Association of human growth hormone and calcium phosphate by dynamic compaction: in vitro biocompatibility and bioactivity.

The association of therapeutic agents with biomaterials has been achieved through various techniques, such as coating of the ceramic block surface or drug incorporation into ceramics. The dynamic compaction method recently was developed to consolidate drug-loaded calcium phosphate powder without a sintering step. In the present work, human recombinant growth hormone was loaded on biphasic calcium phosphate powder and consolidated by a specific process of cold sintering (dynamic compaction). Analyses of the biocompatibility of compacted pellets (mouse L929 fibroblastic cell culture) and the bioactivity of the drugs released by them (growth hormone bioassay) were performed. This report demonstrates the biocompatibility of the compacts prepared by dynamic compaction. L929 cell proliferation was maintained and the capacity to secrete fibronectin was conserved in the presence of compacted materials. Comparison of released growth hormone integrity, revealed by radioimmunoassay and eluted stain bioassay, has shown that the biological activity of growth hormone was totally preserved after dynamic compaction. However, 35% of loaded growth hormone was not released in our experimental conditions, probably because of the inaccessibility of growth hormone within the granulated compacts. Dynamic compaction shows good potential for the production of biomaterials capable of releasing therapeutic agents in situ.