In vivo imaging and biodistribution

All animal experiments complied with the Wenzhou Medical University’s Policy on the Care and Use of Laboratory Animals. Protocols for animal studies were approved by the Wenzhou Medical University Animal Policy and Welfare Committee. BALB/cA nu/nu female mice (18–22 g) bearing HCT116 tumors with volume approximately 150 mm³ were intravenously (iv) injected with free ICG (2 mg/kg) or ICG-loaded PCH nanoparticles (ICG/PCH) (2 mg/kg equivalent ICG) (n=6). At 6 hours, 24 hours, and 48 hours after injection, the intensity of fluorescence signal in animals was observed using an in vivo imaging system (CRi maestro, Cambridge Research & Instrumentation, Inc., Hopkinton, MA, USA) with the excitation wavelength of 704 nm and a filter of 735 nm. Some mice in each group were sacrificed at 24 hours after injection, and the organs such as heart, liver, spleen, lung, kidneys, and tumor were excised for fluorescent imaging.