Stimuli-responsive hydrogels with adaptable mechanical properties are attractive for a wide variety of applications, including self-healing materials, drug delivery reservoirs, and for mechanobiology studies. In this work, anthracene (Ant)-functionalized PEG hydrogels are prepared as an on-demand stiffening material. Hydrogel formation is achieved via 365 nm light-mediated intermolecular [4+4] photocycloaddition between anthracene end-groups on 8-arm 20 kDa PEG-Ant chains. Gel evolution was controlled either in one or multiple steps by shuttering the light source on and off (A). The reaction is compatible with cell culture media and does not require a radical initiator that can elicit cellular toxicity. For PEG-Ant solutions in PBS at pH 7.4, photodimerization proceeds with a rate constant between 0.72-0.93 L-mol-1sec-1 at 10 mW/cm2 irradiation, which is comparable to typical click reactions. Furthermore, when the macromolecular precursors are only partially reacted, unnreacted Ant groups can be subsequently photopatterned to stiffen the gel or incorporate biological signals to permit localized presentation of cues to cells. As a proof of concept, a hydrogel with 35 mol% of unreacted Ant groups was photopatterned with a heterobifunctional Ant-PEG3400-rhodamine linker (1-10 min, 10 mW/cm2) (B). To demonstrate its feasibility as a scaffold to study mechanobiology, C2C12 myoblast cell lines were cultured on static and stiffening hydrogels (2 mM Ant-GRGDS, E’=3-24 kPa). C2C12 cells were observed to increase their cell area upon in situ stiffening (C). In summary, PEG-Ant hydrogels offer a simple but robust platform to produce multifunctional gels can be used for diverse biomaterial applications.

On demand stiffening poly(ethylene glycol) (PEG) hydrogels via [4+4] photocycloaddition of anthracenes

256th National Meeting (2018)

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