Indocyanine green (ICG) is a FDA-approved near-infrared (NIR) cyanine dye used in medical diagnostics. However, the utility of ICG remains limited by its unstable optical property, and concentration-dependent aggregation and precipitation. A chitosan-arginine conjugate (CS- N-Arg) was developed to increase the stability of ICG in physiological buffer saline via formation of strong electrostatic interactions between ICG and CS- N-Arg. The CS- N-Arg/ICG complex prevented ICG from aggregation and precipitation, thus it could serve as a theranostic nanomaterial for image-guided photothermal cancer therapy. The CS- N-Arg/ICG NPs showed excellent photostability, clear fluorescent images, and rapid temperature rise under laser irradiation. Cell viability assay indicated that CS- N-Arg/ICG NPs could efficiently suppress the growth of doxorubicin (DOX) resistant breast cancer cell (MCF-7/ADR cells) under NIR photothermal treatments. In combination of DOX with CS- N-Arg/ICG NPs, a combined effect was observed in MCF-7/ADR breast cancer cells due to dual hyperthermia and chemical therapeutic effects. The present observations suggest that CS- N-Arg/ICG NPs can effectively deliver ICG molecules to MCF-7/ADR breast cancer cells and overcome DOX resistance in the cells by hyperthermia.
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