Imaging with near-infrared fluorescing colloidal particles is emerging as an attractive tool for therapeutics and diagnostics in nanoparticle-based medicine. We report here on a general approach for the activation/deactivation of emission of near-infrared emitting nanoparticles. Sub-100 nm poly(propargyl acrylate) (PA) particles were synthesized and surface modified through copper-catalyzed azide/alkyne cycloaddition to attach azide-terminated squaraine derivative (azSQ), a near-infrared emitter, and poly(ethylene glycol) (azPEG) chains. The emission of functionalized particles is deactivated when dispersed in aqueous solutions due to the aggregation of the hydrophobic azSQ. The fluorescence of azSQ on the particles can be switched on when the fluorophores complex with serum albumin to form host/ guest assemblies, while the disruption of the azSQ/ albumin assemblies is utilized to turn off the emission of the functionalized particles. To achieve the deactivation, the fluorescing particles were incubated with trypsin which digests the albumin. The fragments of peptide chains cannot form complexes with the azSQ and causes the fluorophore to dimerize once again and subsequently the emission of particles is switched off. The activation/ deactivation of functionalized particles was also demonstrated in vitro in A549 and UMSCC22A cells using confocal studies. The confocal studies suggested that the particles were taken up by cells through endocytosis and accumulated into lysosomes.

Switchable fluorescence of near-infrared nanoparticles via protein interaction

245th National Meeting (2013)

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