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Ag nanoclusters of 5 atoms, Ag 5 , synthesized by a kinetic control method, show exceptional catalytic activities for the redox elimination of radicals. Their use as catalytic radical scavengers in industrially relevant processes involving detrimental free radical formation, such as polymer stabilization, is here demonstrated, opening a new class of catalytic antiradicals with many potential industrial and/or biomedical applications. [Display omitted] Silver nanoclusters of five atoms (Ag 5) display outstanding catalytic activities for the deactivation of radicals. Using 2,2-diphenyl-1‑picrylhydrazyl (DPPH) radical as a model system, we observed a fast radical reduction to DPPH anions using only [Ag 5 ] 3 to 4 orders of magnitude less than [DPPH]. Moreover, nanoclusters remain stable at the end of the reaction, and can deactivate again DPPH radicals at the same rate, indicating that they act as anti-radical catalysts. The radical scavenger catalytic activity of Ag 5 proceeds selectively through the oxidation of methanol (used to dissolve the radical) to formaldehyde, which is supported by DFT calculations. The obtained catalytic rate constants are almost 2 orders of magnitude higher than oxidases, and more than 4 orders of magnitude larger than graphene quantum dots. We also show that Ag 5 not only catalyze the reduction of radicals but also their oxidation, promoting the inhibition of the autoxidation mechanisms of hydrocarbon polymers, which are very sensitive to the presence of radicals. For this purpose, thin films of two industrially relevant polymers (polyisoprene and acrylonitrile–butadienestyrene copolymer), were exposed to standard simulated photo-ageing conditions in the presence of Ag 5. Using Attenuated Total Reflection-FTIR and DFT modeling we observed that, although Ag 5 nanoclusters, with ≈ 15% surface coverage, do not totally inhibit the oxidation, they favour a decomposition that yields inactive products, in contrast with the more detrimental ketone formation pathway. These results not only open new possibilities for developing a post-process inhibition of polymer degradation, for which nowadays there are no efficient procedures, but also, they could be used as very efficient dual-redox catalytic radical scavengers for different industrial or biomedical purposes. [ABSTRACT FROM AUTHOR]

Low atomicity clusters present properties dependent on the size, due to the quantum confinement, with well‐defined electronic structures and high stability. Here it is shown that Ag5 clusters catalyze the complete oxidation of sulfur to S+6. Ag5 catalytic activity increases with different oxidant species in the order O2 ≪ H2O2 < OH•. Selective oxidation of thiols on the cysteine residues of glutathione and thioredoxin is the primary mechanism human cells have to maintain redox homeostasis. Contingent upon oxidant concentration, Ag5 catalyzes the irreversible oxidation of glutathione and thioredoxin, triggering apoptosis. Modification of the intracellular environment to a more oxidized state to mimic conditions within cancer cells through the expression of an activated oncogene (HRASG12V) or through ARID1A mutation, sensitizes cells to Ag5 mediated apoptosis. While cancers evolve to evade treatments designed to target pathways or genetic mutations that drive them, they cannot evade a treatment that takes advantage of aberrant redox homeostasis, which is essential for tumor progression and metastasis. Ag5 has antitumor activity in mice with orthotopic lung tumors reducing primary tumor size, and the burden of affected lymphatic nodes. The findings suggest the unique intracellular redox chemistry of Ag5 may lead to new redox‐based approaches to cancer therapy. [ABSTRACT FROM AUTHOR]

Synthesis and purification of metal clusters without strong binding agents by wet chemical methods are very attractive for their potential applications in many research areas. However, especially challenging is the separation of uncharged clusters with only a few number of atoms, which renders the usual techniques very difficult to apply. Herein, we report the first efficient separation of Ag2 and Ag3 clusters using the different entropic driving forces when such clusters interact with DNA, into which Ag3 selectively intercalates. After sequential dialysis of the samples and denaturalizing the DNA‐Ag3 complex, pure Ag2 can be found in the dialysate after extensive dialysis. Free Ag3 is recovered after DNA denaturation. [ABSTRACT FROM AUTHOR]

Cancer therapy, catalysis, low atomicity clusters, silver clusters, sulfur oxidation Keywords: cancer therapy; catalysis; low atomicity clusters; silver clusters; sulfur oxidation EN cancer therapy catalysis low atomicity clusters silver clusters sulfur oxidation 1 1 1 07/20/22 20220718 NES 220718 B Antitumoral Agents b In article number 2113028, M. Arturo López-Quintela, Fernando Domínguez, and co-workers report that Ag SB 5 sb clusters show unique catalytic activities to oxidize thiols. This oxidation is tunable by relevant biological oxidants species (hydrogen peroxide and hydroxyl radical), allowing Ag SB 5 sb to inhibit the thiol-based antioxidants leading to the selective death of tumor proliferating cells. [Extracted from the article]