In situ assembly of the collagen–polyacrylamide interpenetrating network hydrogel: Enabling decoupled control of stiffness and degree of swelling

• Collagen/acrylamide gels made via radical polymerization and Michael reaction.
• Independency between hydrogel stiffness and swelling established.
• Amines from collagen linked to vinyl groups on acrylamide.
• This easy-to-use hydrogel can be used in advanced cell culture and drug delivery.

In the past several decades, hydrogels have been extensively studied for use in various biomedical and industrial applications. Successful use of hydrogels in these applications greatly relies on the ability to control mechanical and transport properties in a refined manner; however, current hydrogel design often encounters an undesirable inverse dependency between the degree of swelling and elastic modulus. To resolve this challenge, we hypothesized that an interpenetrating network (IPN) gel in which collagen fibers are chemically linked to a polymeric gel would allow us to control the elastic modulus over a broad range while reducing the change in the degree of swelling. We examined this hypothesis by preparing a collagen–polyacrylamide IPN gel via in situ assembly, so that two disparate networks are chemically linked via Michael reaction between collagen and polyacrylamide. The resulting IPN gel successfully demonstrated the independency between the degree of swelling and the elastic modulus. We suggest that the results of this study will be broadly useful in controlling hydrogel properties in an elaborate manner, in turn advancing various molecular and cell therapies.

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