Polyelectrolyte multilayer coatings for short/long-term release of antibacterial agents

Abstract

Osteomyelitis caused by orthopedic and cranial implants infection is the principal cause of implant failure, septicemia, and even death; it is an urgent issue with prevalence rates ranging from 4% to 10% in industrialized countries. Bioactive and multifunctional materials such as bioglass, biometal, and biopolymer are commonly used in biomedical fields; however, it is still a challenge to fabricate effective antibacterial coatings. The purpose of this study is to use layer-by-layer technology to develop an antibacterial coating with outer and inner portions for short/long-term release of antibacterial agents. Antibiotics would be released immediately after implant and antibacterial silver ions in the long term. In this study, polyelectrolyte multilayers (PEMs) comprised of collagen as the cationic layers and γ-poly-glutamic acid as the anionic layers were coated onto the 316L stainless steel substrate via a spin coating technique. A chitosan buffer layer was designed and placed in the middle of the coating. 1 mol% silver additive 58S bioactive glass (SiO2: CaO: P2O5 = 60: 36: 4 in mol%) was introduced into the inner γ-poly-glutamic acid layers, while gentamicin was added to the outer layer.Herein, it is demonstrated that bioactive glass was successfully incorporated into the PEM coatings which had a total thickness of about 61.4 ± 2.8 μm (via SEM) and good hydrophilicity with a contact angle of 34.91°. The PEMs had a hardness of 0.18 ± 0.02 GPa, Young's modulus of 3.85 ± 0.32 GPa, and roughness of 394.7 nm. In the short-term, the PEM coatings would release gentamicin and silver ions, while the long-term controlled release of silver ions served as an antibacterial. The PEM coatings were not only effective as an antibacterial, as seen in the zone of inhibition test, but also biocompatible with rat bone marrow mesenchymal stem cells (BMSCs), as seen in the MTT assay. Therefore, we believe that this technology will have great potential in the surface modification of orthopedic and cranial implants due to its antibacterial, tissue restoration, and osseointegration properties.