Modulation of RGD-functionalized polyelectrolyte multilayer membranes for promoting osteoblast function.

Layer-by-layer deposition of polyelectrolyte multilayer (PEM) membranes has recently been applied successfully to a number of biomedical applications. This simple and versatile technique provides a broad surface modification platform, for example, for the display of biomolecules such as cell-adhesion peptides. In this work, we investigated the effects of PEM coatings on RGD-immobilization and osteoblast cell culture. RGD-containing peptides were conjugated to the amino groups of poly(allylamine hydrochloride) (PAH), and then adsorbed on top of 10-layer PAH/poly(acrylic acid) (PAA) multilayer membranes that were assembled at either pH 2.0 or pH 6.5. MG63 osteoblast-like cells were then seeded and cultured on the RGD-conjugated surfaces. We found that the cells adhered to and grew better on the RGD-conjugated PEM membranes. Furthermore, the cells grew better on the RGD-conjugated PEM coatings assembled at pH 6.5 than those assembled at pH 2.0. On the other hand, MG63 cells exhibited better differentiated phenotype on the pH 2.0 coatings compared to the pH 6.5 coatings with respect to alkaline phosphatase activity and calcium deposition, while cells did not express osteoblast phenotype on the PAH surfaces. These results clearly show that the base PEM membranes play an important role in RGD-immobilization and osteoblast functions.