Enhanced bone cell functions on poly(ε-caprolactone) triacrylate networks grafted with polyhedral oligomeric silsesquioxane nanocages

Abstract

Poly(ε-caprolactone) triacrylate (PCLTA) developed in our laboratory is a photo-crosslinkable, injectable, and biodegradable polymeric biomaterial for diverse tissue engineering applications. To engineer its physical properties for bone regeneration, we incorporated PCLTA networks with a photo-reactive methacryl isobutyl polyhedral oligomeric silsesquioxane (POSS), which is a silicon-based monomer with a nano-sized cage. Homogeneous nanohybrid networks were prepared by photo-crosslinking POSS with two PCLTAs having molecular weights of ∼7000 and ∼20,000 g/mol at the POSS weight compositions (ϕPOSS) of 0–20%. The lower-molecular-weight PCLTA resulted in amorphous networks while the higher one resulted in semi-crystalline networks. POSS nanocages tethered in the PCLTA networks greatly enhanced the mechanical and rheological properties, but did not significantly alter the surface wettability and the capability of adsorbing serum proteins from cell culture media. Better mouse pre-osteoblastic MC3T3-E1 cell attachment, spreading, and proliferation were found on the stiffer PCLTA20k networks than on the PCLTA7k ones, and on the networks with ϕPOSS of 10–20% than the networks containing no POSS. Mineralization of MC3T3-E1 cell cultured for two weeks showed a significantly higher alkaline phosphatase activity and more mineralized nodules on the PCLTA20k networks with ϕPOSS of 10–20%, in correlation with their enhanced mechanical properties. The present results indicated that this series of nanohybrid PCLTA/POSS networks with improved mechanical properties and osteoconductivity has great potential as scaffolding materials for bone repair and regeneration.