Composite fluorescent nanoparticles for biomedical imaging.

Area of Science:

• Biomedical Imaging
• Materials Science
• Nanotechnology

Background:

• Biomedical imaging requires advanced fluorophores that are nontoxic, photostable, and nonquenching.
• Existing fluorophores often face limitations in stability and performance within biological environments.

Purpose of the Study:

• To encapsulate a novel, hydrophobic pentacene-based fluorescent dye within polymeric nanoparticles (NPs) or nanocarriers (NCs).
• To utilize the Flash NanoPrecipitation (FNP) process for creating these functionalized NPs.
• To evaluate the suitability of these encapsulated dyes for advanced fluorescent imaging applications.

Main Methods:

• Polymeric nanoparticles and dye-loaded micelles were synthesized using the Flash NanoPrecipitation (FNP) technique.
• Characterization involved dynamic light scattering, fluorescence spectroscopy, UV-VIS absorbance spectroscopy, and confocal microscopy.
• Förster resonant energy transfer (FRET) modeling was employed to understand fluorescence quenching mechanisms.

Main Results:

• Fluorescent NPs were successfully fabricated with core loadings ranging from <1% to 78% by weight, with optimal fluorescence at 2.3 wt.%.
• Particle diameters ranged from 20 to 250 nm, with fluorescence intensity scaling linearly with nanoparticle core volume.
• The encapsulated dye exhibited absorption peaks at 458, 575, and 625 nm, and emission peaks at 635 and 695 nm, with concentration-independent spectral properties within the NP core.

Conclusions:

• Et-TP5, a pentacene derivative, was successfully encapsulated into NCs via FNP, yielding a highly photostable and nonquenching fluorophore.
• The hydrophobic nature of the dye and its localization within the NP core prevent self-quenching and interaction with biological systems.
• This encapsulation strategy allows for a 25-fold increase in dye delivery compared to surface conjugation, demonstrating utility in quantifying nanoparticle binding.