This presentation will describe a novel reaction cascade for detecting the effects of small mechanical stresses in hydrogels. Due to their highly hydrated nature and mechanical tunability, hydrogels are common scaffolds for cell growth and tissue engineering. To grow viable tissue for applications such as cardiovascular repair and cartilage replacement, the mechanical properties of the gels must be controlled to mimic the native tissue. Additionally, the hydrogel scaffold must retain its mechanical integrity for the duration of cellular development. It is therefore important to be able to detect scaffold degradation as early as possible in order to monitor and improve upon implant performance. Since hydrogel failure begins with breakage of the crosslinks, a sensor for these bond breakages would provide a means for early detection. We hypothesized that the radicals formed upon bond breakage would react with the ambient water in the hydrogel to form hydroxyl radicals, which in turn could activate certain masked fluorophores to produce a fluorescent signal. We synthesized a series of hydrogels from 4-arm poly(ethylene glycol) derivatives with crosslinks of varying strength and a range of moduli for each crosslink type. These were loaded with the masked fluorophore 3’-(p-aminophenyl) fluorescein. The gels were then subjected to compressive stress at strains up to 30 %. We observed fluorescence activation at compressive stresses as low as 5 kPa, with the effect of compression primarily dependent on the crosslink strength; as crosslink strength decreased, fluorescence activation increased. We also saw a dependence of fluorescence activation on the modulus of the gel, with the activation decreasing as modulus increased. In future studies we will adapt this system to study mechanical variability and defects within cell-laden hydrogels.

Novel mechanochemical reaction cascade for sensing bond breakage in hydrogels

249th National Meeting (2015)

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