Biodistribution of Liposomes in vivo

To study the biodistribution and targeting ability of multifunctional immunoliposomes in vivo, DiR, a lipophilic fluorescent probe, was used to label the liposomes. DiR-loaded liposomes were prepared using the film dispersion method noted above. C57BL/6 (6–8 weeks of age, 20 g/b) mice were injected with B16-F10 cells subcutaneously in the right flank at a density of 1×10⁶. When the tumor volume reached 100 mm³, the tumor-bearing mice were divided into three randomized groups. They were then intravenously injected with free DiR, DiR@SSLs, or DiR@aPDL1-SSLs (DiR: 150 μg/kg). The biodistribution of the liposomes was observed using an in vivo optical imaging system (IVIS Spectrum, Xenogen, Alameda, CA, USA) at 1, 2, 4, 8, 12, and 24 h post-liposome injection. Mice were sacrificed after 24 h and the tumors and main organs were harvested for imaging in vitro. The images were processed using Living Image 4.3.1 software.