The effects of dimethyl 3,3'-dithiobispropionimidate di-hydrochloride cross-linking of collagen and gelatin coating on porous spherical biphasic calcium phosphate granules.

Collagen- and gelatin-coated porous spherical granule was prepared by slurry dripping process using biphasic calcium phosphate powder. The coating was stabilized by cross-linking with dimethyl 3,3'-dithiobispropionimidate di-hydrogenchloride (DTBP). Afer DTBP cross-linking, the nanostructure of collagen- and gelatin-coated surfaces was changed from smooth to fibrous and net-like structure. Excellent cross-linking of the coating was seen as indicated by the differential scanning calorimetry thermogram and the Fourier transform infrared spectroscopy spectra. After cross-linking the relative intensities of the Fourier transform infrared spectroscopy peaks were decreased and amide bands were shifted to the left. The interaction of gelatin with DTBP cross-linking agent was stronger than that with collagen according to differential scanning calorimetry and Fourier transform infrared spectroscopy results. The compressive strength of the granular bone substitutes increased significantly after the coating process and gelatin coated biphasic calcium phosphate granules showed highest value at 3.68 MPa after cross-linking. Porosity was greater than 63% and did not change significantly with coating. Biocompatibility investigation by in vitro and in vivo showed that the coating improved the cell proliferation marginally. However, the cross-linking process did not jeopardize the excellent biocompatibility of collagen and gelatin. The in vivo study confirms better bone formation behavior of the cross-linked gelatin and collagen coated samples investigated for 8 weeks in vivo.