Synthesis and mechanical characterization of polyacrylamide (PAAm) hydrogels with different stiffnesses for large-batch cell culture applications

The impact of mechanical cues on cell behavior is increasingly being recognized, rendering hydrogel platforms that mimic the extracellular matrix indispensable in in vitro cell biology research. Here, we present a step-by-step protocol for synthesis and rheological characterization of polyacrylamide (PAAm) hydrogels with varying stiffnesses, produced as large circular unattached gels customizable in shape and size. We outline methods for their use in cell culture and downstream applications involving secretome or cell analysis, and protein visualization by fluorescence microscopy.

This protocol is based on the recent work of Shi & Janmey who describe a novel and straightforward method for the production of large PAAm hydrogels for bulk cell culture and mechanobiology studies. ¹ Their procedure results in one large gel that is not attached to a supporting surface and therefore can be transferred and/or stamped to generate PAAm gels of custom shapes and sizes. The aim of this step-by-step procedure is therefore not to improve the reported protocol, but to create a clearly outlined and repeatable protocol that enables a smooth implementation in any lab for a diverse audience. In addition, our protocol describes besides harvesting of cells also the collection of secretome for downstream biochemical analyses, as well as immunofluorescence labeling using antibodies that can readily be multiplexed for optimization of labeling conditions.