Biological Studies of New Implant Materials Based on Carbon and Polymer Carriers with Film Heterostructures Containing Noble Metals

This paper presents pioneering results on the evaluation of noble metal film hetero-structures to improve some functional characteristics of carbon-based implant materials: carbon-composite material (CCM) and carbon-fiber-reinforced polyetheretherketone (CFR-PEEK). Metal-organic chemical vapor deposition (MOCVD) was successfully applied to the deposition of Ir, Pt, and PtIr films on these carriers. A noble metal layer as thin as 1 µm provided clear X-ray imaging of 1–2.5 mm thick CFR-PEEK samples. The coated and pristine CCM and CFR-PEEK samples were further surface-modified with Au and Ag nanoparticles (NPs) through MOCVD and physical vapor deposition (PVD) processes, respectively. The composition and microstructural features, the NPs sizes, and surface concentrations were determined. In vitro biological studies included tests for cytotoxicity and antibacterial properties. A series of samples were selected for subcutaneous implantation in rats (up to 3 months) and histological studies. The bimetallic PtIr-based heterostructures showed no cytotoxicity in vitro, but were less biocompatible due to a dense two-layered fibrous capsule. AuNP heterostructures on CFR-PEEK promoted cell proliferation in vitro and exhibited a strong inhibition of bacterial growth (p < 0.05) and high in vitro biocompatibility, especially Au/Ir structures. AgNP heterostructures showed a more pronounced antibacterial effect, while their in vivo biocompatibility was better than that of the pristine CFR-PEEK, but worse than that of AuNP heterostructures

Application of Biocompatible Noble Metal Film Materials to Medical Implants: TiNi Surface Modification

Recently, film materials based on the combination of noble metals have showed promising results for surface modification of medical implants, allowing both to improve biocompatibility and to acquire the increased antibacterial effect. An important challenge here is to combine the developed coating morphology, which is favorable for biological response, with a high protective function, which, on the contrary, requires a compact coating microstructure. In this work, we aimed to solve this problem with respect to the TiNi implant material. We have tested two types of compact thin sublayers: Iridium (Ir’), formed by metal-organic chemical vapor deposition (MOCVD), and gold (Au), formed by physical vapor deposition (PVD). Subsequently these sublayers were coated with a developed-columnar-iridium (Ir) by MOCVD. Features of the microstructure, chemical and phase composition of all these film materials were studied using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The changes in the characteristics of TiNi martensitic transformation due to MOCVD experiments were also studied by differential scanning calorimetry (DSC). The biocompatibility of Ir’/TiNi, Au/TiNi, Ir/Ir’/TiNi, Ir/Au/TiNi samples was assessed by cytoxicity testing (Man-1 cells) and measuring of nickel content in the biological extracts. The application of both sublayers effectively reduces the release of nickel, which was previously shown for Ir/TiNi samples. This prevents the toxic effect. Note that the Ir’ sublayer better protects against nickel release, while the Au sublayer promotes cell proliferation