Antimicrobial and Antioxidant Activity of the Biologically Synthesized Tellurium Nanorods; A Preliminary In vitro Study

A review of recent advances in the use of complex metal nanostructures for biomedical applications from diagnosis to treatment

Complex metal nanostructures represent an exceptional category of materials characterized by distinct morphologies and physicochemical properties. Nanostructures with shape anisotropies, such as nanorods, nanostars, nanocages, and nanoprisms, are particularly appealing due to their tunable surface plasmon resonances, controllable surface chemistries, and effective targeting capabilities. These complex nanostructures can absorb light in the near-infrared, enabling noteworthy applications in nanomedicine, molecular imaging, and biology. The engineering of targeting abilities through surface modifications involving ligands, antibodies, peptides, and other agents potentiates their effects. Recent years have witnessed the development of innovative structures with diverse compositions, expanding their applications in biomedicine. These applications encompass targeted imaging, surface-enhanced Raman spectroscopy, near-infrared II imaging, catalytic therapy, photothermal therapy, and cancer treatment. This review seeks to provide the nanomedicine community with a thorough and informative overview of the evolving landscape of complex metal nanoparticle research, with a specific emphasis on their roles in imaging, cancer therapy, infectious diseases, and biofilm treatment. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Diagnostic Tools > Diagnostic Nanodevices.

In situ, synthesis of chitosan fabricated tellurium nanoparticles for improved antimicrobial and anticancer applications

The emergence of antibiotic resistance has had a severe impact on human health and economic burdens, drawing attention to the development of novel antimicrobial therapies. Polymer-metal composites have shown evidence of therapeutic applications by exerting antimicrobial effects and delivering these antimicrobials with biocompatibility. Therefore, this study prepared and characterized chitosan (CS)-fabricated tellurium nanoparticles (Te NPs) for enhanced antimicrobial, antioxidant, and cytotoxicity applications. The CS-Te NPs were spherical, polydisperse, and distributed within the CS matrix with an average size of 37.48 ± 14.56 nm, as confirmed by TEM analysis. CS-Te NPs exhibited positive zeta potential in neutral (pH 7.0: 7.90 ± 1.86 mV) and acidic environment. XRD analysis confirmed the crystalline nature of CS-Te NPs, and these nanoparticles exhibited good thermal and less porosity. A higher release of Te ions occurred from CS-Te NPs at an acidic pH. Further, CS-Te NPs displayed stronger antibacterial and antibiofilm activity against E. coli and S. enterica. Furthermore, CS-Te NPs exhibited significant free radical scavenging activity against ABTS and DPPH free radicals. Moreover, these nanoparticles demonstrated cytotoxicity against cancerous cells (A549 and PC3 cells) when compared to normal cells (NIH3T3 cells). Therefore, this study suggests that CS-Te NPs could serve as a substantial therapeutic agent.

Biosynthesis of gallic acid fabricated tellurium nanoparticles (GA-Te NPs) for enhanced antibacterial, antioxidant, and cytotoxicity applications

The development of antibiotic resistance and the onset of diverse forms of cancer necessitate the utilization of innovative multifunctional biocompatible materials. The synthesis of metal and metalloid nanoparticles through eco-friendly means demonstrates promising potential in therapeutic and diagnostic domains. Among these materials, Tellurium (Te) exhibits exceptional characteristics and finds application in numerous fields; nevertheless, its usage in biological applications has been somewhat limited, primarily due to its inherent toxicity. Furthermore, nanomaterials developed from Te have not garnered adequate research attention. Conversely, nanomaterials fashioned using biomolecules augment their biological efficacy and applicability. Therefore, the present work focuses on synthesizing the tellurium nanoparticles (Te NPs) using the antioxidant molecule gallic acid (GA) and evaluating their biological activity and toxicity for the first time. The study evidenced that GA-Te NPs are spherical and monodispersed, with an average size of 19.74 ± 5.3 nm. XRD analysis confirmed a hexagonal crystalline structure for GA-Te NPs, and FTIR analysis evidenced the capping of GA on Te NPs. GA-Te NPs (MIC: 1.56 μg/mL) strongly reduce the growth and biofilm formation of S. aureus, E. coli, and S. enterica. Additionally, GA-Te NPs at a concentration of 50 μg/mL cause a significant level of toxicity in BT474 breast cancer cells but not in NIH3T3 cells. Unexpectedly, GA-Te NPs at concentrations <250 μg/mL do not cause hemolysis in red blood cells (RBC) Besides, the way of utilizing the lower concentrations of therapeutics could result in ecological safety. Therefore, the study concludes that GA-Te NPs could be used as potential multifunctional agents.

Microbial mechanisms to transform the super-trace element tellurium: a systematic review and discussion of nanoparticulate phases

Tellurium is a super-trace metalloid on Earth. Owing to its excellent physical and chemical properties, it is used in industries such as metallurgy and manufacturing, particularly of semiconductors and - more recently - solar panels. As the global demand for tellurium rises, environmental issues surrounding tellurium have recently aroused concern due to its high toxicity. The amount of tellurium released to the environment is increasing, and microorganisms play an important role in the biogeochemical cycling of environmental tellurium. This review focuses on novel developments on tellurium transformations driven by microbes and includes the following sections: (1) history and applications of tellurium; (2) toxicity of tellurium; (3) microbial detoxification mechanisms against soluble tellurium anions including uptake, efflux and methods of reduction, and reduced ability to cope with oxidation stress or repair damaged DNA; and (4) the characteristics and applications of tellurium nanoparticles (TeNPs) produced by microbes. This review raises the awareness of microorganisms in tellurium biogeochemical cycling and the growing applications for microbial tellurium nanoparticles.

Green synthesis of biogenetic Te(0) nanoparticles by high tellurite tolerance fungus Mortierella sp. AB1 with antibacterial activity

Tellurite [Te(IV)] is a high-toxicity metalloid. In this study, a fungus with high Te(IV) resistance was isolated. Strain AB1 could efficiently reduce highly toxic Te(IV) to less toxic Te(0). The reduced products formed rod-shaped biogenetic Te(0) nanoparticles (Bio-TeNPs) intracellularly. Further TEM-element mapping, FTIR, and XPS analysis showed that the extracted Bio-TeNPs ranged from 100 to 500 nm and consisted of Te(0), proteins, lipids, aromatic compounds, and carbohydrates. Moreover, Bio-TeNPs exhibited excellent antibacterial ability against Shigella dysenteriae, Escherichia coli, Enterobacter sakazakii, and Salmonella typhimurium according to inhibition zone tests. Further growth and live/dead staining experiments showed that E. coli and S. typhimurium were significantly inhibited by Bio-TeNPs, and cells were broken or shriveled after treatment with Bio-TeNPs based on SEM observation. Additionally, the antioxidant and cytotoxicity tests showed that the Bio-TeNPs exhibited excellent antioxidant capacity with no cytotoxicity. All these results suggested that strain AB1 showed great potential in bioremediation and Bio-TeNPs were excellent antibacterial nanomaterials with no cytotoxicity.

Investigation into the Antibacterial Mechanism of Biogenic Tellurium Nanoparticles and Precursor Tellurite

Antibacterial tellurium nanoparticles have the advantages of high activity and biocompatibility. Microbial synthesis of Te nanoparticles is not only a green technology but builds new ecological relationships in diverse environments. However, the antibacterial mechanism of Te nanoparticles is largely unclear. In this study, we report the bacterial synthesis of rod-shaped Te nanoparticles (BioTe) with high antibacterial activity against Escherichia coli. Morphology and permeability examination indicates that membrane damage is the primary reason for the antibacterial activity of BioTe, rather than ROS production and DNA damage. Moreover, a comparison of transcriptome and relative phenotypes reveals the difference in antibacterial mechanisms between BioTe and tellurite. Based on our evidence, we propose an antibacterial mode of rod-shaped BioTe, in which positively charged BioTe interact with the cell membrane through electrostatic attraction and then penetrate the membrane by using their sharp ends. In contrast, tellurite toxicity might be involved in sulfur metabolism.

Synthesis of "Naked" TeO2 Nanoparticles for Biomedical Applications

Chalcogenide nanoparticles have become a very active field of research for their optoelectronic and biological properties. This article shows the production of tellurium dioxide nanoparticles (TeO₂ NPs) by pulsed laser ablation in liquids. The produced nanoparticles were spherical with a diameter of around 70 nm. The energy band gap of those nanoparticles was determined to be around 5.2 eV. Moreover, TeO₂ NPs displayed a dose-dependent antibacterial effect against antibiotic-resistant bacteria such as multidrug-resistant Escherichia coli (MDR E. coli) and methicillin-resistant Staphylococcus aureus (MR S. aureus). The "naked" nature of the nanoparticle surface helped to eradicate the antibiotic-resistant bacteria at a very low concentration, with IC50 values of ∼4.3 ± 0.9 and 3.7 ± 0.2 ppm for MDR E. coli and MR S. aureus, respectively, after just 8 h of culture. Further, the IC50 values of the naked TeO₂ NPs against melanoma (skin cancer) and healthy fibroblasts were 1.6 ± 0.7 and 5.5 ± 0.2 ppm, respectively, for up to 72 h. Finally, to understand these optimal antibacterial and anticancer properties of the TeO₂ NPs, the reactive oxygen species generated by the nanoparticles were measured. In summary, the present in vitro results demonstrate much promise for the presently prepared TeO₂ NPs and they should be studied for a wide range of safe antibacterial and anticancer applications.

Anti-Pseudomonas aeruginosa biofilm activity of tellurium nanorods biosynthesized by cell lysate of Haloferax alexandrinus GUSF-1(KF796625)

Pseudomonas aeruginosa, an opportunistic human pathogen, is a major health concern as it grows as a biofilm and evades the host's immune defenses. Formation of biofilms on catheter and endotracheal tubes demands the development of biofilm-preventive (anti-biofilm) approaches and evaluation of nanomaterials as alternatives to antibiotics. The present study reports the successful biosynthesis of tellurium nanorods using cell lysate of Haloferax alexandrinus GUSF-1 (KF796625). The black particulate matter had absorption bands at 0.5 and 3.6 keV suggestive of elemental tellurium; showed x-ray diffraction peaks at 2θ values 24.50°, 28.74°, 38.99°, 43.13°, 50.23° and displayed a crystallite size of 36.99 nm. The black nanorods of tellurium were an average size of 40 nm × 7 nm, as observed in transmission electron microscopy. To our knowledge, the use of cell lysate of Haloferax alexandrinus GUSF-1 (KF796625) as a green route for the biosynthesis of tellurium nanorods with a Pseudomonas aeruginosa biofilm inhibiting capacity is novel to haloarchaea. At 50 µg mL^-1, these tellurium nanorods exhibited 75.03% in-vitro reduction of biofilms of Pseudomonas aeruginosa ATCC 9027, comparable to that of ciprofloxacin, which is used in treatment of Pseudomonas infections. Further, the observed ability of these nanoparticles to inhibit the formation of Pseudomonas biofilms is worthy of future research perusal.

Aloe Vera-Mediated Te Nanostructures: Highly Potent Antibacterial Agents and Moderated Anticancer Effects

Cancer and antimicrobial resistance to antibiotics are two of the most worrying healthcare concerns that humanity is facing nowadays. Some of the most promising solutions for these healthcare problems may come from nanomedicine. While the traditional synthesis of nanomaterials is often accompanied by drawbacks such as high cost or the production of toxic by-products, green nanotechnology has been presented as a suitable solution to overcome such challenges. In this work, an approach for the synthesis of tellurium (Te) nanostructures in aqueous media has been developed using aloe vera (AV) extracts as a unique reducing and capping agent. Te-based nanoparticles (AV-TeNPs), with sizes between 20 and 60 nm, were characterized in terms of physicochemical properties and tested for potential biomedical applications. A significant decay in bacterial growth after 24 h was achieved for both Methicillin-resistant Staphylococcus aureus and multidrug-resistant Escherichia coli at a relative low concentration of 5 µg/mL, while there was no cytotoxicity towards human dermal fibroblasts after 3 days of treatment. AV-TeNPs also showed anticancer properties up to 72 h within a range of concentrations between 5 and 100 µg/mL. Consequently, here, we present a novel and green approach to produce Te-based nanostructures with potential biomedical applications, especially for antibacterial and anticancer applications.

Tellurium: A new active element for innovative multifunctional bioactive glasses

Bioactive glasses have been widely investigated for their ability to release ions with therapeutic effect. In this paper, a silica based bioactive glass was doped with a low amount of tellurium dioxide (1 and 5 mol%) to confer antibacterial and antioxidant properties. The obtained glasses were characterized in terms of morphology, composition, structure, characteristic temperatures and in vitro bioactivity. Moreover, comprehensive analyses were carried out to estimate the cytocompatibility, the antibacterial and antioxidant properties of Te-doped glasses. The performed characterizations demonstrated that the Te insertion did not interfere with the amorphous nature of the glass, the substitution of SiO₂ with TeO₂ led to a slight decrease in T_g and a TeO₂ amount higher than 1 mol% can induce a change in the primary crystal field. In vitro bioactivity test demonstrated the Te-doped glass ability to induce the precipitation of hydroxyapatite. Finally, the biological characterization showed a strong antibacterial and antioxidant effects of Te-containing glasses in comparison with the control glass, demonstrating that Te is a promising element to enhance the biological response of biomaterials.

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.

Fate and effect of in-house synthesized tellurium based nanoparticles on bacterial biofilm biomass and architecture. Challenges for nanoparticles characterization in living systems

The unexpected impact of nanoparticles on environment and human health remains as a matter of concern. In this sense, understanding the interaction between nanoparticles and biological indicators such as microorganism may help to understand their fate and effect in environmental systems. However, the adverse effect of nanoparticles greatly depends on their properties and, therefore, a precise evaluation of nanoparticles physicochemical characteristics is mandatory as the first step in accurately elucidating their behaviour in different ecosystems. Here in this work, in house-synthesized tellurium-based nanoparticles have been fully characterized for first time by means of a multi-method approach. Once characterized, the effect of these nanoparticles on Staphylococcus aureus and Escherichia coli biofilm biomass and structure was explored and quantified for first time. Moreover, the morphological transformations of tellurium based nanoparticles within the confines of a biofilm are also highlighted. Architectural metric calculations evidenced that nanoparticles were able to reduce the biovolume of the biofilm produced for both bacteria. Interestingly, the interaction between nanoparticles and bacterial communities led to the transformation of tellurium nanoparticles from sphere to rod-shaped nanoparticles. These findings open new insights into the behaviour of a type of uncommon nanoparticles such as tellurium-based nanoparticles on microbial communities.

Plug-In Safe-by-Design Nanoinorganic Antibacterials

Due to antimicrobial resistance and the adverse health effects that follow broad and inappropriate use of antibacterial agents, new classes of antibacterials with broad and strong bactericidal activity and safety for human use are urgently required globally, increasingly so with the onset of climate change. However, R&D in this field is known to be rarely profitable, unless a cost-effective, flexible, and convenient platform that ensures the production of workable candidate antibacterials can be developed. To address this issue, inorganic nanomaterials have been considered for their bactericidal activities, yet further investigations of composition crystalline modifications and/or surface biomaterial coatings are still required to provide effective and safe antibacterial nanoparticles. In this study, we developed a plug-in system comprising a spark plasma reactor and a flow heater under nitrogen gas flow to supply precursor inorganic nanoparticles (Cu-Te configuration) that can be modulated in-flight at different temperatures. From antibacterial and toxicological assays in both in vitro and in vivo models, bactericidal and toxicological profiles showed that the plug-in system-based platform can be used to identify key parameters for producing safe-by-design agents with antibacterial activity [>88% (in vitro) and >80% (in vivo) in antibacterial efficiency] and safety (>65% in in vitro viability and >60% in in vivo survival rate).

Antimicrobial and anti-biofilm activities of Bi subnitrate and BiNPs produced by Delftia sp. SFG against clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, and Proteus mirabilis

In the present study Delftia sp. Shakibaie, Forootanfar, and Ghazanfari (SFG), was applied for preparation of biogenic Bi nanoparticles (BiNPs) and antibacterial and anti-biofilm activities of the purified BiNPs were investigated by microdilution and disc diffusion methods. Transmission electron micrographs showed that the produced nanostructures were spherical with a size range of 40-120 nm. The measured minimum inhibitory concentration of both the Bi subnitrate and BiNPs against three biofilms producing bacterial pathogens of Staphylococcus aureus, Pseudomonas aeruginosa, and Proteus mirabilis were found to be above 1280 µg/ml. Addition of BiNPs (1000 µg/disc) to antibiotic discs containing tobramycin, nalidixic acid, ceftriaxone, bacitracin, cefalexin, amoxicillin, and cefixime significantly increased the antibacterial effects against methicillin-resistant S. aureus (MRSA) in comparison with Bi subnitrate (p < 0.05). Furthermore, the biogenic BiNPs decreased the biofilm formation of S. aureus, P. aeruginosa, and P. mirabilis to 55, 85, and 15%, respectively. In comparison to Bi subnitrate, BiNPs indicated significant anti-biofilm activity against P. aeruginosa (p < 0.05) while the anti-biofilm activity of BiNPs against S. aureus and P. mirabilis was similar to that of Bi subnitrate. To sum up, the attained results showed that combination of biogenic BiNPs with commonly used antibiotics relatively enhanced their antibacterial effects against MRSA.