Abstract
Among the plethora of available metal(loid) nanomaterials (NMs), those containing selenium are interesting from an applicative perspective, due to their high biocompatibility. Microorganisms capable of coping with toxic Se-oxyanions generate mostly Se nanoparticles (SeNPs), representing an ideal and green alternative over the chemogenic synthesis to obtain thermodynamically stable NMs. However, their structural characterization, in terms of biomolecules and interactions stabilizing the biogenic colloidal solution, is still a black hole that impairs the exploitation of biogenic SeNP full potential. Here, spherical and thermodynamically stable SeNPs were produced by a metal(loid) tolerant Micrococcus sp. Structural characterization obtained by Scanning Electron Microscopy (SEM) revealed that these SeNPs were surrounded by an organic material that contributed the most to their electrosteric stabilization, as indicated by Zeta (ζ) potential measurements. Proteins were strongly adsorbed on the SeNP surface, while lipids, polysaccharides, and nucleic acids more loosely interacted with SeNMs as highlighted by Fourier Transform Infrared Spectroscopy (FTIR) and overall supported by multivariate statistical analysis. Nevertheless, all these contributors were fundamental to maintain SeNPs stable, as, upon washing, the NM-containing extract showed the arising of aggregated SeNPs alongside Se nanorods (SeNRs). Besides, Density Functional Theory (DFT) calculation unveiled how thiol-containing molecules appeared to play a role in SeO32− bioreduction, stress oxidative response, and SeNP stabilization.
Highlights
The rapid and exponential growth of nanotechnology during the last 40 years has led to the development of many synthetic procedures to generate nanomaterials (NMs) featuring different sizes, shapes, and compositions for varioustechnological purposes [1]
Micrococcus sp. cells were negatively affected by the metabolic controlled growth conditions, as highlighted by cell death events occurring after 48 h of bacterial incubation (Figure S2a), which is in line with previous observations [12]
The obtained negative surface charges may derive from diverse biomolecules present in the Organic Material (OM) surrounding Se nanoparticles (SeNPs), such as proteins,lipids, nucleic acids, and polysaccharides [10], being in line with the results reported for other biogenic SeNMs [30,31,35,36,37]
Summary
The rapid and exponential growth of nanotechnology during the last 40 years has led to the development of many synthetic procedures to generate nanomaterials (NMs) featuring different sizes, shapes, and compositions for various (bio)technological purposes [1]. Selenium nanostructures (SeNSs) have gained technological interest, due to their physical-chemical versatility [2] and their efficiency as components of renewable energy production devices, constituting an important alternative over fossil-fuel technologies [3]. SeNMs feature high biocompatibility, being Se an essential micronutrient for living organisms, favoring SeNS (bio)technological and biomedical applications compared to other metal-based NMs [4]. Alternative synthetic methodologies are needed to produce green SeNMs, among which, those based on environmental-friendly bacteria and biocompatible chemical
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