Impact of Physico-Chemical Properties of Cellulose Nanocrystal/Silver Nanoparticle Hybrid Suspensions on Their Biocidal and Toxicological Effects

International audienceThere is a demand for nanoparticles that are environmentally acceptable, but simultaneously efficient and low cost. We prepared silver nanoparticles (AgNPs) grafted on a native bio-basedsubstrate (cellulose nanocrystals, CNCs) with high biocidal activity and no toxicological impact.AgNPs of 10 nm are nucleated on CNCs in aqueous suspension with content from 0.4 to 24.7 wt%.XANES experiments show that varying the NaBH4/AgNO3 molar ratio affects the AgNP oxidationstate, while maintaining an fcc structure. AgNPs transition from 10 nm spherical NPs to 300 nmtriangular-shaped AgNPrisms induced by H2O2 post-treatment. The 48 h biocidal activity of the hybrid tested on B. Subtilis is intensified with the increase of AgNP content irrespective of the Ag+/Ag0ratio in AgNPs, while the AgNSphere−AgNPrism transition induces a significant reduction of biocidal activity. A very low minimum inhibitory concentration of 0.016 mg AgNP/mL is determined. Anew long-term biocidal activity test (up to 168 h) proved efficiency favorable to the smaller AgNPs.Finally, it is shown that AgNPs have no impact on the phagocytic capacity of mammalian cells