Biocompatibility and degradation of an injectible nano-sized composite bone substitute
- Author:
Liang GE
1
Author Information
1. Department of Orthopedics
- Publication Type:Journal Article
- From:
Academic Journal of Second Military Medical University
2006;27(10):1121-1126
- CountryChina
- Language:Chinese
-
Abstract:
Objective: To evaluate the in vitro cytotoxicity, in vivo response and degradation of a new injectable nanohydroxyapatite(n-HA)/calcium sulphate hemihydrate(CSH) bone substitute in rabbits and to discuss its possible bio-degeneration mechanism. Methods: Pure CSH, n-HA, 10%n-HA+CSH, 20%n-HA+CSH, and 40%n-HA+CSH (the last 3 containing 10%, 20%, and 40% n-HA, respectively) were subjected to MTT assay for their in vitro cytotoxicities. 20%n-HA+CSH was implanted into rabbits' muscle and bone defects in the right femur, and the general conditions of rabbits, the pathological and TEM manifestations of tissues, and the imaging alterations were all observed 5 days, 2, 3, 4, 6, 8, and 12 weeks after implantation. Results: Test of cytotoxicity showed that the average cell proliferation rate was over 77% after treated with the solutions of 5 bone substitutes(P<0.05), with the cytotoxicity being 0-1 (non-toxic). No general reaction was found in rabbits implanted with 20%n-HA+CSH and the weight of animals increased steadily. 20%n-HA+CSH implanted in the muscle underwent a layer-by-layer degradation from 5 days after implantation and was almost completely degraded after 8 weeks, with no fibrosis, calcification or ectopic ossification. H-E staining showed that at the early stage the degraded materials were surrounded and wrapped by inflammatory cells; the fibroblasts gradually turned into fibrous cells encircling the degraded material. TEM observations indicated that the degradation was characterized by a cytophagic process and no cytotoxic signs were found in the phagocytes after phagocytosis. X-ray examination showed new osteoid and premature trabeculae scattered over the defective region 6 weeks after implantation, and there was normal trabecular tissue 8-12 weeks later. Conclusion: 20%n-HA+CSH has no obvious in vitro cytotoxicity, but has good biocompatibility. The in vivo degradation of 20%n-HA+CSH may be mediated by cytophagic process in a layer-by-layer manner. It degrades completely within 8-12 weeks, which is suitable for bone regeneration.
