Two-Photon Responsive Photoremovable Protecting Groups PRPGs as Drug Delivery Systems

To increse the applicability of PRPGs in terms of higher wavelength or lower energy activation, we introduced an alternative approch rather than developing new NIR-active PRPGs i.e., utilizing two-photon activity of a particular chromophore. Our group has developed various two-photon responsive PRPGs that cage and release bioactive molecules by two-photon (NIR) light sources. The newly developed two-photon activated PRPGs are Carbazole fused o-hydroxycinnamate, β‑Carboline, naphthalene attached p-hydroxyphenacyl, bis-benzothiazole, naphthyridine, and fluorene derivatives.  Recently, our group has developed Binol based two-photon responsive PRPG with a large TP cross-section (~140 GM at 800 nm). These newly developed fluorescent two-photon responsive PRPGs have been utilized for the controlled release of dual anticancer drugs with real-time monitoring ability in the NIR region. Interestingly, some of these PRPGs were able to generate singlet oxygen on two-photon excitation and hence used for a synergistic combination of chemotherapy and PDT for cancer treatment.