In Vivo Biodistribution Studies using IVIS Imaging

Three days after surgery, mice were injected with NP-loaded IR780 retro-orbitally (0.7 mg/kg IR780, 5 mg/kg of NPs).⁹⁷ Mice were monitored via XENOGEN/IVIS imaging system (PerkinElmer) longitudinally (780 nm/820 nm for IR780). IVIS images were taken at multiple time points for 2 weeks after injection using 2% isoflurane gas for anesthesia. Quantification of NP biodistribution from IVIS imaging was achieved by measuring the total radiant efficiency of regions of interest (right femurs) and normalizing to saline and day 0. Tissue distribution was also analyzed by IVIS 24 and 48 h after injection by measuring IR780 signal in dissected organs. Specimens were also embedded and cut using a cryostat and imaged at 40× magnification using an Olympus VS110 Virtual Microscopy System for whole-slide scanning. Visiopharm software was utilized to determine the area of cells (DAPI) and NP-loaded IR780.⁹⁸