This talk will focus on our recent efforts towards characterizing mechanochemical bond breakage in soft materials. Hydrogels are promising substrates and frameworks for cell growth and tissue engineering, particularly for cardiovascular repair and cartilage replacement. For these applications, it is important to maintain careful control over gel mechanical properties so that these hydrogels not only match the properties of the desired tissue for replacement but also retain their integrity for extended periods. Since the failure of hydrogels begins with the breakage of crosslinks within the structure, methods are needed to sense this initial breakage. However, most strategies that utilize mechanochemistry require large strain deformations to obtain signal. Here, we report two methods for quantifying bond breakage. It was hypothesized that nonspecific covalent bond breakage would produce radicals that would react with water to produce reactive oxygen species, which in turn could activate fluorophores sensitive to oxidation. First, it was found that gels loaded with the masked fluorophore 3-(aminophenyl)-fluorescein became fluorescent during compression, even with as little as 5 kPa of pressure. The effect of compression on fluorescence activation was found to depend primarily on the strength of the crosslinking functional group in hyperbranched PEG hydrogels. Next, we found that because hydrogen peroxide was the dominant species produced by this process, the enzyme horseradish peroxidase could catalyze mechanochemical reactions resulting from strain on the hydrogels. As a result, new colorimetric and fluorimetric studies were developed that could quantify hydrogen peroxide production, and thus chemical bond breakage, with micromolar sensitivity. The ability to couple mechanochemical reactions with enzyme-catalyzed processes will be discussed as well.<br/>

Mechanochemistry of hydrogels: Quantifying small numbers of bond breakages in weak materials

254th National Meeting (2017)

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