A new porous titanium-nickel alloy: part 2. Sensitization, irritation and acute systemic toxicity evaluation.

Porous titanium-nickel (PTN) represents a new biomaterial with orthopedic applications as a long-term implant. Because of its nickel content, PTN was tested for its potential to stimulate sensitization, irritation, and systemic toxicity reactions after semi-physiological extraction. In order to do so, an in vivo biocompatibility evaluation was performed following three ISO-standardized methods using accepted animal models for immunity testing: the classical skin sensitization assay (Buehler patch test) in guinea pigs, the rabbit intracutaneous test, and the systemic injection test in mice. The Buehler patch test in guinea pigs revealed no significant change in skin reactions such as erythema or swelling between the induction and the challenge period. In the rabbit intracutaneous irritation test, no irritation or sensitization reactions were observed in saline-extracted PTN samples. Negligible to slight irritation was observed at some of the sites involving PTN samples extracted in cottonseed oil, however the resulting primary irritation index was similar to the one elicited by the blank solution itself. Finally, no toxic symptoms were observed with any of the mice injected with porous titanium-nickel extracts during the acute systemic toxicity test. Based on the above results, porous titanium-nickel is considered to be a non-sensitizing, non-irritant, and non-toxic biomaterial for medical applications.