Bright far-red/near-infrared conjugated polymer nanoparticles for in vivo bioimaging

Abstract

A highly emissive far-red/near-infrared (FR/NIR) fluorescent conjugated polymer (CP), poly[(9,9-dihexylfluorene)-co-2,1,3-benzothiadiazole-co-4,7- di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PFBTDBT10) is designed and synthesized via Suzuki polymerization. Formulation of PFBTDBT10 using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000) and DSPE-PEG5000-folate as the encapsulation matrix yielded CP-loaded DSPE-PEG-folic acid nanoparticles (CPDP-FA NPs) with bright FR/NIR fluorescence (27% quantum yield) and a large Stoke's shift of 233 nm in aqueous solution. CPDP-FA NPs show improved thermal/photostabilities and larger Stoke's shifts as compared to commercially available quantum dots (Qdot 655) and organic dyes such as Alexa Fluor 555 and Rhodamine 6G. In vivo studies of CPDP-FA NPs on a hepatoma H22 tumor-bearing mouse model reveal that they could serve as an efficient FR/NIR fluorescent probe for targeted in vivo fluorescence imaging and cancer detection in a high contrast and specific manner. Together with the negligible in vivo toxicity, CPDP-FA NPs are promising FR/NIR fluorescent probes for future in vivo applications. Bright far-red/near-infrared conjugated polymer nanoparticles with surface folate ligand and 27% quantum yield in aqueous media are synthesized via a one-step lipid-PEG-folate formulation. The obtained nanoparticles show good thermal/photostabilities and a large Stoke's shift, which compare favorably with commercially available quantum dots (Qdot 655) and organic dyes (Alexa Fluor 555 and Rhodamine 6G), making them a safe and efficient FR/NIR fluorescent probe for targeted in vivo fluorescence imaging and cancer detection in a high contrast and specific manner. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.