MMP2 and neoplasm: When the cGAMP@dual-anti-Exos aggregate in tumor tissue, peptides PLGVA connected with anti-PD-L1 will be cut off by the abundant matrix metalloproteinase enzyme (MMP-2) in the tumor microenvironment, so that anti-PD-L1 can separate from the exosomes and bind to the PD-L1 receptor of tumor cells to block the immune checkpoint molecules (Scheme 1(b)).