Selenium doped calcium phosphate biomimetic coating on Ti6Al4V orthopedic implant material for anti-cancer and anti-bacterial purposes

Yılmaz, Bengi
In order to prevent recurrent osteosarcoma in patients undergone surgical resection for implant insertion and infection around implant site, which is a very common complication after surgery, it is very important to functionalize the surface. In this study, to combine the effective antioxidant and potential anti-cancer and anti-bacterial properties of selenium with the high biocompatibility and bioactivity of hydroxyapatite, selenium was added to the structure of hydroxyapatite via biomimetic method and coated on Ti6Al4V plates. Firstly, 1.5×SBF (solution with ion concentrations at 1.5 times that of normal simulated body fluid, SBF) and selenate (SeO42−) ion added 1.5×SBF solutions were prepared. The pretreated Ti6Al4V plates were coated with pure or selenium added hydroxyapatite by immersing them into these solutions. The surface and micro-structure of the resulting coatings were characterized by SEM, EDS, XRD, ICP-MS, FTIR and Raman spectroscopy. From SEM micrographs, it was observed that the nucleation had already started on the 4th day of immersion, the precipitation continued around the nucleation sites with increasing immersion time and thecalcium phosphate precipitate grew in the form of half-spheres in both of the solutions. Selenium-containing coatings, similar to the coatings obtained from the normal 1.5×SBF, exhibited the standard hydroxyapatite XRD peaks. There were no significant differences observed in the FTIR spectra. However, there was an extra band at 764 cm-1 in the Raman spectrum of the selenate added coating that demonstrates the successful incorporation of selenium into the structure of hydroxyapatite. Additionally, selenium was detected in all of the coatings obtained from selenate added 1.5×SBF with different immersion times ranging from 4 to 21 days via ICP-MS method. According to the scratch test results, the critical lateral forces of the coatings varied between 60 and 80 mN. In addition, cell viability tests were performed by using normal human osteoblasts (hFOB 1.19) and osteosarcoma cells (Saos-2). It was determined that adding 100μl solution, which contains 5×10-8 g selenium, into 1ml of the cell culture media provided the optimum concentration of selenium in terms of inhibiting the growth of Saos-2 cells while promoting the growth of hFOB 1.19 cells. However, the cell viability of both of the cell types, which were seeded directly on the pure or selenium containing coatings, was less than that of the control group, which was seeded on tissue culture plastic. In order to evaluate the anti-bacterial property of the coatings, the adhesion and proliferation behavior of S. epidermidis bacteria was studied. It was shown that the number of bacteria was decreased in the supernatant media of the coating which is obtained from the selenate added 1.5×SBF at 14th day of immersion with respect to pure HA coating and control.