In-situ synthesis and immobilization of silver nanoparticles on microfibrillated cellulose for long-term antibacterial applications

Synthesis of nanocomposites containing silver nanoparticles (AgNPs) has drawn growing interest owing to their antimicrobial activity and tuneable physicochemical properties. In this study, we report the surface modification of microfibrillated cellulose (MFC) with bio-inspired polydopamine (PDA) followed by in-situ growth and immobilization of AgNPs. The resultant AgNPs-PDA-MFC nanocomposites were characterized by UV–Vis spectrophotometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The results showed that crystalline face-centered cubic AgNPs with a mean diameter of 19.1 nm were randomly and firmly immobilized on MFC. The attenuated total reflection Fourier transform infrared analysis results confirmed the formation of AgNPs, and the content of silver in AgNPs-PDA-MFC was determined by thermogravimetry. The aqueous suspension of AgNPs-PDA-MFC was stable during 30 days of storage. Antibacterial activity of the AgNPs-PDA-MFC nanocomposites was evaluated with Escherichia coli and Staphylococcus aureus. Importantly, AgNPs-PDA-MFC exhibited excellent long-term antibacterial activity. This was ascribed to the extremely slow but sustained release of silver from the AgNPs-PDA-MFC (0.56% in 14 days). Furthermore, the application of AgNPs-PDA-MFC as coating and filling agents was preliminarily evaluated. This study suggests that the AgNPs-PDA-MFC nanocomposites with long-term antibacterial performance provide a promising solution for fighting against pathogenic bacteria. Graphic abstract