Casein phosphopeptides-vaterite calcium carbonate enhance cytocompatibility and osteoinductivity of poly(l -lactic acid)

Abstract

Although calcium carbonate has been proved to be effective in neutralizing the acid degradation products of poly(l-lactic acid) (PLLA), it has no osteoinductivity. In this study, casein phosphopeptides (CPPs)-containing CaCO3 vaterite were synthesized by fast precipitation in an aqueous solution of CaCl2, Na2CO3, and 2 mg/ml of CPPs. CaCO3–PLLA composite membranes (P-vaterite–CPP) were prepared (CaCO3/PLLA =1:2) and exhibited uniform structure and increased hydrophilicity. These composite membranes enhanced hydroxyapatite formation after incubated in simulated body fluid at 37°C for 7 days. The P-vaterite–CPP membranes promoted human bone marrow stromal cells (hBMSCs) proliferation 4 and 7 days after seeding. Scanning electron microscope images of hBMSCs on the composite membranes exhibited a polygonal and unevenly spreading morphology. Immunofluorescent staining of cytoskeleton and focal adhesion showed that hBMSCs had more stress fibers and were more spreading, indicating a good cell adhesion on the CPPs-containing composite membranes. Osteogenesis related genes (alkaline phosphatase, collagen type, osteocalcin, and osteopontin) expressions were significantly higher on the CPPs-containing membranes than those on the CPPs-free membranes (P < 0.05). It can be concluded that the addition of CPPs induces vaterite formation and thus improve cytocompatibility and osteoinductivity of PLLA. POLYM. COMPOS., 36:1213–1223, 2015. © 2014 Society of Plastics Engineers