Intercellular-constructed CTSB-responsive T2-type micromolecular magnetic resonance contrast agent and preparation method thereof

The invention discloses an intracellular CTSB-responsive T2-type small-molecular magnetic resonance contrast agent and a preparation method thereof, and is characterized in that the contrast agent contains a CTSB specific enzyme cutting substrate, a potential cysteine motif with a disulfide bond, 2-cyano-benzothiazole and a 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid gadolinium structure combined with a lysine side chain, and the CTSB-responsive T2-type small-molecular magnetic resonance contrast agent is prepared from the CTSB-responsive T2-type small-molecular magnetic resonance contrast agent. A click condensation reaction between 2-cyanobenzothiazole and D-cysteine can occur in cancer cells with high CTSB expression, so that Gd-based nanoparticles are formed in situ, the intracellular concentration of Gd is improved, the retention time of Gd is prolonged, and the T2 weighted magnetic resonance contrast of CTSB overexpression tumors is enhanced, so that the Gd-based nanoparticles can be