MMP9 and infarction: Intravenously injected, this nanocarrier sensed MMP-9, transforming from discrete spherical particles (15–20 nm) to a grid-like structure, remaining at the infarction site for up to four weeks, and facilitating long-term local accumulation, particularly during vascular leakage and MMP-9 overexpression post-acute myocardial infarction [178].