Degradable polyethylene glycol (PEG) hydrogels provide platforms for drug delivery and tissue engineering. End group modification of poly(ethylene glycol) (M<sub>n </sub>= 2,000 g/mol) yielded polyether precursors with pH-sensitive and photocurable end groups. UV-initiated binary thiol-acrylate crosslinking with varied amount of thiol-functionalized three-arm PEG (THIOCURE® ETTMP 1300) developed pH-degradable networksSmall angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA) confirmed that the stoichiometric offset of thiols and acrylates controlled crosslink density. Spectroscopic monitoring of a released dye established controlled degradation studies, which quantified the hydrogels’ degradation rate. Hydrogels displayed bulk degradation in acidic solution. Low crosslink density gels degraded fully in aqueous solutions of pH (3.4) within 72 h while the highly crosslinked gels fully degraded over 3 wks. All hydrogels displayed long term stability in phosphate buffered saline of pH (7.4) beyond 3 mo making them ideal hydrogels for selective degradation and release in low pH environments.

Degradation of acetal functionalized hydrogels from binary thiol-acrylate photopolymerization

ACS Spring 2022

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