110 research outputs found
Nitric oxide releasing plasma polymer coating with bacteriostatic properties and no cytotoxic side effects
No full textPublished on 19 March 2015We report a stable plasma polymer coating, using isopentyl nitrite as a volatile precursor, which releases nitric oxide at bacteriostatic concentrations when contacted with water, inhibiting bacterial growth without cytotoxic side effects to human mesenchymal stem/stromal cells.Thomas D. Michl, Bryan R. Coad, Michael Doran, Michael Osiecki, Morteza Hasanzadeh Kafshgari, Nicolas H. Voelcker, Amanda Hüsler, Krasimir Vasilev and Hans J. Griesse
Cell Wall Responses to Biotrophic Fungal Pathogen Invasion
No full textFirst published: 15 November 2019To a plant the surrounding environment is filled with microbial organisms looking to take advantage of the bountiful resources held within. In order for a pathogen to access the internal nutrients it must gain entry through the plant cell outer layers that consist of the cuticular wax and the plant cell wall. This barrier is a complex structure composed of diverse waxes, lipids, polysaccharides, proteins, lignin, and antimicrobial compounds and plays many crucial roles during plant defence, growth, and development. We now have more evidence than ever about the dynamic nature of the cell wall providing various interaction-dependent passive and active defence responses, hence justifying a necessity of evolving such a complex structure. Here we summarise the current understanding of this multi-layered defence system, using the biotrophic interaction between barley and the causal agent of powdery mildew, Blumeria graminis f. sp. hordei (Bgh).Jamil Chowdhury, Bryan R. Coad, Alan Littl
A substrate-independent method for surface grafting polymer layers by atom transfer radical polymerization: reduction of protein adsorption
No full textAvailable online 11 October 2011
Link to a related website: https://digital.library.adelaide.edu.au/dspace/bitstream/2440/111895/3/hdl_111895.pdf, Open Access via UnpaywallAbstract not availableBryan R. Coad, Yi Lu, Laurence Meaghe
Polyethyleneimine for copper absorption: kinetics, selectivity and efficiency in artificial seawater
No full textPublished on 29 May 2014.Polyethyleneimine (PEI) is known to bind copper ions effectively and selectively. However, this is the first report on PEI-based materials for copper scavenging from ultra-low concentrations in seawater matrixes. The findings are relevant for water purification and sensing applications as well as extraction of copper from oceans.Johan B. Lindén, Mikael Larsson, Bryan R. Coad, William M. Skinner and Magnus Nydé
A novel flash detection algorithm for single molecule counting with TIRF microscopy
No full textA novel algorithm, Adjacent Pixel Temporal Intensity Correlation (APTIC), was developed to detect single fluorescent molecules by their stochastic emission patterns; photoblinking and photobleaching. The algorithm was evaluated using simulated image data and Total Internal Reflection Fluorescence Microscopy (TIRF-M) to count the number fluorescently labelled protein molecules adsorbed onto glass substrates modified by Radio Frequency Glow Discharge (RFGD) deposition. By selecting an appropriate correlation threshold, the algorithm was capable of detecting synthetic flashes with a signal-to-noise ratio (SNR) as low as 2.0 with 90% sensitivity. The methodology holds great promise for mapping the amount and distribution of biomolecules on surfaces.Joseph Radford, Liyuan Wang, JingJing Li, Bryan R. Coad, Clive D. McFarland, Robert E. Nordo
ToF-SIMS multivariate analysis of surface-grafted small bioactive molecules
No full textLink to a related website: https://digital.library.adelaide.edu.au/dspace/bitstream/2440/113363/3/hdl_113363.pdf, Open Access via UnpaywallIn the development of bioactive coatings on biomaterials, it is essential to characterize the successful fabrication and the uniformity of intended coatings by sensitive surface analytical techniques, so as to ensure reliable interpretation of observed biointerfacial responses. This can, however, be challenging when small bioactive molecules are grafted onto biomaterials surfaces at sub- and near-monolayer densities. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) provides the required sensitivity, but ion signals from small grafted molecules may still be dominated by fragment ions from the underlying polymer. In such cases, multivariate analysis provides valuable enhancement of spectral data, as illustrated here by examples comprising the surface grafting of bioactive serrulatane molecules, the peptide GRGDSP, the oligonucleotide 15-thymidine, and the antifungal compound Amphotericin B. The authors also show how ToF-SIMS plus principal component analysis can distinguish between covalent grafting and physisorption of the antibiotics caspofungin and micafungin.Marek Jasieniak, Bryan R. Coad and Hans J. Griesser
Antifungal coatings by caspofungin immobilization onto biomaterials surfaces via a plasma polymer interlayer
No full textPublished Online: 14 October 2015
Link to a related website: https://digital.library.adelaide.edu.au/dspace/bitstream/2440/123749/2/hdl_123749.pdf, Open Access via UnpaywallNot only bacteria but also fungal pathogens, particularly Candida species, can lead to biofilm infections on biomedical devices. By covalent grafting of the antifungal drug caspofungin, which targets the fungal cell wall, onto solid biomaterials, a surface layer can be created that might be able to provide long-term protection against fungal biofilm formation. Plasma polymerization of propionaldehyde (propanal) was used to deposit a thin (∼20 nm) interfacial bonding layer bearing aldehyde surface groups that can react with amine groups of caspofungin to form covalent interfacial bonds for immobilization. Surface analyses by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed the intended grafting and uniformity of the coatings, and durability upon extended washing. Testing for fungal cell attachment and ensuing biofilm formation showed that caspofungin retained activity when covalently bound onto surfaces, disrupting colonizing Candida cells. Mammalian cytotoxicity studies using human primary fibroblasts indicated that the caspofungin-grafted surfaces were selective in eliminating fungal cells while allowing attachment and spreading of mammalian cells. These in vitro data suggest promise for use as antifungal coatings, for example, on catheters, and the use of a plasma polymer interlayer enables facile transfer of the coating method onto a wide variety of biomaterials and biomedical devices.Stefani S. Griesser, Marek Jasieniak, Bryan R. Coad, and Hans J. Griesse
Individual and population quantitative analyses of calcium flux in T-cells activated on functionalized material surfaces
No full textWe have developed a novel method for activating T-cells on material surfaces that enable individual and population-based analyses of intracellular calcium flux, as a quantitative measure of T-cell receptor engagement. Functionalized material surfaces were created using a plasma-polymerized foundation layer to immobilize stimulatory T-cell ligands, which could induce T-cell receptor-dependent calcium flux in naive T-cells. Real-time confocal microscopic detection and quantification of calcium flux using paired fluorescent ratiometric probes facilitated the tracking and analysis of response profiles of individual T-cells, as well as population analyses using a combination of individual T-cell events. This type of combined analysis cannot be achieved using traditional population-based flow cytometric approaches, and thus provides a logical step towards developing the capacity to assess the magnitude and quality of inherently heterogeneous effector T-cell responses to antigenic challenge.Susan N. Christo, Ghafar. T. Sarvestani, Stefani S. Griesser, Bryan R. Coad, Hans J. Griesser, Krasimir Vasilev, Michael P. Brown, Kerrilyn R. Diener and John D. Haybal
Synthesis of highly functionalised plasma polymer films from protonated precursor ions via the plasma alpha-gamma transition
No full textData source: Supplementary information, http://www.rsc.org/suppdata/c6/cp/c6cp08630f/c6cp08630f1.pdfChemically functionalized surfaces may be produced via plasma polymerization, however a high degree of functional group retention is often difficult to achieve. Here, the plasma polymerization of three structurally related ester precursors, ethyl isobutyrate (EIB), methyl isobutyrate (MIB) and ethyl trimethylacetate (ETMA) is compared at low and high pressure. In moving from a low pressure to higher pressure regime, significant changes in the plasma chemistry and resulting plasma polymer deposit were observed with much higher retention of chemical functionality at the higher pressure observed. Until now these changes would have been attributed to a decrease in the energy/molecule, however we show by direct measurement of the chemistry and physics of the plasma that there is fundamental shift in the properties of the plasma and surface interactions which explain the results. At low pressure (a regime) precursor fragmentation and neutral deposition dominate resulting in poor functional group retention. Increasing the pressure such that the sheath region close to surfaces becomes collisional (g regime) favours production of protonated precursor ions which retain functionality and dominate the deposition process rather than radical species.Solmaz Saboohi, Bryan R. Coad, Hans J. Griesser, Andrew Michelmore and Robert D. Shor
Polymer brush gradients grafted from plasma-polymerized surfaces
No full textPublished: June 26, 2014A new method for generating a surface density gradient of polymer chains is presented. A substrate-independent polymer deposition technique was used to coat materials with a chemical gradient based on plasma copolymerization of 1,7-octadiene and allylamine. This provided a uniform chemical gradient to which initiators for atom transfer radical polymerization (ATRP) were immobilized. After surface-initiated atom transfer radical polymerization (SI-ATRP), poly(2-hydroxyethyl methacrylate) (PHEMA) chains were grafted from the surface and the measured thickness profiles provided direct evidence for how surface crowding provides an entropic driving force resulting in chain extension away from the surface. Film thicknesses were found to increase with the position along the gradient surface, reflecting the gradual transition from collapsed to more extended surface-tethered polymer chains as the grafting density increased. The method described is novel in that the approach provides covalent linkages from the polymer coating to the substrate and is not limited to a particular surface chemistry of the starting material.Bryan R. Coad, Tugba Bilgic, and Harm-Anton Klo
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