A comparative evaluation of green colloidal silver variants for enhanced stability and bioactivity.

Colloidal silver (CS) is at the forefront of enhancing novel consumer products formulations & packaging. However, conventional synthesis methods pose challenges, including toxicity, high costs, and poor colloidal stability. Green synthesis using plant extracts offers a sustainable alternative by leveraging natural bioactive compounds. This study compares CS synthesized via a patented plant-based method (CSBX3), Lemon Juice (CSLJ), and Green Tea (CSGT), with a commercial reference (CSRef). Characterization using UV-Vis, DLS, SEM, Zeta Potential, and EDS assessed particle size, stability, and composition under stress conditions: long-term storage (60 days), varying temperatures (4-37 °C), pH (3-11), and phosphate-buffered saline (PBS). Antioxidant activity was evaluated and antimicrobial efficacy against E.coli and Listeria to determine MIC. CSBX3 and CSLJ showed superior stability under various stress conditions CSBX3 retained colloidal stability both at low temperatures (3.97% size reduction at 4 °C) and in PBS (14.2% in SPR intensity). CSLJ displayed strong steric stabilization, showing minimal size variation in PBS. Zeta potential and SEM analyses confirmed that CSBX3 maintained dispersion and particle uniformity across neutral and alkaline pH, while CSGT showed significant aggregation. CSGT and CSBX3 showed the most potent antimicrobial and antioxidant properties (20% higher antioxidant activity than other CS solutions and over 90% bacterial eradication within 24 h). These results highlight the potential of green-synthesized CS for food, biomedical, and personal care applications.