Preparation and characterization of polyelectrolyte multilayer coatings on 316L stainless steel for antibacterial and bone regeneration applications

A polyelectrolyte multilayer (PEM) coating was fabricated via the alternate deposition of collagen (Col) and poly (gamma-glutamic acid) (gamma-PGA) onto 316L stainless steel with chitosan as a barrier in the middle layer using spin assisted layer-by-layer assembly. The gamma-PGA layers were loaded with vancomycin (VA) and strontium containing bioactive glass (SrBG) for antibacterial and bone regeneration applications. The physicochemical properties of the obtained films were characterized by X-ray diffractometry, Fourier-transform infrared spectroscopy, white light interferometry, scanning electron microscopy, water contact angle, hardness, and reduced Young's modulus. The biomineralization process of these films in simulated body fluids (SBF) was assessed. The PEM/VA/SrBG composite films exhibited a smoother and more uniform distribution of particles on the substrate surface. These films exhibited intense surface roughness and good wettability with a contact angle of 58.12. The PEM/VA/SrBG film showed intensified mechanical properties that may enhance cell attachment and bone regeneration ability. Thus, loading SrBG onto the implant film surface may improve osseointegration activity. The PEM/VA/SrBG film performed intense bioactivity with resulting formation of apatite layer after immersion in SBF. These PEM composite films exhibited antibacterial properties with the release of VA from the film surface. Based on the MTT assay results, the composite films exhibited excellent biocompatibility with bone marrow mesenchymal stem cells. The histology results indicated that the composite films possess enhanced angiogenesis and bone regeneration ability on 21 days that could grow onto the film surface for tissue engineering. Therefore, PEM/VA/SrBG composite films have excellent potential for orthopedic implant applications based on their intense antibacterial, osseointegration, and bone regeneration properties.