Near-infrared fluorescing IR820-chitosan conjugate for multifunctional cancer theranostic applications

This study reports the preparation and characterization of IR820-chitosan conjugates that have potential multifunctional imaging-hyperthermia applications in cancer. The conjugates were formulated by covalent coupling of chitosan to a carboxyl derivatized IR820, and studied for optical imaging and hyperthermia applications. IR820-chitosan conjugates were able to generate heat upon exposure to 808 nm laser and produce hyperthermic cell growth inhibition in cancer cell lines MES-SA, SKOV-3 and Dx5. The level of cell growth inhibition caused by hyperthermia was significantly higher for IR820-chitosan compared to IR820 in MES-SA and Dx5 cells. Fluorescent microscope images of these cancer cell lines after 3-h exposure to 5 mu M IR820-chitosan showed that the conjugates can be used for in vitro near-infrared imaging. In an in vivo rat model, the conjugates accumulated in the liver after i.v. injection and were excreted through the gastrointestinal tract, demonstrating a different biodistribution when compared to the free dye. The accumulation of these conjugates in bile with subsequent gastrointestinal excretion allows for potential applications as gastrointestinal contrast agents and delivery vehicles. This formulation can potentially be used in multifunctional cancer theranostics. (C) 2012 Elsevier B.V. All rights reserved.