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The objective of this study was to determine how the incorporation of surface-modified alumoxane nanoparticles into a biodegradable fumarate-based polymer affects in vivo bone biocompatibility (characterized by direct bone contact and bone ingrowth) and in vivo degradability. Porous scaffolds were fabricated from four materials: poly(propylene fumarate)/ propylene fumarate-diacrylate (PPF/PF-DA) polymer alone; a macrocomposite consisting of PPF/ PF-DA polymer with boehmite microparticles; a nanocomposite composed of PPF/PF-DA polymer and mechanically-reinforcing surface-modified alumoxane nanoparticles; and a low molecular weight PPF polymer alone (tested as a degradation control). Scaffolds were implanted in the lateral femoral condyle of adult goats for 12 weeks and evaluated by micro-computed tomography and histological analysis. For all material groups, small amounts of bone, some soft tissue, and a few inflammatory elements were observed within the pores of scaffolds, though many pores remained empty or filled with fluid only. Direct contact between scaffolds and surrounding bone tissue was also observed in all scaffold types, though less commonly. Minimal in vivo degradation occurred during the 12 weeks of implantation in all materials. These results demonstrate that the incorporation of alumoxane nanoparticles into porous PPF/PF-DA scaffolds does not significantly alter in vivo bone biocompatibility or degradation.

Biomimetically deposited calcium phosphate-based coatings of prostheses can serve as a vehicle for the targeted delivery of growth factors to the local implant environment. Based on indirect evidence in previous studies we hypothesize that such agents are liberated gradually from the coating via a cell-mediated degradation. In the present study, we tested this hypothesis by investigating the release mechanism and its kinetics by use of a radiolabeled osteogenic agent ( I-BMP-2) under conditions in which native cell populations with a coating-degradative potential were either absent or present. The release of I-BMP-2 was monitored for 5 weeks, either in vitro or after implantation at an ectopic (subcutaneous) site in rats in vivo. Only from implants that bore a coating-incorporated depot of bone morphogenetic protein 2 (BMP-2) was the agent released slowly and steadily over 5 weeks, that is, 50% of the loaded dose was liberated in vivo (5 to 10% weekly), as against 14.6% in vitro (less than 1% weekly). The coatings bearing an incorporated depot of BMP-2 underwent significant cell-mediated degradation, whereas under cell-free conditions no degradation occurred, and the spontaneous release of BMP-2 was negligible. Our findings confirm this carrier system to be a suitable vehicle for the sustained and cell-mediated delivery of BMP-2. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2363-2371, 2018.

No abstract

The results of this study indicate that a substantial improvement of the osteogenic response to titanium implants can be achieved by the deposition of an electrosprayed CaP coating. The enrichment of the coating with 1 microg TGF-beta1 has only a marginal effect.