In Vitro Osteogenic Differentiation and Biomineralization Facet of Phosphorylated Porous Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Poly(ε-caprolactone): an Osteogenic Platform for Regenerative Bone Tissue Engineering

A regenerative construct that mimics the natural bone tissue microenvironment and establishes a better cell-material interface is mandatory in reconstructive orthopedics. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a natural polyester that holds excellent biocompatibility and favorable biofunctional features, is restricted for its independent use as a bone regenerative scaffold owing to its fragile nature, long degradation time, and high crystallinity. In this context, sustaining the pluses, PHBV was functionalized by controlled phosphorylation (p-PHBV) through an established method reported by our group to introduce hydrophilicity and trigger biomimetic mineralization and osteogenesis. Subsequently, blends of p-PHBV with poly(ε-caprolactone) (p-PHBV/PCL) in varying ratios (20:80, 30:70, 40:60, and 50:50) were prepared to complement each other. A systematic approach unveiled that the p-PHBV/PCL37 (p-PHBV/PCL is 30:70) has the best features, including decent water uptake capacity and gradual weight loss at ambient physiological pH and temperature, among the compositions. The phosphorylation has enhanced the hydrophilicity (water uptake and contact angle) and added surface roughness (SEM) to the polymer matrix: it promoted adherence of rat bone marrow mesenchymal stem cells (rBMSCs) to p-PHBV/PCL37 (confocal imaging) and eventually primed the calcium phosphate nucleation and matrix mineralization (alizarin red S and von Kossa staining) than nonphosphorylated PHBV/PCL37. The p-PHBV/PCL37 also exhibited hints of surface erosion that progressed to about 36% weight loss in 6 months. Further, F-actin remodeling and the time-sensitive relationship of osteogenic markers, alkaline phosphatase and osteocalcin, expression (ELISA and qRT-PCR), as evidenced in the cells, validate taking up p-PHBV/PCL37 as an efficient bone regenerative platform. In summary, the p-PHBV/PCL37 as such could initiate lineage selection of rBMSCs to the osteogenic differentiation process that aids osteoblast formation.