Far-Red/Near-Infrared Conjugated Polymer Nanoparticles for Long-Term In Situ Monitoring of Liver Tumor Growth.

The design and synthesis is reported for a fluorescent conjugated polymer (CP), poly{[4,4,9,9-tetrakis(4-(octyloxy)phenyl-4,9-dihydro--indaceno[1,2-b:5,6-b']dithiophene)]---[4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole]} (PIDT-DBT), with absorption and emission profiles fallen within far-red/near infrared (FR/NIR) region and further demonstrate its application in long-term in vitro cell tracing and in vivo imaging of liver tumor growth. PIDT-DBT-Tat nanoparticles (NPs) have an absorption maximum at ≈600 nm with an emission maximum at ≈720 nm in water. In vitro cell tracing studies reveal that PIDT-DBT-Tat NPs can trace HepG2 liver cancer cells over 8 d. In vivo imaging results indicate that PIDT-DBT-Tat NPs can monitor liver tumor growth for more than 27 d in a real-time manner. Both in vitro and in vivo studies demonstrate that PIDT-DBT-Tat NPs are superior to commercial Qtracker 705 as fluorescent probes. This study demonstrates for the first time the feasibility for long-term in vivo imaging of tumor growth by utilizing CP-based fluorescent probes, which will encourage the development of NIR fluorescent CPs for in vivo bioimaging.