BME Seminar Series: Anant Agrawal, M.S. Candidate

Porous Nanocrystalline Silicon Membranes as Highly Permeable and Molecularly Thin Substrates for Cell Culture Applications

Abstract

Porous nanocrystalline silicon (pnc-Si) is new type of silicon material with potential uses in lab-on-a-chip devices, cell culture, tissue engineering, biosensing and drug delivery. The pnc-Si material is a 15 nm thin, free-standing, nanoporous membrane made with highly scalable silicon manufacturing. Because pnc-Si membranes are approximately 1000 times thinner than any polymeric membrane, the permeability of pnc-Si to small solutes is orders-of-magnitude greater than conventional materials. As cell culture substrates, pnc-Si membranes could overcome the shortcomings of membrane materials used in commercial transwell devices and enable new types of culture devices for the precise control and manipulation of cellular microenvironments. The current study investigates the feasibility of pnc-Si as a cell culture substrate by comparing cell adhesion, morphology, growth kinetics and viability on pnc-Si to conventional tissue culture substrates. By each of these metrics, the behaviors of both immortalized cells (3T3-L1 fibroblast cell line) and primary vascular endothelial cells (HUVEC) were found to be highly similar on pnc-Si, polystyrene and glass.

Significantly, pnc-Si was found to dissolve in cell culture media over several days without cytotoxic effects and membrane stability could be tuned by modifying the density of a superficial native oxide layer through post production rapid thermal processing and additional surface treatment like aminosilanization. The adhesion of HUVEC to treated pnc-Si transwell hybrids was found to be comparable to commercial transwells. To demonstrate one of the novel experiments enabled by pnc-Si: co-culture across a molecularly-thin highly permeable membrane, different populations of neutrophils were attached to opposite sides of pnc-Si membranes and imaged via fluorescence microscopy. Collectively, the results establish pnc-Si as a viable new substrate for cell culture and a new type of degradable biomaterial. Pnc-Si membranes should find many uses in bioscience including the study of molecular transport through cell monolayers, as molecularly thin dividers for the study of cell-cell communication, and as biodegradable scaffolds for three-dimensional tissue constructs.