OBJECTIVETo evaluate the biocompatibility of pectin/poly vinyl alcohol composite (CoPP) hydrogel for use as a prosthetic nucleus pulposus material.

METHODSThe in vitro cytotoxicity of CoPP hydrogel was tested in NCTC L929 cells, which were divided into normal control group, negative control group [treated with poly (vinyl alcohol) hydrogel, PVA], experimental group (treated with CoPP) and positive control group (0.64% phenol). The optical density of the cells on days 2, 4, and 7 of the corresponding treatments was determined and the relative growth rate calculated. For in vivo biocompatibility evaluation, dehydrated CoPP and PVA hydrogel were respectively implanted into the left and right gluteus of SD rats, and the wound healing and general status were observed. The muscular tissues containing the implants were taken 1, 4, and 12 weeks after the implantation for gross observation and microscopic observation of the inflammatory cell infiltration (ICI) and formation of the fibrous capsulation around the implants.

RESULTSThe L929 cells incubated with PVA and CoPP group both grew well, with relative growth rate over 80% and 75%, respectively. The cytotoxicity of PVA and CoPP was both lower than grade 1. In contrast, the relative growth rate in the positive control group was below 24%, with cytotoxicity over grade 4. In the SD rats, ICI of grade IV occurred in the muscular tissues around the PVA and CoPP implants at 1 week without formation of complete capsule, and at 4 weeks, ICI was lowered to grade 1 with grade 4 capsular reaction. Till week 12, the ICI and capsular reaction were both first grade.

CONCLUSIONCoPP hydrogel has in vitro grade 0 or 1 cytotoxicity and causes only mild inflammation after implantation in rats, suggesting good biocompatibility of the material.