Anticancer activity of biostabilized selenium nanorods synthesized by Streptomyces bikiniensis strain Ess_amA-1

A State-of-the-Art Systemic Review on Selenium Nanoparticles: Mechanisms and Factors Influencing Biogenesis and Its Potential Applications

Selenium is a trace element required for the active function of numerous enzymes and various physiological processes. In recent years, selenium nanoparticles draw the attention of scientists and researchers because of its multifaceted uses. The process involved in chemically synthesized SeNPs has been found to be hazardous in nature, which has paved the way for safe and ecofriendly SeNPs to be developed in order to achieve sustainability. In comparison to chemical synthesis, SeNPs can be synthesized more safely and with greater flexibility utilizing bacteria, fungi, and plants. This review focused on the synthesis of SeNPs utilizing bacteria, fungi, and plants; the mechanisms involved in SeNP synthesis; and the effect of various abiotic factors on SeNP synthesis and morphological characteristics. This article discusses the synergies of SeNP synthesis via biological routes, which can help future researchers to synthesize SeNPs with more precision and employ them in desired fields.

The progress of research on the application of redox nanomaterials in disease therapy

Redox imbalance can trigger cell dysfunction and damage and plays a vital role in the origin and progression of many diseases. Maintaining the balance between oxidants and antioxidants in vivo is a complicated and arduous task, leading to ongoing research into the construction of redox nanomaterials. Nanodrug platforms with redox characteristics can not only reduce the adverse effects of oxidative stress on tissues by removing excess oxidants from the body but also have multienzyme-like activity, which can play a cytotoxic role in tumor tissues through the catalytic oxidation of their substrates to produce harmful reactive oxygen species such as hydroxyl radicals. In this review, various redox nanomaterials currently used in disease therapy are discussed, emphasizing the treatment methods and their applications in tumors and other human tissues. Finally, the limitations of the current clinical application of redox nanomaterials are considered.

Biogenic Selenium Nanoparticles in Biomedical Sciences: Properties, Current Trends, Novel Opportunities and Emerging Challenges in Theranostic Nanomedicine

Selenium is an important dietary supplement and an essential trace element incorporated into selenoproteins with growth-modulating properties and cytotoxic mechanisms of action. However, different compounds of selenium usually possess a narrow nutritional or therapeutic window with a low degree of absorption and delicate safety margins, depending on the dose and the chemical form in which they are provided to the organism. Hence, selenium nanoparticles (SeNPs) are emerging as a novel therapeutic and diagnostic platform with decreased toxicity and the capacity to enhance the biological properties of Se-based compounds. Consistent with the exciting possibilities offered by nanotechnology in the diagnosis, treatment, and prevention of diseases, SeNPs are useful tools in current biomedical research with exceptional benefits as potential therapeutics, with enhanced bioavailability, improved targeting, and effectiveness against oxidative stress and inflammation-mediated disorders. In view of the need for developing eco-friendly, inexpensive, simple, and high-throughput biomedical agents that can also ally with theranostic purposes and exhibit negligible side effects, biogenic SeNPs are receiving special attention. The present manuscript aims to be a reference in its kind by providing the readership with a thorough and comprehensive review that emphasizes the current, yet expanding, possibilities offered by biogenic SeNPs in the biomedical field and the promise they hold among selenium-derived products to, eventually, elicit future developments. First, the present review recalls the physiological importance of selenium as an oligo-element and introduces the unique biological, physicochemical, optoelectronic, and catalytic properties of Se nanomaterials. Then, it addresses the significance of nanosizing on pharmacological activity (pharmacokinetics and pharmacodynamics) and cellular interactions of SeNPs. Importantly, it discusses in detail the role of biosynthesized SeNPs as innovative theranostic agents for personalized nanomedicine-based therapies. Finally, this review explores the role of biogenic SeNPs in the ongoing context of the SARS-CoV-2 pandemic and presents key prospects in translational nanomedicine.

Recent Trends and Developments in Multifunctional Nanoparticles for Cancer Theranostics

Conventional anticancer treatments, such as radiotherapy and chemotherapy, have significantly improved cancer therapy. Nevertheless, the existing traditional anticancer treatments have been reported to cause serious side effects and resistance to cancer and even to severely affect the quality of life of cancer survivors, which indicates the utmost urgency to develop effective and safe anticancer treatments. As the primary focus of cancer nanotheranostics, nanomaterials with unique surface chemistry and shape have been investigated for integrating cancer diagnostics with treatment techniques, including guiding a prompt diagnosis, precise imaging, treatment with an effective dose, and real-time supervision of therapeutic efficacy. Several theranostic nanosystems have been explored for cancer diagnosis and treatment in the past decade. However, metal-based nanotheranostics continue to be the most common types of nonentities. Consequently, the present review covers the physical characteristics of effective metallic, functionalized, and hybrid nanotheranostic systems. The scope of coverage also includes the clinical advantages and limitations of cancer nanotheranostics. In light of these viewpoints, future research directions exploring the robustness and clinical viability of cancer nanotheranostics through various strategies to enhance the biocompatibility of theranostic nanoparticles are summarised.

Biogenic Selenium Nanoparticles and Their Anticancer Effects Pertaining to Probiotic Bacteria—A Review

Selenium nanoparticles (SeNPs) can be produced by biogenic, physical, and chemical processes. The physical and chemical processes have hazardous effects. However, biogenic synthesis (by microorganisms) is an eco-friendly and economical technique that is non-toxic to human and animal health. The mechanism for biogenic SeNPs from microorganisms is still not well understood. Over the past two decades, extensive research has been conducted on the nutritional and therapeutic applications of biogenic SeNPs. The research revealed that biogenic SeNPs are considered novel competitors in the pharmaceutical and food industries, as they have been shown to be virtually non-toxic when used in medical practice and as dietary supplements and release only trace amounts of Se ions when ingested. Various pathogenic and probiotic/nonpathogenic bacteria are used for the biogenic synthesis of SeNPs. However, in the case of biosynthesis by pathogenic bacteria, extraction and purification techniques are required for further useful applications of these biogenic SeNPs. This review focuses on the applications of SeNPs (derived from probiotic/nonpathogenic organisms) as promising anticancer agents. This review describes that SeNPs derived from probiotic/nonpathogenic organisms are considered safe for human consumption. These biogenic SeNPs reduce oxidative stress in the human body and have also been shown to be effective against breast, prostate, lung, liver, and colon cancers. This review provides helpful information on the safe use of biogenic SeNPs and their economic importance for dietary and therapeutic purposes, especially as anticancer agents.

Emerging Roles of Green-Synthesized Chalcogen and Chalcogenide Nanoparticles in Cancer Theranostics

The last few decades have seen an overwhelming increase in the amount of research carried out on the use of inorganic nanoparticles. More fascinating is the tremendous progress made in the use of chalcogen and chalcogenide nanoparticles in cancer theranostics. These nanomaterials, which were initially synthesized through chemical methods, have now been efficiently produced using different plant materials. The paradigm shift towards the biogenic route of nanoparticle synthesis stems from its superior advantages of biosafety, eco-friendliness, and simplicity, among others. Despite a large number of reviews available on inorganic nanoparticle synthesis through green chemistry, there is currently a dearth of information on the green synthesis of chalcogens and chalcogenides for cancer research. Nanoformulations involving chalcogens such as sulfur, selenium, and tellurium and their respective chalcogenides have recently emerged as promising tools in cancer therapeutics and diagnosis. Similar to other inorganic nanoparticles, chalcogens and chalcogenides have been synthesized using plant extracts and their purified biomolecules. In this review, we provide an up-to-date discussion of the recent progress that has been made in the plant-mediated synthesis of chalcogens and chalcogenides with a special focus on their application in cancer theranostics.

Myco-Synthesized Molluscicidal and Larvicidal Selenium Nanoparticles: A New Strategy to Control Biomphalaria alexandrina Snails and Larvae of Schistosoma mansoni with an In Silico Study on Induced Oxidative Stress

Schistosomiasis is a tropical disease with socioeconomic problems. The goal of this study was to determine the influence of myco-synthesized nano-selenium (SeNPs) as a molluscicide on Biomphlaria alexandrina snails, with the goal of reducing disease spread via non-toxic routes. In this study, Penicillium chrysogenum culture filtrate metabolites were used as a reductant for selenium ions to form nano-selenium. The SeNPs were characterized via UV-Vis spectrophotometer, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). Myco-synthesized SeNPs had a significant molluscicidal effect on B. alexandrina snails after 96 h of exposure at a concentration of 5.96 mg/L. SeNPs also had miracidicidal and cercaricidal properties against S. mansoni. Some alterations were observed in the hemocytes of snails exposed to SeNPs, including the formation of pseudopodia and an increasing number of granules. Furthermore, lipid peroxide, nitric oxide (NO), malondialdehyde (MDA), and glutathione s-transferase (GST) increased significantly in a dose-dependent manner, while superoxide dismutase (SOD) decreased. The comet assay revealed that myco-synthesized SeNPs could cause breaks in the DNA levels. In silico study revealed that SeNPs had promising antioxidant properties. In conclusion, myco-synthesized SeNPs have the potential to be used as molluscicides and larvicides.

Radiation Shielding Tests of Crosslinked Polystyrene-b-Polyethyleneglycol Block Copolymers Blended with Nanostructured Selenium Dioxide and Boron Nitride Particles

In this work, gamma-ray shielding features of crosslinked polystyrene-b-polyethyleneglycol block copolymers (PS-b-PEG) blended with nanostructured selenium dioxide (SeO2) and boron nitride (BN) particles were studied. This research details several radiation shielding factors i.e., mass attenuation coefficient (μm), linear attenuation coefficient (μL), radiation protection efficiency (RPE), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP). The irradiation properties of our nanocomposites were investigated with rays from the 152Eu source (in the energy intervals from 121.780 keV to 1408.010 keV) in a high-purity germanium (HPGe) detector system, and analyzed with GammaVision software. Moreover, all radiation shielding factors were determined by theoretical calculus and compared with the experimental results. In addition, the morphological and thermal characterization of all nanocomposites was surveyed with various techniques i.e., nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). Acceptable compatibility was revealed and observed in all nanocomposites between the experimental and theoretical results. The PS-b-PEG copolymer and nanostructured SeO2 and BN particles exerted a significant effect in enhancing the resistance of the nanocomposites, and the samples with high additive rates exhibited better resistance than the other nanocomposites. From the achieved outcomes, it can be deduced that our polymer-based nanocomposites can be utilized as a good choice in the gamma-irradiation-shielding discipline.

The Effect of Organoselenium Compounds on Histone Deacetylase Inhibition and Their Potential for Cancer Therapy

Genetic and epigenetic changes alter gene expression, contributing to cancer. Epigenetic changes in cancer arise from alterations in DNA and histone modifications that lead to tumour suppressor gene silencing and the activation of oncogenes. The acetylation status of histones and non-histone proteins are determined by the histone deacetylases and histone acetyltransferases that control gene transcription. Organoselenium compounds have become promising contenders in cancer therapeutics. Apart from their anti-oxidative effects, several natural and synthetic organoselenium compounds and metabolites act as histone deacetylase inhibitors, which influence the acetylation status of histones and non-histone proteins, altering gene transcription. This review aims to summarise the effect of natural and synthetic organoselenium compounds on histone and non-histone protein acetylation/deacetylation in cancer therapy.

Inhibition of Quorum Sensing and Virulence Factors of Pseudomonas aeruginosa by Biologically Synthesized Gold and Selenium Nanoparticles

The development of microbial resistance requires a novel approach to control microbial infection. This study implies the microbial synthesis of nanometals and assessment of their antivirulent activity against Pseudomonas aeruginosa. Streptomyces isolate S91 was isolated from soil with substantial ability for growth at high salts concentrations. The cell-free supernatant of S91was utilized for the synthesis of Au-NPs and Se-NPs. The 16S rRNA sequence analysis of Streptomyces S91 revealed that S91 had a high similarity (98.82%) to Streptomyces olivaceous. The biosynthesized Au-NPs and Se-NPs were characterized using a UV-Vis spectrophotometer, dynamic light scattering, transmission electron microscopy, energy dispersive X-ray diffraction and Fourier-transform infrared spectroscopy. The quorum sensing inhibitory (QSI) potential of Au-NPs and Se-NPs and the antivirulence activity was examined against P. aeruginosa. The QSI potential was confirmed using RT-PCR. The synthesized Au-NPs and Se-NPs were monodispersed spherical shapes with particle size of 12.2 and 67.98 nm, respectively. Au-NPs and Se-NPs eliminated QS in P. aeruginosa at a concentration range of 2.3-18.5 µg/mL for Au-NPs and 2.3-592 µg/mL for Se-NPs. In addition, Au-NPs and Se-NPs significantly inhibited QS-related virulence factors, such as pyocyanin, protease and, elastase in P. aeruginosa. At the molecular level, Au-NPs and Se-NPs significantly suppressed the relative expression of QS genes and toxins. Hence, the biosynthesized Au-NPS and Se-NPS could be substantial inhibitors of QS and virulence traits of P. aeruginosa.

Two new selenite reducing bacterial isolates from paddy soil and the potential Se biofortification of paddy rice

Selenium (Se) is an essential element for human health. Se-enriched agricultural products can promote people's intake of Se. Microorganisms play an important role in Se cycling. In this study, two new bacterial strains were isolated from paddy soil and were identified as Chitinophaga sp. and Comamonas testosteroni, respectively. More than 44% and 39% of 1.0 mM selenite were reduced in 84 h by them using yeast extract as carbon source, respectively. Scanning electron microscope (SEM) and Energy dispersive X-ray spectrometry (EDS) results indicated that the reduction product of selenite was nanometer Se. These strains could promote the available Se in soil and the content of Se in rice plants in pot experiments. Organic combined Se in soils was increased up to 35%, accompanied by the 92% and 130% increase of Se in rice plants. To our best knowledge, this is the first report of Se reduction by Chitinophaga. This work might provide a prospective strategy for microbial fortification of Se in corps.

Biomedical potential of Anabaena variabilis NCCU-441 based Selenium nanoparticles and their comparison with commercial nanoparticles

Selenium nanoparticles (SeNPs) are gaining importance in the field of medicines due to their high surface area and unique properties than their other forms of selenium. In this study, biogenic selenium nanoparticles (B-SeNPs) were synthesized using cyanobacteria and their bioactivities (antioxidant, antimicrobial, anticancer and biocompatibility) were determined for comparison with commercially available chemically synthesized selenium nanoparticles (C-SeNPs). Color change of reaction mixture from sky blue to orange-red indicated the synthesis of biogenic SeNPs (B-SeNPs). UV-Vis spectra of the reaction mixture exhibited peak at 266 nm. During optimization, 30 °C of temperature, 24 h of time and 1:2 concentration ratio of sodium selenite and cell extract represented the best condition for SeNPs synthesis. Various functional groups and biochemical compounds present in the aqueous extract of Anabaena variabilis NCCU-441, which may have possibly influenced the reduction process of SeNPs were identified by FT-IR spectrum and GC-MS. The synthesized cyanobacterial SeNPs were orange red in color, spherical in shape, 10.8 nm in size and amorphous in nature. The B-SeNPs showed better anti-oxidant (DPPH, FRAP, SOR and ABTS assays), anti-microbial (antibacterial and antifungal) and anti-cancer activitities along with its biocompatibility in comparison to C-SeNPs suggesting higher probability of their biomedical application.

Microbe-Mediated Biosynthesis of Nanoparticles: Applications and Future Prospects

Nanotechnology is the science of nano-sized particles/structures (~100 nm) having a high surface-to-volume ratio that can modulate the physical, chemical and biological properties of the chemical compositions. In last few decades, nanoscience has attracted the attention of the scientific community worldwide due to its potential uses in the pharmacy, medical diagnostics and disease treatment, energy, electronics, agriculture, chemical and space industries. The properties of nanoparticles (NPs) are size and shape dependent. These characteristic features of nanoparticles can be explored for various other applications such as computer transistors, chemical sensors, electrometers, memory schemes, reusable catalysts, biosensing, antimicrobial activity, nanocomposites, medical imaging, tumor detection and drug delivery. Therefore, synthesizing nanoparticles of desired size, structure, monodispersity and morphology is crucial for the aforementioned applications. Recent advancements in nanotechnology aim at the synthesis of nanoparticles/materials using reliable, innoxious and novel ecofriendly techniques. In contrast to the traditional methods, the biosynthesis of nanoparticles of a desired nature and structure using the microbial machinery is not only quicker and safer but more environmentally friendly. Various microbes, including bacteria, actinobacteria, fungi, yeast, microalgae and viruses, have recently been explored for the synthesis of metal, metal oxide and other important NPs through intracellular and extracellular processes. Some bacteria and microalgae possess specific potential to fabricate distinctive nanomaterials such as exopolysaccharides, nanocellulose, nanoplates and nanowires. Moreover, their ability to synthesize nanoparticles can be enhanced using genetic engineering approaches. Thus, the use of microorganisms for synthesis of nanoparticles is unique and has a promising future. The present review provides explicit information on different strategies for the synthesis of nanoparticles using microbial cells; their applications in bioremediation, agriculture, medicine and diagnostics; and their future prospects.

Green Synthesis of Selenium and Tellurium Nanoparticles: Current Trends, Biological Properties and Biomedical Applications

The synthesis and assembly of nanoparticles using green technology has been an excellent option in nanotechnology because they are easy to implement, cost-efficient, eco-friendly, risk-free, and amenable to scaling up. They also do not require sophisticated equipment nor well-trained professionals. Bionanotechnology involves various biological systems as suitable nanofactories, including biomolecules, bacteria, fungi, yeasts, and plants. Biologically inspired nanomaterial fabrication approaches have shown great potential to interconnect microbial or plant extract biotechnology and nanotechnology. The present article extensively reviews the eco-friendly production of metalloid nanoparticles, namely made of selenium (SeNPs) and tellurium (TeNPs), using various microorganisms, such as bacteria and fungi, and plants' extracts. It also discusses the methodologies followed by materials scientists and highlights the impact of the experimental sets on the outcomes and shed light on the underlying mechanisms. Moreover, it features the unique properties displayed by these biogenic nanoparticles for a large range of emerging applications in medicine, agriculture, bioengineering, and bioremediation.

Green Synthesis of Metallic Nanoparticles and Their Prospective Biotechnological Applications: an Overview

The green synthesis of nanoparticles (NPs) using living cells is a promising and novelty tool in bionanotechnology. Chemical and physical methods are used to synthesize NPs; however, biological methods are preferred due to its eco-friendly, clean, safe, cost-effective, easy, and effective sources for high productivity and purity. High pressure or temperature is not required for the green synthesis of NPs, and the use of toxic and hazardous substances and the addition of external reducing, stabilizing, or capping agents are avoided. Intra- or extracellular biosynthesis of NPs can be achieved by numerous biological entities including bacteria, fungi, yeast, algae, actinomycetes, and plant extracts. Recently, numerous methods are used to increase the productivity of nanoparticles with variable size, shape, and stability. The different mechanical, optical, magnetic, and chemical properties of NPs have been related to their shape, size, surface charge, and surface area. Detection and characterization of biosynthesized NPs are conducted using different techniques such as UV-vis spectroscopy, FT-IR, TEM, SEM, AFM, DLS, XRD, zeta potential analyses, etc. NPs synthesized by the green approach can be incorporated into different biotechnological fields as antimicrobial, antitumor, and antioxidant agents; as a control for phytopathogens; and as bioremediative factors, and they are also used in the food and textile industries, in smart agriculture, and in wastewater treatment. This review will address biological entities that can be used for the green synthesis of NPs and their prospects for biotechnological applications.

Synthesis and Characterization of Black Currant Selenium Nanoparticles (Part I)

The present study aimed to synthesize selenium nanoparticles (SeNPs) using aqueous extract of black currant as a reducing agent. The green synthesized black currant selenium nanoparticles (BCSeNPs) were identified by color change. The characterization of SeNPs was achieved by Ultraviolet-visible (UV–VIS) spectroscopy, scanning electron microscopy (SEM), X–ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR). These tests were used to detect: stability, morphology, size, crystalline nature, and functional groups present on the surface of BCSeNPs. The results revealed appearance of the brick-red color indicating the specific color of selenium nanoparticles, and UV-Vis spectroscopy showed band absorbance at 265 nm of intense surface plasmon resonance manifesting the formation and stability of the prepared BCSeNPs. The SEM image showed the prevalence of spherical selenium nanosized, XRD at 2θ revealed crystallin selenium nanoparticles, the size was in the average of 18-50 nm. Furthermore, FTIR revealed the presence of functional groups of the plant which act as stabilizing and reducing agents. In conclusion, the aqueous black currant extract can act as a reducing and capping agent to synthesize BCSeNPs in nano-scale size by a simple method

Processing of Metals and Metalloids by Actinobacteria: Cell Resistance Mechanisms and Synthesis of Metal(loid)-Based Nanostructures

Metal(loid)s have a dual biological role as micronutrients and stress agents. A few geochemical and natural processes can cause their release in the environment, although most metal-contaminated sites derive from anthropogenic activities. Actinobacteria include high GC bacteria that inhabit a wide range of terrestrial and aquatic ecological niches, where they play essential roles in recycling or transforming organic and inorganic substances. The metal(loid) tolerance and/or resistance of several members of this phylum rely on mechanisms such as biosorption and extracellular sequestration by siderophores and extracellular polymeric substances (EPS), bioaccumulation, biotransformation, and metal efflux processes, which overall contribute to maintaining metal homeostasis. Considering the bioprocessing potential of metal(loid)s by Actinobacteria, the development of bioremediation strategies to reclaim metal-contaminated environments has gained scientific and economic interests. Moreover, the ability of Actinobacteria to produce nanoscale materials with intriguing physical-chemical and biological properties emphasizes the technological value of these biotic approaches. Given these premises, this review summarizes the strategies used by Actinobacteria to cope with metal(loid) toxicity and their undoubted role in bioremediation and bionanotechnology fields.

Histopathological assessment of protective effects of selenium nanoparticles on rat hepatocytes exposed to Gamma radiation

Gamma radiation are used in many medical and technical applications, however, it is one of the most dangerous kinds of radiation and can be harmful to the body. The present study was designed to clarify the protective effects of the selenium supplementation as selenium nanoparticle and selenite selenium in rat liver against Gamma irradiation with different intensities of 2.00 and 8.00 Gy. A total number of 45 healthy male Wistar rats were randomly divided into nine groups of five each. The radiation procedure was carried out in the Cobalt 60 equipment in Omid hospital, Urmia. The animals were simultaneously immobilized in a transparent acrylic plate and exposed to different intensities of 2.00 and 8.00 Gy radiations on day 7th and 14th of the experiment. After 72 hr after the last radiation, the animals were euthanized, and blood and liver tissue were collected. Histological analyses revealed the radiation-induced hepatic injury in rats, which included vacuolated cytoplasm, liver necrosis, fibrosis, and vascular lesions followed by a significant increase in alanine transaminase, alanine transaminase, alkaline phosphatase, and Gamma-glutamyl transferase. Selenium nanoparticles bear a more potent antioxidant effect in comparison with selenium selenite and can effectively protect the liver cell against Gamma radiation at a dose of 8.00 Gy.

Eco-Friendly Greener Synthesis of Nanoparticles

The exploitation of naturally obtained resources like biopolymers, plant-based extracts, microorganisms etc., offers numerous advantages of environment-friendliness and biocompatibility for various medicinal and pharmaceutical applications, whereas hazardous chemicals are not utilized for production protocol. Plant extracts based synthetic procedures have drawn consideration over conventional methods like physical and chemical procedures to synthesize nanomaterials. Greener synthesis of nanomaterials has become an area of interest because of numerous advantages such as non-hazardous, economical, and feasible methods with variety of applications in biomedicine, nanotechnology and nano-optoelectronics, etc.

Natural Metallic Nanoparticles for Application in Nano-Oncology

Here, the various types of naturally synthesized metallic nanoparticles, which are essentially composed of Ce, Ag, Au, Pt, Pd, Cu, Ni, Se, Fe, or their oxides, are presented, based on a literature analysis. The synthesis methods used to obtain them most often involve the reduction of metallic ions by biological materials or organisms, i.e., essentially plant extracts, yeasts, fungus, and bacteria. The anti-tumor activity of these nanoparticles has been demonstrated on different cancer lines. They rely on various mechanisms of action, such as the release of chemotherapeutic drugs under a pH variation, nanoparticle excitation by radiation, or apoptotic tumor cell death. Among these natural metallic nanoparticles, one type, which consists of iron oxide nanoparticles produced by magnetotactic bacteria called magnetosomes, has been purified to remove endotoxins and abide by pharmacological regulations. It has been tested in vivo for anti-tumor efficacy. For that, purified and stabilized magnetosomes were injected in intracranial mouse glioblastoma tumors and repeatedly heated under the application of an alternating magnetic field, leading to the full disappearance of these tumors. As a whole, the results presented in the literature form a strong basis for pursuing the efforts towards the use of natural metallic nanoparticles for cancer treatment first pre-clinically and then clinically.

Effects of process conditions and yeast extract on the synthesis of selenium nanoparticles by a novel indigenous isolate Bacillus sp. EKT1 and characterization of nanoparticles

Selenium nanoparticles (SeNPs) are attractive nanomaterials for application in medical diagnosis, because their toxicities are lower than the elemental selenium which is a functional element and essential for human. In the current study, SeNPs synthesis capability of a novel soil originated indigenous Bacillus isolate was investigated. In this context, effects of processing conditions (SeO₂ concentration, pH, temperature, and time), and yeast extract supplementation on the synthesis of SeNPs have been tested. In addition, nanoparticles were characterized and antioxidant capacity was determined. The cell-free supernatant of the bacterium, which was obtained after the cultivation of the isolate in nutrient broth at 33 °C for 24 h, was used for the synthesis. During the synthesis color change from light yellow to red-orange was an indication of the formation of SeNPs. Effect of SeO₂ concentration was tested on the formation of nanoparticles and at concentrations higher than 10 mM, there was no formation of nanoparticles. The best production was achieved at 6.4 mM concentration, at pH 9 and 33 °C in 72 h. Field emission scanning electron microscopy (FESEM) images revealed that SeNPs were spherical in shape having the diameters between 31 and 335 nm, and the average diameter was determined to be 126 nm. Energy dispersive X-ray spectroscopy analysis confirmed the presence of elemental selenium. SeNPs possessed significant antioxidant activity that the scavenging capacity was up to 56.5 ± 5% (IC₅₀ 322.8 μg/mL).

Population Kinetics and Mechanistic Aspects of Saccharomyces cerevisiae Growth in Relation to Selenium Sulfide Nanoparticle Synthesis

Biosynthesis of nanoparticles (NPs) by microorganisms is a cost- and energy-effective approach. However, how the production of NPs affects the population of producing organism remains as an unresolved question. The present study aimed to evaluate the kinetics of Saccharomyces cerevisiae growth in relation to synthesis of selenium sulfide nanoparticles by using a population model. To this end, the population of S. cerevisiae cells was investigated in terms of colony forming units (CFU) in the presence of the substrate in different time points. Fluctuation of sulfite reductase (SiR) activity, expression of MET5 and MET10 genes, and concentrations of sulfite and selenium were evaluated to support the population findings. CFU values in the test groups were lower than those in the control counterparts. The rise and fall of the SiR activity and MET5 and MET10 gene expression conformed to the variations of CFU values. The rate of reduction in the selenium and sulfite concentrations tended to decrease over the time. In conclusion, the cells population was negatively and positively affected by selenium and sulfite concentrations, respectively. The indirect relationship of the selenium ions concentration in the path analysis revealed that the product, selenium sulfide nanoparticles, caused this drop in S. cerevisiae cells population.

Specificity of Biogenic Selenium Nanoparticles for Prostate Cancer Therapy With Reduced Risk of Toxicity: An in vitro and in vivo Study

Selenium deficiency is associated with many physiological disorders including the high risk of cancer. The rehabilitation of selenium with different selenium supplements, however, fails due to their low therapeutic index. Therefore, it is advantageous to have a less toxic form of selenium for supplementation with potentially high anticancer activity. Here we show Bacillus licheniformis derived biogenic selenium nanoparticles at a minimal concentration of 2 μg Se/ml induce necroptosis in LNCaP-FGC cells, without affecting the RBC integrity. Real-time gene expression analysis indicated the overexpression of tumor necrotic factor (TNF) and interferon regulatory factor (IRF1) and decreased expression of androgen receptor (AR) and prostate-specific antigen (PSA). Furthermore, histopathological analysis showed the subsequent oral administrations of 10 times higher concentration of these endotoxin free selenium nanoparticles in C3H/HeJ mice (50 mg Se/kg of body weight), induce significantly lower toxicity compared to the L-selenomethionine (5 mg Se/kg). Our study suggested that the biogenic SeNP could emerge as the safest form of selenium supplementation with potent anticancer activity.

Microbial Nanotechnology: Challenges and Prospects for Green Biocatalytic Synthesis of Nanoscale Materials for Sensoristic and Biomedical Applications

Nanomaterials are increasingly being used in new products and devices with a great impact on different fields from sensoristics to biomedicine. Biosynthesis of nanomaterials by microorganisms is recently attracting interest as a new, exciting approach towards the development of 'greener' nanomanufacturing compared to traditional chemical and physical approaches. This review provides an insight about microbial biosynthesis of nanomaterials by bacteria, yeast, molds, and microalgae for the manufacturing of sensoristic devices and therapeutic/diagnostic applications. The last ten-year literature was selected, focusing on scientific works where aspects like biosynthesis features, characterization, and applications have been described. The knowledge, challenges, and potentiality of microbial-mediated biosynthesis was also described. Bacteria and microalgae are the main microorganism used for nanobiosynthesis, principally for biomedical applications. Some bacteria and microalgae have showed the ability to synthetize unique nanostructures: bacterial nanocellulose, exopolysaccharides, bacterial nanowires, and biomineralized nanoscale materials (magnetosomes, frustules, and coccoliths). Yeasts and molds are characterized by extracellular synthesis, advantageous for possible reuse of cell cultures and reduced purification processes of nanomaterials. The intrinsic variability of the microbiological systems requires a greater protocols standardization to obtain nanomaterials with increasingly uniform and reproducible chemical-physical characteristics. A deeper knowledge about biosynthetic pathways and the opportunities from genetic engineering are stimulating the research towards a breakthrough development of microbial-based nanosynthesis for the future scaling-up and possible industrial exploitation of these promising 'nanofactories'.

Fungal formation of selenium and tellurium nanoparticles

The fungi Aureobasidium pullulans, Mortierella humilis, Trichoderma harzianum and Phoma glomerata were used to investigate the formation of selenium- and tellurium-containing nanoparticles during growth on selenium- and tellurium-containing media. Most organisms were able to grow on both selenium- and tellurium-containing media at concentrations of 1 mM resulting in extensive precipitation of elemental selenium and tellurium on fungal surfaces as observed by the red and black colour changes. Red or black deposits were confirmed as elemental selenium and tellurium, respectively. Selenium oxide and tellurium oxide were also found after growth of Trichoderma harzianum with 1 mM selenite and tellurite as well as the formation of elemental selenium and tellurium. The hyphal matrix provided nucleation sites for metalloid deposition with extracellular protein and extracellular polymeric substances localizing the resultant Se or Te nanoparticles. These findings are relevant to remedial treatments for selenium and tellurium and to novel approaches for selenium and tellurium biorecovery.

Influence of Bacterial Physiology on Processing of Selenite, Biogenesis of Nanomaterials and Their Thermodynamic Stability

We explored how Ochrobactrum sp. MPV1 can convert up to 2.5 mM selenite within 120 h, surviving the challenge posed by high oxyanion concentrations. The data show that thiol-based biotic chemical reaction(s) occur upon bacterial exposure to low selenite concentrations, whereas enzymatic systems account for oxyanion removal when 2 mM oxyanion is exceeded. The selenite bioprocessing produces selenium nanomaterials, whose size and morphology depend on the bacterial physiology. Selenium nanoparticles were always produced by MPV1 cells, featuring an average diameter ranging between 90 and 140 nm, which we conclude constitutes the thermodynamic stability range for these nanostructures. Alternatively, selenium nanorods were observed for bacterial cells exposed to high selenite concentration or under controlled metabolism. Biogenic nanomaterials were enclosed by an organic material in part composed of amphiphilic biomolecules, which could form nanosized structures independently. Bacterial physiology influences the surface charge characterizing the organic material, suggesting its diverse biomolecular composition and its involvement in the tuning of the nanomaterial morphology. Finally, the organic material is in thermodynamic equilibrium with nanomaterials and responsible for their electrosteric stabilization, as changes in the temperature slightly influence the stability of biogenic compared to chemogenic nanomaterials.

Physical-Chemical Properties of Biogenic Selenium Nanostructures Produced by Stenotrophomonas maltophilia SeITE02 and Ochrobactrum sp. MPV1

Stenotrophomonas maltophilia SeITE02 and Ochrobactrum sp. MPV1 were isolated from the rhizosphere soil of the selenium-hyperaccumulator legume Astragalus bisulcatus and waste material from a dumping site for roasted pyrites, respectively. Here, these bacterial strains were studied as cell factories to generate selenium-nanostructures (SeNS) under metabolically controlled growth conditions. Thus, a defined medium (DM) containing either glucose or pyruvate as carbon and energy source along with selenite () was tested to evaluate bacterial growth, oxyanion bioconversion and changes occurring in SeNS features with respect to those generated by these strains grown on rich media. Transmission electron microscopy (TEM) images show extra- or intra-cellular emergence of SeNS in SeITE02 or MPV1 respectively, revealing the presence of two distinct biological routes of SeNS biogenesis. Indeed, the stress exerted by upon SeITE02 cells triggered the production of membrane vesicles (MVs), which surrounded Se-nanoparticles (SeNPs_{SeITE02-G_e} and SeNPs_{SeITE02-P_e} with average diameter of 179 ± 56 and 208 ± 60 nm, respectively), as highlighted by TEM and scanning electron microscopy (SEM), strongly suggesting that MVs might play a crucial role in the excreting mechanism of the SeNPs in the extracellular environment. On the other hand, MPV1 strain biosynthesized intracellular inclusions likely containing hydrophobic storage compounds and SeNPs (123 ± 32 nm) under pyruvate conditioning, while the growth on glucose as the only source of carbon and energy led to the production of a mixed population of intracellular SeNPs (118 ± 36 nm) and nanorods (SeNRs; average length of 324 ± 89). SEM, fluorescence spectroscopy, and confocal laser scanning microscopy (CLSM) revealed that the biogenic SeNS were enclosed in an organic material containing proteins and amphiphilic molecules, possibly responsible for the high thermodynamic stability of these nanomaterials. Finally, the biogenic SeNS extracts were photoluminescent upon excitation ranging from 380 to 530 nm, whose degree of fluorescence emission (λ_em = 416–640 nm) was comparable to that from chemically synthesized SeNPs with L-cysteine (L-cys SeNPs). This study offers novel insights into the formation, localization, and release of biogenic SeNS generated by two different Gram-negative bacterial strains under aerobic and metabolically controlled growth conditions. The work strengthens the possibility of using these bacterial isolates as eco-friendly biocatalysts to produce high quality SeNS targeted to possible biomedical applications and other biotechnological purposes.

Toxicological responses of surfactant functionalized selenium nanoparticles: A quantitative multi-assay approach

The utilization of selenium nanomaterials (Se Nps) in material and biological science is quickly growing, crafting an imperative need for toxicological evaluation of the exposure prospective and environmental consequences of Se Nps. The combination of quantitative multi-assay approach into environmental toxicological analysis has provided novel opportunities to build up effective markers and scrutinize the means of venomous nature of Se Nps in the current study. In the present work, we analyzed the toxicological effect of bare and surface functionalized Se Nps by using multi assay viz. seed germination studies as a function of concentration of SeNps and by using antifungal assays. The influence of SeNps on bacterial activities were also investigated by using the S. aureus, E. coli, P. aeruginosa and S. typhi bacterial strains as widespread marker species for antibacterial studies. The ocular assessment of chlorophyll content was maximum for Brij coated Se NPs (98%) as compared to bare (20%), SDS (45%) and CTAB (38%) coated SeNps. The existence of chromosomal aberrations in root meristems of A. cepa(A. cepa) with computed MI values of 16, 25, 33 and 52% for bare, CTAB, SDS and Brij coated particles has indicated the genotoxic effects of SeNps. The biocompatible nature of Brij coated Se Nps was observed from the faster mobility of DNA in gel electrophoresis studies. The investigational studies in the current work appraise the toxicity and measure the competence of obtained data to characterize possibilities of probable threats, prominence of data requirement and breaches that must be filled to diminish the ambiguities about the safe use of Se Nps.

Proteins enriched in charged amino acids control the formation and stabilization of selenium nanoparticles in Comamonas testosteroni S44

Elemental selenium nanoparticles (SeNPs) are useful in medicine, environmental remediation and in material science. Biosynthesized SeNPs (BioSeNPs) by bacteria are cheap, eco-friendly and have a lower cytotoxicity in comparison with chemically synthesized ones. Organic matters were found to cap on the surface of BioSeNPs, but the functions were still not entirely clear. The purified BioSeNPs were coated in a thick layer of organic substrates observed by transmission electron microscopy (TEM). Fourier Transform Infrared (FT-IR) and quantitative detection of the coating agents showed that one gram of purified BioSeNPs bound 1069 mg proteins, 23 mg carbohydrates and only very limited amounts of lipids. Proteomics of BioSeNPs showed more than 800 proteins bound to BioSeNPs. Proteins enriched in charged amino acids are the major factor thought to govern the formation process and stabilization of BioSeNPs in bacteria. In view of the results reported here, a schematic model for the molecular mechanism of BioSeNPs formation in bacteria is proposed. These findings are helpful for the artificial green synthesis of stable SeNPs under specific condition and guiding the surface modification of SeNPs for medicine application.

siRNA-loaded selenium nanoparticle modified with hyaluronic acid for enhanced hepatocellular carcinoma therapy

Background

Small interfering RNA (siRNA) as a new therapeutic modality holds promise for cancer treatment. However, the traditional viral carriers are prone to immunogenicity and risk of insertional mutagenesis.

Methods

In order to provide a tumor-targeted delivery carrier of siRNA in cancer therapy, the hyaluronic acid (HA)-selenium (Se)-polyethylenimine (PEI) nanoparticle (NP) was fabricated by decorating SeNP with HA as a tumor-targeting moiety and by linking the polycationic polymers polyethylenimine PEI onto the surface of SeNP. The siRNA was loaded to the surface of SeNP HA-Se-PEI via the electrostatic interaction between siRNA and PEI to prepare the functionalized SeNP HA-Se-PEI@siRNA.

Results

The HA-Se-PEI@siRNA was internalized into the HepG2 cell mainly in a clathrin-mediated endocytosis manner. Owing to the active tumor-targeted effect mediated by HA, HA-Se-PEI@siRNA achieved the obvious higher transfection efficiency, greater gene silencing ability, and stronger cytotoxicity in the HepG2 cell compared with the passive tumor-targeted NP Se-PEI@siRNA. The knockdown of hairy and enhancer of split 5 by HA-Se-PEI@siRNA induced the HepG2 cell cycle arrest at the G0/G1 phase and apoptosis. Furthermore, the treatment with HA-Se-PEI@siRNA resulted in greater antitumor efficacy compared with the Se-PEI@siRNA in vitro and in vivo. In addition, the HA-Se-PEI@siRNA was almost no toxic to the key organs of mice.

Conclusion

These findings provided an alternative therapeutic route for targeted cancer treatments.

Expanding beyond canonical metabolism: Interfacing alternative elements, synthetic biology, and metabolic engineering

Metabolic engineering offers an exquisite capacity to produce new molecules in a renewable manner. However, most industrial applications have focused on only a small subset of elements from the periodic table, centered around carbon biochemistry. This review aims to illustrate the expanse of chemical elements that can currently (and potentially) be integrated into useful products using cellular systems. Specifically, we describe recent advances in expanding the cellular scope to include the halogens, selenium and the metalloids, and a variety of metal incorporations. These examples range from small molecules, heteroatom-linked uncommon elements, and natural products to biomining and nanotechnology applications. Collectively, this review covers the promise of an expanded range of elemental incorporations and the future impacts it may have on biotechnology.

New generation of drug delivery systems based on ginsenoside Rh2-, Lysine- and Arginine-treated highly porous graphene for improving anticancer activity

In this study, Rh2-treated graphene oxide (GO-Rh2), lysine-treated highly porous graphene (Gr-Lys), arginine-treated Gr (Gr-Arg), Rh2-treated Gr-Lys (Gr-Lys-Rh2) and Rh2-treated Gr-Arg (Gr-Arg-Rh2) were synthesized. MTT assay was used for evaluation of cytotoxicity of samples on ovarian cancer (OVCAR3), breast cancer (MDA-MB), Human melanoma (A375) and human mesenchymal stem cells (MSCs) cell lines. The percentage of apoptotic cells was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. The hemolysis and blood coagulation activity of nanostructures were performed. Interestingly, Gr-Arg, Gr-Lys, Gr-Arg-Rh2, and Gr-Lys-Rh2 were more active against cancer cell lines in comparison with their cytotoxic activity against normal cell lines (MSCs) with IC50 values higher than 100 μg/ml. The results of TUNEL assay indicates a significant increase in the rates of TUNEL positive cells by increasing the concentrations of nanomaterials. Results were also shown that aggregation and changes of RBCs morphology were occurred in the presence of GO, GO-Rh2, Gr-Arg, Gr-Lys, Gr-Arg-Rh2, and Gr-Lys-Rh2. Note that all the samples had effect on blood coagulation system, especially on PTT. All nanostrucure act as antitumor drug so that binding of drugs to a nostructures is irresolvable and the whole structure enter to the cell as a drug.

Speeding up bioproduction of selenium nanoparticles by using Vibrio natriegens as microbial factory

Selenium and selenium nanoparticles (SeNPs) are extensively used in biomedicine, electronics and some other industrial applications. The bioproduction of SeNPs is gaining interest as a green method to manufacture these biotechnologically relevant products. Several microorganisms have been used for the production of SeNPs either under aerobic or anaerobic conditions. Vibrio natriegens is a non-pathogenic fast-growing bacterium, easily cultured in different carbon sources and that has recently been engineered for easy genetic manipulation in the laboratory. Here we report that V. natriegens was able to perfectly grow aerobically in the presence of selenite concentrations up to 15 mM with a significant survival still observed at concentrations as high as 100 mM selenite. Electron microscopy and X-ray spectroscopy analyses demonstrate that V. natriegens cells growing aerobically in selenite-containing LB medium at 30 °C produced spherical electron-dense SeNPs whose size ranged from 100-400 nm. Selenite reduction just started at the beginning of the exponential growth phase and the release of SeNPs was observed after cell lysis. Remarkably, V. natriegens produced SeNPs faster than other described microorganisms that were proposed as model bioreactors for SeNPs production. Thus, the fast-growing V. natriegens bacterium becomes a suitable biocatalyst for bioremediation of selenite and for speeding-up the eco-friendly synthesis of SeNPs.

Biogenic selenium and its hepatoprotective activity

Elemental selenium nanoparticles (SeNPs) have multiple biological activities. In this study, we investigated the protective effects of biogenic SeNPs (BioSeNPs) on CCl₄-induced liver damage in mice. The results showed that: (i) when compared to sodium selenite (SS), BioSeNPs has a similar tissue distribution after intragastrical administration to mice; (ii) BioSeNPs and SS showed comparable efficacy in increasing the activities of glutathione peroxidase and thioredoxin reductase in liver cell lines, mice blood and liver; (iii) pretreatment with BioSeNPs inhibiting the elevation of activities of various enzymes significantly which included aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase and liver lipid peroxide (p < 0.05 or p < 0.01) in CCl₄-treated mice; (iv) activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) were significantly increased (p < 0.05 or p < 0.01) after a pretreatment with BioSeNPs in CCl₄-treated mice; (v) histopathological damages in the liver from CCl₄-treated mice were ameliorated by a pretreatment with BioSeNPs. In conclusion, these results have shown that BioSeNPs is able to protect the liver from CCl₄-induced hepatic damage via increasing the antioxidant capacity and inhibiting oxidative damage. BioSeNPs may have the potential to be used as a trace element food supplement inducing antioxidant bioactivities.

A Summary of New Findings on the Biological Effects of Selenium in Selected Animal Species-A Critical Review

Selenium is an essential trace element important for many physiological processes, especially for the functions of immune and reproductive systems, metabolism of thyroid hormones, as well as antioxidant defense. Selenium deficiency is usually manifested by an increased incidence of retention of placenta, metritis, mastitis, aborts, lowering fertility and increased susceptibility to infections. In calves, lambs and kids, the selenium deficiency demonstrates by WMD (white muscle disease), in foals and donkey foals, it is associated with incidence of WMD and yellow fat disease, and in pigs it causes VESD (vitamin E/selenium deficiency) syndrome. The prevention of these health disorders can be achieved by an adequate selenium supplementation to the diet. The review summarizes the survey of knowledge on selenium, its biological significance in the organism, the impact of its deficiency in mammalian livestock (comparison of ruminants vs. non-ruminants, herbivore vs. omnivore) and possibilities of its peroral administration. The databases employed were as follows: Web of Science, PubMed, MEDLINE and Google Scholar.

Redox-active nanomaterials for nanomedicine applications

Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials.

Green synthesis of selenium nanoparticles using Acinetobacter sp. SW30: optimization, characterization and its anticancer activity in breast cancer cells

The aim of this study was to synthesize selenium nanoparticles (SeNPs) using cell suspension and total cell protein of Acinetobacter sp. SW30 and optimize its synthesis by studying the influence of physiological and physicochemical parameters. Also, we aimed to compare its anticancer activity with that of chemically synthesized SeNPs in breast cancer cells. Cell suspension of Acinetobacter sp. SW30 was exposed to various physiological and physicochemical conditions in the presence of sodium selenite to study their effects on the synthesis and morphology of SeNPs. Breast cancer cells (4T1, MCF-7) and noncancer cells (NIH/3T3, HEK293) were exposed to different concentrations of SeNPs. The 18 h grown culture with 2.7×10⁹ cfu/mL could synthesize amorphous nanospheres of size 78 nm at 1.5 mM and crystalline nanorods at above 2.0 mM Na₂SeO₃ concentration. Polygonal-shaped SeNPs of average size 79 nm were obtained in the supernatant of 4 mg/mL of total cell protein of Acinetobacter sp. SW30. Chemical SeNPs showed more anticancer activity than SeNPs synthesized by Acinetobacter sp. SW30 (BSeNPs), but they were found to be toxic to noncancer cells also. However, BSeNPs were selective against breast cancer cells than chemical ones. Results suggest that BSeNPs are a good choice of selection as anticancer agents.

Characterization and Potential Applications of a Selenium Nanoparticle Producing and Nitrate Reducing Bacterium Bacillus oryziterrae sp. nov

A novel nitrate- and selenite reducing bacterium strain ZYK^T was isolated from a rice paddy soil in Dehong, Yunnan, China. Strain ZYK^T is a facultative anaerobe and grows in up to 150, 000 ppm O₂. The comparative genomics analysis of strain ZYK^T implies that it shares more orthologues with B. subtilis subsp. subtilis NCIB 3610^T (ANIm values, 85.4–86.7%) than with B. azotoformans NBRC 15712^T (ANIm values, 84.4–84.7%), although B. azotoformans NBRC 15712^T (96.3% 16S rRNA gene sequence similarity) is the closest Bacillus species according to 16S rRNA gene comparison. The major cellular fatty acids of strain ZYK^T were iso-C_14:0 (17.8%), iso-C_15:0 (17.8%), and C_16:0 (32.0%). The polar lipid profile consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and an unidentified aminophospholipid. Based on physiological, biochemical and genotypic properties, the strain was considered to represent a novel species of the genus Bacillus, for which the name Bacillus oryziterrae sp. nov. is proposed. The type strain is ZYK^T (=DSM 26460^T =CGMCC 1.5179^T). Strain ZYK^T can reduce nitrate to nitrite and ammonium and possesses metabolic genes for nitrate reduction including nar, nap and nrf. Biogenic selenium nanoparticles of strain ZYK^T show a narrow size distribution and agree with the gaussian distribution. These selenium nanoparticles show significant dose-dependent inhibition of the lung cancer cell line H157, which suggests potential for application in cancer therapy.

Reduction of selenite to Se(0) nanoparticles by filamentous bacterium Streptomyces sp. ES2-5 isolated from a selenium mining soil

Background

Selenium (Se) is an essential trace element in living systems. Microorganisms play a pivotal role in the selenium cycle both in life and in environment. Different bacterial strains are able to reduce Se(IV) (selenite) and (or) Se(VI) (selenate) to less toxic Se(0) with the formation of Se nanoparticles (SeNPs). The biogenic SeNPs have exhibited promising application prospects in medicine, biosensors and environmental remediation. These microorganisms might be explored as potential biofactories for synthesis of metal(loid) nanoparticles.

Results

A strictly aerobic, branched actinomycete strain, ES2-5, was isolated from a selenium mining soil in southwest China, identified as Streptomyces sp. based on 16S rRNA gene sequence, physiologic and morphologic characteristics. Both SEM and TEM-EDX analysis showed that Se(IV) was reduced to Se(0) with the formation of SeNPs as a linear chain in the cytoplasm. The sizes of the SeNPs were in the range of 50–500 nm. The cellular concentration of glutathione per biomass decreased along with Se(IV) reduction, and no SeNPs were observed in different sub-cellular fractions in presence of NADPH or NADH as an electron donor, indicating glutathione is most possibly involved in vivo Se(IV) reduction. Strain ES2-5 was resistant to some heavy metal(loid)s such as Se(IV), Cr(VI) and Zn(II) with minimal inhibitory concentration of 50, 80 and 1.5 mM, respectively.

Conclusions

The reducing mechanism of Se(IV) to elemental SeNPs under aerobic condition was investigated in a filamentous strain of Streptomyces. Se(IV) reduction is mediated by glutathione and then SeNPs synthesis happens inside of the cells. The SeNPs are released via hypha lysis or fragmentation. It would be very useful in Se bioremediation if Streptomyces sp. ES2-5 is applied to the contaminated site because of its ability of spore reproduction, Se(IV) reduction, and adaptation in soil.

Multifunctional selenium nanoparticles as carriers of HSP70 siRNA to induce apoptosis of HepG2 cells

Small interfering RNA (siRNA) as a new therapeutic modality holds promise for cancer treatment, but it is unable to cross cell membrane. To overcome this limitation, nanotechnology has been proposed for mediation of siRNA transfection. Selenium (Se) is a vital dietary trace element for mammalian life and plays an essential role in the growth and functioning of humans. As a novel Se species, Se nanoparticles have attracted more and more attention for their higher anticancer efficacy. In the present study, siRNAs with polyethylenimine (PEI)-modified Se nanoparticles (Se@PEI@siRNA) have been demonstrated to enhance the apoptosis of HepG2 cells. Heat shock protein (HSP)-70 is overexpressed in many types of human cancer and plays a significant role in several biological processes including the regulation of apoptosis. The objective of this study was to silence inducible HSP70 and promote the apoptosis of Se-induced HepG2 cells. Se@PEI@siRNA were successfully prepared and characterized by various microscopic methods. Se@PEI@siRNA showed satisfactory size distribution, high stability, and selectivity between cancer and normal cells. The cytotoxicity of Se@PEI@siRNA was lower for normal cells than tumor cells, indicating that these compounds may have fewer side effects. The gene-silencing efficiency of Se@PEI@siRNA was significantly much higher than Lipofectamine 2000@siRNA and resulted in a significantly reduced HSP70 mRNA and protein expression in cancer cells. When the expression of HSP70 was diminished, the function of cell protection was also removed and cancer cells became more sensitive to Se@PEI@siRNA. Moreover, Se@PEI@siRNA exhibited enhanced cytotoxic effects on cancer cells and triggered intracellular reactive oxygen species, and the signaling pathways of p53 and AKT were activated to advance cell apoptosis. Taken together, this study provides a strategy for the design of an anticancer nanosystem as a carrier of HSP70 siRNA to achieve synergistic cancer therapy.