Transforming growth factor (TGF)-beta1 releasing tricalcium phosphate/chitosan microgranules as bone substitutes.

Purpose: Tricalcium phosphate (TCP)/chitosan composite microgranules were developed as bone substitutes and tissue engineering scaffolds with the aim of obtaining a high bone forming efficacy. The microgranules have the ability to fill various types of defect sites with closer packing. In addition, the transforming growth factor-beta 1 (TGF-beta1) was added to the microgranules in order to improve bone-healing efficacy.

Methods: TCP/chitosan microgranules were fabricated by dropping a TCP suspended chitosan solution into a NaOH/ethanol solution. TGF-beta1 was incorporated into the TCP/chitosan microgranules by soaking the microgranules into the TGF-beta1 solution. Scanning electron microscopy (SEM) observations as well as experiments examining the release of TGF-beta1 from chitosan and TCP/chitosan microgranules were performed. SEM was used to examine the cell morphologies on the microgranules, and the extent of cell proliferation was evaluated using a dimethyl-thiazol tetrazolium bromide (MTT) assay. The differentiated cell function was assessed by measuring the alkaline phosphatase activity as well as performing an osteocalcin assay.

Results: The size of the prepared microgranules was 350-500 microm and TCP powders were observed on the surface of the microgranules. TGF-beta1 was released from the TCP/chitosan microgranules at a therapeutic concentration for 4 weeks. The proliferation of osteoblasts on the TGF-beta1 loaded microgranules was the highest among the microgranules. SEM indicated that the seeded osteoblastic cells were firmly attached to the microgranules and proliferated in a multilayer fashion. The ALPase activity and osteocalcin content of all the samples increased during the culture period.

Conclusions: These results suggest that the TCP/chitosan microgranules are potential bone substitutes with a drug releasing capacity and a osteoblastic cells culture scaffold.