Extracellular Polymeric Substances Govern the Surface Charge of Biogenic Elemental Selenium Nanoparticles

Abstract

The origin of the organic layer covering colloidal biogenic elemental selenium nanoparticles (BioSeNPs) is not known, particularly in the case when they are synthesized by complex microbial communities. This study investigated the presence of extracellular polymeric substances (EPS) on BioSeNPs. The role of EPS in capping the extracellularly available BioSeNPs was also examined. Fourier transform infrared (FT-IR) spectroscopy and colorimetric measurements confirmed the presence of functional groups characteristic of proteins and carbohydrates on the BioSeNPs, suggesting the presence of EPS. Chemical synthesis of elemental selenium nanoparticles in the presence of EPS, extracted from selenite fed anaerobic granular sludge, yielded stable colloidal spherical selenium nanoparticles. Furthermore, extracted EPS, BioSeNPs, and chemically synthesized EPS-capped selenium nanoparticles had similar surface properties, as shown by ζ-potential versus pH profiles and isoelectric point measurements. This study shows that the EPS of anaerobic granular sludge form the organic layer present on the BioSeNPs synthesized by these granules. The EPS also govern the surface charge of these BioSeNPs, thereby contributing to their colloidal properties, hence affecting their fate in the environment and the efficiency of bioremediation technologies.

Biogenic selenium nanoparticles synthesized by Stenotrophomonas maltophilia SeITE02 loose antibacterial and antibiofilm efficacy as a result of the progressive alteration of their organic coating layer

“…As reported in previous studies (Jain et al ., 2015; Cremonini et al ., 2016; Lampis et al ., 2017), biogenic SeNPs from the bacterial strain Stenotrophomonas maltophilia SeITE02 present a complex organic cap consisting of different biomolecules such as proteins, lipids and carbohydrates. In order to evaluate the possible influence of such an organic coating layer on the biological reactivity of these biogenic SeNPs (here called SeNPs‐24 and also untreated SeNPs), different and progressively more aggressive denaturants were applied to the nanoparticles.…”

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…Similarly, a stronger NP-cell association was observed between nC 60 and Gram negative E. coli (155-342 ng-C 60 /g-dry cell mass) than with Gram positive Bacillus subtilis (21-41 ng-C 60 /g-dry cell mass) [123]. EPS, dissolved or bound to cell wall [124] have been shown to affect the physicochemical properties and stability of ENMs [15,22,58,125], and can also mediate heteroaggregation between NPs (and other nanomaterials) and cells [114,116,119]. Environmental factors such as media ionic strength, pH, and NOM or other dispersing agents can also influence heteroaggregation between NPs and microorganisms [107,[114][115][116].…”

“…NOM is mainly the residual from plants and animals materials, as well as some of the biocolloids mentioned before [15,22,58]. NOM has been shown to interact strongly with ENMs [59], modifying their surfaces and in general making them more bioavailable [60,61].…”

“…The importance of NOM on the aggregation behavior of nanoparticles has led to many studies. However, due to the complex composition of NOM, most of the studies consider a specific composition of NOM, such as fulvic acid [43] or humic acid, and more recently, microbial EPS [58,[87][88][89]. In addition, although a number of studies have provided a clear understanding of the role of NOM in a homoaggregation system [14,80,90], there are very few studies that address the role of NOM in heteroaggregation [91].…”

A comparison of fate and toxicity of selenite, biogenically, and chemically synthesized selenium nanoparticles to zebrafish (Danio rerio) embryogenesis

“…dissolution, entry into cells, surface chemistry, and reactivity) into consideration (Buchs et al, 2013;Winkel et al, 2012). Although the average particle size of nano-Se b is more than 100 nm, microbially produced Se(0) is often referred to as nano-Se in the literature (Jain et al, 2015;Srivastava & Mukhopadhyay, 2013;Zhang et al, 2011). In addition, the particles of nano-Se b formed by microorganisms are colloidal in nature (Buchs et al, 2013); hence the term nano-selenium is used in this paper.…”