Towards prevention of biofilm formation: Ti6Al7Nb modified with nanocomposite layers of chitosan and Ag/Au nanoparticles

Implant-associated infections are the major concern for failure of arthroplasty operations. The functionalisation of implant surface can provide solutions to the problem by either inhibiting the adherence of the bacteria or introducing a contact-killing mechanism. This work is focused on Ti6Al7Nb biomedical alloy modification involving chemical and plasma surface activation, followed by the deposition of chitosan layers enhanced with metal nanoparticles. A benign method using chitosan as an efficient reducing and stabilizing agent was applied to produce Au and Ag nanoparticles in situ with the size of ca. 20 nm and 5 nm, respectively. Piranha solution and O2/NH3/Ar plasma were used as a surface activation method, while Au and Ag NPs provide antimicrobial properties, as a viable alternative to the antibiotic-based approach. The surface topography on submicrometre scale of deposited layers was evaluated. Chitosan and chitosan–Ag NPs composite layers showed excellent hydrophilicity, characterised by wetting angles below 13°. Modified alloy showed minimal toxicity towards MG-63 cell line in vitro, acceptable corrosion resistance and release of titanium, aluminium as well as niobium ions from the resulting modified alloys. The chitosan layers were proven to uphold satisfactory Au (over 2.8 mg/dm3) and Ag (over 5.1 mg/dm3) ion dosages up to 96h.