Culture of mammalian cells on patterned superhydrophilic/superhydrophobic silicon nanowire arrays

Interfacing nanowires and living cells is highly interesting in various fields including biomedical implants, biosensors or drug delivery. Vertically aligned silicon nanowire (SiNW) arrays prepared by the stain etching technique were investigated in this study. Chemical modification with octadecyltrichlorosilane (OTS) led to the formation of superhydrophobic SiNW surface with a contact angle around 160 degrees. A micropatterned superhydrophilic/superhydrophobic SiNW surface was fabricated using standard optical lithography techniques. Here we report on Chinese Hamster Ovary K1 (CHO) cell culture on patterned superhydrophilic/superhydrophobic silicon nanowire surfaces. It was found that the cells adhered selectively to the superhydrophilic regions while cell adhesion was almost completely suppressed on the superhydrophobic surface. Transmission electron microscopy analysis showed that the cell cytoplasmic projections penetrate the hydrophilic silicon nanowires layer and coat the nanowires, leading to an intimate surface contact and thus a strong adhesion. On the superhydrophobic surface, the cell cytoplasmic projections remained on the top of wires. The nonfouling of the superhydrophobic SiNW substrate was attributed to a stable Cassie-Baxter state, limiting the contact with the culture medium. Another interesting finding from this study is the corrosion of the superhydrophilic SiNW surface in phosphate-buffered saline (PBS) solution.