(123e) In Vitro Effects of Polyurethane Composites with Surface Modified Fillers On the Differentiation of Osteoclastic Cells

Injectable polyurethane(PU)/mineralized-filler composites offer a minimally invasive procedure for treating bone defects. In order to remodel effectively, these materials must undergo coupled cellular resorption and new bone deposition after implantation. PU/mineralized-filler composites have been shown to support new bone deposition. However, since the first phase of remodeling involves osteoclastic resorption, the objective of the present work was to study the effect of PU composites with surface modified fillers on the differentiation and function of osteoclastic cells in vitro. It was hypothesized that differences in the scaffold’s characteristics (partly determined by the interactions between the filler and the matrix) could affect the cellular behavior. Allograft bovine bone and b-tricalcium phosphate (b-TCP) were surface modified to promote interactions with the PU phase. Allograft bone was surface demineralized, and polycaprolactone (PCL) was grafted on the surface of b-TCP particles. No significant differences were observed between the mechanical behavior of the bone composites, while the grafted PCL on b-TCP significantly improved the mechanical properties of the composites compared to the unmodified b-TCP. Osteoclast precursor cells were purified from mouse bone marrow cells and seeded on the composites and dentin (control). The cells were fed with macrophage colony stimulating factor (MCSF) and receptor activator of nuclear factor kB ligand (RANKL) and cultured up to 21 days. Differentiation rates were monitored by staining the samples for tartrate resistant acid phosphatase (TRAP) at days 5,13, and 21. Differences between the differentiation rates of the osteoclastic-like cells seeded on composites with un-modified vs. modified fillers were identified suggesting that the surface chemistry of the fillers impacts the cellular behavior. This information provides insight into the formulation of bioactive PU composites that actively participate in the bone healing process.