Metallo-Supramolecular Helical Fibres from Chiral Phenylacetylene Monomers: Cation Induced Self-Assembly

Chiral metallo-supramolecular fibres can be easily obtained by mixing a chloroform solution of a phenylacetylene monomer (PA) that bears a chiral sulfoxide group as pendant, with different equivalents of a methanolic solution of AgClO4 . Thus, while the PA is found molecularly dissolved in chloroform, the addition of Ag+ ions induce its aggregation through the formation of an axially chiral metallo-supramolecular aggregate with high thermal stable properties. In this case, the ability of the metal ion to coordinate the PA triple bond, combined with the argentophilicity of the metal ion and the planarity of the phenylacetylene drives to the formation of a helical coordination polymer, whose P or M axial chirality is determined by the chirality of the sulfoxide used as substituent of the PA. Depending on the PA/Ag+ (mol/mol) ratio, it is possible to tune the morphology of the metallo-supramolecular aggregate from chiral fibers to chiral gel.

Amino-OPE glycosides and blue light: a powerful synergy in photodynamic therapy

Herein we report the synthesis and biological properties of sugar-conjugated oligophenylene ethynylene (OPE) dyes, used as novel photosensitizers (PSs) for photodynamic treatment (PDT) under blue light. The OPE-bearing glycosides at both ends are successfully prepared by a Pd-catalyzed Sonogashira cross-coupling reaction. The live-cell imaging studies have shown that these OPE glycosides (including glucose, mannose and maltose derivatives) efficiently penetrate the cytoplasm of cultured HeLa cancer cells. No dark toxicity was observed, but upon irradiating the cells under blue light an extraordinary photodynamic effect was observed at low concentrations (10^-6-10^-8 M). The localization studies indicate that OPE-glucose 1 and OPE-mannose 2 have Golgi patterns, whereas OPE-maltose 3 could be in lysosomes. The PDT and morphological studies in HeLa cells treated with sublethal doses of PS 1-3 revealed that cell death occurs by necrosis.

Eosin Y-Functionalized Upconverting Nanoparticles: Nanophotosensitizers and Deep Tissue Bioimaging Agents for Simultaneous Therapeutic and Diagnostic Applications

Functionalized upconverting nanoparticles (UCNPs) are promising theragnostic nanomaterials for simultaneous therapeutic and diagnostic purposes. We present two types of non-toxic eosin Y (EY) nanoconjugates derived from UCNPs as novel nanophotosensitizers (nano-PS) and deep-tissue bioimaging agents employing light at 800 nm. This excitation wavelength ensures minimum cell damage, since the absorption of water is negligible, and increases tissue penetration, enhancing the specificity of the photodynamic treatment (PDT). These UCNPs are uniquely qualified to fulfil three important roles: as nanocarriers, as energy-transfer materials, and as contrast agents. First, the UCNPs enable the transport of EY across the cell membrane of living HeLa cells that would not be possible otherwise. This cellular internalization facilitates the use of such EY-functionalized UCNPs as nano-PS and allows the generation of reactive oxygen species (ROS) under 800 nm light inside the cell. This becomes possible due to the upconversion and energy transfer processes within the UCNPs, circumventing the excitation of EY by green light, which is incompatible with deep tissue applications. Moreover, the functionalized UCNPs present deep tissue NIR-II fluorescence under 808 nm excitation, thus demonstrating their potential as bioimaging agents in the NIR-II biological window.

Turn-on Fluorescent Biosensors for Imaging Hypoxia-like Conditions in Living Cells

We present the synthesis, photophysical properties, and biological application of nontoxic 3-azo-conjugated BODIPY dyes as masked fluorescent biosensors of hypoxia-like conditions. The synthetic methodology is based on an operationally simple N=N bond-forming protocol, followed by a Suzuki coupling, that allows for a direct access to simple and underexplored 3-azo-substituted BODIPY. These dyes can turn on their emission properties under both chemical and biological reductive conditions, including bacterial and human azoreductases, which trigger the azo bond cleavage, leading to fluorescent 3-amino-BODIPY. We have also developed a practical enzymatic protocol, using an immobilized bacterial azoreductase that allows for the evaluation of these azo-based probes and can be used as a model for the less accessible and expensive human reductase NQO1. Quantum mechanical calculations uncover the restructuration of the topography of the S₁ potential energy surface following the reduction of the azo moiety and rationalize the fluorescent quenching event through the mapping of an unprecedented pathway. Fluorescent microscopy experiments show that these azos can be used to visualize hypoxia-like conditions within living cells.

Aldehydes as Photoremovable Directing Groups: Synthesis of Pyrazoles by a Photocatalyzed [3+2] Cycloaddition/Norrish Type Fragmentation Sequence

A straightforward methodology for the regioselective synthesis of pyrazoles has been developed by a domino sequence based on a photoclick cycloaddition followed by a photocatalyzed oxidative deformylation reaction. Distinguishing features of this protocol include an unprecedented photoredox-catalyzed Norrish type fragmentation under green-light irradiation and the use of α,β-unsaturated aldehydes as synthetic equivalents of alkynes, where the aldehyde is acting as a novel photoremovable directing group.