Porous silicon substrates support osteogenic differentiation of mesenchymal stem cells

Osteoblastic differentiation of mesenchymal stem cells (MSCs) on planar silicon (bare silicon), and porous silicon (microporous and nanoporous) fabricated by electrochemical etching of silicon in ethanol-HF based electrolyte was investigated. MSCs were allowed to differentiate into osteoblasts on all the three substrates with the addition of osteogenic differentiation media, and observations were made at an interval of day 7, day 14, and day 21. Immunofluorescence assays were conducted to observe for expressions of bone proteins such as osteopontin (OP) and osteonectin (ON) that are considered as markers of osteogenic lineage. Cell proliferation was determined using the MTT assay. Calcium mineral deposits of these differentiated MSCs were quantified using the Alizarin Red assay. The differentiated MSCs tend to produce both OP and ON on all the three substrates and the amount of OP and ON expressed increased overtime. A decrease in cell proliferation was observed on day 14 in comparison to day 7. Quantification of calcium mineral deposits show that nanoporous-Si induces the highest level of calcium mineral production in comparison to bare and microporous-Si when cultured for a period of 21 days. The data suggest that nanoporous silicon is a suitable scaffold for the differentiation of MSCs to osteoblasts, and provides future potentials for its use in animal experiments.