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

Dafne Musino,Gautier Landrot,Thierry Rabilloud,Bastien Dalzon,Cécile Lelong,Camille Rivard,Sylvie Luche,Isabelle Capron,Julie Devcic

doi:10.3390/nano11071862

Abstract

There 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-based substrate (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 oxidation state, while maintaining an fcc structure. AgNPs transition from 10 nm spherical NPs to 300 nm triangular-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+/Ag0 ratio 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. A new 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.

Highlights

A range of CNC/AgNP hybrids was produced by adding various amounts of Ag precursor (AgNO3 ) to a CNC aqueous suspension, varying the AgNP content from 0.4 wt%
The formation of AgNPs resulted from the aggregation of monomeric Ag particles obtained by a reduction to zero-valence Ag atoms [28], and was confirmed by the presence of a dominant in-plane absorption peak at λmax ~400 nm in the UV/vis spectra (Figure 1a) whose intensity increased with AgNP content
The results showed that the interatomic distances in the CNC/AgNP hybrids did not significantly change in comparison with the metallic silver distances and that the space group of the AgNPs still corresponded to the fcc silver structure, as indicated by X-ray Diffraction Spectroscopy (XRD)

Summary

Introduction

Silver nanoparticles (AgNPs) have emerged as one of the most efficient biocidal agents, limiting or preventing microorganisms’ growth [1,2,3,4]. Even if the exact action mechanism of AgNPs on bacteria is still not completely understood, several authors consider that their antimicrobial effect is mainly due to the release of the Ag+ ions. These ions can interact with the components of the cell (e.g., thiols) [12], inducing structural and morphological changes in bacteria [10,12,13]

Methods

Results

Conclusion