Labeling of Amine-Modified Material Surfaces with PFB-Fluorescein

Introduction: Fluorescent labeling is a widely used method for visualizing and tracking materials. 5-(Pentafluorobenzoylamino) fluorescein (PFB-F) is a dye in which the pentafluorobenzoylamino group substituent functions as a reactive linker. While PFB-F has been used for labeling biomolecules, its application in labeling surfaces has not been explored yet. Here, we report straightforward method for attaching PFB-F to amine-modified material surfaces requiring only dimethyl sulfoxide (DMSO) solvent and room temperature (RT). Methods: We conducted nuclear magnetic resonance (NMR) and thin layer chromatography (TLC) analysis on a mock reaction involving PFB-F and N -butylamine to evaluate the process of attachment via the PFB linker. PFB-F was also reacted with poly-L-lysine to evaluate conjugation to polymers bearing primary amine groups. Silica nanoparticles (SiNPs) labeled with PFB-F were administered to nematode worms, followed by confocal fluorescence microscopy. Results: NMR and TLC analysis confirmed covalent bonding between PFB-F and primary amines via nucleophilic aromatic substitution (S N Ar) involving displacement of at least one fluorine atom. PFB-F was successfully conjugated to poly-L-lysine, demonstrating efficient reaction with polymers containing primary amine groups. SiNPs labeled with PFB-F were ingested by nematode worms and successfully tracked in vivo. Discussion: These results demonstrate that PFB-F is a versatile and effective reagent for stable surface labeling. This study paves the way for broader applications of PFB-F in material design. Keywords: fluorescein, PFB-F, nanoparticles, material surface, conjugate chemistry, C. elegans