Effective control of foodborne pathogen contamination is a significant challenge to the food industry, but the development of new antibacterial nanotechnologies offers new opportunities. Notably, selenium nanoparticles have been extensively studied and successfully applied in various food fields. Selenium nanoparticles act as food antibacterial agents with a number of benefits, including selenium as an essential trace element in food, prevention of drug resistance induction in foodborne pathogens, and improvement of shelf life and food storage conditions. Compared to physical and chemical methods, biogenic selenium nanoparticles (Bio-SeNPs) are safer and more multifunctional due to the bioactive molecules in Bio-SeNPs. This review includes a summarization of (1) biosynthesized of Bio-SeNPs from different sources (plant extracts, fungi and bacteria) and their antibacterial activity against various foodborne bacteria; (2) the antibacterial mechanisms of Bio-SeNPs, including penetration of cell wall, damage to cell membrane and contents leakage, inhibition of biofilm formation, and induction of oxidative stress; (3) the potential antibacterial applications of Bio-SeNPs as food packaging materials, food additives and fertilizers/feeds for crops and animals in the food industry; and (4) the cytotoxicity and animal toxicity of Bio-SeNPs. The related knowledge contributes to enhancing our understanding of Bio-SeNP applications and makes a valuable contribution to ensuring food safety.

Heavy metal accumulation and pathogenic bacteria cause adverse effects on aquaculture. The active surface of selenium (Se) nanoparticles can mitigate these effects. The present study used Se-resistant Bacillus subtilis AS12 to fabricate biological Se nanoparticles (Bio-SeNPs). The double-edged Bio-SeNPs were tested for their ability to reduce the harmful effects of heavy metals and bacterial load in Nile tilapia (Oreochromis niloticus) and their respective influences on fish growth, behavior, and health. The Bio-SeNPs have a spherical shape with an average size of 77 nm and high flavonoids and phenolic content (0.7 and 1.9 g g-1 quercetin and gallic acid equivalents, respectively), resulting in considerable antioxidant and antibacterial activity. The Bio-SeNPs (3-5 μg ml-1) in the current study resolved two serious issues facing the aquaculture industry, firstly, the population of pathogenic bacteria, especially Aeromonas hydrophilia, which was reduced by 28-45% in fish organs. Secondly, heavy metals (Cd and Hg) at two levels (1 and 2 μg ml-1) were reduced by 50-87% and 57-73% in response to Bio-SeNPs (3-5 μg ml-1). Thus, liver function parameters were reduced, and inner immunity was enhanced. The application of Bio-SeNPs (3-5 μg ml-1) improved fish gut health, growth, and behavior, resulting in fish higher weight gain by 36-52% and a 40% specific growth rate, compared to controls. Furthermore, feeding and arousal times increased by 20-22% and 28-53%, respectively, while aggression time decreased by 78% compared to the control by the same treatment. In conclusion, Bio-SeNPs can mitigate the accumulation of heavy metals and reduce the bacterial load in a concentration-dependent manner, either in the fish media or fish organs.

With the wide application of selenium nanoparticles (SeNPs) in pharmaceutical fields, the toxicity assessment is of great significance. In this study, zebrafish were selected as model organisms to compare the toxicity of SeNPs derived from biological and chemical methods. The results showed that the size of bio-SeNPs was about 5-fold bigger than chem-SeNPs. When exposed to SeNPs for 96 h, LC50 of bio-SeNPs and chem-SeNPs was 1.668 mg/L and 0.699 mg/L, respectively. Compared with the control, the results showed a significant increase in oxidative toxicity index (P < 0.05), such as glutathione (GSH), superoxide dismutase (SOD) of the liver, and gill in SeNPs-treated group. The neurotoxicity index, such as acetylcholinesterase (AchE) and Na+-K+-ATP enzyme activity, was significantly decreased both in the liver and gill (P < 0.05). It was found that the toxicity of bio-SeNPs to the liver and gill of zebrafish was lower than chem-SeNPs and the toxicity to the liver was higher than gill. In this study, the toxicity of chem-SeNPs and bio-SeNPs to the target organs of zebrafish were systematically evaluated, which provided the basis for the safe application of SeNPs synthesized by different pathways.

Selenite reductase CsrF overexpressed Escherichia coli was used as a microbial factory to produce Se(0) nanoparticles (Bio-SeNPs). The Bio-SeNPs were characterized by transmission electronic microscopy, element mapping, scanning electron microscopy, energy-dispersive X-ray spectrographs, Zeta-potential, dynamic light scattering, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The results indicated that Bio-SeNPs are irregular spheres with diameters from 60 to105 nm and mainly consist of Se(0), proteins and lipids. Furthermore, it exhibited maximum adsorption capacity for anionic dye (congo red) at acidic pH and cationic dyes (safranine T and methylene blue) at alkaline pH. To gain more insight, adsorption kinetics, adsorption isotherms and adsorption thermodynamics studies were carried out. These results showed that the adsorption capacities of congo red, safranine T and methylene blue were 1577.7, 1911.0 and 1792.2 mg/g, respectively. These adsorption processes were spontaneous and primarily physical reactions. In addition, Bio-SeNPs can be effectively reused by 200 mmol/L NaCl. To the best of our knowledge, this is the first report of adsorption removal dyes by Bio-SeNPs. The adsorption capacities of Bio-SeNPs for congo red, safranine T and methylene blue were 6.8%, 25.2% and 49.0% higher than that for traditional bio-based materials, respectively.