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 (CS_BX3), Lemon Juice (CS_LJ), and Green Tea (CS_GT), with a commercial reference (CS_Ref). 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. CS_BX3 and CS_LJ showed superior stability under various stress conditions CS_BX3 retained colloidal stability both at low temperatures (3.97% size reduction at 4 °C) and in PBS (14.2% in SPR intensity). CS_LJ displayed strong steric stabilization, showing minimal size variation in PBS. Zeta potential and SEM analyses confirmed that CS_BX3 maintained dispersion and particle uniformity across neutral and alkaline pH, while CS_GT showed significant aggregation. CS_GT and CS_BX3 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.