Biosynthesis of Mn3O4 nanoparticles using leaf extract of Cicer Arietinum for oxidase mimicking and antibacterial activities

Abstract

Biosynthesized metal oxide nanoparticles (MONPs) have triggered a substantial research interest due to their advancements and diverse applications. In this study, aqueous phase green synthesis of Mn₃O₄ nanoparticles (NPs) using Cicer Arietinum leaf extract was elucidated for the first time. The phytochemicals of the extract can act as potential reducing and capping agents in the nanoparticle's fabrication process. The tailored Mn₃O₄ NPs were characterized using various techniques, including UV–Vis, FE-SEM, EDS, FTIR, and XRD. The results revealed the formation of pure Mn₃O₄NPs with an average crystallite diameter of 13.51 ± 0.24 nm. Biologically synthesized Mn₃O₄ NPs exhibited oxidase-like activity and can catalyze the oxidation of 3, 3′, 5, 5′ -tetramethylbenzidine (TMB) to produce a blue oxidized TMB (ox-TMB). The kinetic K_m and V_max parameters were determined for the synthesized Mn₃O₄ nanozymes to be 0.0333 mM and 1.11 × 10⁻⁸ M s⁻¹, respectively. Accordingly, an efficient colorimetric detection of ascorbic acid (AA) was attained based on fading the blue color of ox-TMB. The colorimetric system showed good linearity (R² = 0.9935) at concentration levels ranging from 10 to 70 μM, with LOD of 6.3 μM, and high selectivity for detecting AA in orange juice samples with reasonable accuracy and precision. The antibacterial activity of biosynthesized Mn₃O₄ NPs was also tested against bacterial growth of both types of gram positive and gram negative using well diffusion method. The prepared Mn₃O₄ NPs possess remarkable antibacterial effect particularly on gram positive bacteria of Enterococcus faecalis. This study highlighted the use of Cicer Arietinum leaf waste for the synthesis of Mn₃O₄ NPs as nanozymes and potential antibacterial agents, suggesting their applications in biochemical sensing, pharmaceutical, and food packaging.