Poly(vinylidene) fluoride membranes coated by heparin/collagen layer-by-layer, smart biomimetic approaches for mesenchymal stem cell culture

Abstract

The use of piezoelectric materials in tissue engineering has grown over the years since bone inherent piezoelectricity was discovered. Combination of piezoelectric polymers with magnetostrictive nanoparticles (MNPs) allows magnetoelectric stimulation of cells by applying an external magnetic field. This magnetic field deforms the mangetostrictive nanoparticles within the polymer matrix, deforming the polymer itself, which leads to a surface charge variation, due to the piezoelectric effect. Poly(vinylidene) fluoride (PVDF) is the piezoelectric polymer with the largest piezoelectric coefficients, which makes it a perfect candidate for osteogenic differentiation. In this study we present PVDF membranes containing magnetostrictive nanoparticles and a biomimetic layer-by-layer (LbL) coating as candidates for mesenchymal stem cells culture. PVDF membranes 20 % (w/v), without and with cobalt ferrite oxide (PVDF-CFO) 10 % (w/w), were produced by non-solvent induced phase separation (NIPS). PVDF and PVDF-CFO membranes were found to be asymmetric, with a skin-like surface. Their crystallinity degree ranged from 65 % to 61 % and their electroactive -phase content, was 51.8 % and 55.6 % for PVDF and PVDF-CFO, respectively. Amine groups were grafted on the membrane’s surface, by using an alkali treatment, providing positive charges for the assembly of heparin/collagen layers by LbL technique. Five layers of each polyelectrolyte were deposited, ending in a collagen one. Ninhydrin test and X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of free amines on the surface, indicative of a homogeneous LbL coating. Human mesenchymal stem cells (hMSC) were used to test cell proliferation in a short-term culture (1,3 and 7 days). Nucleus cell counting showed that LbL favored cell proliferation in PVDF-CFO membranes compared with non-coated ones.