The extracellular matrix (ECM) provides dynamic biophysical cues to influence cell behavior. Physiological events such as fibrosis regression and stem cell differentiation are associated with gradual softening of the ECM. In this study, we developed a cell encapsulation system capable of undergoing on-demand matrix softening independent of regular protease activity (<b>Fig. 1A</b>). PEG-peptide hydrogels were fabricated using peptide crosslinkers that are both sensitive and insensitive to enzymatic cleavage. Specifically, sortase A (SrtA), an enzyme widely used in molecular labeling and modification, was utilized to cleave the peptide crosslinkers containing a SrtA substrate, LPRTG. The degree of softening was tuned by adjusting the ratio of SrtA-sensitive (G: LPRTG) and SrtA-insensitive (A: LPRTA) linkers (<b>Fig. 1B</b>). The rate of softening was also tuned by changing the enzyme concentration. Importantly, we demonstrated that on demand softening promoted spreading of human mesenchymal stem cells (hMSCs) in 3D. Specifically, hMSCs exhibited rounded morphologies in both non-dynamic stiff and pre-softened hydrogels. On the other hand, significantly more cell spreading was observed in the dynamically softened hydrogels.

On-demand softening of hydrogels through SrtA-mediated transpeptidation

2019 Spring National Meeting

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