<i>In Vitro</i> Evaluation of Biomimetic Incorporation and Release Kinetics of BMP2 on Functionalized Bio-Oss<sup>®</sup> Block

Abstract

Objective: To functionalize the Bio-Oss® Block with biomimetic coating incorporating BMP2 and evaluate the release kinetics of the incorporated BMP2 In Vitro.Materials and methods: Bio-Oss® Blocks were prepared with the size of 7mm x 10mm x 4mm. Each block was immersed and suspended in 300ml 5-fold-concentrated modified Tyrode solution for 24 hours to form a seeding substratum. BMP2 at the concentration of 10ug/ml was added into 120ml supersaturated calcium phosphate solution and co-precipitated within the growing layer for 48 hours. The loading amount of incorporated BMP2 was determined using enzyme-linked immunosorbent assay . The surface characterization of the coating was evaluated by scanning electron microscopy. The distribution of coating-incorporated protein was mapped by a confocal laser-scanning microscope. BMP2 release profiles from the functionalized blocks under different circumstances were monitored. Results: The total loading of BMP2 in a BMP2-incorporated-block is 50.35 ± 6.41μg. The crystalline coating layer deposited on both the superficial surfaces and internal surfaces of the blocks. The BMP2 was distributed homogeneously in the whole block. The coating-incorporated depot of BMP2 barely released in Tris-HCl buffered solution (pH of 7.4). However, when the functionalized blocks were immersed in Citric acid-Sodium citrate buffered solution (pH of 5), or were co-cultured with osteoclasts, the coating-incorporated BMP2 depot showed a sustained release.Conclusions: BMP2 were successfully incorporated onto and into the Bio-Oss® Blocks. A sustained delivery of a lower concentration of BMP2 (μg-BMP2) from Bio-Oss® Block was achieved in acidic solution or with the mediation of osteoclasts.