ABSTRACT
Ultrabright fluorescent nanoparticles (NPs) hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical coassembly with cyanostar anion-receptor complexes. These small-molecule ionic isolation lattices (SMILES) ensure spatial and electronic isolation to prohibit aggregation quenching of dyes. We report a simple, one-step supramolecular approach to formulate SMILES materials into NPs. Rhodamine-based SMILES NPs stabilized by glycol amphiphiles show high fluorescence quantum yield (30 %) and brightness per volume (5000â M-1 cm-1 /nm3 ) with 400 dye molecules packed into 16-nm particles, corresponding to a particle absorption coefficient of 4×107 â M-1 cm-1 . UV excitation of the cyanostar component leads to higher brightness (>6000â M-1 cm-1 / nm3 ) by energy transfer to rhodamine emitters. Coated NPs stain cells and are thus promising for bioimaging.
Subject(s)
Fluorescent Dyes/chemistry , Nanoparticles/chemistry , Rhodamines/chemistry , Small Molecule Libraries/chemistry , HEK293 Cells , Humans , Molecular Structure , Optical Imaging , Particle Size , Ultraviolet RaysABSTRACT
Efficient organic photosensitizers are attractive for cancer cell ablation in photodynamic therapy. Bright fluorescent photosensitizers are highly desirable for simultaneous imaging and therapy. However, due to fundamental competition between emission and singlet oxygen generation, design attempts to increase singlet oxygen generation almost always leads to the loss of fluorescence. Herein, it is shown for the first time that nanocrystallization enables a simultaneous and significant increase in the brightness and singlet oxygen generation of an organic photosensitizer. Spectroscopic studies show simultaneous enhancement in the visible light absorption and fluorescence after nanocrystallization. The enhanced absorption of visible light in nanocrystals is found to translate directly to the enhanced singlet oxygen production, which shows a higher ability to kill HeLa cells as compared to their amorphous counterpart.
ABSTRACT
Persistent room-temperature phosphorescence (RTP) in pure organic materials has attracted great attention because of their unique optical properties. The design of organic materials with bright red persistent RTP remains challenging. Herein, we report a new design strategy for realizing high brightness and long lifetime of red-emissive RTP molecules, which is based on introducing an alkoxy spacer between the hybrid units in the molecule. The spacer offers easy Br-H bond formation during crystallization, which also facilitates intermolecular electron coupling to favor persistent RTP. As the majority of RTP compounds have to be confined in a rigid environment to quench nonradiative relaxation pathways for bright phosphorescence emission, nanocrystallization is used to not only rigidify the molecules but also offer the desirable size and water-dispersity for biomedical applications.
Subject(s)
Luminescent Measurements/methods , Nanoparticles/chemistry , Organic Chemicals/chemistry , Temperature , Bromine/chemistry , Cell Line, Tumor , Color , Humans , Hydrogen Bonding , Microscopy, Electron, ScanningABSTRACT
A new bottom-up nanocrystallization method is developed to fabricate highly fluorescent organic nanocrystals in aqueous media using an aggregation-induced emission fluorogen (AIEgen) as an example. The nanocrystallization strategy leads to the fabrication of uniform nanocrystals of 110 ± 10 nm size in aqueous media, which shows over 400% increase in brightness as compared to the amorphous nanoaggregates.
