Mechanism of cellular uptake, localization and cytotoxicity of organic nanoparticles

Water-dispersed organic nanoparticles (NPs) were prepared from a conjugated molecule 2,5,2',5'-tetra(4'-N,N-diphenylaminostyryl)biphenyl (DPA-TSB). As a potential material for photodynamic therapy, we investigated cellular toxicity by using fluorescence confocal microscopy and Western blotting. Our results demonstrated that the cells treated with DPA-TSB NPs showed an increase in apoptosis accompanied by the increased expression of Bax protein, decreased expression of Bcl-2 protein and caspase-3 protein, the decreased mitochondrial membrane potential and the release of ROS. Using inhibitors of endocytosis can block nanoparticles uptake, indicating that DPA-TSB NPs entered the cells via an energy-dependent manner, mostly through clathrin-mediated and caveolae-mediated processes.