Oxidation of Hydrogen Sulfide to Polysulfide and Thiosulfate by a Carbon Nanozyme: Therapeutic Implications with an Emphasis on Down Syndrome

Hydrogen sulfide (H2S) is a noxious, potentially poisonous, but necessary gas produced from sulfur metabolism in humans. In Down Syndrome (DS), the production of H2S is elevated and associated with degraded mitochondrial function. Therefore, removing H2S from the body as a stable oxide could be an approach to reducing the deleterious effects of H2S in DS. In this report we describe the catalytic oxidation of hydrogen sulfide (H2S) to polysulfides (HS2+n−) and thiosulfate (S2O32−) by poly(ethylene glycol) hydrophilic carbon clusters (PEG‐HCCs) and poly(ethylene glycol) oxidized activated charcoal (PEG‐OACs), examples of oxidized carbon nanozymes (OCNs). We show that OCNs oxidize H2S to polysulfides and S2O32− in a dose‐dependent manner. The reaction is dependent on O2 and the presence of quinone groups on the OCNs. In DS donor lymphocytes we found that OCNs increased polysulfide production, proliferation, and afforded protection against additional toxic levels of H2S compared to untreated DS lymphocytes. Finally, in Dp16 and Ts65DN murine models of DS, we found that OCNs restored osteoclast differentiation. This new action suggests potential facile translation into the clinic for conditions involving excess H2S exemplified by DS. Oxidized carbon nanozymes catalytically oxidize hydrogen sulfide to polysulfides and thiosulfate in an oxygen‐dependent manner. In this report the reaction kinetics of polysulfide and thiosulfate formation both in a cell‐free setting and intracellularly and present the possible role of these nanozymes as a supportive therapy in Down Syndrome, a condition where hydrogen sulfide production is detrimentally elevated.