The current global pandemic crisis caused by the outbreak of the SARS-CoV-2 virus has caused more than 0.7 million deaths worldwide and forcing social distancing among the people affecting the...

The photodynamic activities of selected copper(II) complexes [Cu(L 1 )B]ClO 4 (1,2) and [Cu(L 2 )B]ClO 4 (3,4), where L 1 = 2-[(pyridin-2-yl)methyleneamino]phenol, L 2 = 2-[(pyridin-2yl)methyleneamino]benzenethiol and B are 1H-imidazo[4,5-f ]-[1,10]phenanthroline (L 3 ) and 1-(pyren-2-yl)-1H-imidazo[4,5-f ]-[1,10]phenanthroline (L 4 ), were studied in detail in a structureactivity relationship (SAR)-based approach to explore the role of S-coordination to Cu II in photodynamic therapy (PDT) to human cervical cancer (HeLa) cells. Although all of the complexes were toxic in the dark (IC 50 ≈ 10 μM), we observed enormous enhancement (about 10 fold) in the cytotoxicity of the complexes in visible light (400-700 nm, 10 J cm -2 ), resulting in IC 50 ≈ 1.0 μM. Intracellular reactive oxygen species (ROS) generated in the HeLa cells during photoactivation of the complexes was [a]

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Iron­(III)-phenolate/carboxylate complexes exhibiting photoredox chemistry and photoactivated reactive oxygen species (ROS) generation at their ligand-to-metal charge-transfer (LMCT) bands have emerged as potential strategic tools for photoactivated chemotherapy. Herein, the synthesis, in-depth characterization, photochemical assays, and remarkable red light-induced photocytotoxicities in adenocarcinomic human immortalized human keratinocytes (HaCaT) and alveolar basal epithelial (A549) cells of iron­(III)-phenolate/carboxylate complex of molecular formula, [Fe­(L1)­(L2)] (1), where L1 is bis­(3,5 di-tert-butyl-2-hydroxybenzyl)­glycine and L2 is 5-(1,2-dithiolan-3-yl)-N-(1,10-phenanthroline-5-yl)­pentanamide, and the gold nanocomposite functionalized with complex 1 (1-AuNPs) are reported. There was a significant red shift in the UV–visible absorption band on functionalization of complex 1 to the gold nanoparticles (λmax: 573 nm, 1; λmax: 660 nm, 1-AuNPs), rendering the nanocomposite an ideal candidate for photochemotherapeutic applications. The notable findings in our present studies are (i) the remarkable cytotoxicity of the nanocomposite (1-AuNPs) to A549 (IC50: 0.006 μM) and HaCaT (IC50: 0.0075 μM) cells in red light (600–720 nm, 30 J/cm2) while almost nontoxic (IC50 > 500 μg/mL, 0.053 μM) in the dark, (ii) the nontoxicity of 1-AuNPs to normal human diploid fibroblasts (WI-38) or human peripheral lung epithelial (HPL1D) cells (IC50 > 500 μg/mL, 0.053 μM) both in the dark and red light signifying the target-specific anticancer activity of the nanocomposite, (iii) localization of 1-AuNPs in mitochondria and partly nucleus, (iv) remarkable red light-induced generation of reactive oxygen species (ROS: 1O2, •OH) in vitro, (v) disruption of the mitochondrial membrane due to enhanced oxidative stress, and (vi) caspase 3/7-dependent apoptosis. A similar cytotoxic profile of complex 1 was another key finding of our studies. Overall, our current investigations show a new red light-absorbing iron­(III)-phenolate/carboxylate complex-functionalized gold nanocomposite (1-AuNPs) as the emerging next-generation iron-based photochemotherapeutic agent for targeted cancer treatment modality.