Nanocellulose-Silver Nanoparticle Nanocomposites for Hydrogel, Aerogel, and Film Development: Antibacterial
Luiz Gustavo Ribeiro1,2,3, Yelin Ko3, Juan P Hinestroza3
1Development and Innovation Laboratory, Instituto Butantan, São Paulo, São Paulo 05503-900, Brazil.
Abstract:
A green and sustainable strategy was employed for the in situ formation of silver nanoparticles (AgNPs) within a TEMPO-oxidized cellulose nanofibril (CNF) matrix, using CNF as both a reducing and stabilizing system. AgNPs formation was confirmed by the presence of a surface plasmon resonance band at approximately 420 nm, while DLS indicated colloidal dispersion and transmission electron microscopy (TEM) revealed predominantly spherical nanoparticles, mostly in the 10-20 nm range, associated with the CNF network. The CNF-AgNP nanocomposite dispersion was further processed into hydrogels, films, and aerogels, which were characterized by transmission electron microscopy (TEM), rheology, tensile testing, field-emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). Further, the actual silver content in the CNF-AgNP hydrogel was determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The hydrogel exhibited shear-thinning behavior, whereas the films showed a tensile strength of 1.39 MPa and thermal stability up to approximately 100 °C. The CNF-AgNP composites inhibited the growth of Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis through disk diffusion assays, while CNF alone showed negligible antibacterial activity. In the Zebrafish (Danio rerio) Embryo Toxicity Test (FET Test), end points such as embryo coagulation, lack of somite formation, nondetachment of the tail, and absence of heartbeat were assessed for CNF-AgNPs that induced acute lethality (LC50) of 1.115 μM at 96 h, whereas CNF dilutions were nontoxic under the tested conditions. Overall, TEMPO-oxidized CNF enabled the fabrication of multifunctional CNF-AgNP hydrogels, films, and aerogels with antibacterial activity and reduced acute embryotoxicity compared with free silver ions. Further studies addressing silver release kinetics, long-term exposure, and performance under real-world conditions are warranted to substantiate their environmental and biomedical safety.
