Poly L lysine-modified PHBV based nanofibrous scaffolds for bone cell mineralization and osteogenic differentiation

Regulation of cell-scaffold interactions is an important factor for modulating the cellular activity in bone tissue engineering applications. Tailoring the physical and chemical properties of the scaffolds to better mimic the extracellular matrix (ECM) of native bone is a more effective strategy for enhancing the cell-scaffold interactions. In this work, we aim at investigating the novel poly L lysine (PLL)-modified poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-hydroxyapatite/bredigite (HABR) nanofibrous scaffolds towards bone tissue engineering. The PHBV-HABR scaffolds were modified with PLL through two different routes: (i) covalent attachment of PLL to the surface of PHBV-HABR nanofibrous scaffolds using EDC/NHS, and (ii) blending of PLL with PHBV-HABR nanofibers. Characterization of the resultant nanofibrous scaffolds was done using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, contact angle, atomic force microscopy (AFM) and tensile strength. According to the results obtained from contact angle measurements and AFM analysis, PLL surface modified PHBV-HABR scaffolds exhibited higher wettability and surface roughness than PLL blended PHBV-HABR and unmodified PHBV-HABR scaffolds. Cell–scaffold interactions were investigated by culturing human fetal osteoblast (hFob) cells, whereby the cell proliferation, mineralization, alkaline phosphatase activity, and bone protein expression was evaluated. Results demonstrated that the cells seeded on PLL surface modified PHBV-HABR displayed enhanced cell adhesion and proliferation compared to cells seeded on other scaffolds, as proved by SEM and MTS assay. Additionally, the enhanced osteogenic differentiation of hFob incubated on PLL surface modified PHBV-HABR was confirmed by ALP activity, alizarin red-s staining and immunofluorescence staining of osteocalcin, suggesting the potential application of PLL surface modified PHBV-HABR nanofibrous scaffolds for bone regeneration.