The fate of hydrous titanium dioxide nanoparticles (nTiO2, diameter 50-500 nm) in the aquatic environment was analyzed using the MicrotoxTM luminescent bacterial toxicity test, the in vitro developmental toxicity test using zebrafish (Danio rerio), and the in vivo freshwater bioaccumulation test using a brown trout (Salmo trutta). nTiO2 solutions were found to be toxic in the Microtox assay, with EC50 values of 8.9 and 3.1 mg L(-1) after 28 days exposure at pH 7 and 9, respectively. nTiO2 was found to be bioavailable, with bioaccumulation factors of > 10 in zebrafish at 42 days (and > 4 in brown trout at 14 days). The whole-body concentration of nTiO2 was highest in the ovaries of the zebrafish, followed by the gills, heart, liver, intestines, and brain. The presence of nTiO2 was detected in larval and reproductive tissues of S. trutta, but not in the liver, gills, kidney, or brain. nTiO2 was also found in the liver of the adult fish. Histological examinations of tissues from the zebrafish and brown trout confirmed the presence of nTiO2 particles in the liver and gonads, while there was no indication of aggregation or agglomeration of nTiO2 particles in the body tissues.
The development of porous titanium implants is essential for successful clinical use of titanium dental implants. In this study, we investigated whether a hydroxyapatite (HA) coating on titanium implants is capable of enhancing the osseointegration process. A titanium implant with a diameter of 4 mm and a length of 5 mm was used for this study. The surface of the implant was ground to a roughness of Ra = 0.25 microm and HA coating was deposited on the surface of the implant. The HA coating consisted of a mixture of hydroxyapatite and SiO2, which was obtained by a sol-gel method. The surface of the HA coated implant was characterized by X-ray diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. In vitro, the bone cells were cultured on the surface of the HA coated implant. The bone cells were stained with alkaline phosphatase (ALP) staining kit.
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