv) = 120 degrees, theta(rec) = 80 degrees) showed carbonated hydroxyapatite growth covering the surface. On the other hand, the s les with high surface grafting yield (76% and 100%), a globular graft morphology and hydrophilic surfaces (theta(adv) = 60 degrees and 80 degrees, theta(rec) = 25 degrees and 15 degrees, respectively) exhibited irregular growth of non-apatitic CaP minerals. Irreversibly adsorbed protein measured after a 1h immersion in serum solution was quantified by the amount of nitrogen on the surface using XPS, as well as by weight increase. All grafted membranes adsorbed 3-6 times more protein than the unmodified membrane. The s le with the highest surface coverage adsorbed the most protein. Osteoblast-like SaOS-2 cells cultured for 3 h revealed significantly higher levels of cell attachment on all grafted membranes compared to unmodified ePTFE. Although the morphology of the cells was heterogeneous, in general, the higher grafted surfaces showed a much better cell morphology than both the low surface-grafted and the control unmodified s le. The suite of in vitro tests confirms that a judicious choice of grafted monomer such as the phosphate-containing methacrylate monomer (MOEP) significantly improves the bioactivity of ePTFE in vitro.
Grafting of acrylic acid‐co‐itaconic acid onto ePTFE and characterization of water uptake by the graft copolymers
Publisher: Wiley
Date: 30-09-2014
DOI: 10.1002/APP.41482
Argon plasma treatment-induced grafting of acrylic acid onto expanded poly(tetrafluoroethylene) membranes
Publisher: Elsevier BV
Date: 11-2013
A novel strategy for preparing mechanically robust ionically cross-linked alginate hydrogels
Publisher: IOP Publishing
Date: 24-03-2011
DOI: 10.1088/1748-6041/6/2/025010
Abstract: The properties of alginate films modified using two cross-linker ions (Ca(2+) and Ba(2+)), comparing two separate cross-linking techniques (the traditional immersion (IM) method and a new strategy in a pressure-assisted diffusion (PD) method), are evaluated. This was achieved through measuring metal ion content, water uptake and film stability in an ionic solution ([Ca(2+)] = 2 mM). Characterization of the internal structure and mechanical properties of hydrated films were established by cryogenic scanning electron microscopy and tensile testing, respectively. It was found that gels formed by the PD technique possessed greater stability and did not exhibit any delamination after 21 day immersion as compared to gels formed by the IM technique. The Ba(2+) cross-linked gels possessed significantly higher cross-linking density as reflected in lower water content, a more dense internal structure and higher Young's modulus compared to Ca(2+) cross-linked gels. For the Ca(2+) cross-linked gels, a large improvement in the mechanical properties was observed in gels produced by the PD technique and this was attributed to thicker pore walls observed within the hydrogel structure. In contrast, for the Ba(2+) cross-linked gels, the PD technique resulted in gels that had lower tensile strength and strain energy density and this was attributed to phase separation and larger macropores in this gel.
Evaluation of an ultrasonic-assisted mechanical stirring technique for the synthesis of an efficient nano-photocatalyst
Publisher: Springer Science and Business Media LLC
Date: 09-03-2018
Characterization of alginate–lactoferrin beads prepared by extrusion gelation method
Publisher: Elsevier BV
Date: 02-2016
Phosphorylation of alginate
Publisher: American Chemical Society (ACS)
Date: 07-03-2011
DOI: 10.1021/BM1011773
Abstract: Phosphorylation of alginate was achieved using a heterogeneous urea hosphate reaction. The degree and stereoselectivity of phosphorylation as well as the effects on the physical properties of the polysaccharide were investigated by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, inductively coupled plasma optical-emission spectroscopy (ICP-OES), and size exclusion chromatography (SEC). Multidimensional NMR studies of the phosporylated alginate revealed that phosphorylation of the M residues occurred predominantly at the C3 (equatorial) carbon of the polysaccharide ring. In addition, a more comprehensive assignment of the (1)H NMR spectrum of alginate, compared with those previously reported in the literature, is provided here. Hydrogel materials were formed from ionically cross-linked blends of phosphorylated alginate and alginate. These blended hydrogels showed an enhanced resistance to degradation by chelating agents compared with cross-linked alginate hydrogels and a reduction in their mineralization potential.
Evaluation of surface layer stability of surface-modified polyester biomaterials
Publisher: American Vacuum Society
Date: 11-2020
DOI: 10.1116/6.0000687
Abstract: Surface modification of biomaterials is a strategy used to improve cellular and in vivo outcomes. However, most studies do not evaluate the lifetime of the introduced surface layer, which is an important aspect affecting how a biomaterial will interact with a cellular environment both in the short and in the long term. This study evaluated the surface layer stability in vitro in buffer solution of materials produced from poly(lactic-co-glycolic acid) (50:50) and polycaprolactone modified by hydrolysis and/or grafting of hydrophilic polymers using grafting from approaches. The data presented in this study highlight the shortcomings of using model substrates (e.g., spun-coated films) rather than disks, particles, and scaffolds. It also illustrates how similar surface modification strategies in some cases result in very different lifetimes of the surface layer, thus emphasizing the need for these studies as analogies cannot always be drawn.
Chitosan Nanomedicine in Cancer Therapy: Targeted Delivery and Cellular Uptake
Publisher: Wiley
Date: 19-03-2021
Abstract: Nanomedicine has gained much attention for the management and treatment of cancers due to the distinctive physicochemical properties of the drug-loaded particles. Chitosan's cationic nature is attractive for the development of such particles for drug delivery, transfection, and controlled release. The particle properties can be improved by modification of the polymer or the particle themselves. The physicochemical properties of chitosan particles are analyzed in 126 recent studies, which allows to highlight their impact on passive and active targeted drug delivery, cellular uptake, and tumor growth inhibition (TGI). From 2012 to 2019, out of 40 in vivo studies, only 4 studies are found reporting a reduction in tumor size by using chitosan particles while all other studies reported tumor growth inhibition relative to controls. A total of 23 studies are analyzed for cellular uptake including 12 studies reporting cellular uptake mechanisms. Understanding and exploiting the processes involved in targeted delivery, endocytosis, and exocytosis by controlling the physicochemical properties of chitosan particles are important for the development of safe and efficient nanomedicine. It is concluded based on the recent literature available on chitosan particles that combination therapies can play a pivotal role in transformation of chitosan nanomedicine from bench to bedside.
Alginate-based drug delivery devices
Publisher: Elsevier
Date: 2010
Biomimetic synthesis and tensile properties of nanostructured high volume fraction hydroxyapatite and chitosan biocomposite films
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B914798E
Controlled release of heparin from poly(ε-caprolactone) electrospun fibers
Publisher: Elsevier BV
Date: 03-2006
DOI: 10.1016/J.BIOMATERIALS.2005.10.028
Abstract: Sustained delivery of heparin to the localized adventitial surface of grafted blood vessels has been shown to prevent the vascular smooth muscle cell (VSMC) proliferation that can lead to graft occlusion and failure. In this study heparin was incorporated into electrospun poly(epsilon-caprolactone) (PCL) fiber mats for assessment as a controlled delivery device. Fibers with smooth surfaces and no bead defects could be spun from polymer solutions with 8%w/v PCL in 7:3 dichloromethane:methanol. A significant decrease in fiber diameter was observed with increasing heparin concentration. Assessment of drug loading, and imaging of fluorescently labeled heparin showed homogenous distribution of heparin throughout the fiber mats. A total of approximately half of the encapsulated heparin was released by diffusional control from the heparin/PCL fibers after 14 days. The fibers did not induce an inflammatory response in macrophage cells in vitro and the released heparin was effective in preventing the proliferation of VSMCs in culture. These results suggest that electrospun PCL fibers are a promising candidate for delivery of heparin to the site of vascular injury.
Functionalised polycaprolactone films and 3D scaffolds via gamma irradiation-induced grafting
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3TB20267D
Novel phosphate-grafted ePTFE copolymers for optimum in vitro mineralization
Publisher: IOP Publishing
Date: 19-07-2010
DOI: 10.1088/1748-6041/5/4/045010
Abstract: Surface modification via graft copolymerization is an attractive method for optimizing polymers used in biomedical applications. We developed a novel method using a mixed solvent system (either water and dichloromethane (DCM) or water, methanol and DCM) consisting of two solvent phases for grafting 2-(methacryloyloxy)ethyl phosphate onto expanded polytetrafluoroethylene (ePTFE). This new method resulted in the fabrication of grafted membranes with greater grafting extents (GEs) (as evaluated from x-ray photoelectron spectroscopy (XPS)) in the organic phase than those obtained when grafting was carried out in a single phase. It also made it possible to graft in the aqueous phase, a process that is otherwise inhibited by the concomitant formation of large amounts of highly crystalline homopolymer. Thorough characterization of the grafted membranes using gravimetric, XPS and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) not only permitted evaluation of the grafting outcomes but also made it possible to analyze their dependence on monomer concentration and solvent composition. A selection of membranes was tested for their in vitro mineralization capacity using simulated body fluid. It was found that an 'ideal' mineralization outcome, i.e. a uniform coating of carbonated hydroxyapatite (cHAP) formed on the s le grafted in the aqueous phase of the water/DCM two-phase solvent system. A detailed discussion bringing together these results, as well as results from a series of earlier studies, allows conclusions regarding polymer chemistry and the topology necessary for cHAP mineralization.
Hydroxyapatite mineralization in the presence of anionic polymers
Publisher: American Chemical Society (ACS)
Date: 28-08-2013
DOI: 10.1021/CG400447E
Calcium phosphate nucleation on surface-modified PTFE membranes
Publisher: Springer Science and Business Media LLC
Date: 2003
Abstract: Highly porous PTFE membranes are currently being used in facial reconstructive surgery. The present study aims at improving this biomaterial through creating a more bioactive surface by introducing ionic groups onto the surface. The unmodified PTFE membrane does not induce inorganic growth after immersion in simulated body fluid (SBF) for up to 4 weeks. Copolymeric grafting with acrylic acid (AAc) by means of gamma irradiation and subsequent in vitro testing in SBF reveals that this copolymer initially acts as an ion-exchange material and subsequently induces growth of a calcium phosphate phase (Ca/P=2.7) when large amounts (15%) of pAAc are introduced onto the membrane surface. This copolymer is not expected to function well from a biomaterials perspective since SEM showed the pores on the surface to be partly blocked. In contrast, the surface of monoacryloxyethyl phosphate (MAEP)-modified s les is altered at a molecular level only. Yet the modified materials are able to induce calcium phosphate nucleation when the external surface coverage is 44% or above. The initial inorganic growth on these membranes in SBF has a (Ca+Mg)/P ratio of 1.1 (presumably Brushite or Monetite). The secondary growth, possibly calcium-deficient apatite or tricalcium phosphate, has a (Ca+Mg)/P ratio of 1.5. This result is a promising indicator of a bioactive biomaterial.
Bionanohydroxyapatite/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Composites with Improved Particle Dispersion and Superior Mechanical Properties
Publisher: American Chemical Society (ACS)
Date: 15-03-2008
DOI: 10.1021/CM703045U
Evaluation of the in vivo fate of ultrapure alginate in a BALB/c mouse model
Publisher: Elsevier BV
Date: 06-2021
Adsorption of Well-Defined Fluorine-Containing Polymers onto Poly(tetrafluoroethylene)
Publisher: American Chemical Society (ACS)
Date: 17-10-2008
DOI: 10.1021/LA802300Q
Abstract: Adsorption of well-defined fluorinated polymers onto clinically relevant poly(tetrafluoroethylene) (PTFE) substrates offers an attractive method for modifying the surface properties of chemically inert PTFE. Reversible addition-fragmentation chain transfer (RAFT) was successfully used for synthesis of the polymers in this study: the homopolymers poly(2,3,4,5,6-pentafluorostyrene) (PFS), poly(2,2,3,3-tetrafluoropropyl acrylate) (PTFPA), and poly(2,2,3,3-tetrafluoropropyl methacrylate) (PTFPMA) as well as their block copolymers with tert-butyl acrylate ( (t)BA). Water-soluble blocks were synthesized through the hydrolysis of the t-butyl side groups of P( (t)BA) to the corresponding carboxylic acid. Adsorption of selected polymers onto PTFE from a series of solvents (methyl ethyl ketone (MEK), dimethylformamide (DMF), fluorobenzene (FB), dichloromethane (DCM)) was investigated using X-ray photoelectron spectroscopy (XPS) and sessile water drop measurements. The three homopolymers studied all adsorbed irreversibly (i.e., were not removed by washing) from organic solvents at ambient temperature. PFS displayed the highest adsorption, and was attributed to strong hydrophobic interactions. From angle-resolved XPS it was concluded that PFS became impregnated into the PTFE substrate down to depths of 100 A when using FB as a solvent. The carboxylic acid-containing block copolymers adsorbed more effectively from DMF (a good solvent for the poly(acrylic acid) block) compared to MEK. The resulting modified PTFE substrates displayed high stability with respect to desorption in aqueous solution, yet conformational changes of the adsorbed polymer resulted in a switchable hydrophobic-hydrophilic surface (in air or water, respectively). These results highlight the success of a facile and simple approach to irreversibly adsorb functional polymers to a nonfunctional fluorinated surface.
Inorganic polymer composites for bone regeneration and repair
Publisher: Elsevier
Date: 2014
Comprehensive characterization of grafted expanded poly(tetrafluoroethylene) for medical applications
Publisher: American Chemical Society (ACS)
Date: 02-09-2010
DOI: 10.1021/LA1010677
Abstract: Successful implantation of any biomaterial depends on its mechanical, architectural, and surface properties. Materials with good bulk properties seldom possess the appropriate surface characteristics required for good biointegration. The present study investigates the results of surface modification of a highly porous, fully fluorinated polymeric substrate, expanded poly(tetrafluoroethylene) (ePTFE), with a view to improving the surface bioactivity and hence ultimately its biointegration. Modification involved gamma irradiation-induced graft copolymerization with the monomers monoacryloxyethyl phosphate (MAEP) and methacryloxyethyl phosphate (MOEP) in various solvent systems (water, methanol, methyl ethyl ketone, and mixtures thereof). In order to determine the penetration depth of the graft copolymer into the pores and/or the bulk of the ePTFE membranes, angle-dependent X-ray photoelectron spectroscopy (XPS) and magnetic resonance imaging (MRI) were used. It was found that the penetration depth was critically affected by the choice of monomer and solvent as well as by the technique used to remove dissolved oxygen from the grafting mixture: nitrogen degassing versus vacuum. Difficulties due to the porous nature of the membranes in establishing the lateral position of the graft copolymers were largely overcome by combining data from microattenuated total reflectance Fourier transfer infrared (μ-ATR-FTIR) mapping and time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging. Results show that the large variation in graft heterogeneity found between different s les is largely an effect of the underlying substrate and choice of monomer. The results from this study provide the necessary knowledge and experimental data to control both the graft copolymer lateral position and depth of penetration in these porous ePTFE membranes.
Protein adsorption to poly(tetrafluoroethylene) membranes modified with grafted poly(acrylic acid) chains
Publisher: American Vacuum Society
Date: 05-2020
DOI: 10.1116/6.0000137
Abstract: Protein adsorption to biomaterial surfaces is important for the function of such materials with anchorage-dependent cell adhesion requiring the presence of adsorbed proteins. The current study evaluated five solid surfaces with poly(acrylic acid) (PAA) grafted from the surface of a poly(tetrafluoroethylene) membrane with respect to the adsorption of serum albumin (SA), lactoferrin (Lf), and lysozyme (Lys) from a phosphate buffer and NaCl solution or water for specific combinations. With the use of x-ray photoelectron spectroscopy, the relative amounts and protein layer thickness were evaluated. SA adsorption was governed by ionic repulsive forces and hydrophobic interactions as evidenced from an increase in the protein adsorption at lower pH (6.5 compared to 7.4) and a correlation with surface coverage when water (pH 6.5) was used as the medium. The adsorption of Lf and Lys followed similar trends for all s les. In general, ionic attractive forces dominated and a strong correlation of increasing protein adsorption with the PAA chain length was evident. This study concluded that all surfaces appear suitable for use in biomaterial applications where tissue ingrowth is desired and that the enhanced protein adsorption in a medium with high ionic strength (e.g., biological fluid) correlates with the PAA chain length rather than the surface coverage.
Interactions between different forms of bovine lactoferrin and sodium alginate affect the properties of their mixtures
Publisher: Elsevier BV
Date: 06-2015
THE CRYSTAL-STRUCTURES OF RAC-BIS(1,2-ETHANEDIAMINE)(2-THIOOXAMATO-N,O)COBALT(III) TRIFLUOROMETHANESULFONATE MONOHYDRATE AT 110 AND 296 K AND THEIR RELATION TO THE REVERSIBLE PHASE-TRANSITION AT 155 K
Publisher: Danish Chemical Society
Date: 1995
Composite materials for bone repair
Publisher: Elsevier
Date: 2017
Evaluation of techniques used for visualisation of hydrogel morphology and determination of pore size distributions
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2MA00932C
Abstract: This study evaluated stimulated emission depletion (STED) microscopy, atomic force microscopy (AFM), and cryogenic scanning electron microscopy (Cryo-SEM), for visualising the morphology and obtaining pore size information of agarose hydrogels.
In-vitro digestion of different forms of bovine lactoferrin encapsulated in alginate micro-gel particles
Publisher: Elsevier BV
Date: 2016
In vitro mineralization of dual grafted polytetrafluoroethylene membranes
Publisher: American Vacuum Society
Date: 30-05-2017
DOI: 10.1116/1.4984012
Abstract: The modification of biomaterials by radiation induced grafting is a promising method to improve their bioactivity. Successful introduction of carboxyl and amine functional groups on the surface of a polytetrafluoroethylene membrane was achieved by grafting of acrylic acid (AA) and 2-aminoethyl methacrylate hydrochloride (AEMA) using simultaneous gamma irradiation grafting. Chemical characterization by attenuated total reflectance Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy confirmed the presence of amine and carboxylate functionalities and indicated that all protonated amines formed ion pairs with carboxyl groups, but not all carboxyl are involved in ion pairing. It was found that the irradiation doses (2, 5, or 10 kGy) affected the grafting outcome only when sulfuric acid (0.5 or 0.9 M) was added as a polymerization enhancer. The use of the inorganic acid successfully enhanced the total graft yield (GY), but the changes in the graft extent (GE) were not conclusive. Dual functional films were produced by either a one- or a two-step process. Generally, higher GY and GE values were observed for the s les produced by the two-step grafting of AA and AEMA. The in vitro mineralization in 1.5× simulated body fluid (SBF) induced the formation of carbonated hydroxyapatite as verified by FITR. All s les showed an increase in weight after mineralization with significantly larger increases observed for the s les which had the 1.5× SBF changed every third day compared to every seventh. For the dual functional s les, it was found that the s le grafted by the one-step method shows a significantly higher increase in weight despite a much lower GY compared to the s le prepared by the two-step method and this was attributed to the different architecture of grafted chains.
Enhancing expanded poly(tetrafluoroethylene) (ePTFE) for biomaterials applications
Publisher: Wiley
Date: 18-02-2014
DOI: 10.1002/APP.40533
Reduction of the in vitro pro-inflammatory response by macrophages to poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.BIOMATERIALS.2006.05.010
Abstract: This study evaluates the pro-inflammatory response to the thermoplastic biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) through the analysis of cellular responses in vitro. The murine macrophage RAW264.7 cell line was cultured on solvent cast PHBV films, which was found to induce pro-inflammatory activity that required direct contact between the material and the macrophages. The identity of the pro-inflammatory stimulus was determined by culturing bone marrow-derived macrophages from bacterial lipopolysaccharide (LPS) hyporesponsive C3H/HeJ mice and CpG non-responsive TLR9-/- mice on PHBV. The lack of a pro-inflammatory response by the C3H/HeJ cells indicates that the pro-inflammatory agent present within PHBV is predominately LPS while the TLR9-/- macrophages confirmed that CpG-containing bacterial DNA is unlikely to contribute to the activity. A series of purification procedures was evaluated and one procedure was developed that utilized hydrogen peroxide treatment in solution. The optimized purification was found to substantially reduce the pro-inflammatory response to PHBV without adversely affecting either the molecular structure or molecular weight of the material thereby rendering it more amenable for use as a biomaterial in vivo.
Evaluation of properties and specific energy consumption of spinifex-derived lignocellulose fibers produced using different mechanical processes
Publisher: Springer Science and Business Media LLC
Date: 22-06-2019
Characterisation of amine functionalised poly(3-hydroxybuturate-co-3-hydroxyvalerate) surfaces
Publisher: Elsevier BV
Date: 07-2011
Comparison between polyethylene glycol and zwitterionic polymers as antifouling coatings on wearable devices for selective antigen capture from biological tissue
Publisher: American Vacuum Society
Date: 07-10-2015
DOI: 10.1116/1.4932055
Abstract: Selective capture of disease-related proteins in complex biological fluids and tissues is an important aim in developing sensitive protein biosensors for in vivo applications. Microprojection arrays are biomedical devices whose mechanical and chemical properties can be tuned to allow efficient penetration of skin, coupled with highly selective biomarker capture from the complex biological environment of skin tissue. Herein, the authors describe an improved surface modification strategy to produce amine-modified polycarbonate arrays, followed by the attachment of an antifouling poly(sulfobetaine-methacrylate) (pSBMA) polymer or a linear polyethylene glycol (PEG) polymer of comparative molecular weight and hydrodynamic radius. Using a “grafting to” approach, pSBMA and linear PEG coatings yielded comparative antifouling behavior in single protein solutions, diluted plasma, or when applied to mouse flank skin penetrating into the vascularized dermal tissue. Interestingly, the density of immobilized immunoglobulin G (IgG) or bovine serum albumin protein on pSBMA surfaces was significantly higher than that on the PEG surfaces, while the nonspecific adsorption was comparable for each protein. When incubated in buffer or plasma solutions containing dengue non-structural protein 1 (NS1), anti-NS1-IgG-coated pSBMA surfaces captured significantly more NS1 in comparison to PEG-coated devices. Similarly, when wearable microprojection arrays were applied to the skin of dengue-infected mice using the same coatings, the pSBMA-coated devices showed significantly higher capture efficiency (& -fold increase in signal) than the PEG-coated substrates, which showed comparative signal when applied to naïve mice. In conclusion, zwitterionic pSBMA polymers (of equivalent hydrodynamic radii to PEG) allowed detection of dengue NS1 disease biomarker in a preclinical model of dengue infection, showing significantly higher signal-to-noise ratio in comparison to the PEG controls. The results of this study will be useful in the future development of a range of protein biosensors designed for use in vivo.
Methacryloxyethyl phosphate-grafted expanded polytetrafluoroethylene membranes for biomedical applications
Publisher: Wiley
Date: 20-10-2005
DOI: 10.1002/PI.1902
Correction to: Evaluation of properties and specific energy consumption of spinifex-derived lignocellulose fibers produced using different mechanical processes
Publisher: Springer Science and Business Media LLC
Date: 04-02-2020
Gelation Kinetics and Viscoelastic Properties of Pluronic and α-Cyclodextrin-Based Pseudopolyrotaxane Hydrogels
Publisher: American Chemical Society (ACS)
Date: 19-09-2013
DOI: 10.1021/BM401168H
Abstract: The results of a systematic investigation into the gelation behavior of α-cyclodextrin (α-CD) and Pluronic (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers) pseudopolyrotaxane (PPR) hydrogels are reported here in terms of the effects of temperature, α-CD concentration, and Pluronic type (Pluronic F68 and Pluronic F127). It was found that α-CD significantly modifies the gelation behavior of Pluronic solutions and that the PPR hydrogels are highly sensitive to changes in the α-CD concentration. In some cases, the addition of α-CD was found to be detrimental to the gelation process, leading to slower gelation kinetics and weaker gels than with Pluronic alone. However, in other cases, the hydrogels formed in the presence of the α-CDs reached higher moduli and showed faster gelation kinetics than with Pluronic alone and in some instances α-CD allowed the formation of hydrogels from Pluronic solutions that would normally not undergo gelation. Depending on composition and ratio of α-CD/Pluronic, these highly viscoelastic hydrogels displayed elastic shear modulus values ranging from 2 kPa to 7 MPa, gelation times ranging from a few seconds to a few hours and self-healing behaviors post failure. Using dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS), we probed the resident structure of these systems, and from these insights we have proposed a new molecular mechanism that accounts for the macroscopic properties observed.
Physico-chemical properties of different forms of bovine lactoferrin
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.FOODCHEM.2013.05.139
Abstract: Three forms of bovine lactoferrin (Lf), apo-, native- and holo- with 0.9%, 12.9% and 99.7% iron content, respectively, were characterised for their physico-chemical properties. Colour, surface tension, thermal properties, particle charge and rheological behaviour of Lf were found to be affected by the form of Lf. The surface tension of Lf tends to decrease with decrease in iron content. The Circular Dichroism (CD) spectra confirmed that all forms of Lf had similar secondary structures while the tertiary structure was different for holo-Lf. The Differential Scanning Calorimeter (DSC) analysis showed that the apo- and holo-Lf in aqueous solution displayed thermal denaturation temperatures of 71±0.2 and 91±0.5 °C, respectively, suggesting that the iron saturation of Lf tends to increase its thermal stability. The study of particle charge properties (ζ-potential) in 1 mM KCl salt solution showed that apo-Lf reached the net charge of zero in the pH range 5.5-6.5 whereas native and holo-Lf in the pH range 8.0-9.0. The apparent viscosity of 1% (wt/wt) solution of the different forms of Lf showed no difference between apo- and native-Lf (≈1.4 mPas) while the value was significantly higher (2.38 mPas) for holo-Lf.
Influence of a diene impurity on the molecular structure of phosphate-containing polymers with medical applications
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B803223H
Abstract: We have demonstrated that the unacknowledged presence of almost 30% diene impurity in some commercial phosphate monomers had not only a significant effect on the molecular structure (topology) of a series of synthesized polymers but the instability of the ester functionalities during these polymerizations resulted in unexpectedly complex co-polymer chemistry.
Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) composite biomaterials for bone tissue regeneration: In vitro performance assessed by osteoblast proliferation, osteoclast adhesion and resor
Publisher: Wiley
Date: 21-02-2007
DOI: 10.1002/JBM.A.31174
Abstract: The efficacy of composite materials for bone tissue engineering is dependent on the materials' ability to support bone regeneration whilst inducing a minimal inflammatory response. In this study we examined the in vitro osteogenic and inflammatory properties of poly(3-hydroxybutyrate-co-3-valerate) (PHBV) with various calcium phosphate-reinforcing phases: nano-sized hydroxyapatite (HA) submicron-sized calcined hydroxyapatite (cHA) and submicron-sized beta-tricalcium phosphate (beta-TCP), using bioassays of cultured osteoblasts, osteoclasts, and macrophages. Our study showed that the addition of a nano-sized reinforcing phase to PHBV, whilst improving osteogenic properties, also reduces the proinflammatory response. Proinflammatory responses of RAW264.7/ELAM-eGFP macrophages to PHBV were shown to be markedly reduced by the introduction of a reinforcing phase, with HA/PHBV composites having the lowest inflammatory response. Osteoclasts, whilst able to attach to all the materials, failed to form functional actin rings or resorption pits on any of the materials under investigation. Cultures of osteoblasts (MC3T3-E1) readily attached and mineralised on all the materials, with HA/PHBV inducing the highest levels of mineralization. The improved biological performance of HA/PHBV composites when compared with cHA/PHBV and beta-TCP/PHBV composites is most likely a result of the nano-sized reinforcing phase of HA/PHBV and the greater surface presentation of mineral in these composites. Our results provide a new strategy for improving the suitability of PHBV-based materials for bone tissue regeneration.
In vitro mineralization of functional polymers
Publisher: Elsevier BV
Date: 09-2015
Tensile properties and in vitro degradation of P(TMC-co-LLA) elastomers
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TB00202H
Abstract: The degradation mechanism of P(TMC- co -LLA) films was dependent on the LLA content and found to transition from heterogeneous to homogeneous bulk degradation.
Effects of Varying Heptylamine and Propionaldehyde Plasma Polymerization Parameters on Mesenchymal Stem Cell Attachment
Publisher: Wiley
Date: 29-08-2012
The in vivo assessment of a novel scaffold containing heparan sulfate for tissue engineering with human mesenchymal stem cells
Publisher: Springer Science and Business Media LLC
Date: 11-08-2007
DOI: 10.1007/S10735-007-9129-Y
Abstract: Human mesenchymal stem cells (hMSCs) are an attractive tissue engineering avenue for the repair and regeneration of bone. In this study we detail the in vivo performance of a novel electrospun polycaprolactone scaffold incorporating the glycosaminoglycan heparan sulfate (HS) as a carrier for hMSC. HS is a multifunctional regulator of many key growth factors expressed endogenously during bone wound repair, and we have found it to be a potent stimulator of proliferation in hMSCs. To assess the potential of the scaffolds to support hMSC function in vivo, hMSCs pre-committed to the osteogenic lineage (human osteoprogenitor cells) were seeded onto the scaffolds and implanted subcutaneously into the dorsum of nude rats. After 6 weeks the scaffolds were retrieved and examined by histological methods. Implanted human cells were identified using a human nuclei-specific antibody. The host response to the implants was characterized by ED1 and ED2 antibody staining for monocytes/macrophages and mature tissue macrophages, respectively. It was found that the survival of the implanted human cells was affected by the host response to the implant regardless of the presence of HS, highlighting the importance of controlling the host response to tissue engineering devices.
Hydrolytically Degradable Polyrotaxane Hydrogels for Drug and Cell Delivery Applications
Publisher: American Chemical Society (ACS)
Date: 12-12-2014
DOI: 10.1021/BM501615P
Abstract: Self-assembled pseudopolyrotaxane (PPR) hydrogels formed from Pluronic polymers and α-cyclodextrin (α-CD) have been shown to display a wide range of tailorable physical and chemical properties that may see them exploited in a multitude of future biomedical applications. Upon the mixing of both components, these self-assembling hydrogels reach a metastable thermodynamic state that is defined by the concentrations of both components in solution and the temperature. However, at present, their potential is severely limited by the very nature by which they form and hence also disassemble. Even if the temperature is kept constant, PPR hydrogels will dissociate and collapse within a few hours when immersed in a liquid (such as cell culture media) that contains a lower concentrations of, or no, Pluronic or α-CD due to differences in chemical potential driving dissolution. In this article, an enzymatically mediated covalent cross-linking function and branched eight-arm poly(ethylene glycol) (PEG) were thus introduced into the PPR hydrogels to improve their robustness to such environmental changes. The eight-arm PEG also acted as an end-capping group to prevent the dethreading of the α-CD molecules. The covalent cross-linking successfully extended the lifetime of the hydrogels when placed in cell culture media from a few hours to up to 1 week, with the ability to control the degradation rate (now initiated by hydrolysis of the introduced ester bonds and not by dissolution) by changing the amount of eight-arm PEG present in the hydrogels. Highly tunable hydrogels were obtained with an elastic modulus between 20 and 410 kPa and a viscous modulus between 150 Pa and 22 kPa by varying the concentrations of α-CD and eight-arm PEG. Sustained release of a model drug from the hydrogels was achieved, and viability of mouse fibroblasts encapsulated in these hydrogels was assessed. These self-assembling, hydrolytically degradable, and highly tunable hydrogels are seen to have potential applications in tissue engineering relying on controlled drug or cell delivery to sites targeted for repair.
A novel composite porous coating approach for bioactive titanium‐based orthopedic implants
Publisher: Wiley
Date: 12-09-2012
DOI: 10.1002/JBM.A.34372
Abstract: Surface modification of titanium-based implants is considered a highly effective solution to enhance osseointegration. This study describes a novel Ti/hydroxyapatite (HA) composite porous coating produced using a cold spraying technique. Experimental results indicate desirable open-cell structure with 50-150 μm pore size and 60-65% macroporosity. In particular, the reinforced HA particles are exposed to the surface of the coating resulting in enhanced mineralization ability in simulated body fluid. None of the coatings displayed a cytotoxic response in SaOS-2 cells cultured in vitro for up to 48 h. The bond strength between the porous coating and the Ti substrate was found to be 20 MPa. These properties are comparative to or better than products currently on the market and thus this novel coating has potential use in orthopedics.
Use of Two-Step Grafting to Fabricate Dual-Functional Films and Site-Specific Functionalized Scaffolds
Publisher: American Chemical Society (ACS)
Date: 29-01-2015
DOI: 10.1021/LA504629H
Abstract: Polycaprolactone (PCL) is a widely utilized bioresorbable polymer in tissue engineering applications. However, the absence of intrinsic functional groups in the polymer backbone necessitates the incorporation of functional chemistries to enable the further addition of bioactive molecules to PCL-based surfaces and scaffolds. The current study aimed to incorporate two different functional groups, amine and carboxylate, first on two-dimensional (2D) spin-coated PCL films and, thereafter, throughout all surfaces within three-dimensional (3D) porous PCL-based scaffolds, produced using the thermally induced phase separation (TIPS) method, but in a spatially separated manner. Specifically, gamma irradiation induced grafting of acrylic acid (AA) and 2-aminoethyl methacrylate hydrochloride (AEMA) onto PCL was performed in selected solvents and the resulting substrates were characterized using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements to determine the surface free energy. Results demonstrated that stepwise graft copolymerization of AEMA and AA allows the fabrication of dual-functional surfaces, with chemistry depending on the order of grafting of the two monomers. In addition, 3D scaffolds could be decorated exclusively with carboxylate groups in the interior, while the outer surface displayed dual-functionality. This simple surface modification methodology, with the ability to create spatially separated surface functional groups throughout 3D porous scaffolds post their fabrication, has the potential to be applied to many current and future scaffold systems being investigated in the field of tissue engineering.
Delivery of dermatan sulfate from polyelectrolyte complex-containing alginate composite microspheres for tissue regeneration
Publisher: American Chemical Society (ACS)
Date: 28-02-2012
DOI: 10.1021/BM201821X
Abstract: Dermatan sulfate (DS) is a glycosaminoglycan (GAG) with a great potential as a new therapeutic agent in tissue engineering. The aim of the present study was to investigate the formation of polyelectrolyte complexes (PECs) between chitosan and dermatan sulfate (CS/DS) and delivery of DS from PEC-containing alginate/chitosan/dermatan sulfate (Alg/CS/DS) microspheres for application in tissue regeneration. The CS/DS complexes were initially formed at different conditions including varying CS/DS ratio (positive/negative charge ratio), buffer, and pH. The obtained CS/DS complexes exhibited stronger electrostatic interaction, smaller complex size, and more stable colloidal structure when chitosan was in large excess (CS/DS 3:1) and prepared at pH 3.5 as compared to pH 5 using acetate buffer. The CS/DS complexes were subsequently incorporated into an alginate matrix by spray drying to form Alg/CS/DS composite microspheres with a DS encapsulation efficiency of 90-95%. The excessive CS induced a higher level of sustained DS release into Tris buffer (pH 7.4) from the microspheres formulated at pH 3.5 however, the amount of CS did not have a significant effect on the release from the microspheres formulated at pH 5. Significant cell proliferation was stimulated by the DS released from the microspheres in vitro. The present results provide a promising drug delivery strategy using PECs for sustained release of DS from microspheres intended for site-specific drug delivery and ultimately for use in tissue engineering.
Electrospinning and mechanical properties of P(TMC-co-LLA) elastomers
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7TB00137A
Abstract: P(TMC- co -LLA) elastomers have shown great potential for various biomaterial and tissue engineering applications.
Investigations into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) surface properties causing delayed osteoblast growth
Publisher: Informa UK Limited
Date: 2007
DOI: 10.1163/156856207781554046
Abstract: Osteoblast proliferation is sensitive to material surface properties. In this study, the proliferation of MC3T3 E1-S14 osteoblastic cells on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films with different surface characteristics was investigated with the aim of evaluating the cause of a lag in cell growth previously observed. The solvent-cast films were prepared using three different solvents/solvent mixtures which produced PHBV films with both a rough (at the air interface) and smooth (at the glass interface) surface. Investigation of the surface roughness by scanning electron and scanning probe microscopy revealed that the surfaces had features that were different in both average lateral size and average litude (Ra 20-200 nm). Water contact angles showed that all surfaces were hydrophobic in nature (thetaA in the range 69-82 degrees ). The lateral distribution of surface crystallinity of the films was evaluated by use of micro-attenuated total reflectance Fourier transform infrared (ATR-FT-IR) by determining the surface crystallinity index (CI) which was found to differ between s les. MC3T3-E1-S14 osteoblasts were cultured on the six surfaces and proliferation was determined. After 2 days, cell proliferation on all surfaces was significantly less than on the control substrate however, after 4 days cell proliferation was optimal on three surfaces. It was concluded that the initial lag on all substrates was due to the hydrophobic nature of the substrates. The ability of the cells to recover on the materials was attributed to the degree of heterogeneity of the crystallinity and surface roughness: s les with a roughness of 80 nm were found to support cell proliferation. In addition, the lateral surface features influenced the proliferation of osteoblasts on the PHBV film surface.
Exciting new developments at the 5th International Symposium on Surface and Interface of Biomaterials
Publisher: American Vacuum Society
Date: 12-2015
DOI: 10.1116/1.4936957
Abstract: Materials intended for use as implantable or diagnostic devices are required not only to display the required functional bulk properties but also have surface properties that elicit a desired biological response, and do so with high selectivity. The area of surface functionalization approaches and bioactive coatings for biomaterials and biomedical devices has been the subject of much research over several decades yet, many challenges still remain to be solved. The 5th International Symposium on Surface and Interface of Biomaterials (ISSIB) held in Sydney (Australia) in April 2015 was an ideal forum to discuss the most recent developments in biomaterial surface modification, characterization, and evaluation of biological responses. The conference covered a range of topics including antimicrobial coatings, analysis of biomaterial surfaces and interfaces, biomolecules and cells at surfaces and interfaces, nanoparticles, functional coatings, patterned biomaterials, nanofabrication, bioreactors, and biosensors. In this special conference issue, the authors include papers that detail some of the highlights from the meeting.
Tailorable cell culture platforms from enzymatically cross-linked multifunctional poly(ethylene glycol)-based hydrogels
Publisher: American Chemical Society (ACS)
Date: 15-01-2013
DOI: 10.1021/BM301652Q
Abstract: As stem-cell-based therapies rapidly advance toward clinical applications, there is a need for cheap, easily manufactured, injectable gels that can be tailored to carry stem cells and impart function to such cells. Herein we describe a process for making hydrogels composed of hydroxyphenyl propionic acid (HPA) conjugated, branched poly(ethylene glycol) (PEG) via an enzyme mediated, oxidative cross-linking method. Functionalization of the branched PEG with HPA at varying degrees of substitution was confirmed via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and (1)H NMR. The versatility of this hydrogel system was exemplified through variations in the degree of HPA substitution, polymer concentration, and the concentration of cross-linking reagents (horseradish peroxidase and H(2)O(2)), which resulted in a range of mechanical properties and gelation kinetics for these gels. Cross-linking of the PEG-HPA conjugate with a recombinantly produced Fibronectin fragment (Type III domains 7-10) encouraged attachment and spreading of human mesenchymal stem cells (hMSCs) when assessed in both two-dimensional and three-dimensional formats. Interestingly, when encapsulated in both nonfunctionalized and functionalized cross-linked PEG-HPA gels, MSCs showed good viability over all time periods assessed. With tunable gelation kinetics and mechanical properties, these hydrogels provide a flexible in vitro cell culture platform that will likely have significant utility in tissue engineering as an injectable delivery platform for cells to sites of tissue damage.
Interactions between Chitosan and Alginate Dialdehyde Biopolymers and Their Layer-by-Layer Assemblies
Publisher: American Chemical Society (ACS)
Date: 27-05-2015
DOI: 10.1021/ACS.BIOMAC.5B00383
Abstract: Biopolymers are researched extensively for their applications in biomaterials science and drug delivery including structures and complexes of more than one polymer. Chemical characterization of complexes formed between chitosan (CHI) and alginate dialdehyde (ADA) biopolymers established that while electrostatic interactions dominate (as determined from X-ray photoelectron spectroscopy (XPS)) covalent cross-linking between these biopolymers also contribute to their stability (evidenced from immersion in salt solution). It was furthermore found that imine bond formation could not be directly detected by any of the techniques XPS, FTIR, (1)H NMR, or fluorescence. The layer-by-layer assemblies of the biopolymers formed on silica colloids, glass slides, and alginate hydrogel beads were evaluated using XPS, as well as zeta potential measurements for the silica colloids and changes to hydration properties for the hydrogels. It was found that the degree of oxidation of ADA affected the LbL assemblies in terms of a greater degree of CHI penetration observed when using the more conformationally flexible biopolymer ADA (higher degree of oxidation).
Responses in vivo to purified poly(3-hydroxybutyrate-co-3-hydroxyvalerate) implanted in a murine tibial defect model
Publisher: Wiley
Date: 08-12-2009
DOI: 10.1002/JBM.A.32238
Abstract: Effective bone biomaterials provide structural support for bone regeneration and elicit minimal inflammatory or toxic effects in vivo. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a bacterially derived biodegradable polymer that possesses suitable mechanical strength for use as a bone biomaterial and has a slow rate of degradation in biological environments. Our previous in vitro study showed that many PHBV preparations are contaminated with bacterial lipopolysaccharide, and we developed a purification procedure to substantially remove it. Here, we have evaluated the in vivo biocompatibility of PHBV purified by H(2)O(2) treatment and solvent extraction. We utilized a murine tibial defect model consisting of a hole drilled through the diameter of the tibial diaphysis into which nonporous cylindrical plugs of purified PHBV were implanted. The animals were sacrificed at 1 week and 4 weeks postsurgery, and tibiae were examined using histological staining. The PHBV implant induced a mild inflammatory response 1 week after injury, which persisted for 4 weeks. Granuloma type tissues formed only when the implant protruded into the overlaying tissue. Woven bone formation occurred adjacent to the implant, which gave rise to lamellar bone and stabilized the implant indicating that the PHBV did not affect this process. Our data validated the murine defect model and indicate that solid PHBV induces a mild tissue reaction with bone deposition adjacent to the implant with no fibrous tissue present at 4 weeks post surgery.
Radiation-induced grafting of acrylic acid onto expanded poly(tetrafluoroethylene) membranes
Publisher: Elsevier BV
Date: 12-2012
Attachment of poly(acrylic acid) to 3-aminopropyltriethoxysilane surface-modified hydroxyapatite
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3TB21110J
Akermanite reinforced PHBV scaffolds manufactured using selective laser sintering
Publisher: Wiley
Date: 22-03-2019
DOI: 10.1002/JBM.B.34349
Abstract: Scaffold assisted tissue engineering presents a promising approach to repair diseased and fractured bone. For successful bone repair, scaffolds need to be made of biomaterials that degrade with time and promote osteogenesis. Compared to the commonly used ß-tricalcium phosphate scaffolds, Akermanite (AKM) scaffolds were found to degrade faster and promote more osteogenesis. The objective of this study is to synthesize AKM micro and nanoparticle reinforced poly(3-hydroxybutyrate-co-3-hydroxyvalerate PHBV) composite scaffolds using selective laser sintering (SLS). The synthesized composite scaffolds had an interconnected porous microstructure (61-64% relative porosity), large specific surface areas (31.1-64.2 mm
Interactions between alginate and chitosan biopolymers characterized using FTIR and XPS
Publisher: American Chemical Society (ACS)
Date: 26-06-2007
DOI: 10.1021/BM070014Y
Abstract: This study investigates alginate-chitosan polyelectrolyte complexes (PECs) in the form of a film, a precipitate, as well as a layer-by-layer (LbL) assembly. The focus of this study is to fully characterize, using the complementary techniques of Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) in combination with solution stability evaluation, the interactions between alginate and chitosan in the PECs. In the FTIR spectra, no significant change in the band position of the two carbonyl vibrations from alginate occurs upon interaction with different ionic species. However, protonation of the carboxylate group causes a new band to appear at 1710 cm(-1), as anticipated. Partial protonation of the amine group of chitosan causes the appearance of one new band ( approximately 1530 cm(-1)) due to one of the -NH3+ vibrational modes (the other mode overlaps the amide I band). Importantly, the position of the two main bands in the spectral region of interest in partly protonated chitosan films is not dependent on the extent of protonation. XPS N 1s narrow scans can, however, be used to assess the degree of amine protonation. In our alginate-chitosan film, precipitate, and LbL assembly, the bands observed in the FTIR correspond to the species -COO- and -NH3+, but their position is not different from each of the single components. Thus, the conclusion of the study is that FTIR cannot be used directly to identify the presence of PECs. However, in combination with XPS (survey and narrow N 1s scans) and solution stability evaluation, a more complete description of the structure can be obtained. This conclusion challenges the assignment of FTIR spectra in the literature.
Evaluation of the impact of freezing preparation techniques on the characterisation of alginate hydrogels by cryo-SEM
Publisher: Elsevier BV
Date: 09-2016
Thionyl Chloride Oxidation of Chelated Glycinate in Bis(1,2-ethanediamine) glycinatocobalt(III) : Synthesis of N,O-bond N-Formyl Oxamate and Thiooxamate
Publisher: Danish Chemical Society
Date: 1995
Grafting from cellulose nanofibres with naturally-derived oil to reduce water absorption
Publisher: Elsevier BV
Date: 04-2021
Synthesis and characterization of hydroxyapatite, fluoride-substituted hydroxyapatite and fluorapatite
Publisher: Springer Science and Business Media LLC
Date: 2003
Abstract: Powders of hydroxyapatite (HA), partially fluoride-substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in house using optimum methods to achieve relatively pure powders. These powders were assessed by the commonly used bulk techniques of X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and FT-Raman spectroscopies, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and F-selective electrode. In addition, the current study has employed transmission electron microscopy (TEM), involving morphological observation, electron diffraction and energy-dispersive X-ray spectrometry (EDX), as an effective analytical technique to evaluate the powders at a microscopic level. The HA and fHA particles were elongated platelets about 20 x 60 nm in size, while FA particles were over twice this size. Calcination of the HA and fHA powders at 1000 degrees C for 1 h resulted in increased grain size and crystallinity. The calcined fHA material appeared to possess a crystal structure intermediate between HA and FA, as evidenced by the (3 0 0) peak shift in XRD, as well as by the position of the hydroxyl bands in the FTIR spectra. This result was consistent with electron diffraction of in idual particles. Small levels of impurities in some of the powders were identified by EDX and electron diffraction, and the carbonate content was detected by FTIR. The use of TEM in conjunction with the bulk techniques has allowed a more thorough assessment of the apatites, and has enabled the constituents in these closely related apatite powders to be identified.
Wiki Technologies and Communities: New Approaches to Assessing Individual and Collaborative Learning in the Chemistry Laboratory
Publisher: Wiley
Date: 23-01-2015
Investigating the effect of substrate materials on wearable immunoassay performance
Publisher: American Chemical Society (ACS)
Date: 11-01-2017
DOI: 10.1021/ACS.LANGMUIR.6B03933
Abstract: Immunoassays are ubiquitous across research and clinical laboratories, yet little attention is paid to the effect of the substrate material on the assay performance characteristics. Given the emerging interest in wearable immunoassay formats, investigations into substrate materials that provide an optimal mix of mechanical and bioanalytical properties are paramount. In the course of our research in developing wearable immunoassays which can penetrate skin to selectively capture disease antigens from the underlying blood vessels, we recently identified significant differences in immunoassay performance between gold and polycarbonate surfaces, even with a consistent surface modification procedure. We observed significant differences in PEG density, antibody immobilization, and nonspecific adsorption between the two substrates. Despite a higher PEG density formed on gold-coated surfaces than on amine-functionalized polycarbonate, the latter revealed a higher immobilized capture antibody density and lower nonspecific adsorption, leading to improved signal-to-noise ratios and assay sensitivities. The major conclusion from this study is that in designing wearable bioassays or biosensors, the design and its effect on the antifouling polymer layer can significantly affect the assay performance in terms of analytical specificity and sensitivity.
Dispersion of hydroxyapatite nanoparticles in solution and in polycaprolactone composite scaffolds
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5TB02255J
Abstract: Structure–property–performance in TIPS fabricated nanocomposite scaffolds: influence of polymer–solvent interaction and phase-separation process on the dispersion and surface distribution of particles.
Synthesis of Soluble Phosphate Polymers by RAFT and Their in Vitro Mineralization.
Publisher: American Chemical Society (ACS)
Date: 17-10-2006
DOI: 10.1021/BM060583Q
Abstract: Soluble linear (non-cross-linked) poly(monoacryloxyethyl phosphate) (PMAEP) and poly(2-(methacryloyloxy)ethyl phosphate) (PMOEP) were successfully synthesized through reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization and by keeping the molecular weight below 20 K. Above this molecular weight, insoluble (cross-linked) polymers were observed, postulated to be due to residual diene (cross-linkable) monomers formed during purification of the monomers, MOEP and MAEP. Block copolymers consisting of PMAEP or PMOEP and poly(2-(acetoacetoxy)ethyl methacrylate) (PAAEMA) were successfully prepared and were immobilized on aminated slides. Simulated body fluid studies revealed that calcium phosphate (CaP) minerals formed on both the soluble polymers and the cross-linked gels were very similar. Both the PMAEP polymers and the PMOEP gel showed a CaP layer most probably brushite or monetite based on the Ca/P ratios. A secondary CaP mineral growth with a typical hydroxyapatite (HAP) globular morphology was found on the PMOEP gel. The soluble PMOEP film formed carbonated HAP according to Fourier transform infrared (FTIR) spectroscopy. Block copolymers attached to aminated slides showed only patchy mineralization, possibly due to the ionic interaction of negatively charged phosphate groups and protonated amines.
In vitro biocompatibility and bioactivity of microencapsulated heparan sulfate
Publisher: Elsevier BV
Date: 04-2007
DOI: 10.1016/J.BIOMATERIALS.2007.01.002
Abstract: The glycosaminoglycan sugar heparan sulfate (HS) is an attractive agent for the repair of bone defects due to its ability to regulate endogenous growth factors. The sustained delivery of HS to the localized wound site over the period of healing which can last for over 1 month may prove advantageous for its therapeutic use. In this study we investigated the encapsulation of HS by the water-in oil-in water (W(1)/O/W(2)) technique in polycaprolactone (PCL) microcapsules as a prolonged delivery device. Encapsulation efficiencies of 70% could be achieved by using a 1:1 mixture of dichloromethane (DCM) and acetone as the solvent in the organic phase, while DCM alone gave poor encapsulation. Although addition of polyvinyl alcohol (PVA) to the drug phase did not affect the size or drug loading of the microcapsules, it did however produce a large change in the morphology and drug distribution, which resulted in different release rates. Release from capsules made with PVA in the drug phase reached 60% after 40 days, while those made with water in the drug phase completed release after 20 days. In vitro biocompatibility studies were performed and detected no increase in cell death in human mesenchymal stem cells (hMSC) or induction of an inflammatory response in macrophages after exposure to release products from HS-loaded microcapsules. The released HS retained its ability to increase the proliferation of hMSC after the encapsulation process. These results indicate that encapsulation of HS by the W(1)/O/W(2) method creates a promising device for the repair of bone tissue.
Composite materials for bone repair
Publisher: Elsevier
Date: 2009
Dispersion of hydroxyapatite nanoparticles in natural rubber latex and poly lactic acid based matrices
Publisher: Wiley
Date: 28-01-2022
DOI: 10.1002/APP.52165
Abstract: Hydroxyapatite (HAp)‐polymer composite materials are of interest for materials that interface with or substitute bone tissue. HAp nanoparticles (length 290 nm, width 56 nm) synthesized by a wet chemical method were incorporated (5 wt%) into natural rubber latex (NRL), poly lactic acid (PLA) and NRL/PLA (75/25) solvent cast films using three different methods: dry nanoparticles a dispersion prepared from dry nanoparticles a dispersion prepared through solvent exchange. Common to all composite materials were an improvement in the contact angle by 10%–13% and a reduction in the elongation at break from 430% to 330%–370%. Furthermore, the method of HAp incorporation influenced the properties of the material with the use of dioxane suspension improving the homogeneity of the films as evidenced from visual appearance and SEM. This led to slower water uptake and higher thermal stability with a shift in the PLA melting peak from 296°C to 334°C when compared to pure polymer and composites with poorly dispersed particle.
Complexes of 1-thia-4,7,10-triazacyclododecane ([12]aneN3 S): Synthesis, structure and stability constants
Publisher: Elsevier BV
Date: 11-1999
Introducing Amine Functionalities on a Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Surface: Comparing the Use of Ammonia Plasma Treatment and Ethylenediamine Aminolysis
Publisher: American Chemical Society (ACS)
Date: 13-01-2006
DOI: 10.1021/BM050497A
Abstract: Amine functionalities were introduced onto the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by applying radio frequency ammonia plasma treatment and wet ethylenediamine treatment. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) for chemical composition and Raman microspectroscopy for the spatial distribution of the chemical moieties. The relative amount of amine functionalities introduced onto the PHBV surface was determined by exposing the treated films to the vapor of trifluoromethylbenzaldehyde (TFBA) prior to XPS analysis. The highest amount of amino groups on the PHBV surface could be introduced by use of ammonia plasma at short treatment times of 5 and 10 s, but no effect of plasma power within the range of 2.5-20 W was observed. Ethylenediamine treatment yielded fewer surface amino groups, and in addition an increase in crystallinity as well as degradation of PHBV was evident from Fourier transform infrared spectroscopy. Raman maps showed that the coverage of amino groups on the PHBV surfaces was patchy with large areas having no amine functionalities.
Evaluating the effect of synthesis, isolation, and characterisation variables on reported particle size and dispersity of drug loaded PLGA nanoparticles
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1MA00410G
Abstract: This work provides advice for PLGA-based nanoparticle fabrication and drug encapsulation quantification as well as the minimum required information to be reported allowing reproducibility.
Preparation and characterization of the copolymers obtained by grafting of monoacryloxyethyl phosphate onto polytetrafluoroethylene membranes and poly(tetrafluoroethylene-co-hexafluoropropylene) films
Publisher: Wiley
Date: 20-09-2002
DOI: 10.1002/APP.11177
Graft copolymerization of methoxyacrylethyl phosphate onto expanded poly(tetrafluoroethylene) facial membranes
Publisher: Wiley
Date: 06-05-2010
DOI: 10.1002/APP.31242
Calcium ion‐mediated grafting of a phosphate‐containing monomer
Publisher: Wiley
Date: 24-08-2015
DOI: 10.1002/APP.42808
Improvement of the wet tensile properties of nanostructured hydroxyapatite and chitosan biocomposite films through hydrophobic modification
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0JM03080E
Osteoblasts up-regulate the expression of extracellular proteases following attachment to Poly(β-hydroxybutyrate-co-β-hydroxyvalerate)
Publisher: Elsevier BV
Date: 2009
DOI: 10.1016/J.GENE.2008.09.020
Abstract: MC3T3-E1 cells demonstrate a lag in osteogenic development when seeded onto Poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV), a biomaterial with substantial potential for bone tissue repair. To determine if this was due to the priority of extracellular matrix (ECM) remodelling over other developmental processes, gene expression levels of proteins involved in the production, maintenance and turnover of the ECM were compared between cells grown on PHBV and tissue culture plastic (TCP) 24 h after seeding. When grown on PHBV, MC3T3-E1 cells up-regulated proteins such as the matrix metalloproteinases and down-regulated the expression of proteins such as collagens that are involved in cell-substrate interactions, but in later-stage processes. The results also suggest that proteins such as fibronectin and aggrecan, and particularly osteopontin, may be more suitable candidates for PHBV functionalization for optimal MC3T3-E1 cell growth than proteins like osteonectin, periostin, vitronectin or collagen. This study confirms the importance of understanding the specific response of therapeutically-relevant cells, such as human stem cells, to candidate biomaterial surfaces in order to achieve optimal regenerative therapies.
Encapsulation of a glycosaminoglycan in hydroxyapatite/alginate capsules
Publisher: Wiley
Date: 08-12-2009
DOI: 10.1002/JBM.A.32297
Abstract: The development of suitable vehicles for the delivery of growth-inducing factors to fracture sites is a challenging area of bone repair. Bone-specific glycosaminoglycan molecules are of particular interest because of their high stability and proven effect on bone growth. Calcium alginate capsules are popular as delivery vehicles because of their low immunogenic response they offer a versatile route that enables the controlled release of heparin (a member of the glycosaminoglycan family). In this study, hydroxyapatite (HA)/alginate composite capsules are explored as novel drug delivery vehicles for heparin, using both medium- and low-viscosity alginates. The composition, structure, and stability of the capsules are fully characterized and correlated to the release of heparin in vitro. Heparin is found to associate both with the alginate matrix through polymeric flocculation and also with the HA crystals in the composite beads. The mechanism by which heparin is released is dictated by the stability of the capsule in a particular release media and by the composition of the capsule. The use of medium-viscosity alginate is advantageous with respect to both drug loading and prolonging the release. The inclusion of HA increases the encapsulation efficiency, but because of its destabilizing effect to the alginate hydrogel matrix, it also increases the rate of heparin release. The bioactivity of heparin is fully retained throughout the assembly and release processes.
Studies of the interaction of potassium(I), calcium(II), magnesium(II), and copper(II) with cyclosporin A
Publisher: Elsevier BV
Date: 10-2003
DOI: 10.1016/S0162-0134(03)00288-5
Abstract: Metal ion binding properties of the immunosuppressant drug cyclosporin A have been investigated. Complexation studies in acetonitrile solution using 1H NMR and CD spectroscopy yielded 1:1 metal-peptide binding constants (log(10)K) for potassium(I), <1, magnesium(II), 4.8+/-0.2, and calcium(II), 5.0+/-1.0. The interaction of copper(II) with cyclosporin A in methanol was investigated with UV/visible and electron paramagnetic resonance (EPR) spectroscopy. No complexation of copper(II) was observed in neutral solution. In the presence of base, monomeric copper(II) complexes were detected. These results support the possibility that cyclosporin A has ionophoric properties for biologically important essential metal ions.
Targeted Nanoparticles Based on Alendronate Polyethylene Glycol Conjugated Chitosan for the Delivery of siRNA and Curcumin for Bone Metastasized Breast Cancer Applications
Publisher: Wiley
Date: 15-10-2023
Advances in Encoding of Colloids for Combinatorial Libraries: Applications in Genomics, Proteomics and Drug Discovery
Publisher: Bentham Science Publishers Ltd.
Date: 12-2003
Abstract: The creation of enormous libraries of chemicals and their subsequent screening for bioactivity has been accelerated through recent developments in encoding solid supports. The ability to accurately identify the structure of a biomolecule that has exhibited activity is invaluable and is closer to realisation in the advent of smart nanoscience. In this review the evolution of encoding solid supports as platforms for combinatorial synthesis is traced. Current approaches to encoding solid supports are reviewed and their potential for use as supports for the high-throughput screening of split and mix libraries explored. Finally, a brief consideration of the status of the application of encoded libraries is provided including creative chemical and colloidal encoding.
Mode of heparin attachment to nanocrystalline hydroxyapatite affects its interaction with bone morphogenetic protein-2
Publisher: American Vacuum Society
Date: 16-10-2015
DOI: 10.1116/1.4933109
Abstract: Heparin has a high affinity for bone morphogenetic protein-2 (BMP-2), which is a key growth factor in bone regeneration. The aim of this study was to investigate how the rate of release of BMP-2 was affected when adsorbed to nanosized hydroxyapatite (HAP) particles functionalized with heparin by different methods. Heparin was attached to the surface of HAP, either via adsorption or covalent coupling, via a 3-aminopropyltriethoxysilane (APTES) layer. The chemical composition of the particles was evaluated using X-ray photoelectron spectroscopy and elemental microanalysis, revealing that the heparin grafting densities achieved were dependent on the curing temperature used in the fabrication of APTES-modified HAP. Comparable amounts of heparin were attached via both covalent coupling and adsorption to the APTES-modified particles, but characterization of the particle surfaces by zeta potential and Brunauer–Emmett–Teller measurements indicated that the conformation of the heparin on the surface was dependent on the method of attachment, which in turn affected the stability of heparin on the surface. The release of BMP-2 from the particles after 7 days in phosphate-buffered saline found that 31% of the loaded BMP-2 was released from the APTES-modified particles with heparin covalently attached, compared to 16% from the APTES-modified particles with the heparin adsorbed. Moreover, when heparin was adsorbed onto pure HAP, it was found that the BMP-2 released after 7 days was 5% (similar to that from unmodified HAP). This illustrates that by altering the mode of attachment of heparin to HAP the release profile and total release of BMP-2 can be manipulated. Importantly, the BMP-2 released from all the heparin particle types was found by the SMAD 1/5/8 phosphorylation assay to be biologically active.
Poly(β-hydroxybutyrate-co-β-hydroxyvalerate) Supports in Vitro Osteogenesis
Publisher: Mary Ann Liebert Inc
Date: 07-2005
Abstract: Studies have demonstrated that polymeric biomaterials have the potential to support osteoblast growth and development for bone tissue repair. Poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV), a bioabsorbable, biocompatible polyhydroxy acid polymer, is an excellent candidate that, as yet, has not been extensively investigated for this purpose. As such, we examined the attachment characteristics, self-renewal capacity, and osteogenic potential of osteoblast-like cells (MC3T3-E1 S14) when cultured on PHBV films compared with tissue culture polystyrene (TCP). Cells were assayed over 2 weeks and examined for changes in morphology, attachment, number and proliferation status, alkaline phosphatase (ALP) activity, calcium accumulation, nodule formation, and the expression of osteogenic genes. We found that these spindle-shaped MC3T3-E1 S14 cells made cell-cell and cell-substrate contact. Time-dependent cell attachment was shown to be accelerated on PHBV compared with collagen and laminin, but delayed compared with TCP and fibronectin. Cell number and the expression of ALP, osteopontin, and pro-collagen alpha1(I) mRNA were comparable for cells grown on PHBV and TCP, with all these markers increasing over time. This demonstrates the ability of PHBV to support osteoblast cell function. However, a lag was observed for cells on PHBV in comparison with those on TCP for proliferation, ALP activity, and cbfa-1 mRNA expression. In addition, we observed a reduction in total calcium accumulation, nodule formation, and osteocalcin mRNA expression. It is possible that this cellular response is a consequence of the contrasting surface properties of PHBV and TCP. The PHBV substrate used was rougher and more hydrophobic than TCP. Although further substrate analysis is required, we conclude that this polymer is a suitable candidate for the continued development as a biomaterial for bone tissue engineering.
In vitro degradation study of polyanhydride copolymers / surface grafted hydroxyapatite composites for bone tissue application
Publisher: Elsevier BV
Date: 06-2017
Combining Chemistry and Biology To Create Colloidally Stable Bionanohydroxyapatite Particles: Toward Load-Bearing Bone Applications
Publisher: American Chemical Society (ACS)
Date: 21-06-2008
DOI: 10.1021/LA8005212
Abstract: This study presents a layer by layer assembly on nanohydroxyapatite (nHA) particles with the dual aim of enhancing particle dispersion and biological response to produce superior reinforcements intended for load-bearing applications. The system tested consists of three sequential biological polyelectrolyte layers of heparin (representing glycosaminoglycans), polyhistidine (representing growth factors), and heparin adsorbed onto nHA. The results reveal that the resulting bio-nHA particles with an outer heparin layer are colloidally stable in aqueous solution for 23 days. Adsorption isotherms combined with Ca(2+) release studies allowed a detailed description of each adsorbed layer. Release patterns for each adsorbed layer reveal that the biological polyelectrolytes are, at least in part, released as polyelectrolyte complexes. In conclusion, the combination of its colloidal dispersant properties and osteoinductive potential make the developed bio-nHA particles promising reinforcements to improve current composite biomaterials or bone-engineering scaffolds toward load-bearing dental and orthopedic applications.
Applications of alginate biopolymer in drug delivery
Publisher: Elsevier
Date: 2020
Morphology and Composition of Immunodiffusion Precipitin Complexes Evaluated via Microscopy and Proteomics
Publisher: American Chemical Society (ACS)
Date: 06-04-2021
An organic matrix-mediated processing methodology to fabricate hydroxyapatite based nanostructured biocomposites
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B9NR00062C
Abstract: An amorphous calcium phosphate precursor phase, which forms by adding orthophosphoric acid to a calcium hydroxide suspension, is transformed into crystalline hydroxyapatite by introducing polymer solutions. The nanostructured composite films formed by a solvent casting technique from the concentrated hybrid suspension are characterised for structure and mechanical properties.
Time-of-Flight Secondary Ion Mass Spectrometry Study of the Orientation of a Bifunctional Diblock Copolymer Attached to a Solid Substrate
Publisher: American Chemical Society (ACS)
Date: 24-12-2008
DOI: 10.1021/LA802016B
Abstract: A block copolymer consisting of a phosphate-containing moiety (poly[2-(methacryloyloxy)ethyl phosphate], PMOEP) and a keto-containing moiety (poly[2-(acetoacetoxy)ethyl methacrylate], PAAEMA) showed good stability after attachment to an APS amine-modified glass slide, as did both of the respective homopolymers. The PAAEMA homopolymer can attach to the APS amine groups via covalent linkages, while the PMOEP homopolymer most likely attaches through electrostatic interactions involving deprotonated phosphate and protonated amine groups. To elucidate the conformation of the block copolymer after attachment, particularly with respect to the PMOEP segment orientation, principal component analysis (PCA) of time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of the surface-attached polymer layers was performed. Comparison with the pure homopolymer spectra and interpretation after PCA indicate that the adsorbed conformation is not random. Rather, the copolymer is adsorbed in a conformation that preferentially exposes the PMOEP block toward the outer surface. We thus conclude that the most likely conformation of PMOEP-b-PAAEMA immobilized onto the APS-modified glass slide is via covalent interfacial linkages involving the PAAEMA block with the result that the surface is enriched in PMOEP tails. This in turn implies that under the conditions applied (dry DMF) the covalent coupling of keto groups to the amine groups of the aminated slide is more efficient than the proton transfer required for the generation of electrostatic attractions. This (partially) preferential orientation of the PMOEP-b-PAAEMA copolymer could have significant implications on interfacial interactions such as those involved in nucleation and the subsequent mineralization sequence of events in hydroxyapatite formation. The present study demonstrates that ToF-SIMS is a powerful tool not only for the investigation of the surface composition of adsorbed layers, but also for probing the molecular conformation of such adsorbed block copolymers, though care is required in the PCA analysis of multiple spectra.
Encoding Combinatorial Libraries: A Novel Application of Fluorescent Silica Colloids
Publisher: American Chemical Society (ACS)
Date: 10-11-2000
DOI: 10.1021/LA000995Z
In vitro mineralisation of grafted ePTFE membranes carrying carboxylate groups
Publisher: Elsevier BV
Date: 03-2017
The fabrication and characterization of biodegradable HA/PHBV nanoparticle–polymer composite scaffolds
Publisher: Elsevier BV
Date: 09-2009
DOI: 10.1016/J.ACTBIO.2009.03.017
Abstract: This study reports the fabrication and characterization of nano-sized hydroxyapatite (HA) oly(hydroxyabutyrate-co-hydroxyvalerate) (PHBV) polymer composite scaffolds with high porosity and controlled pore architectures. These scaffolds were prepared using a modified thermally induced phase-separation technique. This investigation focuses on the effect of fabrication conditions on the overall pore architecture of the scaffolds and the dispersion of HA nanocrystals within the composite scaffolds. The morphologies, mechanical properties and in vitro bioactivity of the composite scaffolds were investigated. It was noted that the pore architectures could be manipulated by varying phase-separation parameters. The HA particles were dispersed in the pore walls of the scaffolds and were well bonded to the polymer. The introduction of HA greatly increased the stiffness and strength, and improved the in vitro bioactivity of the scaffolds. The results suggest these newly developed nano-HA/PHBV composite scaffolds may serve as an effective three-dimensional substrate in bone tissue engineering.
Enhanced Oral Vaccine Efficacy of Polysaccharide-Coated Calcium Phosphate Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 17-07-2020
Wiki Laboratory Notebooks: Supporting Student Learning in Collaborative Inquiry-Based Laboratory Experiments
Publisher: Springer Science and Business Media LLC
Date: 20-01-2016
Tailoring Surface Properties To Build Colloidal Diagnostic Devices: Controlling Interparticle Associations
Publisher: American Chemical Society (ACS)
Date: 19-11-2005
DOI: 10.1021/LA051833B
Abstract: The ability to control the surface properties and subsequent colloidal stability of dispersed particles has widespread applicability in many fields. Sub-micrometer fluorescent silica particles (reporters) can be used to actively encode the combinatorial synthesis of peptide libraries through interparticle association. To achieve these associations, the surface chemistry of the small fluorescent silica reporters is tailored to encourage robust adhesion to large silica microparticles onto which the peptides are synthesized. The interparticle association must withstand a harsh solvent environment, multiple synthetic and washing procedures, and biological screening buffers. The encoded support beads were exposed to different solvents used for peptide synthesis, and different solutions used for biological screening including phosphate buffered saline (PBS), 2-[N-morpholino]ethane sulfonic acid (MES) and a mixture of MES and N-(3-dimethyl-aminopropyl)-N'-ethylcarbodiimide (EDC). The number of reporters remaining adhered to the support bead was quantified after each step. The nature of the associations were explored and tested to optimize the efficiency of these phenomena. Results presented illustrate the influence of the surface functionality and polyelectrolyte modification of the reporters. These parameters were investigated through zeta potential and X-ray photoelectron spectroscopy.
Surface chemistry of grafted expanded poly(tetrafluoroethylene) membranes modifies the in vitro proinflammatory response in macrophages
Publisher: Wiley
Date: 11-09-2012
DOI: 10.1002/JBM.A.34408
Abstract: A series of surface-modified expanded poly(tetrafluoroethylene) membranes showed varied levels of in vitro macrophage proinflammatory response. Membranes containing a mixture of phosphate and hydroxyl groups (as determined by X-ray photoelectron spectroscopy analysis) stimulate greater macrophage activation than s les containing a mixture of phosphate and carboxylic acid segments. The types of proteins that adsorbed irreversibly from serum onto the two s les with the highest and lowest cellular response were investigated using surface-matrix-assisted laser desorption ionisation time-of-flight mass spectrometry. Distinct differences in the number and type of proteins that adsorbed were observed between these s les. A correlation was found between the main protein components adsorbed onto the surfaces and the resulting in vitro proinflammatory response. This study strongly supports the hypothesis that the cellular response is not controlled directly by surface properties but is mediated by specific protein adsorption events. This in turn highlights the importance of better understanding and controlling the properties of intelligent surface-modified biomaterials.
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