Surface modification of microporous PVDF membranes for neuron culture

Microporous poly(vinylidene fluoride) (PVDF) membranes with either dense or porous surface were prepared by isothermal immersion-precipitation of a casting solution in coagulation baths of different strengths. Onto the membrane surface, amino acid (l-lysine) or 1,6-hexanediamine (HMDA) was chemically immobilized. The membrane was first grafted with poly(glycidyl methacrylate) (PGMA) by means of plasma-induced free radical polymerization. Then, l-lysine or 1,6-hexanediamine was reacted with epoxy groups in the grafted PGMA to create an ECM environment suited to cell culture. Neuronal cells were cultivated on the formed pristine and surface-modified PVDF membranes. It is found that neurons tend to aggregate into large clusters with neuritic branches on pristine PVDF membranes, whereas for those cultured on the PGMA/PVDF membranes, serious aggregation takes place as well, but without neurites being formed. In contrast, neurons did not aggregate on the l-lysine or HMDA-immobilized membrane. It is also interesting to find that a neuritic network inter-connecting cells is constructed for the former, yet no neurite is observed for the latter membrane. Such phenomenon is thought to be associated with the extra -COOH group in l-lysine with respect to HMDA.