A technique for preparing protein gradients on polymeric surfaces:

A technique for preparing micropatterns and gradients of proteins on polymeric substrates has been developed in this work. Peroxides were generated on the substrate surface by UV preirradiation and they initiated graft polymerization of acrylic acid (AA) onto the surface upon a second UV irradiation. Micropatterns and gradients of poly(acrylic acid) (PAA) were formed when the substrate was placed under or moved with respect to a photomask during UV preirradiation. Protein micropatterns and gradients were fabricated on the surface by covalently linking to the carboxyl groups on PAA chains. To test cell response to the protein gradient surfaces, PC12 pheochromocytoma cells were cultured on laminin-bound substrates in serum-free medium supplemented with nerve growth factor (NGF). It is found that both the attachment and neurite outgrowth behaviors of PC12 cells were dependent on the surface laminin density. However, the unreacted carboxyl groups on the polymer surface negatively affected PC12 cells. This weakened the positive influence from laminin.