Effect of oral Mn-based nanozymes Mn3O4 NPs on morphological, antioxidation, mucosa, and fecal microbial community in mice colons

Mn₃O₄ NPs, manganese-based nanoparticles with multienzyme-like antioxidative activity, have been widely used in anti-inflammatory, anti-tumor, and other related studies, especially those related to Inflammatory Bowel Disease (IBD). However, before formalizing these studies, it is important to assess their oral safety (especially intestinal) to understand its potential adverse effects on biological systems and intestinal health. In this study, we synthesized Mn₃O₄ NP which has been reported to have proven multienzyme-like antioxidative activity based on previous studies. The fixed-dose method was used to evaluate the oral acute toxicity of Mn₃O₄ NPs in mice, followed by 14 days of observation. Then, relative parameters were explored for mice undergoing continuous gavage of 125 mg/kg and 250 mg/kg BW Mn₃O₄ NPs for 20 days. The continuous oral administration of low-dose Mn₃O₄ NPs for 20 days resulted in an increased expression of mRNA of antioxidant genes in mice colon. These changes led to an improvement in the antioxidant capacity of the colon. In contrast, the administration of a high dose of Mn₃O₄ NPs resulted in colonic oxidative damage, and mucosal damage in mice colons, as well as an increase in the ratio of Firmicutes to Bacteroidota of the fecal microbial communities.