Ultrabright Fluorescent Organic Nanoparticles Based on Small-Molecule Ionic Isolation Lattices*.

Area of Science:

• Materials Science
• Nanotechnology
• Biomedical Imaging

Background:

• Ultrabright fluorescent nanoparticles (NPs) are crucial for advanced bioimaging.
• Previous methods achieved bright NPs via hierarchical coassembly of cationic fluorophores and cyanostar anion-receptor complexes into small-molecule ionic isolation lattices (SMILES).
• SMILES prevent aggregation quenching, enhancing dye fluorescence.

Purpose of the Study:

• To develop a simple, one-step method for formulating SMILES materials into NPs.
• To characterize the optical properties and bioimaging potential of these novel NPs.

Main Methods:

• A one-step supramolecular approach was used to create rhodamine-based SMILES NPs.
• Glycol amphiphiles were employed as stabilizers for NP formulation.
• Optical properties, including fluorescence quantum yield and brightness, were measured.

Main Results:

• Rhodamine-based SMILES NPs exhibited a high fluorescence quantum yield (30%) and brightness per volume (5000 M⁻¹ cm⁻¹/nm³).
• Each 16-nm NP contained approximately 400 dye molecules, yielding a particle absorption coefficient of 4×10⁷ M⁻¹ cm⁻¹.
• UV excitation of the cyanostar component enhanced NP brightness (>6000 M⁻¹ cm⁻¹/nm³) via energy transfer.

Conclusions:

• The developed supramolecular method provides a straightforward route to highly fluorescent, stable NPs.
• These NPs demonstrate exceptional brightness and optical properties suitable for demanding bioimaging.
• The NPs successfully stained cells, indicating significant promise for in vitro and in vivo bioimaging applications.