Surface Creasing Instability of Soft Polyacrylamide Cell Culture Substrates

Abstract

Efforts to understand and engineer cell behavior in mechanically soft environments frequently employ two-dimensional cell culture substrates consisting of thin hydrogel layers with low elastic modulus supported on rigid substrates to facilitate culturing, imaging, and analysis. Here we characterize how an elastic creasing instability of the gel surface may occur for the most widely used soft cell culture substrate, polyacrylamide hydrogels, and show that stem cells respond to and change their behavior due to these surface features. The regions of stability and corresponding achievable ranges of modulus are elucidated in terms of the monomer and cross-linker concentrations, providing guidance for the synthesis of both smooth and creased soft cell substrates for basic and applied cell engineering efforts.

Simple Polyacrylamide-based Multiwell Stiffness Assay for the Study of Stiffness-dependent Cell Responses

“…This behavior is common for soft gels that undergo de-hydration and subsequent re-hydration while being geometrically constrained. 34,35 Not all gels crease or crack, thus, it is possible to visually examine the hydrogels prior to use and only use the samples that display a smooth surface. To completely avoid crease formation and cracking, an alternative method to prepare soft hydrogels is depicted on Figure 6.…”

Controlled formation and disappearance of creases

“…Crease-inducing stimuli include temperature, 17 light 18 and electric fields. 19,20 Functions enabled by the formation of creases include the control of chemical patterns, 17,18 enzymatic activity, 17 cellular behavior, 21 and adhesion. 22 Each of these applications depends on how creases form and disappear.…”

Smoothening creases on surfaces of strain-stiffening materials

“…Creases can also form on the interface between two elastic solids . Applications of creases have been explored, including the use of creases to control chemical patterns Yoon et al, 2012), enzymatic activity , cellular behavior (Saha et al, 2010), and adhesion (Chan et al, 2011).…”