Controllable and green synthesis of cellulose nanofiber/silver nanoparticle colloids with excellent biocompatibility and antibacterial activity

The demand for antibiotic-free silver nanoparticle (AgNP) colloids is rising due to concerns over antibiotic resistance. However, conventional synthesis lacks control over AgNP size, dispersibility and stability, limiting their biomedical applications. In this study, cellulose nanofibers (CNFs) served as green reductants and dispersants to controllably synthesize CNF/AgNP colloids under UV irradiation. The process was well-described by fitting curve equations with relative standard deviations below 4.5%. The resulting colloids exhibited excellent stability, with no precipitation after 30 days and a 96.26% Ag⁺ reduction rate. The zeta potential remained between −61.7 and −50.3 mV, indicating strong colloidal stability. The colloids also showed outstanding biocompatibility (cell viability &gt;100%) and strong antibacterial activity (&gt;99.99% inhibition of <i>E. coli</i> and <i>S. aureus</i>). Long-term release studies indicated a sustained Ag⁺ release potential of up to 126 days. This green and controllable method offers a promising route for developing high-performance AgNP colloids for biomedical and antimicrobial applications.