Sonication labile PEG-based hydrogel system for biological component suspension and subsequent degradation†

This work synthesizes poly(ethylene glycol) (PEG) macromers that incorporate a phthalaldehyde moiety located at crosslink junctions. This location facilitates the severing of the polymer network when bond scission of the phthalaldehyde unit occurs with mechanical stimulation. As these networks degrade, the mechanical properties are analyzed to better understand how sonication driven degradation affects a polymer network – specifically looking at the degradation profile in hydrogel systems through the mass loss and storage modulus profiles. Comparison of hydrogels containing phthalaldehyde units with hydrogels that do not have the mechanophore pre- and post-mechanical stimulation provides evidence that the incorporation of the mechanophore at these crosslink junctions reduces the storage modulus by a factor of ten and results in greater than 90% decrease of the gel mass after 15 minutes of probe sonication, leading to breaking the network into soluble daughter fragments. The network degradation conditions of these hydrogels are shown to be compatible with biological component suspension and release for applications such as localized payload release.