Mechanism of protein biofilm formation on Ag-DLC films prepared for application in joint implants

• Published in: Surface & coatings technology 2021-09, Vol.422, p.127553, Article 127553
• Main Authors: Jing, P.P., Su, Y.H., Li, Y.X., Liang, W.L., Leng, Y.X.
• Format: Article
• Language: English
• Subjects: Biofilm; Biofilms; Diamond-like carbon; Diamond-like carbon films; Friction; Hydrogen bonds; Implants; Magnetron sputtering; Plasma enhanced chemical vapor deposition; Prostheses; Protein adsorption; Protein denaturation; Proteins; Residual stress; Serum albumin; Silver; Surface chemistry; Wear resistance
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2021.127553

Silver-doped diamond-like carbon (Ag-DLC) films offer low residual stress, good adhesion, and excellent wear resistance, and thus are promising materials for surface modification of joint prostheses. Further, as proteins are the most abundant component of joint fluid, the wear performance of Ag-DLC films in protein environments warrants investigation. We prepared DLC and 10.0 at.% Ag-DLC films using hybrid deposition technique by combining high-power pulsed magnetron sputtering and high-power pulsed plasma-enhanced chemical vapor deposition. The wear performance of the films was tested using bovine serum albumin (BSA) solution. A biofilm of denatured proteins formed at the friction interface of the Ag-DLC film, which improve wear resistance. Subsequent protein adsorption, Ag+ ions release, and spectroscopic evaluation of the interaction between Ag+ ions and BSA molecules revealed the mechanism of biofilm formation. Ag doping promoted the protein adsorption on film surface and friction interface of Ag-DLC films. Meanwhile, Ag-DLC films released Ag+ ions when exposed in physiological solutions. The released Ag+ ions break the hydrogen bonds and disulfide bonds in proteins and transform the α-helix structure to β-sheet and β-turn structure, thus unfolding the protein, exposing the inner hydrophobic groups, and inducing protein deposition and biofilm formation. The study elucidates the biofilm formation mechanism at the friction interface of Ag-DLC films and counterparts and can aid in design of hardwearing joint implants. [Display omitted] •Ag doping improves the wear resistance of DLC film in BSA solutions.•Biofilm on the counterpart of Ag-DLC film is composed of denatured proteins.•Released Ag+ ions promote the adsorption and denaturation of BSA molecules.•Ag+ ions break the hydrogen and disulfide bonds, unfolding the protein structure.