Degradable magnesium implants: improving bioactive and antibacterial performance by designed hybrid coatings

CERÉ, SILVIA; MERLO, JULIETA LETICIA; BOCCACCINI, ALDO; DETSCH, RAINER; BALLARRE, JOSEFINA

Québec

Workshop; Updates in Bioabsorbable Metals 2020; 2020

Magnesiumalloys are promising candidates materials for bioabsorbable fracture fixationdevices; however, their fast corrosion in aqueous media generates hydrogen gasevolution, which causes pain and swelling. In this study, a hybridbiocompatible and bioactive coating system, composed by a sol-gel silica basedmatrix with bioactive glass micro particles and silica-gentamicinnanoparticles, was developed and applied through spray deposition. This coatingsystem was intended to decrease the magnesium alloy degradation, but also toprovide bioactive and antibacterial properties to the implant surface. The dual-coating system had the purpose of releasinggentamicin sulfate in two shocks in order to attack possible bacteria invasionat the time of implantation and potential remaining colonies after a period oftime. METHODS: Extruded magnesium alloy AZ91D (Al 9.0, Zn 1.0,Fe 0.005, Mn 0.33, Ni 0.002 wt %; MagIC, Magnesium Innovations Center, Germany)sheet was cut into squares of 1 × 1 cm2 and polished. Samples werewashed with acetone, alcohol 96% and distilled water. Two layers ofTEOS-MTES-Bioactive glass and two intercalated layers of Si-G nanoparticleswere deposited by spray. Control samples without coating, or without one or twolayers of nanoparticles were made for comparison. Surface characterization wasachieved by SEM, perfilometry and contact angle. In vitro behaviour of samples in simulated body fluid (SBF) [1] wasstudied during 28 days, using SEM, FTIR and pH measurements to characterize it.Coating antibacterial activity was assessed through an indirect method withGram-positive Staphylococcus aureus and Gram-negative Escherichia coli strains. Effect ofcoating on direct cellular contact was studied using murine stromal ST-2 andosteoblastic MC3T3 cell lines.