Synthesized manganese oxide nanorods: Fabrication, characterization, application in cardiomyocyte protection from oxidative stress during sepsis, and evaluation of biochemical aspects of hemoglobin interaction

Abstract

Oxidative stress during sepsis could play a crucial role in the pathogenesis of several diseases, especially cardiovascular disorders. In fact, myocardial dysfunction during sepsis is caused by a number of chemicals, one of which is hydrogen peroxide (H₂O₂). Therefore, sepsis‐induced cardiomyopathy can be controlled through modulation of oxidative stress. Despite the encouraging pharmacological activities demonstrated by inorganic nanostructures, the mechanisms behind their blood protein interaction and antioxidant activity remain unclear. In order to advance the investigation for fabricating nanostructure platforms and studying their antioxidant effects as well as blood protein binding affinities, we explored the synthesis of manganese oxide (Mn₃O₄) nanorods via hydrothermal method and subsequent characterization using various techniques. The antioxidant effects against H₂O₂-induced oxidative stress in AC16 cardiomyocytes were then evaluated by different cellular and molecular assays. Additionally, the interaction of Mn₃O₄ nanorods with hemoglobin was investigated by experimental and and docking analyses. The results showed that synthesized Mn₃O₄ nanorods had an absorption peak in the range of 260 to 420 nm, vibration bands centered at 510 cm⁻¹, 629 cm⁻¹ and 410 cm⁻¹, 13 distinct XRD peaks, a rod-like morphology with a diameter range of 10 to 75 nm, a hydrodynamic size of 371.7 nm, and a zeta potential of −43.3 mV. Moreover, the antioxidant assays indicated that synthesized Mn₃O₄ nanorods can trigger a protective effect against H₂O₂-induced oxidative stress in AC16 cardiomyocytes through inhibition of reactive oxygen species (ROS) overproduction, increased content of superoxide dismutase (SOD) and catalase and glutathione (GSH), and reduction of caspase-3 activity. Furthermore, the fluorescence quenching mechanism of hemoglobin by Mn₃O₄ nanorods was determined to be controlled by a spontaneous and static quenching process, involvement of hydrogen bonds, a binding affinity (K_b) value of 10⁴ M⁻¹, and number of binding site (n) of around 1.03. Additionally, it was found that Mn₃O₄ nanorods induced a slight conformational change in the hemoglobin structure, where Tyr35 and Trp37 move to a hydrophilic microenvironment. In conclusion, it can be suggested that Mn₃O₄ nanorods with a reasonable plasma protein binding affinity can be used as an antioxidant co-therapy in cardiac dysfunction during sepsis.