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<p>The pursuit of sustainable nanotechnology has sparked renewed interest in biologically synthesized nanoparticles as environmentally benign alternatives to chemically synthesized counterparts. This study reports an eco-friendly synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of <i>Streptomyces parvulus</i> PRA-19. A characteristic surface plasmon resonance at 434&#xa0;nm confirmed AgNP formation. The particles exhibited a hydrodynamic diameter of ~68 nm and stable colloidal behavior, with a zeta potential of −26.6 ± 8.17&#xa0;mV. TEM imaging revealed mostly spherical particles ranging from 2±1 to 40±1&#xa0;nm in size. Elemental silver presence and crystalline nature were validated by EDX, SAED, and XRD. FTIR analysis indicated proteinaceous groups aiding in stabilization, and SDS-PAGE coupled with computational studies identified a 47-kDa alkaline D-peptidase possibly involved in reduction and capping. Functionally, the AgNPs exhibited strong antimicrobial activity against both Gram-positive and Gram-negative bacteria, as well as a fungal strain, with MICs ranging from 16 to 32&#xa0;µg/mL. Protein-coated AgNPs showed slightly higher MICs (32–64&#xa0;µg/mL); yet, both outperformed silver nitrate and closely matched the efficacy of standard antibiotics. Antioxidant potential assessed via DPPH assay revealed a concentration-dependent scavenging effect with 78.24% inhibition at 100&#xa0;µg/mL and an IC₅₀ of 32.74&#xa0;µg/mL. Although less active than ascorbic acid (IC₅₀ = 3.79&#xa0;µg/mL), the AgNPs demonstrated significant free radical neutralization capacity. Together, these findings highlight the dual-functional potential of biogenic AgNPs as antimicrobial and antioxidant agents. Evidence of protein involvement during synthesis supports enhanced stability and functionality, providing a foundation for future applications in biomedical and material sciences. This study also advances insights into microbe-nanoparticle interfaces for rational nanomaterial design.</p>

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Eco-Friendly Biosynthesis of Biofunctional Silver Nanoparticles Using Streptomyces parvulus PRA-19: Protein-capped Structural Insights and Dual Antibacterial-Antioxidant Efficacy

  • 期刊论文

  • 发表日期：

    2025年10月27日

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  • Praveena Ganji,
  • Naga Amrutha Ravi,
  • Sunayana M,
  • Jayasimha R. Daddam,
  • Uma Rajeswari Batchu,
  • Sudheer Kumar Buddana,
  • Prakasham Reddy Shetty

摘要

The pursuit of sustainable nanotechnology has sparked renewed interest in biologically synthesized nanoparticles as environmentally benign alternatives to chemically synthesized counterparts. This study reports an eco-friendly synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of Streptomyces parvulus PRA-19. A characteristic surface plasmon resonance at 434 nm confirmed AgNP formation. The particles exhibited a hydrodynamic diameter of ~68 nm and stable colloidal behavior, with a zeta potential of −26.6 ± 8.17 mV. TEM imaging revealed mostly spherical particles ranging from 2±1 to 40±1 nm in size. Elemental silver presence and crystalline nature were validated by EDX, SAED, and XRD. FTIR analysis indicated proteinaceous groups aiding in stabilization, and SDS-PAGE coupled with computational studies identified a 47-kDa alkaline D-peptidase possibly involved in reduction and capping. Functionally, the AgNPs exhibited strong antimicrobial activity against both Gram-positive and Gram-negative bacteria, as well as a fungal strain, with MICs ranging from 16 to 32 µg/mL. Protein-coated AgNPs showed slightly higher MICs (32–64 µg/mL); yet, both outperformed silver nitrate and closely matched the efficacy of standard antibiotics. Antioxidant potential assessed via DPPH assay revealed a concentration-dependent scavenging effect with 78.24% inhibition at 100 µg/mL and an IC₅₀ of 32.74 µg/mL. Although less active than ascorbic acid (IC₅₀ = 3.79 µg/mL), the AgNPs demonstrated significant free radical neutralization capacity. Together, these findings highlight the dual-functional potential of biogenic AgNPs as antimicrobial and antioxidant agents. Evidence of protein involvement during synthesis supports enhanced stability and functionality, providing a foundation for future applications in biomedical and material sciences. This study also advances insights into microbe-nanoparticle interfaces for rational nanomaterial design.