Indocyanine green-loaded biodegradable tumor targeting nanoprobes for in vitro and in vivo imaging

Indocyanine green (ICG) is a near-infrared (NIR) fluorescence dye for extensive biological application, but limited by its poor aqueous stability in vitro, concentration-dependent aggregation, rapid elimination from the body, and lack of target specificity. In this paper, to overcome these limitations, folate receptor-targeted, ICG dye-doped poly(d,l-lactide-co-glycolide) (PLGA) lipid nanoparticles (FA-ICG-PLGA-lipid NPs) were constructed by a single-step self-assemble and nanoprecipitation method. The prepared FA-ICG-PLGA-lipid NPs exhibited good biocompatibility, monodispersity, excellent NIR penetration ability, significant stability against photobleaching and long circulation time. The intracellular uptake experiment proved the targeting efficacy of the FA-ICG-PLGA-lipid NPs was more effective in folate receptor over-expressing MCF-7 cells than folate receptor negative A549 cells. Furthermore, the in vivo experiments showed the FA-ICG-PLGA-lipid NPs were specifically targeted to the tumor, and its circulation time was much longer than free ICG. These biocompatible and biodegradable NIR-NPs prove a potential application in tumor diagnosis and targeted imaging due to its high aqueous stability, excellent NIR optical properties and significantly targeting property in vivo.