Organic Nanoparticle-Based Fluorescent Chemosensor for Selective Switching ON and OFF of Photodynamic Therapy (PDT)

Photodynamic therapy (PDT) is a non-invasive cancer treatment. For target-specific PDT, targeting "overexpression" of some specific cellular markers will be highly beneficial. As Cu-II content is higher in cancer cells than in normal cells, selective binding with Cu-II can be the most effective mode for intracellular heterogeneity-responsive targeted PDT. Thus, a photosensitizer showing competent PDT activity only after Cu-II chelation is important for tumor-targeted PDT. Herein, we report a new ratiometric fluorescent chemosensor based on anthracene-N-phenylethylenediamine nanoparticles (ANT-pen NPs), which showed fluorescence color change from green to red upon Cu-II chelation. Only the Cu-II-bound state showed selective PDT activity; hence, this color change was used for real-time monitoring of targeted PDT. Cellular images in cancerous HeLa and non-cancerous NIH 3T3 cell lines showed the change in fluorescence of ANT-pen NPs on selective binding with Cu-II in HeLa cells only. MTT assay in both cells suggested massive cell destruction by ANT-pen-Cu-II NPs only in HeLa cells upon visible light exposure, whereas NPs remained non-toxic to NIH 3T3 cells.