Eco-friendly synthesis of silver nanoparticles by Bacillus subtilis and their antibacterial activity

Bio-synthesis and characterization of silver nanoparticles from Trichoderma species against cassava root rot disease

Cassava root rot disease caused by the fungal pathogens Fusarium solani and Lasiodiplodia theobromae produces severe damages on cassava production. This research was conducted to produce and assess silver nanoparticles (AgNPs) synthesized by Trichoderma harzianum for reducing root rot disease. The results revealed that using the supernatants of T. harzianum on a silver nitrate solution changed it to reddish color at 48 h, indicating the formation of AgNPs. Further characterization was identified using dynamic light scattering (DLS) and scanning electron microscope (SEM). DLS supported that the Z-average size is at 39.79 nm and the mean zeta potential is at - 36.5 mV. SEM revealed the formation of monodispersed spherical shape with a diameter between 60-75 nm. The antibacterial action of AgNPs as an antifungal agent was demonstrated by an observed decrease in the size of the fungal colonies using an increasing concentration of AgNPs until the complete inhibition growth of L. theobromae and F. solani at > 58 µg mL-1 and at ≥ 50 µg mL-1, respectively. At in vitro conditions, the applied AgNPs caused a decrease in the percentage of healthy aerial hyphae of L. theobromae (32.5%) and of F. solani (70.0%) compared to control (100%). The SR-FTIR spectra showed the highest peaks in the first region (3000-2800 cm-1) associated with lipids and fatty acids located at 2962, 2927, and 2854 cm-1 in the AgNPs treated samples. The second region (1700-1450 cm-1) consisting of proteins and peptides revealed the highest peaks at 1658, 1641, and 1548 cm-1 in the AgNPs treated samples. The third region (1300-900 cm-1), which involves nucleic acid, phospholipids, polysaccharides, and carbohydrates, revealed the highest peaks at 1155, 1079, and 1027 cm-1 in the readings from the untreated samples. Finally, the observed root rot severity on cassava roots treated with AgNPs (1.75 ± 0.50) was significantly lower than the control samples (5.00 ± 0.00).

Green Synthesis, Characterization and Application of Silver Nanoparticles Using Bioflocculant: A Review

Nanotechnology has emerged as an effective means of removing contaminants from water. Traditional techniques for producing nanoparticles, such as physical methods (condensation and evaporation) and chemical methods (oxidation and reduction), have demonstrated high efficiency. However, these methods come with certain drawbacks, including the significant energy requirement and the use of costly and hazardous chemicals that may cause nanoparticles to adhere to surfaces. To address these limitations, researchers are actively developing alternative procedures that are cost-effective, environmentally safe, and user-friendly. One promising approach involves biological synthesis, which utilizes plants or microorganisms as reducing and capping agents. This review discusses various methods of nanoparticle synthesis, with a focus on biological synthesis using naturally occurring bioflocculants from microorganisms. Bioflocculants offer several advantages, including harmlessness, biodegradability, and minimal secondary pollution. Furthermore, the review covers the characterization of synthesized nanoparticles, their antimicrobial activity, and cytotoxicity. Additionally, it explores the utilization of these NPs in water purification and dye removal processes.

Silver nanoparticles biosynthesis using mixture of Lactobacillus sp. and Bacillus sp. growth and their antibacterial activity

The biosynthesis of nanoparticles offers numerous advantages, including ease of production, cost-effectiveness, and environmental friendliness. In our research, we focused on the bioformation of silver nanoparticles (AgNPs) using a combination of Lactobacillus sp. and Bacillus sp. growth. These AgNPs were then evaluated for their biological activities against multidrug-resistant bacteria. Our study involved the isolation of Bacillus sp. from soil samples and Lactobacillus sp. from raw milk in Dhamar Governorate, Yemen. The synthesized AgNPs were characterized using various techniques such as UV-visible spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The antibacterial properties of the AgNPs were assessed using the modified Kirby Bauer disk diffusion method against multidrug-resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa. Our results demonstrated that the use of a bacterial mixture for biosynthesis led to faster and more effective production of AgNPs compared to using a single bacterium. The UV-visible spectra showed characteristic peaks indicative of silver nanoparticles, while XRD analysis confirmed the crystalline nature of the synthesized particles. FTIR results suggested the presence of capping proteins that contribute to the synthesis and stability of AgNPs. Furthermore, TEM images revealed the size and morphology of the AgNPs, which exhibited spherical shapes with sizes ranging from 4.65 to 22.8 nm. Notably, the antibacterial activity of the AgNPs was found to be more pronounced against Staphylococcus aureus than Pseudomonas aeruginosa, indicating the potential of these nanoparticles as effective antimicrobial agents. Overall, our study highlights the promising antibacterial properties of AgNPs synthesized by a mixture of Lactobacillus sp. and Bacillus sp. growth. Further research is warranted to explore the potential of utilizing different bacterial combinations for enhanced nanoparticle synthesis.

Evaluating the Effect of pH, Temperature and Concentration on Antioxidant and Antibacterial Potential of Spectroscopically, Spectrophotometrically and Microscopically Characterized Mentha Spicata Capped Silver Nanoparticles

The use of traditional plants has been tremendously increased due to their higher biological impact, minimal side effects, and comparatively low cost. Moreover, the emergence of antibacterial resistance is also shifting the scientific community to reconsider herbal remedies which provide relatively safer, cheap and biologically tolerable solutions. The present research was designed to fabricate the Mentha spicata conjugated silver nanoparticles (Me-AgNPs). Furthermore, the assessment of the bactericidal potential of Me-AgNPs against various bacterial strains was another motive behind this study. Fabricated NPs were characterized with the help of the UV-Visible spectrophotometric analysis, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Me-AgNPs showed a significant zone of inhibition (23 ± 0.2 mm) at 8 mg/mL against Staphylococcus aureus and a 4.0 ± 0.2 mm zone of growth inhibition at 2 mg/mL against Aeromonas veronii. The stability of Me-AgNPs was assessed at various pH (4, 7 and 11) and temperatures (25 °C, 4 °C, 37 °C, 75 °C). The significant zones of inhibition (11.3 ± 0.3 mm, 8.3 ± 0.3mm, 14.3 ± 0.3 mm, and 7.6 ± 0.2 mm) were observed at pH 11 against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Klebsiella pneumoniae, respectively. Growth inhibition zones (14.0 ± 0.5 mm and 13.0 ± 0.5 mm) were also determined against B. subtilis and S. aureus at 25 °C. DPPH bioassay was conducted to find the antioxidant properties of Me-AgNPs. The highest (38.66 ± 0.2%) free radical scavenging activity was shown by Me-AgNPs at 4 mg/mL. Present study results concluded that biogenic Me-AgNPs have bactericidal as well as anti-oxidative potential. Moreover, these green synthesized Me-AgNPs could maintain their potency and stability at a wide range of pH and temperature.

Unveiling the cytotoxic and anti-proliferative potential of green-synthesized silver nanoparticles mediated by Colletotrichum gloeosporioides

Fungal endophytes are a putative source of bioactive metabolites that have found significant applications in nanomedicine due to their metabolic versatility. In the present study, an aqueous extract of the fungal endophyte, Colletotrichum gloeosporioides associated with a medicinal plant Oroxylum indicum, has been used for the fabrication of green silver nanoparticles (CgAgNPs) and further evaluated their cytotoxic and anti-proliferative activity. Bioanalytical techniques including UV-Vis spectral analysis revealed a sharp band at 435 nm and functional molecules from the aqueous extract involved in the synthesis of CgAgNPs were evidenced through FTIR. Further, the crystalline nature of CgAgNPs was determined through XRD analysis and microscopy techniques including AFM, TEM and FESEM demonstrated the spherical shape of CgAgNPs exhibiting a crystalline hexagonal lattice and the size was found to be in the range of 9-29 nm. The significant cytotoxic potential of CgAgNPs was observed against breast cancer cells, MDA-MB-231 and MCF-7 with IC50 values of 18.398 ± 0.376 and 38.587 ± 1.828 μg mL-1, respectively. The biochemical study revealed that the treatment of MDA-MB-231 and MCF-7 cells with CgAgNPs reduces glucose uptake, suppresses cell proliferation, and enhances LDH release, indicating reduced cell viability and progression. Moreover, our research revealed differential expression of genes associated with apoptosis, cell cycle inhibition and metastasis suppression, evidencing anti-proliferative activity of CgAgNPs. The main objective of the present study is to harness anti-breast cancer activity of novel biogenic nanoparticles synthesized using the aqueous extract of O. indicum associated C. gloeosporioides and study the underlying mechanistic pathway exerted by these mycogenic nanoparticles.

Optimization of the biosynthesis of silver nanoparticles using bacterial extracts and their antimicrobial potential

In the present study, silver nanoparticles (AgNPs) were biosynthesized using the supernatant and the intracellular extract of Cupriavidus necator, Bacillus megaterium, and Bacillus subtilis. The characterization of the AgNPs was carried out using UV-Vis spectroscopy, FTIR, DLS and TEM. Resazurin microtiter-plate assay was used to determine the antimicrobial action of AgNPs against Escherichia coli. UV-Visible spectra showed peaks between 414 and 460 nm. TEM analysis revealed that the synthesized AgNPs showed mostly spherical shapes. DLS results determined sizes from 20.8 to 118.4 nm. The highest antimicrobial activity was obtained with the AgNPs synthesized with supernatant rather than those using the intracellular extract. Therefore, it was determined that the bacterial species, temperature, pH, and type of extract (supernatant or intracellular) influence the biosynthesis. This synthesis thus offers a simple, environmentally friendly, and low-cost method for the production of AgNPs, which can be used as antibacterial agents.

Optimization of subtilisin production from Bacillus subtilis strain ZK3 and biological and molecular characterization of synthesized subtilisin capped nanoparticles

The increase and dissemination of multi-drug resistant bacteria have presented a major healthcare challenge, making bacterial infections a significant concern. The present research contributes towards the production of bioactive subtilisin from a marine soil isolate Bacillus subtilis strain ZK3. Custard apple seed powder (raw carbon) and mustard oil cake (raw nitrogen) sources showed a pronounced effect on subtilisin production. A 7.67-fold enhancement in the production was evidenced after optimization with central composite design-response surface methodology. Subtilisin capped silver (AgNP) and zinc oxide (ZnONP) nanoparticles were synthesized and characterized by UV-Visible spectroscopy. Subtilisin and its respective nanoparticles revealed significant biological properties such as, antibacterial activity against all tested pathogenic strains with potential against Escherichia coli and Pseudomonas aeruginosa. Prospective antioxidant behavior of subtilisin, AgNP and ZnONP was evidenced through radical scavenging assays with ABTS and DPPH. Subtilisin, AgNP and ZnONP revealed cytotoxic effect against cancerous breast cell lines MCF-7 with IC50of 83.48, 3.62 and 7.57 µg/mL respectively. Characterizations of nanoparticles were carried out by Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis and atomic force microscopy analysis to elucidate the structure, surface and thermostability properties. The study proposes the potential therapeutic applications of subtilisin and its nanoparticles, a way forward for further exploration in the field of healthcare.

Current Overview of Metal Nanoparticles' Synthesis, Characterization, and Biomedical Applications, with a Focus on Silver and Gold Nanoparticles

Metal nanoparticles (NPs) have garnered considerable attention, due to their unique physicochemical properties, that render them promising candidates for various applications in medicine and industry. This article offers a comprehensive overview of the most recent advancements in the manufacturing, characterization, and biomedical utilization of metal NPs, with a primary focus on silver and gold NPs. Their potential as effective anticancer, anti-inflammatory, and antimicrobial agents, drug delivery systems, and imaging agents in the diagnosis and treatment of a variety of disorders is reviewed. Moreover, their translation to therapeutic settings, and the issue of their inclusion in clinical trials, are assessed in light of over 30 clinical investigations that concentrate on administering either silver or gold NPs in conditions ranging from nosocomial infections to different types of cancers. This paper aims not only to examine the biocompatibility of nanomaterials but also to emphasize potential challenges that may limit their safe integration into healthcare practices. More than 100 nanomedicines are currently on the market, which justifies ongoing study into the use of nanomaterials in medicine. Overall, the present review aims to highlight the potential of silver and gold NPs as innovative and effective therapeutics in the field of biomedicine, citing some of their most relevant current applications.

Biogenic selenium nanoparticles: trace element with promising anti-toxoplasma effect

Toxoplasmosis is an opportunistic infection caused by the coccidian Toxoplasma gondii which represents a food and water contaminant. The available chemotherapeutic agents for toxoplasmosis are limited and the choice is difficult when considering the side effects. Selenium is an essential trace element. It is naturally found in dietary sources, especially seafood, and cereals. Selenium and selenocompounds showed anti-parasitic effects through antioxidant, immunomodulatory, and anti-inflammatory mechanisms. The present study evaluated the potential efficacy of environmentally benign selenium nanoparticles (SeNPs) against acute toxoplasmosis in a mouse model. SeNPs were fabricated by nanobiofactory Streptomyces fulvissimus and characterized by different analytical techniques including, UV-spectrophotometry, transmission electron microscopy, EDX, and XRD. Swiss albino mice were infected with Toxoplasma RH strain in a dose of 3500 tachyzoites in 100 μl saline to induce acute toxoplasmosis. Mice were divided into five groups. Group I: non-infected, non-treated, group II: infected, non-treated, group III: non-infected, treated with SeNPs, group IV: infected, treated with co-trimoxazole (sulfamethoxazole/trimethoprim) and group V: infected, treated with SeNPs. There was a significant increase in survival time in the SeNPs-treated group and minimum parasite count was observed compared to untreated mice in hepatic and splenic impression smears. Scanning electron microscopy showed tachyzoites deformity with multiple depressions and protrusions, while transmission electron microscopy showed excessive vacuolization and lysis of the cytoplasm, especially in the area around the nucleus and the apical complex, together with irregular cell boundary and poorly demarcated cell organelles. The present study demonstrated that the biologically synthesized SeNPs can be a potential natural anti-Toxoplasma agent in vivo.

Response surface methodology based optimization of keratinase from Bacillus velezensis strain ZBE1 and nanoparticle synthesis, biological and molecular characterization

The increasing demands of keratinases for biodegradation of recalcitrant keratinaceous waste like chicken feathers has lead to research on newer potential bacterial keratinases to produce high-value products with biological activities. The present study reports a novel keratinolytic bacterium Bacillus velezensis strain ZBE1 isolated from deep forest soil of Western Ghats of Karnataka, which possessed efficient feather keratin degradation capability and induced keratinase production. Production kinetics depicts maximum keratinase production (11.65 U/mL) on 4th day with protein concentration of 0.61 mg/mL. Effect of various physico-chemical factors such as, inoculum size, metal ions, carbon and nitrogen sources, pH and temperature influencing keratinase production were optimized and 3.74 folds enhancement was evidenced through response surface methodology. Silver (AgNP) and zinc oxide (ZnONP) nanoparticles with keratin hydrolysate produced from chicken feathers by the action of keratinase were synthesized and verified with UV-Visible spectroscopy that revealed biological activities like, antibacterial action against Bacillus cereus and Escherichia coli. AgNP and ZnONP also showed potential antioxidant activities through radical scavenging activities by ABTS and DPPH. AgNP and ZnONP revealed cytotoxic effect against MCF-7 breast cancer cell lines with IC50 of 5.47 µg/ml and 62.26 µg/ml respectively. Characterizations of nanoparticles were carried out by Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis and atomic force microscopy analysis to elucidate the thermostability, structure and surface attributes. The study suggests the prospective applications of keratinase to trigger the production of bioactive value-added products and significant application in nanotechnology in biomedicine.

Impact of bacterial synthesized nanoparticles on quality attributes and postharvest disease control efficacy of apricot and loquat

Postharvest fungal attacks on fruits such as apricots and loquats are common. Diseased fruit samples were collected from Murree's local fruit markets. The disease-causing pathogens were identified utilizing molecular, microscopic, and morphological characteristics. Alternaria alternata and Aspergillus niger were identified as the pathogens responsible for brown rot in loquat and black rot in apricot. To combat these fruit diseases, iron oxide (Fe2 O3 ) nanoparticles were synthesized using Bacillus subtilis and were characterized using various techniques. X-ray diffraction examination validated the size of iron oxide nanoparticles. The presence of several capping agents in the synthesized nanoparticles was confirmed by Fourier transform infrared analysis. Scanning electron microscopy revealed the spherical morphology of nanoparticles, whereas energy-dispersive X-ray proved the presence of different elemental compositions. After completing antifungal activities in vitro and in vivo, it was discovered that a nanoparticle concentration of 1.0 mg/mL efficiently suppressed the growth of fungal mycelia. Fungi growth was effectively inhibited in fruit samples treated with 1.0 mg/mL nanoparticles. The results of successful in vitro and in vivo antifungal activities imply that iron oxide (Fe2 O3 ) nanoparticles play an important role in ensuring fruit quality against pathogenic attacks. Bacterial-mediated iron oxide can be widely used because it is less expensive and less harmful to the environment than chemically manufactured fertilizers.

Biosynthesis of metallic nanoparticles by bacterial cell-free extract

The biosynthesis of metallic nanoparticles (MNPs), encompassing noble metals, metal oxides, and sulfides, has gained significant attention in recent years due to their unique properties and wide-ranging applications. However, traditional chemical synthesis methods often involve extreme conditions, harsh chemicals, and negative environmental impacts. Consequently, developing a simple, non-toxic, and eco-friendly approach for MNP synthesis is paramount. One promising method that addresses these concerns is using a bacterial cell-free extract (CFE) as a mediator for biosynthesis. Compared with other biosynthesis production methods, the purification process of MNPs synthesized using bacterial CFEs is much simpler, and CFE production is easier to standardize and reproduce. Bacterial CFEs are rich in various biomolecules, including proteins, enzymes, and peptides, which serve as both reducing and oxidizing agents during MNP formation. These biomolecules act as capping agents, contributing to the stability and monodisperse nature of MNPs. Using bacterial CFEs for MNP synthesis offers several advantages. Firstly, it aligns with eco-friendly practices as a biosynthesis approach. The non-toxic process minimizes environmental damage. Additionally, bacterial CFEs are cost-effective, making large-scale production economically viable. This review provides insights into these mechanisms, highlighting the role of CFE biomolecules and their impact on MNP characteristics. It also investigates the correlation between synthesis parameters, morphologies, and physical, chemical, and biological properties, allowing for tailored MNP design through the biosynthesis conditions. Despite its advantages, bacterial CFE-mediated biosynthesis faces challenges. This review addresses these challenges and discusses potential solutions. It also explores future perspectives, emphasizing areas for further investigation and innovation. In summary, using bacterial CFEs to synthesize MNPs offers significant advantages over other methods. It ensures eco-friendly, non-toxic, and cost-effective production. The review emphasizes the mechanisms and biomolecules involved, showcasing the potential for tailored MNP design. It also addresses challenges and prospects, paving the way for advancements in this field. Furthermore, the originality of this work lies in the exploitation of bacterial CFEs as a highly efficient and scalable platform for MNP synthesis.

Pullulan-based films impregnated with silver nanoparticles from the Fusarium culmorum strain JTW1 for potential applications in the food industry and medicine

Introduction: Biopolymers, such as pullulan, a natural exopolysaccharide from Aureobasidium pullulans, and their nanocomposites are commonly used in the food, pharmaceutical, and medical industries due to their unique physical and chemical properties. Methods: Pullulan was synthesized by the A. pullulans ATCC 201253 strain. Nanocomposite films based on biosynthesized pullulan were prepared and loaded with different concentrations of silver nanoparticles (AgNPs) synthesized by the Fusarium culmorum strain JTW1. AgNPs were characterized by transmission electron microscopy, Zeta potential measurements, and Fourier-transform infrared spectroscopy. In turn, the produced films were subjected to physico-chemical analyses such as goniometry, UV shielding capacity, attenuated total reflection-Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, and their mechanical and degradation properties were assessed. The antibacterial assays of the nanoparticles and the nanocomposite films against both food-borne and reference pathogens, including Listeria monocytogenes, Salmonella infantis, Salmonella enterica, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, were performed using standard methods. Results: AgNPs were small (mean 15.1 nm), spherical, and displayed good stability, being coated with protein biomolecules. When used in higher concentrations as an additive to pullulan films, they resulted in reduced hydrophilicity and light transmission for both UV-B and UV-A lights. Moreover, the produced films exhibited a smooth surface. Therefore, it can be concluded that the addition of biogenic AgNPs did not change the morphology and texture of the films compared to the control film. The nanoparticles and nanocomposite films demonstrated remarkable antibacterial activity against both food-borne and reference bacteria. The highest activity of the prepared films was observed against L. monocytogenes. Discussion: The obtained results suggest that the novel nanocomposite films prepared from biosynthesized pullulan and AgNPs can be considered for use in the development of medical products and food packaging. Moreover, this is the first report on pullulan-based nanocomposites with mycogenic AgNPs for such applications.

A Microfluidic Approach for Synthesis of Silver Nanoparticles as a Potential Antimicrobial Agent in Alginate-Hyaluronic Acid-Based Wound Dressings

The recognized antimicrobial activity of silver nanoparticles is a well-studied property, especially when designing and developing biomaterials with medical applications. As biological activity is closely related to the physicochemical characteristics of a material, aspects such as particle morphology and dimension should be considered. Microfluidic systems in continuous flow represent a promising method to control the size, shape, and size distribution of synthesized nanoparticles. Moreover, using microfluidics widens the synthesis options by creating and controlling parameters that are otherwise difficult to maintain in conventional batch procedures. This study used a microfluidic platform with a cross-shape design as an innovative method for synthesizing silver nanoparticles and varied the precursor concentration and the purging speed as experimental parameters. The compositional and microstructural characterization of the obtained samples was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Four formulations of alginate-based hydrogels with the addition of hyaluronic acid and silver nanoparticles were obtained to highlight the antimicrobial activity of silver nanoparticles and the efficiency of such a composite in wound treatment. The porous structure, swelling capacity, and biological properties were evaluated through physicochemical analysis (FT-IR and SEM) and through contact with prokaryotic and eukaryotic cells. The results of the physicochemical and biological investigations revealed desirable characteristics for performant wound dressings (i.e., biocompatibility, appropriate porous structure, swelling rate, and degradation rate, ability to inhibit biofilm formation, and cell growth stimulation capacity), and the obtained materials are thus recommended for treating chronic and infected wounds.

Updates on Biogenic Metallic and Metal Oxide Nanoparticles: Therapy, Drug Delivery and Cytotoxicity

The ambition to combat the issues affecting the environment and human health triggers the development of biosynthesis that incorporates the production of natural compounds by living organisms via eco-friendly nano assembly. Biosynthesized nanoparticles (NPs) have various pharmaceutical applications, such as tumoricidal, anti-inflammatory, antimicrobials, antiviral, etc. When combined, bio-nanotechnology and drug delivery give rise to the development of various pharmaceutics with site-specific biomedical applications. In this review, we have attempted to summarize in brief the types of renewable biological systems used for the biosynthesis of metallic and metal oxide NPs and the vital contribution of biogenic NPs as pharmaceutics and drug carriers simultaneously. The biosystem used for nano assembly further affects the morphology, size, shape, and structure of the produced nanomaterial. The toxicity of the biogenic NPs, because of their pharmacokinetic behavior in vitro and in vivo, is also discussed, together with some recent achievements towards enhanced biocompatibility, bioavailability, and reduced side effects. Because of the large biodiversity, the potential biomedical application of metal NPs produced via natural extracts in biogenic nanomedicine is yet to be explored.

Recent Advances and Perspectives of Nanomaterials in Agricultural Management and Associated Environmental Risk: A Review

The advancement in nanotechnology has enabled a significant expansion in agricultural production. Agri-nanotechnology is an emerging discipline where nanotechnological methods provide diverse nanomaterials (NMs) such as nanopesticides, nanoherbicides, nanofertilizers and different nanoforms of agrochemicals for agricultural management. Applications of nanofabricated products can potentially improve the shelf life, stability, bioavailability, safety and environmental sustainability of active ingredients for sustained release. Nanoscale modification of bulk or surface properties bears tremendous potential for effective enhancement of agricultural productivity. As NMs improve the tolerance mechanisms of the plants under stressful conditions, they are considered as effective and promising tools to overcome the constraints in sustainable agricultural production. For their exceptional qualities and usages, nano-enabled products are developed and enforced, along with agriculture, in diverse sectors. The rampant usage of NMs increases their release into the environment. Once incorporated into the environment, NMs may threaten the stability and function of biological systems. Nanotechnology is a newly emerging technology, so the evaluation of the associated environmental risk is pivotal. This review emphasizes the current approach to NMs synthesis, their application in agriculture, interaction with plant-soil microbes and environmental challenges to address future applications in maintaining a sustainable environment.

Assessment of antimicrobial activity of chitosan/silver nanoparticles hydrogel and cryogel microspheres

This research investigates the synthesis and characterization of hydrogel and cryogel microspheres that are doped with green synthesised silver nanoparticles (CS-AgNPs). Also, the study assesses the antibacterial activity of hydrogel and cryogel microspheres by comparing them with commercial antibiotics. The porous structure of CS and the adequate dispersion of AgNPs were confirmed by SEM and EDX techniques, respectively. The disk diffusion method and the optical density measurement (OD600) confirm the outstanding antimicrobial activity of CS-AgNPs hydrogel and cryogel microspheres in comparison to antibiotics for both Gram-positive and Gram-negative bacteria. The CS-AgNPs microspheres demonstrate promising antimicrobial and biocompatible agents for medical field applications.

Analysis of the antimicrobial potential of sericin-coated silver nanoparticles against human pathogens

The antibacterial activity of synthetic antimicrobial agents is well known, but most of them have several side effects and are effective against selective microbes. Recently, major concern for the microbiologists is to investigate for some stable, non-toxic, cheap, and eco-friendly antimicrobial agents with a wide range of bactericidal potential. A cost-effective and environmentally friendly alternate has been proposed in the form of green synthesized nanoparticles. The Present study was designed to fabricate sericin-coated silver nanoparticles (S-AgNPs) using sericin as stabilizer and reductant of silver ions and their antibacterial potential was evaluated at various concentrations and temperatures (8, 40, and 50°C). Antimicrobial activities were assessed by the agar well diffusion method. Antibacterial activity of S-AgNPs was measured at different concentrations (1-6 mg/ml) whereas; antifungal activity was tested at 5-20 mg/ml of S-AgNPs. Nanoparticles were characterized by UV-visible spectrophotometer, Fourier transform infrared spectroscopy, and scanning electron microscopy. These nanoparticles significantly subdued the growth of Clostridium difficile (18.7 ± 0.9 mm), Proteus mirabilis (12.3 ± 0.3 mm) and Bacillus licheniformis (10.7 ± 0.9 mm) and Aspergillus flavus (18.7 ± 2.0 mm), Mucor mycetes (13 .0 ± 1.5 mm), Candida albicans (15.3 ± 0.3 mm) and Aspergillus niger (10.0 ± 0.6 mm). S-AgNPs were stable at all temperatures and the maximum growth inhibition was found at 8°C for all pathogenic strains. We concluded that the S-AgNPs could be a potential candidate to inhibit the growth of bacterial and fungal pathogens at a wide range of environmental conditions like temperature. In various biomedical applications including antimicrobial and wound dressings, S-AgNPs can be used in the future to treat various bacterial and fungal infections.

Biogenic copper oxide nanoparticles from Bacillus coagulans induced reactive oxygen species generation and apoptotic and anti-metastatic activities in breast cancer cells

The present study examined the anticancer capabilities of Bacillus coagulans supernatant-produced copper oxide nanoparticles (BC-CuONPs) on MCF-7 and SKBR3 cancer cells. The X-ray diffraction, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, field-emission scanning electron microscopy, energy-dispersive X-ray, dynamic light scattering, and zeta potential techniques were used to characterize BC-CuONPs. This study also investigated the cellular and molecular processes of NPs' anti-proliferative and apoptotic properties on human breast cancer cells and compared them to the commercial pharmaceutical tamoxifen. The size of the spherical NP was from 5 to 47 nm with negative zeta potential. The MTT results showed the great cytotoxic effect of BC-CuONPs against breast cancer cells. The BC-CuONPs inhibited the growth of breast cancer cells in a time- and dose-dependent manner. The up-regulation of BCL2-associated X (BAX), cyclin dependent kinase inhibitor 1A (P21), Caspase 3 (CASP3), and Caspase 9 (CASP9), the down-regulation of BCL2 apoptosis regulator (BCL2), Annexin V-FITC/propidium iodide, and reactive oxygen species (ROS) generation results suggested that BC-CuONPs had a significant apoptotic impact when compared to the control. Scratch tests and vascular endothelial growth factor receptor gene (VEGF) down-regulation demonstrated that BC-CuONPs had anti-metastatic activity. The cell cycle analysis and down-regulation of Cyclin D1 (CCND1) and cyclin dependent kinase 4 (CDK4) revealed that cancer cells were arrested in the sub-G1 phase. Finally, the results showed that the secondary metabolites in the supernatant of Bacillus coagulans could form CuONPs, and biogenic BC-CuONPs showed anti-metastasis and anticancer properties on breast cancer cells while having less adverse effects on normal cells. Therefore, the synthesized CuONPs using B. coagulans supernatant can be shown as a potential candidate for a new therapeutic strategy in cancer management.

Biosynthesis of Silver Nanoparticles Produced Using Geobacillus spp. Bacteria

Silver nanoparticles (AgNPs) are well known for their unique physical and chemical properties, which can be incorporated into a wide range of applications. The growing resistance of microorganisms to antimicrobial compounds promoted the use of AgNPs in antimicrobial therapy. AgNPs can be obtained using physical and chemical methods, but these technologies are highly unfriendly to nature and produce large amounts of side compounds (for example, sodium borohydride and N,N-dimethylformamide). Therefore, alternative technologies are required for obtaining AgNPs. This report focuses on the biosynthesis of silver nanoparticles through the reduction of Ag⁺ with the cell-free secretomes of four Geobacillus bacterial strains, namely, 18, 25, 95, and 612. Only a few studies that involved Geobacillus bacteria in the synthesis of metal nanoparticles, including AgNPs, have been reported to date. The silver nanoparticles synthesized through bio-based methods were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), and zeta potential measurements. UV-Vis spectroscopy showed a characteristic absorbance peak at 410-425 nm, indicative of AgNPs. SEM analysis confirmed that most nanoparticles were spherical. DLS analysis showed that the sizes of the obtained AgNPs were widely distributed, with the majority less than 100 nm in diameter, while the zeta potential values ranged from -25.7 to -31.3 mV and depended on the Geobacillus spp. strain.

Biosynthesis of Metal and Metal Oxide Nanoparticles Using Microbial Cultures: Mechanisms, Antimicrobial Activity and Applications to Cultural Heritage

Nanoparticles (1 to 100 nm) have unique physical and chemical properties, which makes them suitable for application in a vast range of scientific and technological fields. In particular, metal nanoparticle (MNPs) research has been showing promising antimicrobial activities, paving the way for new applications. However, despite some research into their antimicrobial potential, the antimicrobial mechanisms are still not well determined. Nanoparticles' biosynthesis, using plant extracts or microorganisms, has shown promising results as green alternatives to chemical synthesis; however, the knowledge regarding the mechanisms behind it is neither abundant nor consensual. In this review, findings from studies on the antimicrobial and biosynthesis mechanisms of MNPs were compiled and evidence-based mechanisms proposed. The first revealed the importance of enzymatic disturbance by internalized metal ions, while the second illustrated the role of reducing and negatively charged molecules. Additionally, the main results from recent studies (2018-2022) on the biosynthesis of MNPs using microorganisms were summarized and analyzed, evidencing a prevalence of research on silver nanoparticles synthesized using bacteria aiming toward testing their antimicrobial potential. Finally, a synopsis of studies on MNPs applied to cultural heritage materials showed potential for their future use in preservation.

Application of silver nanoparticles synthesized through varying biogenic and chemical methods for wastewater treatment and health aspects

Nanotechnology uses biological and non-biological materials to create new systems at the nanoscale level. In recent years, the use of silver nanomaterials has attracted worldwide attention thanks to their wide range of applications as catalysts in several environmental processes including the degradation of organic pollutants and medicinal biotechnology. This study reports the synthesis of silver nanoparticles (AgNPs) through different methods including the biogenic methods based on leaf extract of Conocarpus erectus and a bacterial strain Pseudomonas sp. as well as chemically based abiotic method and comparison of their dye degradation potential. The synthesis of AgNPs in all samples was confirmed by UV-visible spectroscopy peaks at 418-420 nm. Using scanning electrom microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray differaction (XRD), and X-ray photoelectron spectroscopy (XPS), the biologically synthesized AgNPs were characterized as spherical shape of material with capping proteins that were involved in the stabilization of nanoparticles (NPs). The biologically synthesized AgNPs showed higher degradation (< 90%) of dyes as compared to chemically synthesized NPs. A prominent reduction of total dissolved solids (TDS), electrical conductivity (EC), pH, and chemical oxygen demand (COD) in textile wastewater spiked with reactive black 5 and reactive red 120 was observed by biologically synthesized AgNPs. AgNPs synthesized by Conocarpus erectus and Pseudomonas sp. also showed better characteristic anticancer and antidiabetic activities as compared to chemically synthesized ones. The results of this study suggested that C. erectus and Pseudomonas sp. based AgNPs can be exploited as an eco-friendly and cost-efficient materials to treat the wastewater and potential other polluted environments as well as to serve the medicinal field.

Biofabrication of nanoparticles: sources, synthesis, and biomedical applications

Nanotechnology is an emerging applied science delivering crucial human interventions. Biogenic nanoparticles produced from natural sources have received attraction in recent times due to their positive attributes in both health and the environment. It is possible to produce nanoparticles using various microorganisms, plants, and marine sources. The bioreduction mechanism is generally employed for intra/extracellular synthesis of biogenic nanoparticles. Various biogenic sources have tremendous bioreduction potential, and capping agents impart stability. The obtained nanoparticles are typically characterized by conventional physical and chemical analysis techniques. Various process parameters, such as sources, ions, and temperature incubation periods, affect the production process. Unit operations such as filtration, purification, and drying play a role in the scale-up setup. Biogenic nanoparticles have extensive biomedical and healthcare applications. In this review, we summarized various sources, synthetic processes, and biomedical applications of metal nanoparticles produced by biogenic synthesis. We highlighted some of the patented inventions and their applications. The applications range from drug delivery to biosensing in various therapeutics and diagnostics. Although biogenic nanoparticles appear to be superior to their counterparts, the molecular mechanism degradation pathways, kinetics, and biodistribution are often missing in the published literature, and scientists should focus more on these aspects to move them from the bench side to clinics.

Recent insights into metallic nanoparticles in shelf-life extension of agrifoods: Properties, green synthesis, and major applications

Nanotechnology emerged as a revolutionary technology in various fields of applied sciences, such as biomedical engineering and food technology. The pivotal roles of nanocompounds have been explored in various fields, such as food protection, preservation, and enhancement of shelf life. In this sequence, metallic nanoparticles (MNPs) are proven to be useful in developing products with antimicrobial activity and subsequently improve the shelf life of agrifoods. The major application of MNPs has been observed in the packaging industry due to the combining ability of biopolymers with MNPs. In recent years, various metal nanoparticles have been explored to formulate various active food packaging materials. However, the method of production and the need for risk evaluation are still a topic of discussion among researchers around the world. In general, MNPs are synthesized by various chemical and physical means, which may pose variable health risks. To overcome such issues, the green synthesis of MNPs using microbial and plant extracts has been proposed by various researchers. In this review, we aimed at exploring the green synthesis of MNPs, their properties and characterization, various ways of utilizing MNPs to extend their shelf life, and, most importantly, the risk associated with these along with their quality and safety considerations.

Antifungal Activity of Biosynthesized Silver Nanoparticles (AgNPs) against Aspergilli Causing Aspergillosis: Ultrastructure Study

Currently, nanoparticles and nanomaterials are widely used for biomedical applications. In the present study, silver nanoparticles (AgNPs) were successfully biosynthesized using a cell-free extract (CFE) of Bacillus thuringiensis MAE 6 through a green and ecofriendly method. The size of the biosynthesized AgNPs was 32.7 nm, and their crystalline nature was confirmed by XRD, according to characterization results. A surface plasmon resonance spectrum of AgNPs was obtained at 420 nm. Nanoparticles were further characterized using DLS and FTIR analyses, which provided information on their size, stability, and functional groups. AgNPs revealed less cytotoxicity against normal Vero cell line [IC₅₀ = 155 μg/mL]. Moreover, the biosynthesized AgNPs exhibited promising antifungal activity against four most common Aspergillus, including Aspergillus niger, A. terreus, A. flavus, and A. fumigatus at concentrations of 500 μg/mL where inhibition zones were 16, 20, 26, and 19 mm, respectively. In addition, MICs of AgNPs against A. niger, A. terreus, A. flavus, and A. fumigatus were 125, 62.5, 15.62, and 62.5 μg/mL, respectively. Furthermore, the ultrastructural study confirmed the antifungal effect of AgNPs, where the cell wall's integrity and homogeneity were lost; the cell membrane had separated from the cell wall and had intruded into the cytoplasm. In conclusion, the biosynthesized AgNPs using a CFE of B. thuringiensis can be used as a promising antifungal agent against Aspergillus species causing Aspergillosis.

Green Orange Peel-Mediated Bioinspired Synthesis of Nanoselenium and Its Antibacterial Activity against Methicillin-Resistant Staphylococcus aureus

In this study, green orange peel (GOP) was feasibly evidenced in preparing selenium nanoparticles (SeNPs). Acting as reducing agents, polyphenolic compounds were extracted from GOP at the optimal extraction conditions (at 70 °C for 1.5 h, mass ratio of dried orange peel/distilled water of 5/100). The formation of SeNPs was observed at the wavelength range of 250-300 nm by ultraviolet-visible spectroscopy (UV-vis), and their highest yield could be reached at the following conditions: volume ratio of extract/selenious acid solution (V _Ext/V _Se) of 40/10, synthesis duration of 4 h, selenious acid concentration (C _Se) of 80 mM, and reaction temperature of 120 °C. The highly crystalline structure of SeNPs in the hexagonal phase was characterized by powder X-ray diffraction (XRD) with a lattice parameter of 4.3 Å; meanwhile, their spheres with an average crystal size of 18.3 nm were estimated by high-resolution transmission electron microscope (HR-TEM). The rationale of bioreducing agents extracted from green orange peel for the formation of SeNPs was also recognized by Fourier-transform infrared spectroscopy (FT-IR). The antibacterial investigation of the SeNP sample was assessed against antibiotic-resistant bacteria, typically methicillin-resistant Staphylococcus aureus (MRSA), by executing the zone of inhibition and the minimum inhibitory concentration (MIC) tests. The SeNP sample demonstrated excellent antibacterial activity with an average diameter of inhibition zones of 20.0 ± 0.7 mm and an MIC of 4.94 μg/L. A comparison of the physicochemical properties of SeNPs synthesized from GOP extract by the hydrothermal method with SeNP products from other green reducing agents and other methods as well as its antibacterial activity compared with other nanoparticles and some antibiotics was conducted to highlight the superiority of GOP-mediated green-synthesized SeNPs.

Bactericidal activity of Ag4V2O7/β-AgVO3 heterostructures against antibiotic-resistant Klebsiella pneumoniae

Although Ag-based materials are efficient against antibiotic-resistant bacteria, their high toxicity to living organisms represents a major challenge for obtaining useful products. In this work, we report the bactericidal activity of Ag₄V₂O₇/β-AgVO₃ heterostructures, which proved to be effective against Klebsiella pneumoniae (ATCC 1706, a standard strain; A54970, a multidrug-resistant carbapenemase (KPC)-producing strain; A34057, a multidrug-resistant strain capable of producing extended spectrum beta-lactamases (ESBL); and a community-isolated strain, A58240) at minimum inhibitory concentrations (MIC) as low as 62.5 μg/mL. This activity is higher than that reported for the individual silver vanadates (Ag₄V₂O₇ or β-AgVO₃) owing to the synergistic interactions between both semiconductors. However, the most efficient heterostructure was found to be toxic to mouse 3 T3 fibroblasts and to L. sativa and C. sativus seeds, as indicated by MTT ((4,5 - dimethylthiazol -2yl) 2,5 -diphenylbromide), neutral red assays and germination index measurements. The antimicrobial, phytotoxic and cytotoxic activities were all associated with an efficient generation of reactive oxygen species (ROS) in the heterostructure, especially OH and O₂^- radicals. The ROS production by Ag₄V₂O₇/β-AgVO₃ heterostructures was measured through photodegradation studies with Rhodamine B. While the bactericidal activity of the heterostructures is promising, especially when compared to Ag-based materials, their use in practical applications will require encapsulation either to avoid leaching or to mitigate their toxicity to humans, animals and plants.

Photocatalytic and Antimicrobial Activities of Biosynthesized Silver Nanoparticles Using Cytobacillus firmus

The toxicity of the ecosystem has increased recently as a result of the increased industrial wastewater loaded with organic contaminants, including methylene blue (MB), which exerts serious damage to the environment. Thus, the present work aims to green the synthesis of silver nanoparticles (Ag-NPs) and to evaluate their degradability of notorious MB dye, as well as their antimicrobial activities. Ag-NPs were synthesized by Cytobacillus firmus extract fully characterized by UV-vis, TEM, DLS, XRD, and FTIR. Ag-NPs showed good antibacterial and antifungal activities against Escherichia coli ATCC 25922, Enterococcus feacalis ATCC 29212, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, and Candida albicans ATCC 90028. Moreover, Ag-NPs exhibited a high biodegradability level (98%) of MB dye after 8 h of co-incubation in the presence of sunlight. Additionally, the phytotoxicity of treated MB dye-contaminated water sample showed good germination of Vicia faba as compared with non-treated MB dye-contaminated solution. In conclusion, the herein biosynthesized Ag-NPs demonstrated its feasibility of the purification of contaminated water from microbes and methylene blue dye and the probability of reusing purified water for agricultural purposes.

Characterization of the biosynthesized intracellular and extracellular plasmonic silver nanoparticles using Bacillus cereus and their catalytic reduction of methylene blue

The biosynthesis of silver nanoparticles (Ag NPs) has been studied in detail using two different approaches. For the first time, Bacillus cereus is used for one-pot biosynthesis of capsulated Ag NPs, using both intracellular and extracellular approaches. To discriminate between the produced nanostructures by these two approaches, their structures, nanomorphologies, optical properties, hydrodynamic sizes and zeta potentials are studied using different techniques. Fourier-transform infrared spectroscopy was used to identify the bioactive components responsible for the reduction of Ag⁺ ions into Ag and the growth of stable Ag NPs. Scanning and transmission electron microscopy images displayed spherical and polygon nanomorphology for the intracellular and extracellular biosynthesized Ag NPs. For intracellular and extracellular biosynthesized Ag NPs, a face-centred cubic structure was observed, with average crystallite sizes of 45.4 and 90.8 nm, respectively. In comparison to the noncatalytic reduction test, the catalytic activities of intracellular and extracellular biosynthesized Ag NPs were explored for the reduction of highly concentrated MB dye solution. Extracellular Ag NPs achieved 100% MB reduction efficacy after around 80 min, compared to 50.6% and 24.1% in the presence and absence of intracellular Ag NPs, respectively. The rate of MB reduction was boosted by 22 times with the extracellular catalyst, and by 3 times with the intracellular catalyst. Therefore, the extracellular production process of Ag NPs utilizing Bacillus cereus bacteria might be applied in the industry as a cost-effective way for eliminating the toxic MB dye.

Detect the Antibacterial and Antitumor of synthesized Silver Nanoparticles Using Microbacterium sp

Metal nanoparticles are widely utilized in biotechnology and biomedicine for various applications, including medication delivery, imaging, and bacterial growth control. Silver nanoparticles (AgNPs) were synthesized by bacteria, fungi, algae, and plants. The Study aimed to synthesize nanomaterial with a cost-effective, environmentally friendly, and the uses of AgNPs as antibacterial (against pathogenic bacteria) and anticancer (on MCF7 cell line). In this Study, bacteria were collected from different soil samples. Isolated, purified by selective media, identification genotypically by 16rRNA sequencing analysis, then compared with NCBI, GenBank as Microbacterium sp. Biosynthesis of silver nanoparticles using Microbacterium for extracellular synthesis by reducing silver ions to silver nanoparticles. The color change to brown and reddish-brown was the first indication of the AgNPs formation; physical characterization using UV-Visible spectroscopy showed a wavelength in 489 nm, while X-ray diffraction (XRD) revealed that the silver nanoparticles were crystalline; transmission electron microscope (TEM) image showed that AgNPs spherical in shape with an average diameter of around 50 nm, in SEM (Scanning electron microscope) AgNPs formed with a diameter of 41-44 nm, spherical and uniform, while Energy-dispersive X-ray show very high silver peaks. Bioactivity of AgNPs by antimicrobial on pathogenic bacteria, which collected from Al- Sadr hospital in Misan (identified by using VITEK). This experiment showed that the inhibition zone was rung from (6- 38mm) on pathogenic bacteria; it was tremendous compared with antibiotics (Gentamycin in this project ranged from(7-28.5mm). Antitumor activity of extracellular biosynthesized AgNPs was determined using the MTT test against breast cancer cells (MCF7 cell line), which showed very high results. AgNPs inhibition breast cancer cell line by about 81% at 100ug/ml, indicating that the rate is outstanding. Finally, different biomedical approaches can benefit from AgNPs as antibacterial agents and anticancer agents with many results. Keywords. Silver Nanoparticles, Biosynthesis, Antibacterial, and Antitumor.

Optimization of Bacillus subtilis growth parameters for biosynthesis of silver nanoparticles by using response surface methodology

Silver nanoparticles (AgNPs) are among the most widely biosynthesized and used nanomaterials. They have different unique properties and a wide range of applications. This study is concerned with optimization of the growth conditions of Bacillus subtilis NRC1 for the biosynthesis of AgNPs using two designs of response surface methodology (RSM) statistical analysis. The data obtained from Plackett-Burman design (PBD) followed by central composite design (CCD), showed a good agreement between the experimental and predicted values of AgNPs biosynthesis. The optimum conditions were 0.7% (w/v) casein hydrolysate, 5% dextrin (w/v), pH 7.5 and 57 × 10⁶ CFU/ml inoculum size. The model was highly valid and could be applied with a confidence factor of 99.47%. Minimal inhibitory concentration (MIC) of these AgNPs synthesized using the extracellular filtrate after growth of Bacillus subtilis NRC1 in the optimized medium was found to be 41-43µg/ml for all tested microorganisms with exception of Pseudomonas aeruginosa where MIC was 169 µg/ml.

Activity of Silver Nanoparticles against Staphylococcus spp

Staphylococcus epidermidis is a bacterium that is part of the human microbiota. It is most abundant on the skin, in the respiratory system and in the human digestive tract. Also, Staphylococcus aureus contributes to human infections and has a high mortality rate. Both of these bacterial species produce biofilm, a pathogenic factor increasing their resistance to antibiotics. For this reason, we are looking for new substances that can neutralize bacterial cells. One of the best-known substances with such effects are silver nanoparticles. They exhibited antibacterial and antibiofilm formation activity that depended on their size, shape and the concentration used. In this review, we presented the data related to the use of silver nanoparticles in counteracting bacterial growth and biofilm formation published in scientific papers between 2017 and 2021. Based on the review of experimental results, the properties of nanoparticles prompt the expansion of research on their activity.

Green Synthesis and Potential Antibacterial Applications of Bioactive Silver Nanoparticles: A Review

Green synthesis of silver nanoparticles (AgNPs) using biological resources is the most facile, economical, rapid, and environmentally friendly method that mitigates the drawbacks of chemical and physical methods. Various biological resources such as plants and their different parts, bacteria, fungi, algae, etc. could be utilized for the green synthesis of bioactive AgNPs. In recent years, several green approaches for non-toxic, rapid, and facile synthesis of AgNPs using biological resources have been reported. Plant extract contains various biomolecules, including flavonoids, terpenoids, alkaloids, phenolic compounds, and vitamins that act as reducing and capping agents during the biosynthesis process. Similarly, microorganisms produce different primary and secondary metabolites that play a crucial role as reducing and capping agents during synthesis. Biosynthesized AgNPs have gained significant attention from the researchers because of their potential applications in different fields of biomedical science. The widest application of AgNPs is their bactericidal activity. Due to the emergence of multidrug-resistant microorganisms, researchers are exploring the therapeutic abilities of AgNPs as potential antibacterial agents. Already, various reports have suggested that biosynthesized AgNPs have exhibited significant antibacterial action against numerous human pathogens. Because of their small size and large surface area, AgNPs have the ability to easily penetrate bacterial cell walls, damage cell membranes, produce reactive oxygen species, and interfere with DNA replication as well as protein synthesis, and result in cell death. This paper provides an overview of the green, facile, and rapid synthesis of AgNPs using biological resources and antibacterial use of biosynthesized AgNPs, highlighting their antibacterial mechanisms.

Characterization, cytotoxicity, and genotoxicity properties of novel biomediated nanosized-silver by Egyptian Streptomyces roseolus for safe antimicrobial applications

Multi-drug resistant bacteria are not effectively managed with current treatments, making it a serious global problem. Therefore, there is an essential need for finding new antimicrobial agents. In this regard, silver nanoparticles (Ag-NPs) have been projected as a new generation of antimicrobial agents. Ag-NPs were biomediated by Egyptian Streptomyces roseolus for the first time, which was molecularly identified using 16S rRNA sequencing under accession no. MT071505. Biosynthesized Ag-NPs were characterized using UV-Vis spectroscopy, XRD, TEM, FTIR, and DLS. FTIR analysis confirmed the presence of different bioactive functional groups, such as N-H, C-H, C-O-C, C-NH2, and C=O acting as bioreducing/stabilizing agents for Ag-NPs. Ag-NPs exhibited antimicrobial activity against some multi-drug resistant Gram-positive and Gram-negative pathogens. MBC of Ag-NPs against Listeria monocytogenes and Klebsiella pneumonia were 0.195 and 0.048 mg/mL, respectively, with a tolerance level of 2 confirming its biocidal effect. SEM imaging of Ag-NPs-treated L. monocytogenes and K. pneumonia showed shrunk destroyed cells after 6 h of treatment. Biosynthesized Ag-NPs exhibited IC50 of < 0.3 and 8.21 mg/mL, on normal Human Skin Fibroblast, and Blood Lymphocytes, respectively. IC50 values were significantly higher than its MBC values, with no harmful cytotoxic effect, thus can be safely applied at its biocidal concentration. For biosafety purposes, the genotoxicity of biosynthesized Ag-NPs was assessed using Comet assay for the first time on Blood Lymphocytes, with zero-tail and 100% head intensity indicating non-genotoxic effect. An ecofriendly biomediated synthesis of Ag-NPs was described with easy scale-up, non-toxic by-products, so, it can be recommended as a powerful-safe antimicrobial agent.

Pseudomonas indica-Mediated Silver Nanoparticles: Antifungal and Antioxidant Biogenic Tool for Suppressing Mucormycosis Fungi

Mucormycosis is considered one of the most dangerous invasive fungal diseases. In this study, a facile, green and eco-friendly method was used to biosynthesize silver nanoparticles (AgNPs) using Pseudomonas indica S. Azhar, to combat fungi causing mucormycosis. The biosynthesis of AgNPs was validated by a progressive shift in the color of P. indica filtrate from colorless to brown, as well as the identification of a distinctive absorption peak at 420 nm using UV-vis spectroscopy. Fourier-transform infrared spectroscopy (FTIR) results indicated the existence of bioactive chemicals that are responsible for AgNP production. AgNPs with particle sizes ranging from 2.4 to 53.5 nm were discovered using transmission electron microscopy (TEM). Pattern peaks corresponding to the 111, 200, 220, 311, and 222 planes, which corresponded to face-centered cubic forms of metallic silver, were also discovered using X-ray diffraction (XRD). Moreover, antifungal activity measurements of biosynthesized AgNPs against Rhizopus Microsporus, Mucor racemosus, and Syncephalastrum racemosum were carried out. Results of antifungal activity analysis revealed that the biosynthesized AgNPs exhibited outstanding antifungal activity against all tested fungi at a concentration of 400 µg/mL, where minimum inhibitory concentrations (MIC) were 50, 50, and 100 µg/mL toward R. microsporus, S. racemosum, and M. racemosus respectively. In addition, the biosynthesized AgNPs revealed antioxidant activity, where IC₅₀ was 31 µg/mL when compared to ascorbic acid (0.79 µg/mL). Furthermore, the biosynthesized AgNPs showed no cytotoxicity on the Vero normal cell line. In conclusion, the biosynthesized AgNPs in this study can be used as effective antifungals with safe use, particularly for fungi causing mucormycosis.

A sustainable, top-down mechanosynthesis of carbohydrate-functionalized silver nanoparticles

A method for the production of metal nanoparticles with a tribological process is proposed, aiming at minimising power consumption and risk factors related to unsafe unit operations.

Antimicrobial Efficacy of Biogenic Cobalt and Copper Nanoparticles against Pathogenic Isolates

Biogenic synthesis of cobalt (Co) and copper (Cu) nanoparticles (NPs) was performed using the bacterial strains Escherichia coli and Bacillus subtilis. Prepared NPs were confirmed by a color change to maroon for CoNPs and green for CuNPs. The NPs characterization using FTIR showed the presence of functional groups, i.e., phenols, acids, protein, and aromatics present in the Co and CuNPs. UV-vis spectroscopy of E. coli and B. subtilis CuNPs showed peaks at 550 and 625 nm, respectively. For E. coli and B. subtilis CoNPs, peaks were observed at 300 nm and 350 nm, respectively. Antibacterial and antifungal activity of B. subtilis and E. coli Co and CuNPs was determined at 100 mg/mL concentration against two bacterial strains at 5, 2.5, and 1.5 mg/mL against fungal two strains F. oxysporum and T. viridi, respectively. B. subtilis CuNPs showed significantly higher inhibition zones (ZOI=25.7-29.7 mm) against E. coli and B. subtilis compared to other biogenic NPs. Likewise, B. Subtilis CuNPs showed lower MIC (4.3 ± 6.3) and MBC (5.3 mg/mL) values against both tested isolates. Antifungal activity of B. subtilis and E. coli CuNPs and CoNPs showed a concentration-dependent decrease in ZOI. Among all biogenic NPs, B. subtilis CoNPs showed the highest ZOI (25-30 mm) against F. oxysporum followed by E. coli CuNPs with maximum ZOI (20-27 mm) against T. viridi. Again, B. subtilis CoNPs and E. coli CuNPs showed lowest MIC and MFC values against both fungal isolates. In conclusion, the current study showed that biogenically synthesized B. subtilis Cu or CoNPs can be used as effective antimicrobial agents due to their potential antibacterial and antifungal potential.

Emerging Status of Multidrug-Resistant Bacteria and Fungi in the Arabian Peninsula

Simple Summary

The incidence and developing status of multidrug-resistant bacteria and fungi, as well as their related mortality, is reviewed by a systematic published literature search from nine countries in the Arabian Peninsula. In order to analyse the emerging status and mortality, a total of 382 research articles were selected from a comprehensive screening of 1705 papers. More than 850 deaths reported since 2010 in the Arabian Peninsula due to the infection of multidrug-resistant bacteria and fungi. Multidrug-resistant bacteria Acinetobacter baumannii, Mycobacterium tuberculosis, Staphylococcus aureus, and fungi Candida auris are the most prevalent and causing high deaths. To control these infections and associated deaths in the Arabian Peninsula, continuous preventive measures, accurate methods for early diagnosis of infection, active surveillance, constant monitoring, developing vaccines, eradicating multidrug resistance modulators, and data sharing among countries are required.

Abstract

We aimed to identify the prevalence and emerging status of multidrug-resistant bacteria and fungi and their associated mortality in nine countries in the Arabian Peninsula. Original research articles and case studies regarding multidrug-resistant bacteria and fungi in the Arabian Peninsula, published during the last 10 years, were retrieved from PubMed and Scopus. A total of 382 studies were included as per the inclusion and exclusion criteria, as well as the PRISMA guidelines, from a thorough screening of 1705 articles, in order to analyse the emerging status and mortality. The emerging nature of >120 multidrug-resistant (MDR) bacteria and fungi in the Arabian Peninsula is a serious concern that requires continuous monitoring and immediate preventive measures. More than 50% (n = 453) of multidrug-resistant, microbe-associated mortality (n = 871) in the Arabian Peninsula was due to MDR Acinetobacter baumannii, Mycobacterium tuberculosis and Staphylococcus aureus infection. Overall, a 16.51% mortality was reported among MDR-infected patients in the Arabian Peninsula from the 382 articles of this registered systematic review. MDR A. baumannii (5600 isolates) prevailed in all the nine countries of the Arabian Peninsula and was one of the fastest emerging MDR bacteria with the highest mortality (n = 210). A total of 13,087 Mycobacterium tuberculosis isolates were reported in the region. Candida auris (580 strains) is the most prevalent among the MDR fungal pathogen in the Arabian Peninsula, having caused 54 mortalities. Active surveillance, constant monitoring, the development of a candidate vaccine, an early diagnosis of MDR infection, the elimination of multidrug resistance modulators and uninterrupted preventive measures with enhanced data sharing are mandatory to control MDR infection and associated diseases of the Arabian Peninsula. Accurate and rapid detection methods are needed to differentiate MDR strain from other strains of the species. This review summarises the logical relation, prevalence, emerging status and associated mortality of MDR microbes in the Arabian Peninsula.

Synthetic preparations and atomic scale engineering of silver nanoparticles for biomedical applications

Owing to their peculiar oxidative effect, silver cations (Ag⁺) are well known for their antimicrobial properties and explored as therapeutic agents for biomedical applications. Size control with improved dispersion and stability are the key factors of Ag NPs (silver nanoparticles) to be used in biomedical applications. Silver based nano-materials are highly efficient due to their biological, chemical and physical properties in comparison with bulk silver. Atomic scale fabrication is achieved by rearranging the internal components of a material, in turn, influencing the mechanical, electrical, magnetic, thermal and chemical properties. For instance, size and shape have a strong impact on the optical, thermal and catalytic properties of Ag NPs. Such properties can be tuned by controlling the surface/volume ratio of Ag nanostructures with a small size (ideally <100 nm), in turn showing peculiar biological activity different from that of bulk silver. Silver nanomaterials such as nanoparticles, thin films and nanorods can be synthesized by various physical, chemical and biological methods whose most recent implementations will be described in this review. By controlling the structure-functionality relationship, silver based nano-materials have high potential for commercialization in biomedical applications. Antimicrobial, antifungal, antiviral, and anti-inflammatory Ag NPs can be applied in several fields such as pharmaceutics, sensors, coatings, cosmetics, wound healing, bio-labelling agents, antiviral drugs, and packaging.

Green synthesis of silver nanoparticles with algae and the importance of capping agents in the process

BACKGROUND

Nanoparticle synthesis is a very interesting area of research currently due to the wide applications of nanoparticles. The nanoparticles have a diameter ranging between 1 and 100 nm and they are used in different fields like electronics, pharmaceuticals, cosmetics, biotechnology, medicines, etc. Nanoparticles have gained the interest of researchers due to their large surface-to-volume ratio and their capability to interact effectively with other particles. Several different methods can be used for the production of silver nanoparticles (AgNPs) including chemical, physical, and biological. Out of all the methods, the biological method is considered the cleanest and safest as no toxic chemicals are used in the process. The biological method includes the use of bacteria, fungi, algae, and plant extract for the synthesis. Algal synthesis of AgNPs is especially interesting because of the high capacity of the algae to take in metals and reduce metal ions. Algae is a widely distributed organism and its availability is abundant; an added advantage is their growth under laboratory conditions. These organisms can help in large-scale production at a low cost.

SHORT CONCLUSION

This review article explains the different factors that should be considered for the effective synthesis of AgNPs using algae. Capping agents also affect the stability of nanoparticles. It also sheds light on the importance of capping agents in the synthesis of AgNPs. Alga-mediated synthesis of AgNPs along with the use of different capping agents can help in modulating the stability and size of the nanoparticles, thereby improving its cost-effectiveness and environment-friendly production.

A Review on Silver Nanoparticles: Classification, Various Methods of Synthesis, and Their Potential Roles in Biomedical Applications and Water Treatment

Recent developments in nanoscience have appreciably modified how diseases are prevented, diagnosed, and treated. Metal nanoparticles, specifically silver nanoparticles (AgNPs), are widely used in bioscience. From time to time, various synthetic methods for the synthesis of AgNPs are reported, i.e., physical, chemical, and photochemical ones. However, among these, most are expensive and not eco-friendly. The physicochemical parameters such as temperature, use of a dispersing agent, surfactant, and others greatly influence the quality and quantity of the synthesized NPs and ultimately affect the material’s properties. Scientists worldwide are trying to synthesize NPs and are devising methods that are easy to apply, eco-friendly, and economical. Among such strategies is the biogenic method, where plants are used as the source of reducing and capping agents. In this review, we intend to debate different strategies of AgNP synthesis. Although, different preparation strategies are in use to synthesize AgNPs such as electron irradiation, optical device ablation, chemical reduction, organic procedures, and photochemical methods. However, biogenic processes are preferably used, as they are environment-friendly and economical. The review covers a comprehensive discussion on the biological activities of AgNPs, such as antimicrobial, anticancer anti-inflammatory, and anti-angiogenic potentials of AgNPs. The use of AgNPs in water treatment and disinfection has also been discussed in detail.

Green Synthesis of Metallic Nanoparticles: Applications and Limitations

The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of 1 to 100 nm) make them uniquely suitable for such wide range of functions. The nanoparticles when manufactured using green synthesis methods are especially desirable being devoid of harsh operating conditions (high temperature and pressure), hazardous chemicals, or addition of external stabilizing or capping agents. Numerous plants and microorganisms are being experimented upon for an eco–friendly, cost–effective, and biologically safe process optimization. This review provides a comprehensive overview on the green synthesis of metallic NPs using plants and microorganisms, factors affecting the synthesis, and characterization of synthesized NPs. The potential applications of metal NPs in various sectors have also been highlighted along with the major challenges involved with respect to toxicity and translational research.

Tumor-targeting inorganic nanomaterials synthesized by living cells

Inorganic nanomaterials (NMs) have shown potential application in tumor-targeting theranostics, owing to their unique physicochemical properties. Some living cells in nature can absorb surrounding ions in the environment and then convert them into nanomaterials after a series of intracellular/extracellular biochemical reactions. Inspired by that, a variety of living cells have been used as biofactories to produce metallic/metallic alloy NMs, metalloid NMs, oxide NMs and chalcogenide NMs, which are usually automatically capped with biomolecules originating from the living cells, benefitting their tumor-targeting applications. In this review, we summarize the biosynthesis of inorganic nanomaterials in different types of living cells including bacteria, fungi, plant cells and animal cells, accompanied by their application in tumor-targeting theranostics. The mechanisms involving inorganic-ion bioreduction and detoxification as well as biomineralization are emphasized. Based on the mechanisms, we describe the size and morphology control of the products via the modulation of precursor ion concentration, pH, temperature, and incubation time, as well as cell metabolism by a genetic engineering strategy. The strengths and weaknesses of these biosynthetic processes are compared in terms of the controllability, scalability and cooperativity during applications. Future research in this area will add to the diversity of available inorganic nanomaterials as well as their quality and biosafety.