(A) Near-infrared images of mice at 2, 4, 12, 24, 36 h post-injection of free DiR and DiR-NP; (B) Fluorescence intensities of tumors at different time points (n=3, mean±SD); (C) Ex vivo fluorescence imaging of major organs and tumors 24 hours following injection of free DiR and DiR-NP; and (D) Relative normalized fluorescence intensity of major organs and tumors after 24 hours (n=3, mean±SD).