Osteogenic differentiation of marrow stromal cells cultured on nanoporous alumina surfaces

A major goal in orthopedic biomaterials research is to design implant surfaces, which will enhance osseointegration in vivo. Several microscale as well as nanoscale architectures have been shown to significantly affect the functionality of bone cells i.e., osteoblasts. In this work, nanoporous alumina surfaces fabricated by a two-step anodization process were used. The nanostructure of these surfaces can be controlled by varying the voltage used for anodization process. Marrow stromal cells were isolated from mice and seeded on nanoporous and amorphous (control) alumina surfaces. Cell adhesion, proliferation, and viability were investigated for up to 7 days of culture. Furthermore, the cell functionality was investigated by calcein staining. The cells were provided with differentiation media after 7 days of culture. The alkaline phosphatase (ALP) activity and matrix production were quantified using a colorimetric assay and X-ray photoelectron spectroscopy (XPS) for up to 3 weeks of culture (2 weeks after providing differentiation media). Further, scanning electron microscopy (SEM) was used to investigate osteoblast morphology on these nanoporous surfaces. Over the 3-week study, the nanoporous alumina surfaces demonstrated approximately 45% increase in cell adhesion, proliferation, and viability, 35% increase in ALP activity, and 50% increase in matrix production when compared with the control surfaces.