Influence of different polymeric gels on the ectopic bone forming ability of an osteoinductive biphasic calcium phosphate ceramic.

To evaluate moldable osteoinductive putties for bone repair we combined microstructured biphasic calcium phosphate (BCP) particles with five different polymeric gels, carboxymethyl cellulose (CMC), Pluronic(®) F-127 (PLU), polyvinyl alcohol (PVA), chitosan (CHI) and alginate (ALG). In vitro gel dissolution showed that CMC, PLU and ALG gels dissolved rapidly (within hours), while the CHI gel took several days and the PVA gel did not dissolve within 2 weeks. Implanting the putty formulations into sheep muscle for 12 weeks demonstrated ectopic bone formation in the control BCP group as well as the putties prepared with dissolving gels (CMC, PLU, ALG and CHI). Bone was not seen in the putty comprising PVA. Quantitative data showed that the CMC and PLU gels did not significantly affect the osteoinductivity of BCP granules, while the ALG and CHI gels showed a significant decrease in bone formation. These results suggest that the dissolvability and chemistry of the gels may be factors affecting the osteoinduction of the putties.