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<p>Conventional metallic nanoparticle synthesis relies on toxic chemicals and harsh conditions, limiting biomedical applications and environmental sustainability. This study overcomes these challenges through eco-friendly biosynthesis using the marine bacterium <i>Cytobacillus kochii</i>. strain SW6, offering a sustainable platform for multifunctional nanoparticle production. The optimal conditions for biosynthesis determined using response surface methodology (RSM) were 1.5 mM HAuCl₄, 15&#xa0;mg/mL cell extract, pH 10.5, and 80&#xa0;°C. Comprehensive characterization using DLS, XRD, FTIR, EDAX, TGA-DSC, and HRTEM, confirmed nanoparticle properties, while systematic bioactivity screening evaluated therapeutic and environmental applications. The synthesized Ck-AuNPs demonstrated dose-dependent antioxidant and anti-inflammatory activities (50–250&#xa0;µg/mL) via DPPH radical scavenging, reducing power, and protein denaturation assays. Antibacterial efficacy was observed against <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i> at minimum inhibitory concentrations of 50&#xa0;µg/mL The anti-biofilm activity was observed at minimum biofilm inhibition concentrations (MBIC<sub>50</sub>) of 54 and 60&#xa0;µg/mL for <i>S. aureus</i> and <i>P. aeruginosa</i>, respectively. These findings were supported by the hydrophobicity index, EPS quantification, and microscopic observation. Mechanistic studies revealed ROS-mediated killing through oxidative stress and glutathione depletion, while gelatinase enzyme inhibition demonstrated reduced bacterial virulence. Remarkably, Ck-AuNPs also exhibited excellent biocatalytic degradation of environmental pollutants including methylene blue, phenol red, and 4-nitrophenol, indicating dual biomedical-environmental applications. This green synthesis eliminates toxic reagents while enhancing biocompatibility, producing nanoparticles superior to chemically synthesized counterparts. <i>C. kochii</i> strain SW6 represents the marine bacterial platform for sustainable AuNPs production, offering scalable biotechnology for next-generation therapeutic agents and environmental remediation solutions. The dual functionality positions these nanoparticles as transformative materials for addressing antimicrobial resistance and pollution simultaneously.</p> Graphical Abstract <p></p>

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Multifunctional Biogenic Gold Nanoparticles from Cytobacillus Kochii (Ck-AuNPs): Response Surface Methodology-Driven Synthesis, Characterization and Exploration of their Therapeutic and Catalytic Potential

  • 期刊论文

  • 发表日期：

    2025年11月29日

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  • Vadivel Meyappan,
  • Jayabalan Shilpha,
  • Natarajan Sakthivel

摘要

Conventional metallic nanoparticle synthesis relies on toxic chemicals and harsh conditions, limiting biomedical applications and environmental sustainability. This study overcomes these challenges through eco-friendly biosynthesis using the marine bacterium Cytobacillus kochii. strain SW6, offering a sustainable platform for multifunctional nanoparticle production. The optimal conditions for biosynthesis determined using response surface methodology (RSM) were 1.5 mM HAuCl₄, 15 mg/mL cell extract, pH 10.5, and 80 °C. Comprehensive characterization using DLS, XRD, FTIR, EDAX, TGA-DSC, and HRTEM, confirmed nanoparticle properties, while systematic bioactivity screening evaluated therapeutic and environmental applications. The synthesized Ck-AuNPs demonstrated dose-dependent antioxidant and anti-inflammatory activities (50–250 µg/mL) via DPPH radical scavenging, reducing power, and protein denaturation assays. Antibacterial efficacy was observed against Staphylococcus aureus and Pseudomonas aeruginosa at minimum inhibitory concentrations of 50 µg/mL The anti-biofilm activity was observed at minimum biofilm inhibition concentrations (MBIC50) of 54 and 60 µg/mL for S. aureus and P. aeruginosa, respectively. These findings were supported by the hydrophobicity index, EPS quantification, and microscopic observation. Mechanistic studies revealed ROS-mediated killing through oxidative stress and glutathione depletion, while gelatinase enzyme inhibition demonstrated reduced bacterial virulence. Remarkably, Ck-AuNPs also exhibited excellent biocatalytic degradation of environmental pollutants including methylene blue, phenol red, and 4-nitrophenol, indicating dual biomedical-environmental applications. This green synthesis eliminates toxic reagents while enhancing biocompatibility, producing nanoparticles superior to chemically synthesized counterparts. C. kochii strain SW6 represents the marine bacterial platform for sustainable AuNPs production, offering scalable biotechnology for next-generation therapeutic agents and environmental remediation solutions. The dual functionality positions these nanoparticles as transformative materials for addressing antimicrobial resistance and pollution simultaneously.

Graphical Abstract