4-Aminothiophenol Photodimerization Without Plasmons

The photodimerization of 4-aminothiophenol (PATP) into 4,4’-dimercaptobenzene (DMAB) has been extensively utilized as a paradigm reaction to probe the role of surface plasmons in nanoparticle-mediated light-driven processes. Over the past 25 years, a lively debate about the reaction mechanism involved several research groups. Plasmon-mediated generation of energetic (hot) electrons and holes has been invoked as the main driving-force, although plasmonic heating has recently gained attention. However, either model and their combinations are not sufficient to explain some experimental observations and appear, in some cases, contradictory. No matter the differences, there is a general, firm consensus about the presence of plasmonic nanoparticles (Ag or Au), which has always been considered mandatory for triggering the photoconversion. Here I report the first observation of the PATP-to-DMAB photoreaction in the absence of any plasmonic mediators. In particular, neither plasmonic heating nor charge transfer from hot carriers were exploited. The reaction was observed to occur with different kinetics on plasmon-free TiO2 nanoparticles, as well as on self-standing droplets. Confocal microRaman spectroscopy enabled to investigate the reaction progress in different plasmon-free contexts, either aerobic or anaerobic, suggesting a new interpretation of the photodimerization process, based on direct laser-induced activation of singlet oxygen species. These results provide new insights in light-driven redox processes, elucidating the role of sample morphology, light and oxygen.

Symmetrically Substituted Zn and Al Phthalocyanines and Polymers for Photodynamic Therapy Application

N4 macrocyclic complexes of Al and Zn phthalocyanines with symmetrical imine and imidazole moiety at the periphery were synthesized. The synthesized ligands, complexes, and polymers were purified and characterized to study the structure of the molecule. These synthesized complexes were used for photodynamic therapy application as the diamagnetic Zn and Al have the ability to produce and stabilize singlet oxygen species. The synthesized N4 molecules of aluminum iminomethoxy phenyl phthalocyanine and aluminum ethyl phenyl benzimidazolephthalocyanine showed better activity against MCF-7 cells. These results suggest that this assay may be used as an early biomarker of clinical response.

Synthesis and Photophysical Properties of Tumor-Targeted Water-Soluble BODIPY Photosensitizers for Photodynamic Therapy

The synthesis of three water-soluble lactose-modified 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based photosensitizers with tumor-targeting capabilities is reported, including an investigation into their photodynamic therapeutic activity on three distinct cancer cell lines (human hepatoma Huh7, cervical cancer HeLa, and breast cancer MCF-7 cell lines). The halogenated BODIPY dyes exhibited a decreased fluorescence quantum yield compared to their non-halogenated counterpart, and facilitated the efficient generation of singlet oxygen species. The synthesized dyes exhibited low cytotoxicities in the dark and high photodynamic therapeutic capabilities against the treated cancer cell lines following irradiation at 530 nm. Moreover, the incorporation of lactose moieties led to an enhanced cellular uptake of the BODIPY dyes. Collectively, the results presented herein provide promising insights for the development of photodynamic therapeutic agents for cancer treatment.

Synthesis of pH-Responsive Glycopolymer with End Group Zinc(II) Phthalocyanines as Potential Photosensitizer

A novel end-functionalized glycopolymer poly (3-O-methacryloyl-D-glucofuranose) -b-poly (2-Diethylaminoethyl Methacrylate) (PMAGlc-b-PDEA-ZnTAPc) with zinc (II) teraamaninophthalocyanine was synthesized. First, a pH-responsive copolymer PMAIpG-b-PDEA was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Then PMAIpG-b-PDEA reacted with ZnTAPc and deprotected to form a water-soluble and pH-responsive photosensitizer. The structure of the PMAGlc-b-PDEA-ZnTAPc was characterized by 1H NMR and GPC. The photophysical properties were evaluated by UV-Vis and fluorescence spectra. The PMAGlc-b-PDEA-ZnTAPc can generate singlet oxygen species with good singlet oxygen quantum yields (Φ△=0.38), which is believed to be the major cytotoxic reactive oxygen species (ROS) for photodynamic therapy. The ZnPc functionalized glycopolymer will be used as a potential photosensitizer in the fields of photodynamic therapy.

Photo-excited Toluidine Blue Inhibits Full-Length Tau Aggregation in Alzheimer’ Disease

The aggregates of microtubule-associated protein Tau are the major hallmark of Alzheimer’sdisease. Tau aggregates accumulate intracellularly thus leading to generation of neuronal toxicity.Numerous approaches have been targeted against Tau protein aggregation, which include application of synthetic and natural compounds. Toluidine blue is a basic dye of phenothiazine family, which irradiation with 630 nm light converted to photo-excited form leading to generation of singlet oxygen species. In present work we studied the potency of Toluidine blue and photo-excited Toluidine blue against Tau aggregation. Biochemical and biophysical analysis using ThSfluorescence, SDS-PAGE, CD spectroscopy and electron microscopy suggested that Toluidine blueinhibits the aggregation of Tau in-vitro. The Photo-excited toluidine blue potentially dissolved the matured Tau fibrils, which was indicating disaggregation property of Toluidine blue. The cell biology studies including cytotoxicity assays, ROS production assays suggested Toluidine blue to be a biocompatible dye as reduced ROS levels and cytotoxicity was observed after exposure of Toluidine blue on Tau stressed cells. The photo-excited Toluidine blue modulates the cytoskeleton network in cells, which was supported by immunofluorescence studies of neuronal cells. The studies in UAS Tau E14 transgenic Drosophila model suggested that photo-excited Toluidine blue was potent to restore the survival and memory deficit of Drosophila. The overall findings of our studies suggests that Toluidine blue to be a potent molecule in rescuing the Tau-mediated pathology by inhibiting its aggregation, reducing the cytotoxicity; modulating the tubulin level and behavioral characteristics of Drosophila. Thus Toluidine blue can be addressed as a potent molecule against Alzheimer’s disease.

Photo-excited Toluidine Blue Inhibits Full-Length Tau Aggregation in Alzheimer’ Disease

The aggregates of microtubule-associated protein Tau are the major hallmark of Alzheimer’sdisease. Tau aggregates accumulate intracellularly thus leading to generation of neuronal toxicity.Numerous approaches have been targeted against Tau protein aggregation, which include application of synthetic and natural compounds. Toluidine blue is a basic dye of phenothiazine family, which irradiation with 630 nm light converted to photo-excited form leading to generation of singlet oxygen species. In present work we studied the potency of Toluidine blue and photo-excited Toluidine blue against Tau aggregation. Biochemical and biophysical analysis using ThSfluorescence, SDS-PAGE, CD spectroscopy and electron microscopy suggested that Toluidine blueinhibits the aggregation of Tau in-vitro. The Photo-excited toluidine blue potentially dissolved the matured Tau fibrils, which was indicating disaggregation property of Toluidine blue. The cell biology studies including cytotoxicity assays, ROS production assays suggested Toluidine blue to be a biocompatible dye as reduced ROS levels and cytotoxicity was observed after exposure of Toluidine blue on Tau stressed cells. The photo-excited Toluidine blue modulates the cytoskeleton network in cells, which was supported by immunofluorescence studies of neuronal cells. The studies in UAS Tau E14 transgenic Drosophila model suggested that photo-excited Toluidine blue was potent to restore the survival and memory deficit of Drosophila. The overall findings of our studies suggests that Toluidine blue to be a potent molecule in rescuing the Tau-mediated pathology by inhibiting its aggregation, reducing the cytotoxicity; modulating the tubulin level and behavioral characteristics of Drosophila. Thus Toluidine blue can be addressed as a potent molecule against Alzheimer’s disease.

Selective photooxidation of sulfides mediated by singlet oxygen using visible-light-responsive coordination polymers

A novel visible-light-responsive coordination polymer for highly selective photooxidation of sulfides to produce sulfoxides through singlet oxygen species.