Huang and co‐workers synthesized a PEG‐based hydrogel for intraoral drug delivery to treat periodontitis.[211] The diacrylate‐modified PEG was linked by a Cys‐terminated peptide cross‐linker (CGPQG↓IWGQC), which could be cleaved by MMP‐8. Here, MMP8 is linked to periodontitis.