ID-13-P-2298 Characterization of the porous coatings with incorporated silver deposited by micro-arc oxidation

The development of implants over last eighty years includes improvement of known materials as well as designing new ones to increase their mechanical properties, corrosion resistance in body fluids and biocompatibility. Despite of the significant progress still high number of implants failure is connected with bacterial infections. To reduce the risk of microbial infection during surgery different approaches are proposed. One of them is the modification of the biomaterials surface to prevent bacterial attachment and biofilm formation. Another is the incorporation of antimicrobial agents (e.g. silver, NO, antibiotics) into the coating structure to inhibit bacterial proliferation.

This study shows microscopic characterization of the porous coatings with incorporated silver deposited on commercially pure titanium (CP-Ti) and two-phase (a+b) Ti6Al4V alloy by micro-arc oxidation (MAO) process. The process parameters and electrolyte composition were the same for both materials. Solution used for deposition contained: (CH3COO)2Ca·H2O, Na2PO4 and the addition of 0.001 mol/l of CH3COOAg. Microstructure and chemical composition of the coatings were investigated utilizing SEM- and TEM-EDS techniques.

SEM investigation of the samples plain view showed high porosity and surface development of the coatings (Fig. 1a). The complex microstructure, including specific platelets (red circle in Fig. 1b) and nanometer sized particles (yellow circle in Fig. 1b) was visible around the pores. EDS point analysis of different areas of samples surface showed that platelets contained only Ca, P and O while particles area was composed of around 40 at.% of Ag and additionally Ti, Ca, P and O. Detailed TEM investigation, including phase identification by electron diffraction is in progress. The analyses of sample cross-sections revealed the differences in the coatings thickness between both materials. The thickness of the coating formed on CP-Ti was measured as around 12 μm, while that on Ti6Al4V was around 22 μm thick (Fig. 2). Both coatings had the layered structures. Directly at the substrates, titanium dioxide phases were present, while outer layer was composed of calcium phosphates. The Ag distribution within both coatings was determined using EDS mapping. In the case of CP-Ti, Ag was present around the pores in the TiO2 layer, while in the coating formed on the Ti6Al4V alloy it was accumulated at the interface between titanium dioxide and calcium phosphates layers.

Many reports are proving excellent antibacterial activity of silver releasing materials, however in some case also harmful effect on human cells was observed. To verify biological properties of prepared coatings in vitro cytotoxicity tests with cell cultures are in progress.