title: The influence of sterilization on nitrogen-included ultrananocrystalline diamond for biomedical applications.
abstract: Diamond has shown great potential in different biomedical applications, but the effects of sterilization on its properties have not been investigated. Here, we studied the influence of five sterilization techniques (solvent cleaning, oxygen plasma, UV irradiation, autoclave and hydrogen peroxide) on nitrogen-included ultrananocrystalline diamond. The chemical modification of the diamond surface was evaluated using X-ray photoelectron spectroscopy and water contact angle measurements. Different degrees of surface oxidation and selective sp(2) bonded carbon etching were found following all sterilization techniques, resulting in an increase of hydrophilicity. Higher viabilities of in vitro mouse 3T3 fibroblasts and rat cortical neuron cells were observed on oxygen plasma, autoclave and hydrogen peroxide sterilized diamond, which correlated with their higher hydrophilicity. By examination of apatite formation in simulated body fluid, in vivo bioactivity was predicted to be best on those surfaces which have been oxygen plasma treated and lowest on those which have been exposed to UV irradiation. The charge injection properties were also altered by the sterilization process and there appears to be a correlation between these changes and the degree of oxygen termination of the surface. We find that the modification brought by autoclave, oxygen plasma and hydrogen peroxide were most consistent with the use of N-UNCD in biological applications as compared to samples sterilized by solvent cleaning or UV exposure or indeed non-sterilized. A two-step process of sterilization by hydrogen peroxide following oxygen plasma treatment was then suggested. However, the final choice of sterilization technique will depend on the intended end application.
authors.affiliation: School of Physics, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Wei
authors.initials: W
authors.lastname: Tong
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, Victoria, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Queensland, Australia.
authors.forename: Phong A
authors.initials: PA
authors.lastname: Tran
authors.affiliation: Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Turnley
authors.affiliation: School of Physics, University of Melbourne, Parkville, Victoria, Australia; School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: Morteza
authors.initials: M
authors.lastname: Aramesh
authors.affiliation: School of Physics, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Steven
authors.initials: S
authors.lastname: Prawer
authors.affiliation: Centre for Additive Manufacturing, School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Melbourne, Victoria, Australia.
authors.forename: Milan
authors.initials: M
authors.lastname: Brandt
authors.affiliation: Centre for Additive Manufacturing, School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Melbourne, Victoria, Australia. Electronic address: kate.fox@rmit.edu.au.
authors.forename: Kate
authors.initials: K
authors.lastname: Fox
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018130:Diamond / Q000737:chemistry* / Q000494:pharmacology; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D054020:Lasers, Gas; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D051381:Rats; D013242:Sterilization / Q000379:methods*; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D018130:Diamond; D006861:Hydrogen Peroxide; D009584:Nitrogen
keywords: Bioactivity; Cell culture; Charge injection; Diamond; Nitrogen-included ultrananocrystalline diamond; Sterilization