Emissive Lipid Nanoparticles\nas Biophotonic Contrast\nAgent for Site-Selective Solid Tumor Imaging in Pre-Clinical Models

Small organic dye-based fluorescent agents are highly\npotent in\nsolid tumor imaging but face challenges such as poor photostability,\nnonspecific distribution, low circulation, and weak tumor binding.\nNanocarriers overcome these issues with better physicochemical and\nbiological performance, particularly in cancer imaging. Among the\nvarious nanosized carriers, lipid formulations are clinically approved\nbut yet to be designed as bright nanocontrast agents for solid tumor\ndiagnosis without affecting surrounding tissues. Herein, indocyanine\ngreen (ICG) encapsulated targetable lipid nanoparticles (698 ICG/LNPs)\nas safe contrast agents (∼200 nm) have been developed and tested\nfor solid tumor imaging and biodistribution. Our findings reveal that\nnanoprecipitation produces ICG-LNPs with a unique assembly, which\ncontributes to their high brightness with improved quantum yield (3.5%)\nin aqueous media. The bright, optically stable (30 days) biophotonic\nagents demonstrate rapid accumulation (within 1 h) and prolonged retention\n(for up to 168 h) at the primary tumor site, with better signal intensity\nfollowing a one-time dose administration (17.7 × 10<sup>9</sup> LNP per dose). Incorporated folic acid (735 folic acid/LNPs) helps\nin selective tumor binding and the specific biodistribution of intravenously\ninjected nanoparticles without affecting healthy tissues. Designed\ntargetable ICG-LNP (634 MESF) demonstrates high-contrast fluorescence\nand resolution from the tumor area as compared to the targetable ICG-liposomal\nnanoparticles (532 MESF). Various <i>in vitro</i> and <i>in vivo</i> findings reveal that the cancer diagnostic efficacy\nelicited by designed bright lipid nanoparticles are comparable to\nreported clinically accepted imaging agents. Thus, such LNPs hold\ntranslational potential for cancer diagnosis at an early stage.