Clickable bisreactive small gold nanoclusters for preparing multifunctionalized nanomaterials: application to photouncaging of an anticancer molecule

In this study, we successfully synthesized a small-sized gold nanocluster (2 nm) coated with homogeneous tripeptides bearing azido and amino groups that enable facile multifunctionalizations. Using sodium phenoxide to reduce tetrachloroauric(iii) acid in the presence of the cysteine-containing tripeptide, we efficiently prepared the gold nanoclusters without damaging the azido group. We then utilized this clickable bisreactive nanocluster as a versatile platform for synthesizing multifunctionalized gold nanomaterials. The resulting nanoclusters were conjugated with an anticancer compound connected to an indolizine moiety for photoinduced uncaging, a photodynamic therapy agent acting as a photosensitizer for uncaging, and a cyclic RGD peptide. The cytotoxicity of the multifunctionalized gold nanoclusters was demonstrated through red light irradiation of human lung cancer-derived A549 cells treated with the synthesized nanomaterials. The significant cytotoxicity exhibited by the cells underscores the potential utility of this method in advanced cancer therapies.

Tris(4'-Nitrobiphenyl)amine─An Octupolar Chromophore with High Two-Photon Absorption Cross-Section and Its Application for Uncaging of Calcium Ions in the Near-Infrared Region

Compounds with high two-photon absorption (2PA) performance in the near-infrared region have attracted great attention because of their application in the material and biological science. In this study, we have developed a simple and novel octupolar chromophore, tris(4'-nitrobiphenyl)amine 1, with three nitro peripheral groups attached to a triphenylamine core via biphenyl linkers. A mono-branched analogue 2 has also been prepared to investigate the effects of octupolar and dipolar systems on photophysical and 2PA behaviors. Compound 1, despite having a much simpler structure than the previous three-branched scaffolds, exhibits comparable σ₂ values, reaching 1330 GM at 730 nm and 900 GM at 820 nm in toluene. Combined with an outstanding σ₂/MW ratio (2.2 GM g^-1 mol) and a high fluorescence quantum yield (0.51), 1 displays potential as a promising two-photon (2P) probe for bioimaging. Subsequently, the ethylene glycol tetraacetic acid-substituted derivatives featuring octupolar (3 and 5) or dipolar (4 and 6) character have been synthesized and their one-photon (1P) and 2P photochemical reactions have been examined. Finally, 1P- and 2P-triggered uncaging of Ca²⁺ from these calcium chelators has been confirmed.