Tethered bone morphogenetic protein-2 onto sulfonated-polyrotaxane based surfaces promotes osteogenic differentiation of MC3T3-E1 cells.

Sulfonated-polyrotaxane (PRX)-coated surfaces with tethered bone morphogenetic protein-2 (BMP-2) were designed for inducing osteogenic differentiation of MC3T3-E1 cells (preosteoblasts). Sulfonated-PRX triblock copolymers composed of sulfopropyl ether-modified α-cyclodextrins (α-CDs) threaded onto a poly(ethylene glycol) (PEG) chain as a PRX segment and poly(benzyl methacrylate) (PBzMA) at both terminals of the PEG as anchoring segments were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. BMP-2 tethering on the PRX surfaces with a large number of threaded α-CDs was suitable for the proliferation of MC3T3-E1 cells, regardless of the presence or absence of sulfopropyl groups. However, the differentiation of MC3T3-E1 cells according to mineralization assays and the gene expression levels of runt-related transcription factor 2, alkaline phosphatase, and osteocalcin was markedly enhanced by BMP-2 tethering on the sulfonated-PRX surface. These results suggest that sulfonated-PRX surfaces can effectively promote the proliferation and induce the osteogenic differentiation of MC3T3-E1 cells by the number of threaded α-CDs and tethered-BMP-2 using electrostatic interactions with sulfopropyl groups.