| Click chemistry has been widely noted because of its easy availability of raw materials, high yields, simplicity, mild reaction conditions, and high reaction rates. In recent decades, click chemistry has become one of the most useful and attractive concept in medicine and molecular biology.The condensation reaction between2-cyanobenzothiazole (CBT) and D-cysteine is a classical click reaction happened in the body of firefly. This reaction has the advantage of mild reaction conditions and biocompatibility. Modification of the substrate can initiate the condensation reaction by changing the pH, reduction of disulfide bond, or enzyme cleavage. Fuctionalization of the monomer enables this reaction for broad biomedical applications.This dissertation is based on this condensation reaction platform. We modified the substrate, and developed this reaction for molecular imaging. It can be divided into two parts:(1) The probe is linked with clinical contrast agents Gd-DOTA and combined with the peptide RVRR which is the substrate of furin. After condensation, nanoparticles were formed and can be trapped into the cells. The advantage of this kind of contrast agents is not only the nanomaterials known for us but also the targeting.(2) The fluorescence metal ion Eu replaces the magnetic resonance imaging metal Gd to develop the application of this condensation reaction for two-photon imaging.(3) The probe is linked with biotin which can bind with streptavidin specificly and combined with the peptide DVED which can be recognized and cleaved by caspase-3. After condensation, nanoparticles were formed and enriched with biotin. After adding streptavidin-FITC, the fluorescent intensity has an obvious enhancement than uncondensated one.This dissertation is based on this condensation reaction platform, developed new applications in molecular imaging. These methods have the properties of not only enhancing the efficiency of molecular imaging but also targeting. |
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