Screening Small Metabolites From Cells As Multifunctional Coatings Simultaneously Improves Biocompatibility And Functionality Of Nanosilver

Currently,nanomaterials face a dilemma due to their advantageous properties and potential risks to human health.There are more than 2000 nanomaterial-based products,of which over 50%include Ag.Thus,the wide application of nanosilver（nAg）with irreplaceable biocidal effects is limited.Many methods have been proposed to reduce nanotoxicity,such as the regulation of shapes,sizes and surface modifications.Unfortunately,the resulting improvements in the biocompatibility of nanomaterials are in most cases accompanied by reduced functionality.Here,a strategy to improve both nanomaterial biocompatibility and functionality is established by screening small metabolites from cells as nanomaterial coatings.Firstly,a metabolomics analysis of cells（LO₂）exposed to nanosilver（nAg）is used and it integrates volcano plots（t-tests and fold change analysis）,partial least squares-discriminant analysis（PLS-DA）,and significance analysis of microarrays（SAM）.Adding the downregulated metabolites into cell media,the further analyses of cell viability,oxidative stress,and cell apoptosis further screen out the exact biomolecule which reduces nanotoxicity of nAg.The nanotoxicity and antibacterial ability of nAg coated with the screened biomolecule are further studied.The main results are as follows:（1）6 metabolites（L-aspartic acid,L-malic acid,myoinositol,D-sorbitol,citric acid,and L-cysteine）are identified.The five metabolites other than L-cysteine are downregulated by nAg compared with the control.（2）Analyses of cell viability,oxidative stress,and cell apoptosis reveal that D-sorbitol markedly reduces nAg cytotoxicity.Specifically,the addition of D-sorbitol enhances the cell viability,reduces the production of reactive oxygen species and decreases cell apoptosis simultaneously.（3）Stability of nAg can be enhanced by the addition of D-sorbitol.Small molecule loading,surface oxidation,and ionic release experiments support D-sorbitol as the optimal coating for nAg.The intracellular nAg and Ag⁺are quantified and the concentration ratio of nAg to Ag⁺is enhanced by the addition of D-sorbitol.The mechanism of reduced nanotoxicity lies in the D-sorbitol-induced anti-oxidation and ion release of nAg and the promoted discharge of Ag⁺.（4）D-sorbitol loading improves both biocompatibility of nAg towards cells and the duration of the antibacterial activity of nAg against Escherichia coli and Staphylococcus aureus.The biocidal persistence of nAg-sorbitol is extended beyond 9h,and the biocidal effects at 12 h are significantly higher than those of naked nAg.This work proposes a new strategy to improve the biocompatibility and functionality of nAg simultaneously by screening small metabolites from cells as nanomaterial functional coatings.This method can be applied to mitigate the side effects of other nanomaterials.