Impact of Biogenic and Chemogenic Selenium Nanoparticles on Model Eukaryotic Lipid Membranes

Abstract

Microbial nanotechnology is an expanding research area devoted to producing biogenic metal and metalloid nanomaterials (NMs) using microorganisms. Often, biogenic NMs are explored as antimicrobial, anticancer, or antioxidant agents. Yet, most studies focus on their applications rather than the underlying mechanism of action or toxicity. Here, we evaluate the toxicity of our well-characterized biogenic selenium nanoparticles (bSeNPs) produced by the Stenotrophomonas maltophilia strain SeITE02 against the model yeast Saccharomyces cerevisiae comparing it with chemogenic SeNPs (cSeNPs). Knowing from previous studies that the biogenic extract contained bSeNPs in an organic material (OM) and supported here by Fourier transform infrared spectroscopy, we removed and incubated it with cSeNPs (cSeNPs_OM) to assess its influence on the toxicity of these formulations. Specifically, we focused on the first stages of the eukaryotic cell exposure to these samples─i.e., their interaction with the cell lipid membrane, which was mimicked by preparing vesicles from yeast polar lipid extract or phosphatidylcholine lipids. Fluidity changes derived from biogenic and chemogenic samples revealed that the bSeNP extract mediated the overall rigidification of lipid vesicles, while cSeNPs showed negligible effects. The OM and cSeNPs_OM induced similar modifications to the bSeNP extract, reiterating the need to consider the OM influence on the physical-chemical and biological properties of bSeNP extracts.

Figure 1

Transmission electron microscopy images of (A) the bSeNP extract, (B) cSeNPs, and (C) cSeNPs_OM. (D) Size distribution of SeNPs.

Figure 2

(A) ATR-FTIR spectra of the bSeNP extract, OM, cSeNPs, and cSeNPs_OM, (B) distribution of biomolecules (i.e., lipids, proteins, and polysaccharides), (C) degree of saturation and acyl-chain order, and (D) protein secondary structures based on ATR-FTIR analysis.

Figure 3

Comparative susceptibility curves of SeNPs-containing or -deriving formulations to S. cerevisiae cells grown (A) planktonically or (B) as a biofilm.

Figure 4

Generalized polarization (GP) values of laurdan in yeast polar extract vesicles (YE lipid) incubated with (A) the bSeNP extract (10, 50, or 100 μg/mL), (B) cSeNPs (10, 50, or 100 μg/mL), and (C) the OM (100 μg/mL) or cSeNPs_OM (100 μg/mL). Data are plotted as an average of three replicates ± standard deviation.

Figure 5

Generalized polarization (GP) values of laurdan in POPC vesicles incubated with (A) the bSeNP extract (10, 50, or 100 μg/mL), (B) cSeNPs (10, 50, or 100 μg/mL), and (C) the OM (100 μg/mL) or cSeNPs_OM (100 μg/mL). Data are plotted as an average of three replicates ± standard deviation.

Figure 6

Generalized polarization (GP) values of laurdan in DMPC vesicles incubated with (A) the bSeNP extract (10, 50, or 100 μg/mL), (B) cSeNPs (10, 50, or 100 μg/mL), and (C) the OM (100 μg/mL) or cSeNPs_OM (100 μg/mL). Data are plotted as an average of three replicates ± standard deviation.

Figure 7

Fluorescence anisotropy values of DPH in POPC vesicles incubated with (A) the bSeNP extract (10, 50, or 100 μg/mL), (B) cSeNPs (10, 50, or 100 μg/mL), and (C) the OM (100 μg/mL) or cSeNPs_OM (100 μg/mL). Data are plotted as an average of three replicates ± standard deviation.

Figure 8

Fluorescence anisotropy values of DPH in DMPC vesicles incubated with (A) the bSeNP extract (10, 50, or 100 μg/mL), (B) cSeNPs (10, 50, or 100 μg/mL), and (C) the OM (100 μg/mL) or cSeNPs_OM (100 μg/mL). Data are plotted as an average of three replicates ± standard deviation.