Effects of heterocyclic N-alkyl chain length on cancer cell uptake of near infrared heptamethine cyanine dyes

Cancer theranosis has materialized as a significant alternative to the separate diagnosis and treatment of cancer optimizing efficacy. Based on our previous work, it was determined that esterified heptamethine cyanine dyes were selectively cytotoxic to cancer cells. In order to determine the optimal N-alkyl chain length, a series of nine near-infrared fluorescent heptamethine cyanine dyes with monoester, diester, and diacid functional groups and differing chain lengths of three, six and ten carbons have been synthesized, isolated, and purified. They were characterized by 1H NMR, 13C NMR and mass spectrometry and their optical properties were measured. It was found that dyes with a 6 carbon N-indolenine substituent were the most selective for cancer theranosis in pancreatic cancer cell line S2-013.