BIOLOGICAL EFFECTS AND CYTOTOXICITY OF THE COMPOSITE COMPOSED BY TRICALCIUM PHOSPHATE AND GLUTARALDEHYDE CROSS-LINKED GELATIN

The purpose of this study was to prepare and evaluate the feasibility and cytocompatibility of a composite (GTG) as a large defect bone subs titute. The composite is combined with tricalcium phosphate ceramic pa rticles and glutaraldehyde cross-linked gelatin. Gelatin had been repo rted as an adhesive and biocompatible binder that could accelerate the recovery of damaged soft tissue, but the effects of gelatin when acti ng on the bone tissue is not clear. Thus, it is necessary to determine if the substances released from the GTG composite can facilitate the growth of bone cells. The substances released from the GTG composites after being soaked in deionized distilled water were analyzed by gas c hromatography (GC), ultraviolet and visible absorption spectroscopy (U V-VIS), and inductive-coupled plasma-atomic emission spectrometry (ICP -AES). The cytotoxicity of the GTG composites was assessed by cocultur e of rat osteoblasts in vitro. Extracts were obtained by soaking the G TG composites in deionized distilled water for 1, 2, 4, 7, 14, 28 and 42 d. The extract mixed with complete medium in a ratio of 1:1 was add ed into the cell culture wells containing 1 x 10(4) cells ml(-1) osteo blasts. After culturing for 2 days, the cells attached to the surface of wells were trypsinized and the number calculated by the Neubauer co unting-chamber under the optical microscope. Finally, three samples in each GTG group were examined by scanning electron microscopy (SEM) to observe the morphology of the osteoblasts attached to the surfaces of GTG composites. The examinations of osteoblasts cocultured with the d eveloped GTG composites were used to decide the ideal concentration of glutaraldehyde as a cross-linking agent. The results of extracts cocu ltured with osteoblasts showed that the extracts obtained from the 2, 4 and 8% glutaraldehyde cross-linked GTG composites would inhibit the growth of osteoblasts in the first 4 soaking days. During the 4-7 days soaking, the cell numbers quickly increased with the soaking time, th ereafter, the cell numbers almost reached a constant value. In the ana lyses of substances released from the GTG composites, it was found tha t the gelatin and calcium were gradually released from the GTG composi tes, which were supposed to be nutritious for the growth of the osteob last. The results of osteoblasts cocultured with the GTG composites sh owed that the concentration of glutaraldehyde used as a cross-linking agent should be lower than 8%. Compared to the GTF (composite combined with tricalcium phosphate ceramic particles and formaldehyde cross-li nked gelatin), GTG composites were much suitable for a large defect bo ne substitute in the near future. (C) 1998 Published by Elsevier Scien ce Ltd. All rights reserved.