Microbiological and in vitro degradation response of a magnesium alloy with new surface functionalization for use as temporary bone implants

When a small mechanically resistant bone implant is required, magnesium (Mg) based alloys are promising materials to avoid a second removal surgery. Mg is abundant in the human body and excretable. However, Mg alloys have the disadvantage of fast corrosion rate at early implantation times. One technique to reduce degradation and hydrogen evolution is to use surface modifications in order to control it and to match bone healing rate. Additionally, local antibiotic therapy is preferable than systemic antibiotics because it reduces the risk of infection and potential implant failure. This study investigates the biocorrosion and microbiological response of AZ91 magnesium alloy with a simple and novel carbonate-phosphate pre-treatment and silica-gentamicin nanoparticles, aiming to control initial degradation, enhancing antibacterial properties, and preserving biocompatibility and cellular response. It is shown that the pre-treated alloy diminishes degradation rate in simulated body fluid when compared with the untreated samples, evaluated by different superficial, microscopic, spectroscopic and electrochemical techniques. Hemocompatibility tests and biocompatibility assays with fibroblast cell lines, along with anti-bacterial tests show that the proposed surface modification, present a biocompatible, bioactive and antibacterial surface. This work is a breakthrough in the development of degradable implants for use in orthopaedic surgery where infections are always a concern.