Dental Pulp Stem Cells Adhesion/Proliferation On Porous Silicon Scaffold

Porous silicon (pSi) is a promising biomaterial that is non-toxic and bioresorbable. Surface modifications can offer control over the degradation rate and can also impart properties that promote cell adhesion. Coupling the capacities of Dental Pulp Stem Cells (DPSC) with the pSi properties is a promising tool in regenerative medicine. P-type silicon wafers were etched at a constant current density of 30 mA/cm2 or 300 mA/cm2. The samples were oxidized or hydrosililzed. The topography of surface modified pSi samples was analysed by scanning electronic microscope (SEM) and water contact angle measurement. Dental pulp cells were collected from healthy adults and analyzed by flow cytometry. Cells were incubated on pSi samples for either 4 hours or 24 hours. Cellular morphology on pSi was evaluated with fluorescein diacetate (FDA) staining. Cell proliferation was measured through acid phosphatase activity. After oxidation or hydrosililation, at either 30 or 300 mA/cm2, pSi wafers became clearly hydrophilic. SEM revealed a highly porous surface, with a mean size of pore of 10nm±2 for 30mA/cm2, and 21nm±3 for 300mA/cm2. With flow cytometry, cells were 17% CD34+ and 77% CD146+. Acid phosphatase assay showed that samples etched with 300mA/cm2 tend to offer a better adhesion for cells; the same tendency was observed for hydrosililation treatment. Cells presented the same morphology on pSi as on culture plate. Surface modification, by turning pSi from hydrophobic to hydrophilic, allows cell adhesion. The two tested sizes of pore and the two tested surface treatments allowed adhesion of DPSC. Cell morphology on pSi was similar to culture plates. pSi resorption time is influenced by surface modification and DPSC adhesion is possible on both surface modifications, highlighting an interest for cell/tissue graft. And the tunable size of pore might permit to incorporate growth factors or nutriments inside the scaffold.