Multifunctional stratified composite coatings by electrophoretic deposition and RF co-sputtering for orthopaedic implants

Abstract

In this study, multifunctional stratified antibacterial and bioactive coatings were deposited and characterised. Initially, PEEK/bioactive glass (BG)/ mesoporous bioactive glass nanoparticle (MBGN) layers with a thickness of 110–120 μm were deposited on stainless steel substrates using electrophoretic deposition (EPD). Thin silver nanocluster-silica composite layers with a thickness of 70–155 nm were then deposited by radio frequency (RF) co-sputtering on the previously deposited EPD coatings. The deposition was carried for two different sputtering times (20 min and 40 min), which led to different layer thicknesses. PEEK/BG/MBGNs coatings were also deposited via single-step EPD. A comparison between the physicomechanical and biological characteristics of single layer PEEK/BG/MBGNs composite coating and bilayer Ag-PEEK/BG/MBGNs is presented. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) indicated that silver nanoclusters were homogeneously distributed in the multilayered EPD/RF coatings. An apatite-like structure was formed on the surface of the coatings upon immersion in simulated body fluid (SBF) after 1 day. Silver nanoclusters embedded in the silica matrix as a top layer provided controlled release of silver ions which led to a potent antibacterial effect against E. coli and S. carnosus. Single layer coatings exhibited a burst release of Ag ions, which led to antibacterial effects but were toxic to osteoblast cells. Finally, the results of WST-8 assays confirmed that the multi-structured coatings allow osteoblast-like cells to proliferate and attach strongly on the surface of the coatings.

Synthesis and Characterization of Silver–Strontium (Ag-Sr)-Doped Mesoporous Bioactive Glass Nanoparticles

“…However, the controlled release of silver ions <100 ppm (as the case in the present study, see Figure 6) provided a potent antibacterial effect against a wide spectrum of bacteria. The release of silver ions was <100 ppm, which is below the cytotoxic limit of Ag [10,35].…”

“…The variation in zeta potential by the incorporation of Sr and Ag in MBGNs may be associated with the pH change (zeta potential is a function of pH). It is also reported that the addition of Sr in bioactive glass (Sr substitution with Ca) may lead to the pH change and eventually increase the zeta potential compared to the MBGNs [35]. Positive zeta potential (of Sr-MBGNs) increases the solubility of the nanoparticles and may lead to aggregation.…”

Synthesis and Characterization of Silver–Strontium (Ag-Sr) Doped Mesoporous Bioactive Glass Nanoparticles

“…The release of silver ions was <100 ppm, which is below the cytotoxic limit of Ag [10,46]. The cytotoxicity of Ag doped MBGNs depends on the concentration of Ag in MBGNs and the release profile of Ag [29,47].…”

A Brief Insight to the Electrophoretic Deposition of PEEK-, Chitosan-, Gelatin-, and Zein-Based Composite Coatings for Biomedical Applications: Recent Developments and Challenges

“…PEEK-based composite coatings are mechanically robust while showing improved adhesion strength with the substrate, and better wear and corrosion resistance [167]. For example, PEEK/BG coatings applied on 316L-SS showed an adhesion strength of ~15 N, which is suitable for orthopedic applications [95,104]. The adhesion strength of PEEK composite coatings are attributed to the selection of appropriate sintering temperature and deposition parameters.…”

“…This allows the sustained release of drugs for longer time points and the eventual antibacterial effect. PEEK-based composite coatings are an attractive formulation for targeted drug delivery systems, along with the controlled release of antibacterial agents, owing to the favorable topography of the PEEK-based composite coatings [95,104].…”