A Reduction Active Theranostic Nanoparticle for Enhanced Near-Infrared Imaging and Phototherapy by Reducing Glutathione Level in Cancer Cells.

Facile preparation of a tumoral-stimuli-activated theranostic nanoparticle with simple constituents remains a challenge for tumor theranostic nanosystems. Herein we design a simple reductionresponsive turn-on theranostic nanoparticle for achieving fluorescent imaging and phototherapy combination. The theranostic nanoparticle is prepared by a simple one-step dialysis method of reduction active amphiphilic hyperbranched poly(β-amidoamines) and a near-infrared (NIR) dye indocyanine green (ICG). The fluorescence of ICG is quenched by the aggregation-caused quenching (ACQ) effect. The fluorescent intensity of free ICG at 816 nm was ∼40 times as high as that of particulate ICG. After reductive nanoparticles incubated with dithiothreitol (DTT), the size of the nanoparticles increased from 160 nm to 610 nm by Dynamic light scattering (DLS). As nanoparticles were internalized by cancer cells, the disulfide bonds would be cleaved by intracellular reduction agents like glutathione (GSH), leading to the release of entrapped ICG. The released ICG regained its fluorescence for self-monitoring the release and therapeutic effect of ICG by fluorescence spectra and the quantitative evaluation of NIR fluorescence intensity. Remarkably, nanoparticles can also reinforce antitumor efficacy through photodynamic therapy and GSH depletion property. This study provides new insights into designing turn-on theranostic systems.