MMP2 and infection: The MMP2-activatable self-assembled branched peptide (FR17, FFK(GPLGLAGG-YVDKR)Y) consists of (1) the backbone of a self-assembled peptide domain Phe-Phe-Lys-Tyr (FFKY), a variant of Phe-Phe (FF), which is derived from Aβ36; (2) thymopentin (TP5, Arg-Lys-Asp-Val-Tyr, RKDVY), a pentapeptide with perfect hydrophilic property and immune modulation effect, which is applied as the adjunctive therapeutic agent on cancer treatment in clinic to prevent postoperative infection and to activate immune response41,42.