Antibacterial double-layer calcium phosphate/chitosan composite coating on metal implants for tissue engineering

In this study, four different promising two-layer composite coatings on titanium substrates with antibacterial properties were investigated. Two different types of antibacterial agents were used to impart antibacterial properties to the coatings: antibiotic amikacin (in three different concentrations) and zinc. Chitosan, which also has antibacterial properties, was used as a carrier layer for amikacin on a calcium phosphate coating incorporating zinc. This combination should enable long-term antibacterial properties of a bone implant and thus prevent potential complications during wound healing due to bacterial contamination. To examine the physico-chemical properties of the samples, the elemental, chemical and phase compositions, the thickness and the wettability of the coatings were investigated. The release of amikacin from the chitosan coatings was investigated using high-performance liquid chromatography. Antibacterial activity of the prepared coatings was evaluated against five hospital bacteria strains (Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterococcus faecalis, Klebsiella pneumoniae) and one strain from the microbial strain collection (methicillin-resistant Staphylococcus aureus, ATCC 43300). To investigate the cell toxicity of the composite coating, cell adhesion, proliferation and osteogenic differentiation were tested with mesenchymal stem cells. According to the results, the composite coatings with an amikacin concentration of 5.0 and 7.5 percent by weight have the best biological and antibacterial properties.