(A), 4T1 cells incubated (for 1h before FACS analysis) with 1% mPEG(2000)-modified liposomes [PEG(2000)-Lip], 1% TATp-modified liposomes (TATp-Lip), and MMP2-responsive nanocarriers [PEG(3400)/peptide/TATp-Lip] with or without pre-treatment with MMP2; (B), H9C2 cells incubated with PEG(2000)-Lip, TATp-Lip, and MMP2-responsive multifunctional nanocarriers (2C5/peptide/TATp-Lip) with or without pre-treatment with MMP2; (C), 4T1 cells incubated with the same liposome preparations as in (B). The geometric mean of the fluorescence for non-treated cells was defined as 100% (*). Abbreviation: 2C5, mAb 2C5; peptide, MMP2 cleavable peptide; TATp: TAT peptides; Lip, liposomes, Rh-PE, 1,2-dioleoylsn- glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (ammonium salt).