LAUSR

This review covers the application of heptamethine cyanine dye (HMCD) mediated drug delivery. A relatively small number of HMCDs possess tumour targeting abilities, and this has spurred interest from research groups to explore them as drug delivery systems. Their tumour selectivity is primarily attributed to their uptake by certain isoforms of organic anion transporting polypeptides (OATPs) which are over expressed in cancer tissues, although there are other possible mechanisms for the observed selectivity still under investigation. This specificity is confirmed using various cancer cell lines and is accompanied by moderate cytotoxicity. Their retention in tumour tissue is facilitated by the formation of albumin adducts as revealed by published mechanistic studies. HMCDs are also organelle selective dyes with specificity towards mitochondria and lysosomes, and with absorption and emission in the near-infrared region. This makes them valuable tools for biomedical imaging, especially in the field of fluorescence-guided tumour surgery. Furthermore, conjugating anti-tumour agents to HMCDs is providing novel drugs that await clinical testing. HMCD development as theranostic agents with dual tumour targeting and treatment capability signals a new approach to overcome drug resistance (mediated through evasion of efflux pumps) and systemic toxicity, the two parameters which have long plagued drug discovery.