IMMOBILIZATION OF CALCIUM-PHOSPHATE NANO-CLUSTERS INTO ALKOXY-DERIVEDPOROUS TIO2 COATINGS

Alkoxy-derived porous coatings of titanium oxide were fabricated on co mmercially pure titanium substrates by an electrochemical method in me thanolic electrolytes. Nano-clusters of brushite (CaHPO4 . 2H(2)O) wer e immobilized into the pores of the oxide network by reacting these co atings in acidic calcium phosphate solutions at 50 degrees C. The acid -base reaction between calcium phosphate solutions and the hydroxyl gr oups of the oxide network resulted in the formation of nano-clusters o f brushite crystals immobilized inside the oxide pores. This treatment resulted in the conversion of the porous oxide network into a coheren t mass with improved physical integrity. Nano-clusters of brushite cry stals immobilized in the oxide matrix were converted into amorphous ca lcium phosphate (ACP) and poorly crystallized hydroxyapatite (HA) by f urther treatment of the oxide in alkaline solutions. The porous oxide coating also reacted strongly with concentrated phosphoric acid. The p hosphate-modified oxide resulting from this reaction was further treat ed in calcium hydroxide solution to form nano-clusters of poorly cryst allized HA within the oxide network.