Size‐Tunable Fluorescent Unimolecular Nanoparticles (FUNs) for Bright Cancer Imaging

Fluorescent nanoparticles such as quantum dots, carbon dots, and polymeric fluorophore conjugates have shown promising applications for biomedical imaging. It is desirable to develop new fluorescent probes with well-defined particle size, bright fluorescence, high biocompatibility, and easy functionalization. Here, a facile and controllable method is first reported to prepare size-tunable fluorescent unimolecular nanoparticles (FUNs) for biomedical imaging. The FUNs are constructed by the rapid ring-opening polymerization (ROP) of amino acid N-carboxyanhydrides monomers using a fluorescent dye-cored polylysine dendritic macromolecule as the macroinitiator. By precisely adjusting the ratio of the monomer to the macroinitiator, the study customizes FUNs with particle sizes of 30, 60, 90, or 130 nm. The fluorescence quantum yield of the FUNs is up to 6.6-fold of the small molecule dye. It is shown that the particle size-dependent cellular uptake, blood circulation, and tumor entrance by optical imaging with the glutamic acids (Glu)-modified FUNs (FUNs-Glu). The FUNs-Glu with sizes of 30 and 60 nm exhibited superior blood circulation, tumor accumulation, and penetration. These FUNs dendritic dots have the merits of tunable particle size, single-molecule structure, excellent fluorescence properties, and ample groups for surface functionalization, which have great potential for various biomedical imaging.