Interfacial Redox Transformation and Phytochemical Capping Drive the Formation and Protective Bioefficacy of Phyllanthus acidus-Derived Selenium Nanoparticles against Aeromonas hydrophila Infection in Zebrafish

Abstract

This study demonstrates selenium nanoparticle (PAF-SeNPs) synthesis through interfacial redox transformation using Phyllanthus acidus fruit extract as reductant and stabilizing matrix. LC–MS/MS-QTOF profiling revealed redox-active phytochemicals, including gallic acid, caffeic acid, quercetin, kaempferol, and rutin, which facilitated electron transfer across the plant extract–selenium ion interface. These metabolites reduced Se⁴⁺ to elemental Se⁰ while capping the nanoparticle surface, stabilizing the colloidal system. PAF-SeNPs showed a UV–Vis absorption peak at 292 nm, and FTIR analysis confirmed hydroxyl, carbonyl, and amide groups in reduction and capping. PAF-SeNPs displayed spherical morphology with average diameter of ~70.63 nm and negative surface charge (–22.89 mV), indicating stability and monodispersity. Biological evaluation showed potent antibacterial activity against Aeromonas hydrophila with MIC of 62.37 ± 2.20 µg/mL, with antimicrobial mechanism mediated by ROS generation, membrane disruption, and leakage of intracellular biomolecules. In vivo zebrafish embryo studies confirmed biocompatibility (100 µg/mL) and protective efficacy against A. hydrophila infection (75 µg/mL). PAF-SeNPs treatment reduced oxidative stress by suppressing ROS levels, restoring antioxidant enzyme levels (SOD, CAT, and GPx), and downregulating inflammatory mediators (TNF-α, IL-1β, IL-6, and COX-2). Selenium's redox activity and P. acidus phytochemical corona provided antioxidant and anti-inflammatory properties. These findings show interfacial redox transformation and phytochemical capping govern PAF-SeNPs formation, stability, and bioefficacy, indicating potential as eco-safe nanotherapeutics for infection control and aquaculture health management.