BACKGROUND:There is a lack of the research concerning the biocompatibility of nano-hydroxyapatite/polyphenylene sulfide (nHA/PPS) composites.OBJECTIVE:To evaluate the in vivo biocompatibility of nHA/PPS composites based on the completed research in vitro.METHODS:Systemic toxicity test:Sprague-Dawley rats were given the intraperitoneal injection of nHA/PPS extract or normal saline.The general situation,body mass and the histological changes of the liver and kidney were observed at 72 hours after injection.Delayed type hypersensitivity test:nHA/PPS extract or normal saline was injected subcutaneously into the back of the rats.Afterwards,skin irritation symptoms were observed at 72 hours.Local reaction experiment:nHA/PPS composites and polyethylene were respectively implanted into the back of the rats.The pathological changes of the implanted materials and their surrounding tissues were observed at 15 and 30 days after implantation.RESULTS AND CONCLUSION:(1) The rats were in good situation after nHA/PPS injection;the body mass increased steadily,which showed no significant difference from the control group (P ＜ 0.05);the morphology and color of the liver and kidney were normal,and the systemic toxicity of the composite materials was normal according to the degree of toxicity classification.(2) There were no obvious skin irritation symptoms after the subcutaneous injection of nHA/PPS composites,and the primary irritation index was less than 0.4,suggesting a low hypersensitivity.After implantation of nHA/PPS composites,there was no obvious degradation,absorption and rejection,and both the degree of inflammatory reaction (15 days ≤ level Ⅲ,30 days ≤ level Ⅱ) and the thickness of fibrous capsule (15 days ≤ level Ⅲ,30 days ≤ level Ⅱ) revealed the good biocompatibility of the composites.These results suggest that the nHA/PPS composites hold an excellent biocompatibility in vivo.