I-Corps: Commercialization of injection molded nanostructured biomedical consumables

Lehigh University, Bethlehem PA

Investigators

Abstract

Directing and modulating the fate of stem cells poses a primary challenge in the bioscience community. Control of cell behavior is traditionally accomplished using chemical methods; and these methods are inherently useful, but difficulties with cell stability do arise. Currently, cells are grown on tissue culture treated Petri dishes (made from polystyrene or glass). These products, while inexpensive and readily available, can produce undesirable effects on adherent cells. Effects such as premature differentiation and/or aging phenomenon in cells may limit the potential of these cells to be used in future cell therapeutics. This I-Corps team has developed nano-structured multi-well plate inserts for cell culture. These nano-structured substrates, produced using injection molding techniques allow for robust culture of stem cells (both human mesenchymal and other subtypes) in the absence of further chemical treatments, such as oxygen plasma, protein coatings, or other surface modifications; potentially reducing the cost of laboratory cell culture protocols. Through manufacturing, modulation of the nano-structured surface features (llows for either long-term culture of stem cells or controlled differentiation of the cells. The wide variety of cell-substrata interactions made possible as a result would enable a whole new paradigm for stem cell development and differentiation, and allow this science to possibly translate at a faster rate to clinical applications. Biological cells exert mechanical forces in both the horizontal and vertical directions. In general, however, the vertical forces are small compared to horizontal cellular forces (traction forces). Thus, the key to affecting cells via these dominant traction forces is to control substrate compliance in the lateral direction (flexural stiffness). Considering the substrate to be rigid, Hooke's law of elastic deformation can be applied, which for cylindrical columns at the micro- or nano-scale yields a predictable in-plane force-displacement relationship. With precise determination of surface feature dimensions and spacing, micro/nanostructured surface arrays can be designed to yield a range of effective lateral surface compliances. As feature deformation is dictated by the applied force, a finer pitch will position more features under each cell and produce a reduction of the biological traction forces applied to each one. To manufacture these features, the team has taken advantage of injection molding as a high volume and repeatable method to create surface areas conducive to eliciting specific cellular functions. Ultraviolet lithography, combined with deep reactive ion etching, is used to generate micro-features over a relatively large surface area of a silicon wafer. The micro-featured silicon wafer is then used as a mold insert for the micro-injection molding process to create surfaces from a wide variety of thermoplastic polymers. Altering the mold features controls the micro-geometry, which further alters the effective surface stiffness of the polymer substrate and the resultant behavior of the cells - leading to advanced cellular engineering opportunities.