ORCID Profile
0000-0001-7367-3925
Current Organisation
University of South Australia
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Publisher: Wiley
Date: 10-2007
Publisher: Wiley
Date: 02-2008
Publisher: American Chemical Society (ACS)
Date: 16-11-2008
DOI: 10.1021/LA802316P
Abstract: Links between the mechanisms and kinetics of aqueous and dry thermal oxidation of porous silicon (pSi) microparticles have been investigated and the influence on molecular interaction established. zeta potential measurements have established the interplay between the dry oxidation state of pSi microparticles and their interfacial chemistry in aqueous solution, and Fourier transform infrared spectroscopy has demonstrated the effect of immersion time and oxidation temperature on surface chemistry. The influence of aqueous and thermal oxidation on molecular interactions and loading was investigated using methylene blue as a probe molecule. Aqueous immersion of pSi microparticles results in an initial increase in OySiH (y = 1-3) species with increasing immersion times, reducing O2SiH concentration, while O3SiH concentration remained constant. Thermal oxidation from 473 to 1073 K causes the gradual transition from SiySiHx to OySiH and finally OySiOH species. Both aqueous and thermal oxidations had an effect on the zeta potentials of pSi microparticles. Methylene blue discoloration occurred due to its reduction by the SiSiHx-terminated surface thereby demonstrating the reactivity of such species. Aqueous and thermal oxidations modify pSi microparticle surface chemistry, which has therefore shown to influence molecular interactions. Understanding the aqueous oxidation of pSi is crucial when loading pSi from aqueous solution due to its impact on molecular interactions. These molecular interactions play an important role in the loading of pSi since they dictate the attraction of the molecule toward the surface and therefore ultimately the loading level.
Publisher: American Chemical Society (ACS)
Date: 11-06-2008
DOI: 10.1021/JP800950J
Publisher: Elsevier
Date: 2014
Publisher: American Chemical Society (ACS)
Date: 02-01-2018
Abstract: Bacterial infections in healthcare settings are a frequent accompaniment to both routine procedures such as catheterization and surgical site interventions. Their impact is becoming even more marked as the numbers of medical devices that are used to manage chronic health conditions and improve quality of life increases. The resistance of pathogens to multiple antibiotics is also increasing, adding an additional layer of complexity to the problems of employing safe and effective medical procedures. One approach to reducing the rate of infections associated with implanted and indwelling medical devices is the use of polymers that resist the formation of bacterial biofilms. To significantly accelerate the discovery of such materials, we show how state of the art machine learning methods can generate quantitative predictions for the attachment of multiple pathogens to a large library of polymers in a single model for the first time. Such models facilitate design of polymers with very low pathogen attachment across different bacterial species that will be candidate materials for implantable or indwelling medical devices such as urinary catheters, cochlear implants, and pacemakers.
Publisher: American Chemical Society (ACS)
Date: 07-2008
DOI: 10.1021/LA801619V
Abstract: Porous silicon has received considerable interest in recent years in a range of biomedical applications, with its performance determined by surface chemistry. In this work, we investigate the PEGylation of porous silicon wafers using click chemistry. The porous silicon wafer surface chemistry was monitored at each stage of the reaction via photoacoustic Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, whereas sessile drop contact angle and model protein adsorption measurements were used to characterize the final PEGylated surface. This work highlights the simplicity of click-chemistry-based functionalization in tailoring the porous silicon surface chemistry and controlling protein-porous silicon interactions.
Publisher: American Chemical Society (ACS)
Date: 04-08-2010
DOI: 10.1021/LA102367Z
Abstract: Thermal oxidation of porous silicon (pSi) has been used to control interactions with three proteins lysozyme, papain, and human serum albumin (HSA) enabling the influences of protein structure, molecular weight, and charge to be elucidated. Adsorption behavior was assessed via adsorption isotherms while the structures of adsorbed proteins were investigated using a bioactivity assay, FTIR, and zeta potential. Time-of-flight secondary ion mass spectrometry was used to examine protein pore penetration. High protein adsorption onto unoxidized pSi (240-610 microg/m(2)) was attributed to predominately hydrophobic interactions which resulted in structural changes of the adsorbed proteins and significant loss of bioactivity. Thermal oxidation at 400 and 800 degrees C significantly reduced protein adsorption (80-485 microg/m(2)) by reducing hydrophobicity. Oxidation of pSi modified the protein adsorption mechanisms to solely electrostatic attraction for positively charged proteins and structural rearrangement for negatively charged proteins. Adsorption via electrostatic attraction preserved protein bioactivity and zeta potential, thus inferring a retention of their native structure. In contrast, the negative charge and globular structure of HSA resulted in a loss of structure. We have demonstrated that thermal oxidation of pSi can be used to control protein interactions, adsorbed structure, and bioactivity.
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.IJPHARM.2011.01.043
Abstract: We review the application of time-of-flight secondary-ion mass spectrometry (ToF-SIMS) for the surface chemical identification and distribution analysis (mapping) of pharmaceutically relevant materials. Specifically we explore the characterization of both solid state pharmaceuticals and bio-pharmaceuticals by ToF-SIMS highlighting specific case studies concerning the distribution and stability of pharmaceutical actives within solid matrices, the face-specific properties of pharmaceutical crystals and elucidation of the structure/conformation of adsorbed proteins. Finally, potential future applications of ToF-SIMS in pharmaceutics are detailed.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-01-2023
Abstract: Innovative approaches to prevent catheter-associated urinary tract infections (CAUTIs) are urgently required. Here, we describe the discovery of an acrylate copolymer capable of resisting single- and multispecies bacterial biofilm formation, swarming, encrustation, and host protein deposition, which are major challenges associated with preventing CAUTIs. After screening ~400 acrylate polymers, poly( tert -butyl cyclohexyl acrylate) was selected for its biofilm- and encrustation-resistant properties. When combined with the swarming inhibitory poly(2-hydroxy-3-phenoxypropyl acrylate), the copolymer retained the bioinstructive properties of the respective homopolymers when challenged with Proteus mirabilis , Pseudomonas aeruginosa , Staphylococcus aureus , and Escherichia coli . Urinary tract catheterization causes the release of host proteins that are exploited by pathogens to colonize catheters. After preconditioning the copolymer with urine collected from patients before and after catheterization, reduced host fibrinogen deposition was observed, and resistance to erse uropathogens was maintained. These data highlight the potential of the copolymer as a urinary catheter coating for preventing CAUTIs.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA16028J
Abstract: Combining 1 H NMR and sSAXS to discriminate the speciation and structure evolution of lipolysis products for submicron lipid droplets and lipid loaded in porous silica particles.
Publisher: IEEE
Date: 2006
Publisher: Wiley
Date: 03-10-2019
Publisher: American Chemical Society (ACS)
Date: 09-05-2011
DOI: 10.1021/AM2003069
Abstract: The adsorption of nanostructured lyotropic liquid-crystal particles, cubosomes and hexosomes, at surfaces was investigated for potential use in surface-specific agrochemical delivery. Adsorption of phytantriol (PHYT) and glyceryl monooleate (GMO)-based cubosomes and hexosomes, stabilized using Pluronic F127, at tristearin-coated (model leaf surface) and uncoated zinc selenide surfaces was studied using attenuated total reflectance Fourier transform IR (ATR-FTIR) spectroscopy, by quantifying the IR absorbance due to the lipid components of the particles over time. The delivery of an encapsulated hydrophobic model herbicide [dichlorodiphenyldichloroethylene (DDE)] was also examined on the model and real leaf surfaces. The adsorption behavior of the particles by ATR-FTIR was dependent on the internal nanostructure and lipid composition, with PHYT cubosomes adsorbing more avidly at tristearin surfaces than GMO-based cubosomes or hexosomes. There was a direct correlation between DDE associated with the surfaces and the particle adsorption observed in the ATR-FTIR study, strongly implicating particle adsorption with the delivery efficiency. Differences between the mode of interaction of the Pluronic stabilizer with the different lipids and particle nanostructures were proposed to lead to differences in the particle adsorption behavior.
Publisher: MDPI AG
Date: 04-09-0023
Publisher: MDPI AG
Date: 28-11-2019
DOI: 10.3390/PHARMACEUTICS11120634
Abstract: Porous silicon (pSi) continues to receive considerable interest for use in applications ranging from sensors, biological scaffolds, therapeutic delivery systems to theranostics. Critical to all of these applications is pSi degradation and stabilization in biological media. Here we report on progress towards the development of a mechanistic understanding for the dissolution behavior of native (unoxidized) and thermally oxidized (200–600 °C) pSi microparticles. Fourier transform infrared (FTIR) spectroscopy was used to characterize the pSi surface chemistry after thermal oxidation. PSi dissolution was assessed using a USP method II apparatus by monitoring the production of orthosilicic acid, and the influence of gastro-intestinal (GI) fluids were examined. Fitting pSi dissolution kinetics with a sum of the exponential model demonstrated that the dissolution process strongly correlates with the three surface hydride species and their relative reactivity, and was supported by the observed FTIR spectral changes of pSi during dissolution. Finally, the presence of GI proteins was shown to h er pSi dissolution by adsorption to the pSi surface acting as a barrier preventing water attack. These findings are significant in the optimal design of pSi particles for oral delivery and other controlled drug delivery applications.
Publisher: American Chemical Society (ACS)
Date: 16-11-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C1NR11273B
Abstract: Lipid based colloids (e.g. emulsions and liposomes) are widely used as drug delivery systems, but often suffer from physical instabilities and non-ideal drug encapsulation and delivery performance. We review the application of engineered nanoparticle layers at the interface of lipid colloids to improve their performance as drug delivery systems. In addition we focus on the creation of novel hybrid nanomaterials from nanoparticle-lipid colloid assemblies and their drug delivery applications. Specifically, nanoparticle layers can be engineered to enhance the physical stability of submicron lipid emulsions and liposomes, satbilise encapsulated active ingredients against chemical degradation, control molecular transport and improve the dermal and oral delivery characteristics, i.e. increase absorption, bioavailability and facilitate targeted delivery. It is feasible that hybrid nanomaterials composed of nanoparticles and colloidal lipids are effective encapsulation and delivery systems for both poorly soluble drugs and biological drugs and may form the basis for the next generation of medicines. Additional pre-clinical research including specific animal model studies are required to advance the peptide rotein delivery systems, whereas the silica lipid hybrid systems have now entered human clinical trials for poorly soluble drugs.
Publisher: Japan Oil Chemists' Society
Date: 2018
DOI: 10.5650/JOS.ESS14081
Abstract: Studies on the interaction of different generation poly (amido amine) (PAMAM) dendrimers (2G, 4G and 6G) and liposomes of different compositions were carried out by a combined turbidity, dynamic light scattering and atomic force microscopic measurements. Liposomes comprising soy lecithin (SLC, negative surface charge), 1, 2-palmitoyl-sn-glycero-3-phosphatidylcholine (DPPC, mildly positive surface charge), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol (DPPG, negatively charged) and a biologically simulated mixture of DPPC + DPPG (7:3, M/M, negatively charged) were used as model bilayers. 30 wt% cholesterol was used in each combination as it is known to control the fluidity of membrane bilayers. Silica was used as a negatively charged hard sphere model with an aim to compare the results. Both the turbidity and hydrodynamic diameter values of all the liposomes, except DPPC, passed through maxima upon the progressive addition of PAMAM the effect was insignificant in case of DPPC. Formation of dendriosome, a complex formed between dendrimer and liposome, resulted in the charge reversal of the negatively charged liposomes. Interaction between PAMAM and liposome was found to be governed by electrostatic as well as hydrogen bonding. Generation dependent PAMAM activity followed the order: 6G >4G>2G in terms of overall dendrimer concentration. However, interestingly, the order was reverse when PAMAM activity was considered in terms of total end group concentrations. AFM studies reveal the rupture of bilayer structure upon addition of dendrimer.
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.JCIS.2011.07.063
Abstract: Interactions between porous silicon (pSi) particles and probe molecules were evaluated to determine the effect of pSi and probe molecule chemistry on adsorption. Methylene blue, ethyl violet and orange G dyes were chosen for investigation as they possess distinct functionalities and charges. Several distinct pSi surface species were produced via thermal oxidation at 200-800 °C and their effect on adsorption investigated. The adsorption mechanisms were elucidated from equilibrium adsorption and desorption isotherms. Methylene blue adsorption was attributed to electrostatic attraction where a gradual increase in adsorption with oxidation temperature was observed. Significant methylene blue desorption was observed at pH 3, confirming adsorption occurs via electrostatic attraction. Ethyl violet demonstrated an increase in plateau adsorption capacity and affinity with increased oxidation temperatures and adsorption was initially attributed to electrostatic attraction, however desorption of ethyl violet was not observed, thus indicating potential chemisorption. Orange G exhibited high affinity adsorption for Si(y)SiH(x) terminated surfaces but no orange G desorption was detected, indicating a chemisorption adsorption mechanism. It has been successfully demonstrated that the surface modification of pSi enabled the manipulation of molecular interactions. By interacting probe molecules with similar functionalities to drug molecule with pSi, greater understanding of drug-pSi interactions can be ascertained which are of great importance. pSi surface chemistry can be tailored to enable control over molecular interactions and ultimately dictate loading, encapsulation and release behavior.
Publisher: Future Science Ltd
Date: 07-2013
DOI: 10.4155/TDE.13.52
Abstract: Porous silicon (pSi) is a nanostructured carrier system that has received considerable attention over the past 10 years, for use in a wide variety of biomedical applications, including biosensing, biomedical imaging, tissue scaffolds and drug delivery. This interest is due to several key features of pSi, including excellent in vivo biocompatibility, the ease of surface chemistry modification and the control over its 3D porous network structure. With control of these physical parameters pSi has successfully been used for the delivery of a variety of therapeutics, ranging from small-molecule drugs to larger peptide rotein-type therapeutics. In this review, the authors provide a brief overview of pSi fabrication methods, particularly with regard to the need to passivate the highly reactive Si-Hx surface species of native pSi, typically via thermal oxidation, hydrocarbonization or hydrosilylation. This surface modification, in turn, controls both the loading and release of therapeutics. The authors will then report on specific case studies of leading ex les on the use of pSi as a therapeutic-delivery system. Specifically, the first reported in vivo study that demonstrated the use of pSi to improve the delivery of a Biopharmaceutical Classification System Class 2 poorly soluble drug (indomethacin), by using thermally oxidized pSi, is discussed, as well as highlighting a study that determined the biodistribution of 18 F-radiolabeled thermally hydrocarbonized pSi after oral dosing. The authors also report on the development of composite pSi–poly(D,L-lactide-co-glycolide) microparticles for the controlled delivery of protein therapeutics. Finally, the use of pSi in the delivery of bioactives, such as the successful use of thermally carbonized pSi to deliver Melanotan II, an unspecific agonist for the melanocortin receptors that are involved in controlling fluid uptake is discussed. With a growing body of literature reporting the successful use of pSi to deliver a range of therapeutics, we are entering what may be a golden age for this drug-delivery system, which may finally see the long-held promises finally achieved.
Publisher: American Chemical Society (ACS)
Date: 31-08-2012
DOI: 10.1021/LA302435G
Abstract: Nonlamellar liquid crystalline dispersions such as cubosomes and hexosomes have great potential as novel surface-targeted active delivery systems. In this study, the influence of internal nanostructure, chemical composition, and the presence of Pluronic F127 as a stabilizer, on the surface and interfacial properties of different liquid crystalline particles and surfaces, was investigated. The interfacial properties of the bulk liquid crystalline systems with coexisting excess water were dependent on the internal liquid crystalline nanostructure. In particular, the surfaces of the inverse cubic systems were more hydrophilic than that of the inverse hexagonal phase. The interaction between F127 and the bulk liquid crystalline systems depended on the internal liquid crystalline structure and chemical composition. For ex le, F127 adsorbed to the surface of the bulk phytantriol cubic phase, while for monoolein cubic phase, F127 was integrated into the liquid crystalline structure. Last, the interfacial adsorption behavior of the dispersed liquid crystalline particles also depended on both the internal nanostructure and the chemical composition, despite the dispersions all being stabilized using F127. The findings highlight the need to understand the specific surface characteristics and the nature of the interaction with colloidal stabilizer for understanding and optimizing the behavior of nonlamellar liquid crystalline systems in surface delivery applications.
Publisher: MDPI AG
Date: 30-11-2022
DOI: 10.3390/PHARMACEUTICS14122659
Abstract: High-throughput permeation models are essential in drug development for timely screening of new drug and formulation candidates. Nevertheless, many current permeability assays fail to account for the presence of the gastrointestinal mucus layer. In this study, an optimised high-throughput mucus permeation model was developed employing a highly biorelevant mucus mimic. While mucus permeation is primarily conducted in a simple mucin solution, the complex chemistry, nanostructure and rheology of mucus is more accurately modelled by a synthetic biosimilar mucus (BSM) employing additional protein, lipid and rheology-modifying polymer components. Utilising BSM, equivalent permeation of various molecular weight fluorescein isothiocyanate-dextrans were observed, compared with native porcine jejunal mucus, confirming replication of the natural mucus permeation barrier. Furthermore, utilising synthetic BSM facilitated the analysis of free protein permeation which could not be quantified in native mucus due to concurrent proteolytic degradation. Additionally, BSM could differentiate between the permeation of poly (lactic-co-glycolic) acid nanoparticles (PLGA-NP) with varying surface chemistries (cationic, anionic and PEGylated), PEG coating density and size, which could not be achieved by a 5% mucin solution. This work confirms the importance of utilising highly biorelevant mucus mimics in permeation studies, and further development will provide an optimal method for high-throughput mucus permeation analysis.
Publisher: Wiley
Date: 18-12-2022
Abstract: Wound healing is a complex biological process involving close crosstalk between various cell types. Dysregulation in any of these processes, such as in diabetic wounds, results in chronic nonhealing wounds. Fibroblasts are a critical cell type involved in the formation of granulation tissue, essential for effective wound healing. 315 different polymer surfaces are screened to identify candidates which actively drive fibroblasts toward either pro‐ or antiproliferative functional phenotypes. Fibroblast‐instructive chemistries are identified, which are synthesized into surfactants to fabricate easy to administer microparticles for direct application to diabetic wounds. The pro‐proliferative microfluidic derived particles are able to successfully promote neovascularization, granulation tissue formation, and wound closure after a single application to the wound bed. These active novel bio‐instructive microparticles show great potential as a route to reducing the burden of chronic wounds.
Publisher: Wiley
Date: 28-01-2008
DOI: 10.1002/APJ.111
Publisher: IEEE
Date: 2006
Publisher: Informa UK Limited
Date: 03-2009
DOI: 10.1080/08982100802673940
Abstract: The encapsulation and release kinetics of guanosine from liposomes and polyethylene glycol (PEG)-modified liposomes are reported. Specifically, the influence of PEG chain length, PEGylation level, lipid type, drug-loading level, temperature, and solution conditions (i.e., salt and pH effects) on the rate and mechanism for release have been determined. Increasing PEGylation significantly reduced the guanosine release kinetics this is more significant for greater molecular weight PEG and is correlated with the PEG layer thickness. Further, the mechanism for guanosine release changed from diffusion to interfacial control as the PEG level increased. The interfacial structure introduced by PEG also increased the activation energy required for guanosine transport across the lipid bilayer from 14 to 22 kJ mol(-1). Findings from this study provide further insight into optimizing the formulation of Stealth liposomes.
Publisher: Oxford University Press (OUP)
Date: 02-2007
Abstract: Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) is a highly surface sensitive analytical method for surface chemical identification and surface chemical distribution analysis (mapping). Here we have explored the application of ToF-SIMS for the characterization of solid-state pharmaceuticals and highlight specific case studies concerning the distribution and stability of pharmaceutical actives within solid matrices (pellets and polymeric carriers) and the face-specific properties of pharmaceutical crystals.
Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.CIS.2012.03.006
Abstract: Porous silicon (pSi) has a number of unique properties that appoint it as a potential drug delivery vehicle high loading capacity, controllable surface chemistry and structure, and controlled release properties. The native Si(y)SiH(x) terminated pSi surface is highly reactive and prone to spontaneous oxidation. Surface modification is used to stabilize the pSi surface but also to produce surfaces with desired drug delivery behavior, typically via oxidation, hydrosilylation or thermal carbonization. A number of advanced characterization techniques have been used to analyze pSi surface chemistry, including X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry. Surface modification not only stabilizes the pSi surface but determines its charge, wettability and dissolution properties. Manipulation of these parameters can impact drug encapsulation by altering drug-pSi interactions. pSi has shown to be a successful vehicle for the delivery of poorly soluble drugs and protein therapeutics. Surface modification influences drug pore penetration, crystallinity, loading level and dissolution rate. Surface modification of pSi shows great potential for drug delivery applications by controlling pSi-drug interactions. Controlling these interactions allows specific drug release behaviors to be engineered to aid in the delivery of previously challenging therapeutics. Within this review, different pSi modification techniques will be outlined followed by a summary of how pSi surface modification has been used to improve drug encapsulation and delivery.
Publisher: Informa Healthcare
Date: 03-2007
Abstract: Nanostructuring materials can radically change their properties. Two interesting ex les highlighted here are nanoscale porosity inducing biodegradability, and nanoscale confinement affecting the physical form of an entrapped drug. Mesoporous silicon is under increasing study for drug-delivery applications, and is the topic of this review. The authors focus on those properties of most relevance to this application, as well as those recent studies published on small molecule and peptide rotein delivery.
Publisher: Elsevier BV
Date: 02-2023
Publisher: American Chemical Society (ACS)
Date: 04-11-2008
DOI: 10.1021/LA8022858
Abstract: The interaction kinetics of polyamidoamine (PAMAM) dendrimers with supported lipid bilayers of 1,2-sn-glycero-dimyristoylphosphocholine prepared by the vesicle deposition has been probed by optical waveguide lightmode spectroscopy and atomic force microscopy (AFM). In particular, the influence of PAMAM dendrimer generation (G2, G4, and G6) and concentration (1 to 100 nM) on the levels of adsorption and lipid bilayer removal have been determined as a function of time hence interaction kinetics and mechanisms have been further elucidated. Dendrimer interaction kinetics with the lipid bilayer are concentration dependent in a complex manner, with net bilayer removal at 1 and 100 nM and net adsorption at 10 nM these effects are irrespective of dendrimer generation. The pseudo first order rate constant for bilayer removal (at 1 and 100 nM) follows the order G6 > G4 > G2. In contrast, the pseudo first order rate constant for adsorption at 10 nM follows the order G2 > G4 > G6. AFM has confirmed expansion of lipid bilayer defects, hole formation, and adsorption to the bilayer or bilayer defects, and their concentration and generation dependence. These findings have implications when designing dendrimers for specific biopharmaceutical activities, e.g., as drugs, drug delivery vehicles, transfection agents, or antimicrobials.
Publisher: Elsevier BV
Date: 07-2020
Publisher: American Chemical Society (ACS)
Date: 04-10-2008
DOI: 10.1021/LA8020996
Abstract: The adsorption of naphthalene disulfonic acid surface-functionalized dendrimers (generation 4) on to colloidal alumina particles is reported, considering the role of dendrimer core type (ammonia vs benzylhydrylamine-polylysine) and electrolyte addition on the adsorption affinity and interfacial packing and competitive adsorption. Irrespective of the dendrimer core type, the maximum adsorbed amount increased with increasing ionic strength. The adsorption affinity of a benzylhydrylamine-cored SPL-7013 increased with increasing ionic strength, whereas a decrease was observed for the ammonia-cored SPL-2923. At high ionic strengths (>or=10(-1) M NaCl) dendrimers close pack at the interface as an array of equivalent hard spheres, whereas at lower ionic strengths both dendrimers occupy a lower area than theoretically predicted for either cubic or hexagonal close packing, based on double layer repulsion. The additional attraction between dendrimers is attributed to the intercalation of the neighboring dendrons. Adsorption of SPL-2923 is enhanced by the presence of Ca2+ ions and depressed by the presence of HCO3- and HPO4(2-) ions, whereas SPL-7013 adsorption is only depressed by the presence of HPO4(2-) ions, suggesting a dendrimer-specific competitive adsorption process. This work clearly demonstrates the role of dendrimer architecture on adsorption at an interface, a process of fundamental importance to a wide range of dendrimer applications.
Publisher: American Chemical Society (ACS)
Date: 08-06-2010
DOI: 10.1021/LA101253G
Abstract: We demonstrate the application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) in conjunction with multivariate statistics to differentiate trace levels of denatured proteins in adsorbed monolayers specifically, human serum albumin (HSA) on oxidized silicon substrates. Subtle differences in protein conformation due to thermal denaturation of HSA, unable to be determined by dynamic light scattering nor circular dichroism, were differentiated by TOF-SIMS. The fragmentation pattern is highly sensitive to protein conformation, allowing assessment of relative amounts of proteins in mixtures and quantifying amounts of denatured protein in a s le. Discussion is presented on ascribing orientation and conformational differences between s les based upon TOF-SIMS spectra. This has implications for detecting denatured protein in biotechnology and medical applications.
Publisher: SAGE Publications
Date: 2008
Abstract: Sales of four wheel drive (4WD) recreational vehicles in Australia continue to grow at a faster rate than for other vehicle types. Meanwhile anecdotal reporting suggests there is a growing demand for 4WD tourism experiences to Australia's desert areas. To date there has been no segmentation of 4WD tourism markets and this has encouraged destination marketing organizations and product developers in desert areas to adopt a broad-brushed approach for attracting visitors. In this article we present findings from focus groups and surveys of 4WD enthusiasts conducted at large 4WD shows to propose a segmentation of the market. The findings emphasize that the market is not homogeneous. For desert areas, the Explorer-traveller segment expresses a high favourability for trips there however, other segments are important. Those directly and indirectly involved in 4WD tourism should benefit from applying this understanding to develop products and experiences which reflect the motivations and experiential aspirations of their target segments.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9RE00173E
Abstract: A novel single-well prototype high throughput microwave reactor geometry has been produced and shown to be capable of synthesizing an array of non-commercially available methacrylate monomers.
Publisher: MDPI AG
Date: 04-07-2023
DOI: 10.3390/PHARMACEUTICS15071886
Abstract: Paclitaxel (PTX) and 5-fluorouracil (5-FU) are clinically relevant chemotherapeutics, but both suffer a range of biopharmaceutical challenges (e.g., either low solubility or permeability and limited controlled release from nanocarriers), which reduces their effectiveness in new medicines. Anticancer drugs have several major limitations, which include non-specificity, wide biological distribution, a short half-life, and systemic toxicity. Here, we investigate the potential of liposome-micelle-hybrid (LMH) carriers (i.e., drug-loaded micelles encapsulated within drug-loaded liposomes) to enhance the co-formulation and delivery of PTX and 5-FU, facilitating new delivery opportunities with enhanced chemotherapeutic performance. We focus on the combination of liposomes and micelles for co-delivery of PTX and 5_FU to investigate increased drug loading, improved solubility, and transport ermeability to enhance chemotherapeutic potential. Furthermore, combination chemotherapy (i.e., containing two or more drugs in a single formulation) may offer improved pharmacological performance. Compared with in idual liposome and micelle formulations, the optimized PTX-5FU-LMH carriers demonstrated increased drug loading and solubility, temperature-sensitive release, enhanced permeability in a Caco-2 cell monolayer model, and cancer cell eradication. LMH has significant potential for cancer drug delivery and as a next-generation chemotherapeutic.
Publisher: MDPI AG
Date: 06-10-2022
DOI: 10.3390/PHARMACEUTICS14102124
Abstract: The looming antimicrobial resistance pandemic has encouraged the investigation of antimicrobial photodynamic therapy (aPDT) as a promising technology to combat recalcitrant bacterial infections caused by antibiotic resistant strains. Here, we report on the optimization and effective application of gallium protoporphyrin liquid crystalline lipid nanoparticles (GaPP-LCNP) as a photosensitizer for aPDT against the Gram-negative bacteria P. aeruginosa in both planktonic and biofilm modes of growth. LCNP significantly enhanced the performance of GaPP as photosensitizer by two-fold, which was correlated with higher antibacterial activity, reducing the viability of planktonic P. aeruginosa by 7 log10 using 0.8 µM GaPP-LCNP and a light dose of 17 J.cm−2. Importantly, GaPP-LCNP also reduced the viability of biofilms by 6 log10 at relatively low light dose of 34.2 J.cm−2 using only 3 µM GaPP-LCNP. The high antibiofilm activity of GaPP-LCNP at low GaPP-LCNP dose indicated the high efficiency and safety profile of GaPP-LCNP as a promising platform for photodynamic inactivation of recalcitrant infections.
Publisher: Future Science Ltd
Date: 02-2015
DOI: 10.4155/TDE.14.112
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 15-06-2010
DOI: 10.1016/J.IJPHARM.2010.03.061
Abstract: A hybrid silica-liposome nanocapsule system containing insulin has been developed and the encapsulation, protection and release properties are evaluated. The formulation strategy is based on using insulin-loaded 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and cholesterol liposomes as a template for the deposition of inert silica nanoparticles. The influence of formulation and process variables on particle size, zeta potential and liposome entrapment of insulin is reported. The ability to protect against lipolytic degradation and sustain insulin release in vitro in simulated GI conditions is also reported. Depending on the concentration and charge ratio of liposomes and silica nanoparticles, nanoparticle coated liposomes with varied size and zeta potential were obtained with an insulin entrapment efficiency of 70%. The silica nanoparticle coating protected liposomes against degradation by digestive enzymes in vitro the release rate of insulin from silica coated liposomes was reduced in comparison to uncoated liposomes. Thus the liposomal release kinetics and stability can be controlled by including a specifically engineered nanoparticle layer. Silica nanoparticle-liposomes hybrid nanocapsules show promise as a delivery vehicle for proteins and peptides.
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.EJPB.2015.09.018
Abstract: The gastric mucosa provides the entry point for the majority of pathogens, as well as being the induction site for protective immunity however, there remain few ex les of oral vaccines due to the challenges presented by the gastrointestinal route. In this study, we develop a lipid-based multi-compartmental system for oral vaccine delivery. Specifically, we have optimised the formulation of a water-in-oil-in-water double emulsion prepared from a triglyceride - soya bean oil, using surfactants Span 80/Tween 80 and Pluronic F127 to stabilise the internal and external water phases, respectively. Into the internal water phase, we also incorporated a PEGylated liposome, prepared using hydrogenated phosphatidyl choline as a carrier for our model protein, FITC-labelled ovalbumin. We demonstrated the successful incorporation of intact liposomes into the internal water phase of the double emulsion using imaging techniques including cryo-SEM and confocal microscopy. Finally, we use in vitro release studies of FITC-ovalbumin, to provide further confirmation of the multi-compartmental structure of the double emulsion system and demonstrate significant extended release of the entrapped model antigen compared with PEG-liposomes these characteristics are attractive for oral vaccine delivery.
Publisher: Bentham Science Publishers Ltd.
Date: 18-10-2016
Publisher: Elsevier BV
Date: 2021
Publisher: American Chemical Society (ACS)
Date: 31-03-2000
DOI: 10.1021/LA991217D
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.JCONREL.2022.04.035
Abstract: Antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach to aid the fight against looming antibiotic resistance. aPDT harnesses the energy of light through photosenstizers to generate highly reactive oxygen species that can inactivate bacteria and fungi with no resistance. To date aPDT has shown great efficacy against microbes causing localized infections in the skin and the oral cavity. However, its wide application in clinical settings has been limited due to both physicochemical and biological challenges. Over the past decade nanomaterials have contributed to promoting photosensitizer performance and aPDT efficiency, yet further developments are required to establish accredited treatment options. In this review we discuss the challenges facing the clinical application of aPDT and the opportunities that nanotechnology may offer to promote the safety and efficiency of aPDT.
Publisher: American Chemical Society (ACS)
Date: 31-08-2021
Abstract: We report the first successful combination of three distinct high-throughput techniques to deliver the accelerated design, synthesis, and property screening of a library of novel, bio-instructive, polymeric, comb-graft surfactants. These three-dimensional, surface-active materials were successfully used to control the surface properties of particles by forming a unimolecular deep layer on the surface of the particles via microfluidic processing. This strategy deliberately utilizes the surfactant to both create the stable particles and deliver a desired cell-instructive behavior. Therefore, these specifically designed, highly functional surfactants are critical to promoting a desired cell response. This library contained surfactants constructed from 20 molecularly distinct (meth)acrylic monomers, which had been pre-identified by HT screening to exhibit specific, varied, and desirable bacterial biofilm inhibitory responses. The surfactant's self-assembly properties in water were assessed by developing a novel, fully automated, HT method to determine the critical aggregation concentration. These values were used as the input data to a computational-based evaluation of the key molecular descriptors that dictated aggregation behavior. Thus, this combination of HT techniques facilitated the rapid design, generation, and evaluation of further novel, highly functional, cell-instructive surfaces by application of designed surfactants possessing complex molecular architectures.
Publisher: American Chemical Society (ACS)
Date: 09-11-2010
DOI: 10.1021/MP900221E
Abstract: Surface functionalized mesoporous silicon (pSi) microparticles are reported as a solid dispersion carrier for improving dissolution and enhancing the orally administered pharmacokinetics (fasted rat model) of indomethacin (IMC), employed as a model poorly soluble BCS type II drug. IMC was loaded via immersion/solvent evaporation onto the thermally oxidized pSi particles, which provide a stable hydrophilic matrix with a nanoporous structure. The solid state properties of IMC loaded pSi were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, differential scanning calorimetry and thermogravimetric analysis. IMC molecules are encapsulated in a noncrystalline state due to geometric confinement in the nanopores stability of the noncrystalline state has been demonstrated for several months under accelerated storage conditions. The pSi carrier facilitates accelerated immediate release of IMC and enhanced oral delivery performance in comparison with crystalline indomethacin and Indocid i.e. a 4-times reduction on T(max), a 200% increase on C(max) and a significant increase in bioavailability. The in vitro-in vivo correlation is discussed based on the noncompartment model and gives insight into the delivery mechanism for the pSi carrier.
Publisher: American Chemical Society (ACS)
Date: 02-2010
DOI: 10.1016/J.JASMS.2009.10.007
Abstract: TOF-SIMS was applied to study the cross-sectional distribution of methylene blue and papain in porous silicon layers. Elemental and molecular information were used to study their distributions in the porous region and the chemistry of their adsorption. Methylene blue (MW = 284 Da) penetrated to the base to the pores. Positive ions (SiCH(3)(+)) suggest methylene blue binds to the substrate via its methyl groups. Negative fragments (SiOSH(3)(-) and SiO(2)SCH(-)) also suggested chemisorption via O bridging of the substrate Si and methylene blue S. The larger Papain molecule (23,406 Da) distributed itself in a similar manner to methylene blue demonstrating larger molecules can be effectively incorporated into such pore structures.
Publisher: Elsevier BV
Date: 05-2004
Publisher: American Chemical Society (ACS)
Date: 28-12-2010
DOI: 10.1021/BM9010134
Abstract: We report on the role of PAMAM dendrimer concentration and generation (G2, G4, G6) on cell growth and cytotoxicity in HEK293T and HeLa cell lines and make comparisons with dendrimer-induced leakage from liposomes to probe the mechanisms in action. Specifically, we observed a striking transition from cell growth enhancement to a reduction in cell viability at a critical PAMAM dendrimer concentration, that is, approximately 500 nM. Confocal microscopy studies show evidence of a transition from cell membrane adhesion to cell internalization and cell nucleus interaction at equivalent dendrimer concentrations. A dendrimer concentration window of 500-700 nM was identified for effective cell internalization without significant cytotoxicity. Though liposome leakage correlated with cytotoxicity, no quantitative agreement was observed, that is, cells are 100 times (based on surface coverage) more resistant to dendrimers than liposomes. These findings have significant implications in the design of effective drug/gene delivery vehicles based on dendrimers.
Publisher: Bentham Science Publishers Ltd.
Date: 10-03-2015
DOI: 10.2174/1567201811666140822115619
Abstract: The high internal surface area and drug solubilizing capacity of liquid crystal lipids makes them promising oral drug delivery systems. Pluronic F127 is typically used to disperse highly viscous cubic liquid crystal lipids into cubosomes however, such copolymers alter the internal structure and provide little control over enzymatic digestion. This study aimed to use hydrophilic silica nanoparticles to stabilize glyceryl monooleate (GMO) cubosomes prepared by ultrasonication. We investigate the influence of silica nanoparticles size and concentration on the physical (colloidal) and chemical (enzymatic digestion) stability, as well as in vitro solubilization of cinnarizine as a poorly soluble model drug. Silica stabilized nanostructured liquid crystal dispersions (120 nm to150 nm in diameter and zeta potentials of-30 mV to -60 mV) were successfully prepared with excellent long-term stability (<10% size change after 30 days). Silica stabilized GMO cubosomes demonstrated reduced enzymatic digestion compared to pluronic F127 stabilized cubosomes. This reduced digestion was attributed to a combination of adsorbed silica nanoparticles acting as a physical barrier and excess dispersed silica adsorbing/scavenging the lipase enzyme. Under simulated intestinal digestion conditions, silica stabilized GMO cubosomes showed a greater solubilization capacity for cinnarizine, which precipitated in non-crystalline form, in comparison to pure drug suspensions or pluronic F127 stabilized GMO cubosomes. Silica nanoparticle stabilized GMO liquid crystal dispersions are a promising oral delivery vehicle.
Publisher: Walter de Gruyter GmbH
Date: 15-10-2013
Abstract: We investigate the physicochemical characteristics of celecoxib (CEL) entrapped within particles of an oxidized porous silicon matrix (pSiox) determine the oral dose response of CEL compared to pure drug and innovator formulation develop in vivo-in vitro correlation (IVIVC). CEL was loaded into a pSiox matrix by solvent partitioning, with the physical state of the CEL characterized by FTIR, DSC, TGA and XRD, and correlated with in vitro dissolution behavior. Single dose pharmacokinetic parameters of orally dosed CEL were determined in fasted rats for aqueous suspensions of pure CEL, Celebrexr and CEL-pSiox microparticles. Physicochemical testing of CEL-pSiox formulation confirmed the entrapment of CEL within porous nanostructure in an amorphous or non-crystalline form. CEL-pSiox demonstrated superior pharmacokinetics compared with CEL particles or Celebrexr, i.e. increased absolute bioavailability (96.2% vs. 65.2% vs. 88.1%), increased C max (0.91 ± 0.09 μg/mL vs. 0.50 ± 0.16 μg/mL vs. 0.73 ± 0.23 μg/mL) and reduced T max (1.0 ± 0.0 h vs. 2.8 ± 0.8 h vs. 3.4 ± 1.0 h). Single point correlation was established between in vitro dissolution efficiency (% DE) and in vivo absolute bioavailability or C max . Porous silicon microparticles can be formulated as an effective orally dosed solid dispersion preparation for celecoxib
Publisher: MDPI AG
Date: 17-01-2023
DOI: 10.3390/PHARMACEUTICS15020305
Abstract: Cutaneous chronic wounds impose a silent pandemic that affects the lives of millions worldwide. The delayed healing process is usually complicated by opportunistic bacteria that infect wounds. Staphylococcus aureus is one of the most prevalent bacteria in infected cutaneous wounds, with the ability to form antibiotic-resistant biofilms. Recently, we have demonstrated the potential of gallium protoporphyrin lipid liquid crystalline nanoparticles (GaPP-LCNP) as a photosensitizer against S. aureus biofilms in vitro. Herein, we investigate the potential of GaPP-LCNP using a pre-clinical model of infected cutaneous wounds. GaPP-LCNP showed superior antibacterial activity compared to unformulated GaPP, reducing biofilm bacterial viability by 5.5 log10 compared to 2.5 log10 in an ex vivo model, and reducing bacterial viability by 1 log10 in vivo, while unformulated GaPP failed to reduce bacterial burden. Furthermore, GaPP-LCNP significantly promoted wound healing through reduction in the bacterial burden and improved early collagen deposition. These findings pave the way for future pre-clinical investigation and treatment optimizations to translate GaPP-LCNP towards clinical application.
Publisher: Oxford University Press (OUP)
Date: 20-07-2010
DOI: 10.1111/J.2042-7174.2010.00037.X
Abstract: Amiodarone is a low-solubility, high-permeability drug with a narrow therapeutic index and reported bioavailability problems associated with switching formulations. The aim of this study was to identify whether there is variability in drug release and physical characteristics of different commercially available amiodarone hydrochloride formulations in Australia. Four available formulations (innovator Cordarone (COR) and generic products G1, G2 and G3) were tested for drug dissolution, content uniformity, hardness, weight variation, friability and disintegration in accordance with the US Pharmacopeia specifications. The tested formulations exhibited variable dissolution behaviours: G1 and G3 exhibited the fastest dissolution, G2 dissolution was the slowest and Cordarone showed a medium dissolution. After 3 months' exposure to high temperature (40 ± 2°C) and relative humidity (75 ± 5%), the products exhibited a higher degree of disparity, with drug-release profiles of the generics being markedly different from that of Cordarone. This suggests possible implications on bioequivalence for patients who live in warm/tropical regional areas. Most products met the US Pharmacopeia specifications for drug-content uniformity and other test physical characteristics. The results suggested that variability in drug release profiles in vitro of amiodarone formulations might be a potential indicator of compromised bioavailability, causing possible interference with the therapeutic response of the drug.
No related grants have been discovered for Timothy Barnes.