ORCID Profile
0000-0002-5593-4818
Current Organisation
University of Sydney
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Functional Materials | Biochemistry and Cell Biology | Haematology | Synthetic Biology
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Expanding Knowledge in the Biological Sciences |
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3RA43666G
Publisher: Elsevier BV
Date: 04-2013
DOI: 10.1016/J.COLSURFB.2012.11.029
Abstract: Plasma immersion ion implantation (PIII) treatment is a novel method for immobilizing yeast on polymer surfaces by covalent linkage. This study of the immobilization of Saccharomyces cerevisiae in both rehydrated and cultured forms showed that the density of cell attachment on PIII treated polystyrene (PS) was strongly dependent on the pH of the incubation medium and was higher for rehydrated yeast. A study of the surface charge was undertaken to explain this result. A high density of cell attachment occurs in acidic conditions (pH 3-5) and a significantly reduced cell density occurs in neutral and alkaline buffers (pH 6-10) for both types of yeast. Force measurements using atomic force microscopy show that a negative charge is present on polystyrene after PIII treatment. The charge is close to zero at pH 3 to pH 5 and increasingly negative from pH 6 to pH 10. Both rehydrated yeast and cultured yeast have negative electrophoretic mobility in the pH range studied. The repulsive forces are weak in acidic buffers and stronger in neutral and alkaline buffers, in good agreement with the cell densities observed. Rehydrated yeast cells are found to be more hydrophobic than cultured yeasts in the same buffer. The higher hydrophobicity explains the higher attachment of rehydrated yeast compared to cultured yeast.
Publisher: eLife Sciences Publications, Ltd
Date: 13-05-2022
DOI: 10.7554/ELIFE.76262
Abstract: A developing understanding suggests that spatial compartmentalisation in pancreatic β cells is critical in controlling insulin secretion. To investigate the mechanisms, we have developed live-cell subcellular imaging methods using the mouse organotypic pancreatic slice. We demonstrate that the organotypic pancreatic slice, when compared with isolated islets, preserves intact β-cell structure, and enhances glucose-dependent Ca 2+ responses and insulin secretion. Using the slice technique, we have discovered the essential role of local activation of integrins and the downstream component, focal adhesion kinase (FAK), in regulating β cells. Integrins and FAK are exclusively activated at the β-cell capillary interface and using in situ and in vitro models we show their activation both positions presynaptic scaffold proteins, like ELKS and liprin, and regulates glucose-dependent Ca 2+ responses and insulin secretion. We conclude that FAK orchestrates the final steps of glucose-dependent insulin secretion within the restricted domain where β-cell contact the islet capillaries.
Publisher: Wiley
Date: 15-04-2022
Abstract: High surface area carbon coatings are produced by plasma‐enhanced chemical vapour deposition using a high‐voltage dielectric barrier discharge under conditions where aggregates are formed in the plasma and the growing coating is subjected to plasma immersion ion implantation. We extend the Smoluchowski aggregation theory to include the continuous production of monomers to explain the observed microstructure of the coatings as a function of the pressure of deposition. The larger particles show evidence of the accretion of monomers on their surfaces with characteristic voids resulting from island growth. The coatings are subjected to plasma immersion ion implantation using high‐voltage pulses that create radicals for binding biomolecules. The increased surface area by the presence of the aggregated particles binds a significantly higher amount of protein than smooth coatings, making them potentially useful for electrodes, biosensing and drug delivery.
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.MSEC.2018.12.106
Abstract: We report a plasma immersion ion implantation process for functionalizing polymer coated magnetic particles, converting them into a universal covalent binding platform for the simultaneous binding of multiple molecular agents without the need for specialised chemical linking groups. As an ex le, we demonstrate the improvement of wettability and the control of surface charge of polystyrene coated magnetic particles, enhancing biomolecule attachment density with strong covalent binding. We demonstrate the preparation of multifunctional magnetic particles where two or more types of molecule are co-immobilized. This enables a platform technology with simultaneous multiple covalent binding of molecules drawn from oligonucleotides, antibodies and enzymes suitable for targeted nanoparticle diagnostic and therapies.
Publisher: MDPI AG
Date: 08-09-2021
Abstract: Implant devices containing insulin-secreting β-cells hold great promise for the treatment of diabetes. Using in vitro cell culture, long-term function and viability are enhanced when β-cells are cultured with extracellular matrix (ECM) proteins. Here, our goal is to engineer a favorable environment within implant devices, where ECM proteins are stably immobilized on polymer scaffolds, to better support β-cell adhesion. Four different polymer candidates (low-density polyethylene (LDPE), polystyrene (PS), polyethersulfone (PES) and polysulfone (PSU)) were treated using plasma immersion ion implantation (PIII) to enable the covalent attachment of laminin on their surfaces. Surface characterisation analysis shows the increased hydrophilicity, polar groups and radical density on all polymers after the treatment. Among the four polymers, PIII-treated LDPE has the highest water contact angle and the lowest radical density which correlate well with the non-significant protein binding improvement observed after 2 months of storage. The study found that the radical density created by PIII treatment of aromatic polymers was higher than that created by the treatment of aliphatic polymers. The higher radical density significantly improves laminin attachment to aromatic polymers, making them better substrates for β-cell adhesion.
Publisher: Elsevier BV
Date: 12-2022
Publisher: Elsevier BV
Date: 10-2015
Publisher: American Chemical Society (ACS)
Date: 11-2019
Abstract: Catheter-associated biofilms are responsible for a large fraction of hospital acquired infections. Antimicrobial surface coating on catheters providing prevention at source is extensively studied to reduce bacterial adhesion. Antimicrobial peptides such as melimine and Mel4, covalently linked to surfaces, have shown excellent potential in animal and human studies to suppress infection without toxicity. Covalent binding of the peptides on catheter surfaces improves efficacy but so far has been implemented using multistep wet chemical coupling that will impede widespread adoption. Here we demonstrate plasma immersion ion implantation (PIII) as a single step treatment that covalently couples antimicrobial peptides to polyvinyl chloride (PVC). Strong antimicrobial activity was demonstrated by higher than 3 log kill of
Publisher: American Medical Association (AMA)
Date: 30-10-2019
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.COLSURFB.2014.07.026
Abstract: Plasma immersion ion implantation (PIII) treatment of polymers creates a biointerface capable of direct covalent immobilization of biomolecules. The immobilization of protein molecules is achieved by covalent bonds formed between embedded radicals on the treated surface and amino acid side chains and cells can be immobilized through cell-wall proteins. The attachment density of negatively charged entities on a PIII treated surface is inhibited by its negative surface charge at neutral pH. To reduce the negative charge of PIII treated surfaces in phosphate buffer (pH 7.4, 11mM), we develop an effective approach of grafting allylamine monomers onto the treated surface. The results reveal reactions between allylamine and radicals on the PIII treated surface. One of these triggers polymerization, increasing the number of amine groups grafted. As a consequence, the PIII treated polystyrene surface after allylamine exposure becomes more hydrophobic and less negatively charged in phosphate buffer. Using yeast cells as an ex le, we have shown a significant improvement (6-15 times) of cell density immobilized on the PIII treated surface after exposure to allylamine.
Publisher: The Royal Society
Date: 13-06-2012
Abstract: The surface of polytetrafluoroethylene (PTFE) was modified using plasma immersion ion implantation (PIII) with the aim of improving its ability to immobilize yeast. The density of immobilized cells on PIII-treated and -untreated PTFE was compared as a function of incubation time over 24 h. Rehydrated yeast cells attached to the PIII-treated PTFE surface more rapidly, with higher density, and greater attachment strength than on the untreated surface. The immobilized yeast cells were removed mechanically or chemically with sodium hydroxide and the residues left on the surfaces were analysed with Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). The results revealed that the mechanism of cell attachment on both surfaces differs and a model is presented for each. Rapid attachment on the PIII-treated surface occurs through covalent bonds of cell wall proteins and the radicals on the treated surface. In contrast, on the untreated surface, only physisorbed molecules were found in the residue and lipids were more highly concentrated than proteins. The presence of lipids in the residue was found to be a consequence of damage to the plasma membrane during the rehydration process and the increased cell stress was also apparent by the amount of Hsp12 in the protein residue. The immobilized yeast cells on PIII-treated PTFE were found to be as active as yeast cells in suspension.
Publisher: Springer Science and Business Media LLC
Date: 11-05-2019
DOI: 10.1007/S00604-019-3466-X
Abstract: The authors report on a simplified approach to encapsulate upconversion nanoparticles (UCNPs) in polystyrene spheres by mini-emulsion polymerisation. The resulting particles (PS-UCNP) are hydrophilic, stable and suitable for biomolecular recognition and biosensing applications. Also, a strategy was developed for bioconjugation of antibodies onto the surface of the PS-UCNPs by using the bifunctional fusion protein linker-protein G (LPG). LPG mediates the functionalisation of PS-UCNPs with antibodies against digoxigenin allowing for specific labelling of convective PCR (cPCR) licons. Lambda DNA was lified using cPCR on a heat block for 30 min using the digoxigenin labelled forward and biotin labelled reverse primers. The antibody functionalised PS-UCNPs bind to the digoxigenin end of the cPCR licons. Finally, the streptavidin labelled magnetic beads were used to selectively capture the PS-UCNP-labelled cPCR licons and the upconversion signal was detected at 537 nm under 980 nm excitation. This sandwich approach enables direct recognition of the target lambda DNA with a detection limit of 10
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA16034D
Abstract: A novel plasma treatment method was used to activate a polymer surface for oligonucleotide immobilization.
Publisher: The Royal Society
Date: 07-2018
Abstract: The plasma physics of dielectric barrier discharges (DBD) for carrying out ion implantation in insulators is investigated. A hollow cathode DBD excited by high-voltage pulses is suitable for ion bombardment of the surfaces of insulating tubing, porous material, particles and sheets. Plasma immersion ion implantation of insulating surfaces is useful for many applications in medicine and engineering. The ion bombardment of glass is useful for cleaning and surface modification. The ion implantation of polymers creates radicals that are able to bind molecules to their surfaces for applications in medical procedures and diagnostics. A wire diagnostic probe and optical emission spectroscopy are used for experimental work. A theory based on mutual capacitance is developed to convert data from the probe to give implanted charge as a function of pressure, voltage and pulse duration. We find the operating conditions that allow for charge to be implanted and those that achieve the highest implanted charge.
Publisher: American Chemical Society (ACS)
Date: 20-10-2020
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4802352
Publisher: Wiley
Date: 02-2020
DOI: 10.1002/ENG2.12087
Publisher: American Chemical Society (ACS)
Date: 22-12-2023
Publisher: Wiley
Date: 23-08-2021
Abstract: Thrombosis on blood‐contacting medical devices can cause patient fatalities through device failure and unstable thrombi causing embolism. The effect of material wettability on fibrin network formation, structure, and stability is poorly understood. Under static conditions, fibrin fiber network volume and density increase in clots formed on hydrophilic compared to hydrophobic polystyrene surfaces. This correlates with reduced plasma clotting time and increased factor XIIa (FXIIa) activity. These structural differences are consistent up to 50 µm away from the material surface and are FXIIa dependent. Fibrin forms fibers immediately at the material interface on hydrophilic surfaces but are incompletely formed in the first 5 µm above hydrophobic surfaces. Additionally, fibrin clots on hydrophobic surfaces have increased susceptibility to fibrinolysis compared to clots formed on hydrophilic surfaces. Under low‐flow conditions, clots are still denser on hydrophilic surfaces, but only 5 µm above the surface, showing the combined effect of the surface wettability and coagulation factor dilution with low flow. Overall, wettability affects fibrin fiber formation at material interfaces, which leads to differences in bulk fibrin clot density and susceptibility to fibrinolysis. These findings have implications for thrombus formed in stagnant or low‐flow regions of medical devices and the design of nonthrombogenic materials.
Publisher: AIP Publishing
Date: 15-02-2019
DOI: 10.1063/1.5066565
Abstract: We report an electrically conductive carbon film with controllable hydrophilic properties that offers a covalent binding surface containing radicals for biomolecule attachment without using chemical linkers. Films were deposited from an acetylene-containing plasma using plasma immersion ion implantation during growth and subsequently annealed under vacuum. Electrical conductivity, spin density, contact angle, surface energy, surface composition, and covalent binding capability were studied as a function of annealing temperature, revealing three distinct regions. In the first region, surface energy is dominated by polar groups. In the second region, the polar groups are expelled, creating unpaired electrons that dominate the polar component of the surface energy. In the third region, the electrical conductivity rises and the polar component of surface energy falls as the unpaired electrons recombine, leading to an optimum combination of surface energy, spin density, and electrical conductivity for biological applications. It is proposed that persistent radicals are responsible for both high wettability and covalent binding properties. Covalently attached enzyme molecules on the C film can resist stringent washing with detergents. The C films offer the functions of conducting polymers, but with the added features of controllable wettability and a covalent binding capability.
Start Date: 2023
End Date: 12-2025
Amount: $578,178.00
Funder: Australian Research Council
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