Evaluation of osteogenic and antibacterial properties of strontium/silver-containing porous TiO2 coatings prepared by micro-arc oxidation.

Ti and Ti alloys are bioinert materials and two frequent problems associated with them are bacterial infection and lack of osteogenic potential for rapid bone integration. To overcome the problems, the present study incorporated strontium (Sr) and silver (Ag) simultaneously into porous TiO2 coatings through a single-step technique, micro-arc oxidation (MAO). Incorporation of Sr and Ag brought no significant changes to coating micromorphology and physicochemical properties, but endowed TiO2 coatings with both strong antibacterial activity and osteogenic ability. Antibacterial activity increased with Ag contents in the coatings. When Ag content reached 0.58 wt%, the coating showed both excellent short-term (100.0%) and long-term (77.6%) antibacterial activities. Sr/Ag-containing coatings with 18.23 wt% Sr and 0.58 wt% Ag also presented good cytocompatibility for preosteoblast adhesion and proliferation, and promoted preosteoblast osteogenic differentiation both short-termly and long-termly. However, higher Ag content (1.29 wt%) showed toxic effects to preosteoblasts. In summary, MAO is a simple and effective way to incorporate Sr and Ag into porous TiO2 coatings and Sr/Ag-containing TiO2 coating with 18.5 wt% Sr and 0.58 wt% Ag has both good osteogenic activity and strong antibacterial capability short-termly and long-termly. Therefore, such coatings are valuable for clinical application to strengthen osseointegration and long-term high quality use of titanum implants.

Selective sampling and measurement of Cr (VI) in water with polyquaternary ammonium salt as a binding agent in diffusive gradients in thin-films technique.

A diffusive gradients in thin films (DGT) device with polyquaternary ammonium salt (PQAS) as a novel binding agent (PQAS DGT) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed for the selective sampling and measurement of Cr (VI) in water. The performance of PQAS DGT was independent of pH 3-12 and ionic strength from 1 × 10(-3) to 1 molL(-1). DGT validation experiments showed that Cr (VI) was measured accurately as well as selectively by PQAS DGT, whereas Cr (III) was not determined quantitatively. Compared with diphenylcarbazide spectrophotometric method (DPC), the measurement of Cr (VI) with PQAS DGT was agreement with that of DPC method in the industrial wastewater. PQAS-DGT device had been successfully deployed in local freshwater. The concentrations of Cr (VI) determined by PQAS DGT coupled with GFAAS in Nuer River, Ling River and North Lake were 0.73 ± 0.09 µg L(-1), 0.50 ± 0.07 µg L(-1) and 0.61 ± 0.07 µg L(-1), respectively. The results indicate that PQAS DGT device can be used for the selective sampling and measurement Cr (VI) in water and its detection limit is lower than that of DPC method.