Binding of Silver Nanoparticles to Bacterial Proteins Depends on Surface Modifications and Inhibits Enzymatic Activity

Abstract

Here we describe results from a proteomic study of protein-nanoparticle interactions to further the understanding of the ecotoxicological impact of silver nanoparticles (AgNPs) in the environment. We identified a number of proteins from Escherichia coli that bind specifically to bare or carbonatecoated AgNPs. Of these proteins, tryptophanase (TNase) was observed to have an especially high affinity for both surface modifications despite its low abundance in E. coli. Purified TNase loses enzymatic activity upon associating with AgNPs, suggesting that the active site may be in the vicinity of the binding site(s). TNase fragments with high affinities for both types of AgNPs were identified using matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) mass spectrometry. Differences in peptide abundance/presence in mass spectra for the two types of AgNPs suggest preferential binding of some protein fragments based on surface coating. One highbinding protein fragment contained a residue (Arg103) that is part of the active site. Ag adducts were identified for some fragments and found to be characteristic of strong binding to AgNPs rather than association of the fragments with ionic silver. These results suggest a probable mechanism for adhesion of proteins to the most commonly used commercial nanoparticles and highlight the potential effect of nanoparticle surface coating on bioavailability.

Analysis of engineered nanomaterials in complex matrices (environment and biota): General considerations and conceptual case studies

“…For example, enzyme-linked immunosorbent assays, which use specific antibodies and enzymes, have been widely used for the low-level analysis of molecules. The specific association of AgNPs with cell surface proteins [12] and the differential expression of bacterial stress response genes with AgNPs and TiO 2 nanoparticles [13] indicate that biological reporter systems [14] that are highly specific to nanoparticle surfaces could be developed. Biosensors are very sensitive and, because they report on interactions of nanoparticles with living systems [15,16], should provide assessments of bioavailable fractions of nanoparticles, which are highly relevant to understanding exposure.…”

“…Engineered AgNPs and CdSe QDs both have propensity to dissolve, for solutes to thus co-occur with nanoparticles, andbased partly on analogous substances-for solutes to possibly reorganize into nanoparticles in situ [34,35]. The co-occurrence of solutes and nanoparticles can affect nanoparticle bioavailability and uptake [12], which may inform dose and toxicity mechanism assessments. Conceptually, CdSe QDs [36] can dissolve externally to cells or can enter cells either intact after damaging membranes or accumulate in cells as highly reactive toxicants [37].…”

Study on antibacterial alginate-stabilized copper nanoparticles by FT-IR and 2D-IR correlation spectroscopy

“…[4][5][6][7] Alginate is a naturally occurring polysaccharide obtained from marine brown algae, comprising the linear chain of (1,4)-β-d-mannuronic acid and (1,3)-α-l-guluronic acid, has been made in understanding the size, shape, and surface chemistry of metal nanostructures and their influence on biocidal activity. 11 It has emerged that multiple factors cooperate to establish a specific antibacterial activity, mainly dependent on the high surface atom density of the nanoparticles, which includes their size and shape, [12][13][14] particle internalization, 15,16 agglomeration of metal nanostructures over time on in vitro assays, 3,13,17 chemical functionalization of nanoparticles, 18,19 concentration of metal, 3 types of microorganism and initial number of bacterial cells, 3,20,21 and type of assay. 22 A secondary aim of this study was to compare the bactericidal effects of stabilized Cu NPs using various bacterial strains, to reveal strain specificities, and to correlate the phases of composition of Cu NPs with antibacterial activity, eventually leading to better utilization of nanoparticles for specific applications.…”

Detection of the Quorum Sensing Signal Molecule N-Dodecanoyl-DLHomoserine Lactone Below 1 Nanomolar Concentrations using Surface Enhanced Raman Spectroscopy

“…In conventional Raman all bands would scale linearly to our concentration, which is unfortunately not the case for SERS. Furthermore, since Ag ions and Ag nanoparticles have shown to be toxic to bacteria [ 43] future work should use coated Ag nanoparticles. The coatings could be polymers or antibodies and be designed to capture as well as protect the bacteria.…”