Development of Polydimethylsiloxane Substrates with Tunable Elastic Modulus to Study Cell Mechanobiology in Muscle and Nerve

TLDR

Cell mechanics regulate shape, proliferation, migration, and differentiation, and biomaterials that match soft tissue modulus have been used to study this, yet broader physicochemical control is needed. The study hypothesizes that PDMS blends can provide a tunable system to match the elastic modulus of most soft tissues. Blends of Sylgard 527 and 184 were formulated to produce substrates with elastic moduli from 5 kPa to 1.72 MPa, and PC12 and C2C12 cells were used to validate that these substrates support attachment, growth, and enable probing of mechanosensitivity. The resulting substrates offer a three‑order‑of‑magnitude tunability that surpasses other hydrogel and PDMS systems, allow independent control of modulus from surface roughness, energy, and functionalization, and support neuronal and muscle cell attachment, growth, and mechanosensitivity assays.

Abstract

Mechanics is an important component in the regulation of cell shape, proliferation, migration and differentiation during normal homeostasis and disease states. Biomaterials that match the elastic modulus of soft tissues have been effective for studying this cell mechanobiology, but improvements are needed in order to investigate a wider range of physicochemical properties in a controlled manner. We hypothesized that polydimethylsiloxane (PDMS) blends could be used as the basis of a tunable system where the elastic modulus could be adjusted to match most types of soft tissue. To test this we formulated blends of two commercially available PDMS types, Sylgard 527 and Sylgard 184, which enabled us to fabricate substrates with an elastic modulus anywhere from 5 kPa up to 1.72 MPa. This is a three order-of-magnitude range of tunability, exceeding what is possible with other hydrogel and PDMS systems. Uniquely, the elastic modulus can be controlled independently of other materials properties including surface roughness, surface energy and the ability to functionalize the surface by protein adsorption and microcontact printing. For biological validation, PC12 (neuronal inducible-pheochromocytoma cell line) and C2C12 (muscle cell line) were used to demonstrate that these PDMS formulations support cell attachment and growth and that these substrates can be used to probe the mechanosensitivity of various cellular processes including neurite extension and muscle differentiation.