Plasma Deposition of Biomolecules for Enhanced Biomedical Applications
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Plasma Deposition of Biomolecules for Enhanced Biomedical Applications
Liam O’Neill1,2, Barry Twomey1, Peter Dobbyn2 & John O’Donoghue1,2 1
ENBIO, Nova UCD, Belfield Innovation Park, University College Dublin, Belfield, Dublin 4, Ireland 2
PlasMedica, Clonmult, Dungourney, Midleton, Cork, Ireland
ABSTRACT Biomolecules have been traditionally immobilised onto surfaces using wet chemical techniques for various medical applications. Recent decades have seen plasma methods being used to prepare these surfaces through various forms of surface modification, but the direct exposure of biomolecules to plasma has been avoided due to fears that the molecules would be denatured by the energetic plasma species. Recent results are now demonstrating that direct plasma deposition of biomolecule coatings can be achieved. This creates the possibility to directly modify the surface of implants without any form of surface pre-treatment and this opens up the possibility to alter the healing processes. Materials such as collagen, chitosan, catalase and heparin can be effectively deposited onto surfaces with minimal impact on biological performance and without any chemical binders, linkers or impurities. The performance of these materials has been characterised using both in vitro and in vivo methodologies. In a further step, the results of a preclinical trial are presented which reveal that direct deposition of biomolecules onto open wounds can also be achieved and the impact of this on wound healing is measured in an immunocompromised animal model. A non-thermal plasma device was used to deliver collagen on to chronic wounds and the treatment was shown to promote wound closure in a rabbit wound healing model.
INTRODUCTION Plasma processing has been widely used in industry for many decades as a cheap, versatile system for cleaning and etching surfaces. Plasma based coating technology was developed in the 1960’s for semiconductor applications, most notably the deposition of silicon nitride thin films [1]. However, the range of chemistries that could be deposited quickly expanded to embrace a range of materials including organic coatings [2], polymers [3, 4] and siloxanes [5]. High temperature thermal plasma spray systems became widely used in automotive, aerospace and medical arenas as a reliable method to deposit metallic and ceramic coatings on large metal components. Deposition of polymeric coatings was restricted to vacuum deposition systems, where low pressures allowed the creation of low temperature plasma systems that could deposit polymeric materials on to temperature sensitive substrates using Plasma
Enhanced Chemical Vapour Deposition (PECVD). As the monomer vapours are fed into the plasma system, they are exposed to a variety of ions, radicals, metastables and free electrons which results in the molecule undergoing excitation, dissociation, ionisation or the formation of free radicals. Alternatively, interaction with the heavier particles in the plasma can lead to charge transfer, recombination, ionisation, radical-mole
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