A fresh near-infrared fluorescent compound containing two cyclic RGD motifs cypate-[c(RGDfK)]2 (1) was synthesized based on a carbocyanine fluorophore bearing two carboxylic acid groups (cypate) for integrin αvβ3-targeting. novel approaches for exploiting integrin αvβ3 targeting are still needed to improve cancer imaging diagnosis and therapy. As one of the most versatile imaging modalities optical imaging allows noninvasive sensitive and ABCG2 real time imaging of molecular interactions and related functions in cells tissues and systems. In particular optical imaging serves as a powerful tool for bridging the wide gap between preclinical and clinical studies facilitating the discovery of optimal integrin αvβ3-targeted molecules and their subsequent translational studies. 11-14 We previously reported a series of carbocyanine-based near-infrared (NIR) fluorescent probes for tumor-targeted optical imaging organ analysis showed the relatively high uptake of 1 1 in the tumor and the liver compared with the kidneys heart and other tissues (Physique 4C and 4D). The results are in good agreement with the noninvasive optical imaging results. Physique 4 Optical imaging of 1 1 and 2 in mice. (A) optical imaging of tumors (circled areas) at 1 4 and 24 Olmesartan h post -injection; (B) time-dependent tumor uptake; (C) biodistribution of fluorescence at 24 h post-injection; and (D) fluorescence … Divalent and multivalent methods have been widely analyzed in molecular discovery for improving the selectivity specificity and potency of receptor binding Olmesartan as well as the related biological and pharmacological activities.16 28 Clearly increased local concentration and divalent or multivalent interaction can enhance the integrin αvβ3 binding affinity of RGD compounds. Numerous divalent and multivalent RGD peptides for integrin αvβ3-targeted imaging such as 18>F-FPPRGD2 and some fluorescent labeled RGD compounds have also been reported for Olmesartan tumor targeted imaging therapy and drug delivery. 14 16 26 32 Especially it is important to have the suitable linkage between two RGD motifs that can span the two neighboring integrin αvβ3 sites for simultaneous binding. As shown above 1 represents a new type of NIR fluorescent divalent ligands using cypate as both linker and probe. Unlike other flexible linkers the cypate motif consists of ploymethines and benzoindoline rings which might Olmesartan help to pre-organize the divalent RGD ligand for simultaneous binding of two adjacent αvβ3 integrins with decreased binding entropy and enhanced stability of the producing ligand-receptor complex. By comparing with 2 and cypate the significant improvement of 1 1 in tumor localization suggests the enhanced integrin αvβ3-targeting for tumor optical imaging. The results also support our hypothesis that Olmesartan this divalent compound can simultaneously bind to two adjacent integrin αvβ3 proteins and exhibit synergistic effects on receptor- and tumor-targeting. Furthermore the linker of a divalent ligand plays an important role in achieving significant synergistic effects. 4 31 The 27-atom length between the two RGD motifs of 1 1 may be sufficiently long to span two adjacent αvβ3 for simultaneous binding leading to improvement in the integrin αvβ3 binding affinity and related tumor targeting (Physique 5). Therefore compound 1 could serve as a prototype for building and optimizing novel integrin αvβ3-targeted compounds for the early diagnosis and targeted therapy of tumors. Physique 5 The two RGD motifs linked by cypate for simultaneous binding of two αvβ3 integrins. There was high accumulation of 1 1 in the liver (Physique 4) which implies its clearance from flow through the reticuloendothelial program (RES). The solid NIR fluorescence in the mice over 24 h post-injection of just one 1 shows the stability of just one 1 and its own feasible Olmesartan metabolites. As reported previously NIR fluorescent IRDye800-RGD conjugates demonstrated speedy clearance via the kidneys and low tumor fluorescence ensued at 4 h post shot. 38 These distinctions illustrate the key roles from the dye theme as well as the related hydrophilicity in the dynamics of divalent molecular imaging probes. These outcomes provide an understanding into additional structural modification from the cypate theme to reduce nonspecific binding in order to enhance integrin αvβ3 and tumor-selective concentrating on. Noteworthy the modular strategy we have employed for synthesis of just one 1 permits convenient planning of such divalent conjugates in option and on solid support. A huge array of substances with distinct chemical substance and biological features can be acquired by differing the.