Systematic d‑Amino Acid Substitutions to Control Peptide and Hydrogel Degradation in Cellular Microenvironments

Enzymatically degradable peptides are commonly used as linkers within hydrogels for biological applications; however, controlling the degradation of these engineered peptides with different contexts and cell types can prove challenging. In this work, we systematically examined the substitution of d-amino acids (D-AAs) for different l-amino acids in a peptide sequence commonly utilized in enzymatically degradable hydrogels (VPMS↓MRGG) to create peptide linkers with a range of different degradation times, in solution and in hydrogels, and investigated the cytocompatibility of these materials. We found that increasing the number of D-AA substitutions increased the resistance to enzymatic degradation both for free peptide and peptide-linked hydrogels; yet, this trend also was accompanied by increased cytotoxicity in cell culture. This work demonstrates the utility of D-AA-modified peptide sequences to create tunable biomaterials platforms tempered by considerations of cytotoxicity, where careful selection and optimization of different peptide designs is needed for specific biological applications.