Hydrothermal duck-feather keratin as a reagent-free bioreductant and capping matrix for bioactive silver...

The sustainable production of silver nanoparticles (AgNPs) from renewable biowaste would reduce environmental burden and expand green nanotechnology applications. This study reports a hydrothermal extraction route that avoids external chemical reductants, thereby enabling duck-feather keratin to function intrinsically as both a reducing and capping agent in the synthesis of stable, bioactive AgNPs. Extraction was verified using the Lowry assay and SDS-PAGE, confirming preservation of protein content needed for metal coordination. One-factor-at-a-time optimization identified pH 11, 70 °C, 30 mL extract per 1 mM Ag⁺ reaction, and a 24 h duration as optimal conditions, producing uniform spherical nanoparticles having an average (11 nm) with excellent dispersion and long-term optical stability. Characterization by UV-Vis, FTIR, XRD, and SEM-EDX confirmed Ag⁺ reduction, keratin capping, and crystalline face-centered cubic Ag formation. TGA-DTA showed improved thermal stability, while BET surface area increased from 1.55 to 6.32 m²·g⁻¹ after nanoparticle incorporation, indicating enhanced mesoporosity. The synthesized duck-feather keratin silver nanoparticles (DFKSN) demonstrated strong antioxidant activity and potent antibacterial performance, with DDT, MIC, and MBC assays confirming both bacteriostatic and bactericidal effects against Gram-positive and Gram-negative bacteria. The nanoparticles also promoted cytocompatibility in human skin fibroblasts cell (HSF1184) at a dose of 3.0 mg.mL^-1. These findings highlight hydrothermally processed keratin as a scalable, waste-valorizing route for sustainable and eco-friendly nanomaterial production.