Extracellular biosynthesis of silver nanoparticles using the fungus Aspergillus fumigatus

Silver nanoparticles: synthesis, characterisation and biomedical applications

Nanotechnology is a rapidly growing field due to its unique functionality and a wide range of applications. Nanomedicine explores the possibilities of applying the knowledge and tools of nanotechnology for the prevention, treatment, diagnosis and control of disease. In this regard, silver nanoparticles with diameters ranging from 1 to 100 nm are considered most important due to their unique properties, ability to form diverse nanostructures, their extraordinary range of bactericidal and anticancer properties, wound healing and other therapeutic abilities and their cost-effectiveness in production. The current paper reviews various types of physical, chemical and biological methods used in the production of silver nanoparticles. It also describes approaches employing silver nanoparticles as antimicrobial and antibiofilm agents, as antitumour agents, in dentistry and dental implants, as promoters of bone healing, in cardiovascular implants and as promoters of wound healing. The paper also explores the mechanism of action, synthesis methods and morphological characterisation of silver nanoparticles to examine their role in medical treatments and disease management.

Green Synthesis of Metallic Nanoparticles and Their Potential Applications to Treat Cancer

Nanoparticle synthesis using microorganisms and plants by green synthesis technology is biologically safe, cost-effective, and environment-friendly. Plants and microorganisms have established the power to devour and accumulate inorganic metal ions from their neighboring niche. The biological entities are known to synthesize nanoparticles both extra and intracellularly. The capability of a living system to utilize its intrinsic organic chemistry processes in remodeling inorganic metal ions into nanoparticles has opened up an undiscovered area of biochemical analysis. Nanotechnology in conjunction with biology gives rise to an advanced area of nanobiotechnology that involves living entities of both prokaryotic and eukaryotic origin, such as algae, cyanobacteria, actinomycetes, bacteria, viruses, yeasts, fungi, and plants. Every biological system varies in its capabilities to supply metallic nanoparticles. However, not all biological organisms can produce nanoparticles due to their enzymatic activities and intrinsic metabolic processes. Therefore, biological entities or their extracts are used for the green synthesis of metallic nanoparticles through bio-reduction of metallic particles leading to the synthesis of nanoparticles. These biosynthesized metallic nanoparticles have a range of unlimited pharmaceutical applications including delivery of drugs or genes, detection of pathogens or proteins, and tissue engineering. The effective delivery of drugs and tissue engineering through the use of nanotechnology exhibited vital contributions in translational research related to the pharmaceutical products and their applications. Collectively, this review covers the green synthesis of nanoparticles by using various biological systems as well as their applications.

Assessment of antibacterial and anticancer capability of silver nanoparticles extracellularly biosynthesized using Aspergillus terreus

The present study explores biosynthesis of silver nanoparticles (AgNPs) employing extracellular extract of Aspergillus terreus ITCC 9932.15. Modulation of various variables that dictate the biosynthesis of AgNPs, suggested of optimal AgNPs synthesis using AgNO3, 1 mM at pH 8 and temperature, 35 °C. The biosynthesis of AgNPs was observed to be time dependent with incremental particle synthesis till 24 h. Various studies were undertaken to authenticate formation and characterization of AgNPs for size, crystallinity and biomolecules involved. A sharp SPR peak observed at 420 nm in the UV–vis absorption spectra validated synthesis of nanoparticles. These particles exhibited spherical morphology with size ∼25 nm and −16 mV of zeta potential. Further, the existence of proteins and other biomolecules onto the surface of AgNPs was confirmed with FTIR studies. The SAED pattern investigated by employing TEM authenticated the crystallinity of AgNPs. The AgNPs also exhibited potential antibacterial activity against Gram-negative and Gram-positive bacteria (E. coli and P. aeruginosa). In addition, remarkable anticancer activity was obtained in breast cancer cell line (MCF-7).

Eco-Friendly Greener Synthesis of Nanoparticles

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

Biosynthesis and characterization of silver nanoparticles using Ochradenus arabicus and their physiological effect on Maerua oblongifolia raised in vitro

Silver nanoparticles (AgNPs) are presently the most commonly generated engineered nanomaterials and are found in a wide range of agro-commercial products. The present study was designed to synthesize AgNPs biologically using Ochradenus arabicus leaves and investigate their effect on the morphophysiological properties of Maerua oblongifolia raised in vitro. Physicochemical methods (ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy were performed for characterization and for obtaining microphotographs of the AgNPs. Shoots of M. oblongifolia (2–3 cm) grown in Murashige and Skoog medium supplemented with different concentrations of AgNPs (0, 10, 20, 30, 40, or 50 mg L⁻¹) were used. Following 6 weeks of in vitro shoot regeneration, the shoot number, shoot length, leaf number, fresh weight, dry weight, chlorophyll content, total protein, proline level, and antioxidant enzyme activities of the plants were quantified. We found that 20 mg L⁻¹ AgNPs increased the shoot number, shoot length, fresh weight, dry weight, and chlorophyll content of the plants. The maximum total protein was recorded in plants that were administered the lowest dose of AgNPs (10 mg L⁻¹), while high concentrations of AgNPs (40 and 50 mg L⁻¹) increased the levels of proline and the enzymes superoxide dismutase and catalase. Our results indicate that green-synthesized AgNPs may be of agricultural and medicinal interest owing to their effects on plants in vitro.

A Concise Review on Multidimensional Silver Nanoparticle Health Aids and Threats

Benefits and Risk:

AgNps have beneficial approaches for cancer treatment and angiogenesisrelated diseases like rheumatoid arthritis, atherosclerosis, diabetic psoriasis, retinopathy, endometriosis, and adiposity.

Result:

The advancing nanotechnology-based therapy needs to be devised better, and it should offload the hitches of prevailing treatment approaches. Essential studies are required to explain the synergistic effect of two different cytotoxic agents.

Synthesis of bioactive silver nanoparticles using alginate, fucoidan and laminaran from brown algae as a reducing and stabilizing agent

In this report, polysaccharides - alginate, fucoidan, laminaran - were isolated from marine algae Saccharina cichorioides and Fucus evanescens and their activity as a reducing and stabilizing agents in the biogenic synthesis of silver nanoparticles was evaluated. The cytotoxic and antibacterial properties of obtained nanoparticles were also assessed. It was found that all tested polysaccharides could be used as a reducing agent; however, their catalytic activities varied significantly in the following range alginate < fucoidan < laminaran. Nanoparticles demonstrated cytotoxicity against rat C6 glioma cells. It was considerably higher for alginate- and laminaran-obtained nanosilver samples compared to fucoidan. Additionally, silver nanoparticles possessed considerable antibacterial properties more pronounced in fucoidan-obtained samples. Our data demonstrate that different algal polysaccharides can be used for the synthesis of silver nanoparticles with varying bioactivities.

Mycosynthesis of Silver Nanoparticles Using Screened Trichoderma Isolates and Their Antifungal Activity against Sclerotinia sclerotiorum

To control the disease caused by Sclerotinia sclerotiorum, a total of 15 isolates of the Trichoderma species was screened for the biosynthesis of silver nanoparticles (AgNPs). Among them, the highest yield occurred in the synthesis of AgNPs using a cell-free aqueous filtrate of T.virens HZA14 producing gliotoxin. The synthetic AgNPs were charactered by SEM, EDS, TEM, XRD, and FTIR. Electron microscopy studies revealed that the size of AgNPs ranged from 5–50 nm and had spherical and oval shapes with smooth surfaces. Prepared AgNPs interacted with protein, carbohydrate and heterocyclic compound molecules, and especially, interaction patterns of AgNPs with the gliotoxin molecule were proposed. The antifungal activity assays demonstrated that percentage inhibition of the prepared AgNPs was 100, 93.8 and 100% against hyphal growth, sclerotial formation, and myceliogenic germination of sclerotia at a concentration of 200 μg/mL, respectively. The direct interaction between nanoparticles and fungal cells, including AgNPs’ contact, accumulation, lamellar fragment production and micropore or fissure formation on fungal cell walls, was revealed by SEM and EDS. These will extend our understanding of the mechanisms of AgNPs’ action for preventing diversified fungal disease.

The Efficacy of Imipenem Conjugated with Synthesized Silver Nanoparticles Against Acinetobacter baumannii Clinical Isolates, Iran

Carbapenem-resistant Acinetobacter baumannii (CRAB) remains as a serious cause of infectious diseases and septic mortality in hospitalized patients worldwide. This study was conducted to evaluate the antimicrobial effect of imipenem conjugated silver nanoparticles (AgNPs) on resistant isolated A. baumannii from nosocomial infections.The antimicrobial susceptibility test of 100 A. baumannii clinical isolates against different antibiotics was performed. PCR was used to confirm bacterial resistance and to identify different genes encoding Ambler class β-lactamases. The chemically synthesized AgNPs were characterized using UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR). The stability, drug release kinetic, and cytotoxicity (MTT assay) of AgNPs were also investigated. The imipenem were conjugated with AgNPs, and conjugants were characterized as discussed above. Minimum inhibitory concentration (MIC) of the AgNPs and conjugants were tested against A. baumannii isolates and compared with imipenem alone.The results revealed that among all isolated A. baumannii, 76% showed resistant to imipenem (MIC ≥ 64 μg/mL to ≥ 256 μg/mL). The bla_OXA-23, bla_PER, bla_OXA-40, and bla_IMP genes were the most prevalent genes. UV-vis spectroscopy, XRD, TEM, and FTIR analysis confirmed synthesis of AgNPs (average size of 10-40 nm) and conjugation with imipenem. The release of imipenem from AgNPs can be defined as Fickian diffusion model. The MIC values of AgNPs conjugated with imipenem against resistant A. baumannii were decreased in a dose dependent manner and were based on existence of resistant genes. The AgNPs also showed low cytotoxic effects.The results suggest that imipenem-AgNPs has a strong potency as a powerful antibacterial agent against multi-resistant A. baumannii.

Myco-decontamination of azo dyes: nano-augmentation technologies

Effluents of textile, paper, and related industries contain significant amounts of synthetic dyes which has serious environmental and health implications. Remediation of dyes through physical and chemical techniques has specific limitations. Augmented biological decontamination strategies 'microbial remediation' may involve ring-opening of dye molecules besides the reduction of constituent metal ions. Both bacterial and fungal genera are known to exhibit metabolic versatility which can be harnessed for effective bio-removal of the toxic dye contaminants. Ascomycetous/basidiomycetes fungi can effectively decontaminate azo dyes through laccase/peroxidase enzyme-mediated catalysis. The extent, efficacy, and range of fungal dye decontamination can be enhanced by the conjugated application of nanomaterials, including nanoparticles (NPs) and their composites. Fungal cell-enabled NP synthesis- 'myco-farmed NPs', is a low-cost strategy for scaled-up fabrication of a variety of metal, metal oxide, non-metal oxide NPs through oxidation/reduction of dissolved ions/molecules by extracellular biomolecules. Augmented and rapid decontamination of azo dyes at high concentrations can be achieved by the use of myco-farmed NPs, NPs adsorbed fungal biomass, and nano-immobilized fungi-derived bio-catalytical agents. This manuscript will explore the opportunities and benefits of mycoremediation and application of fungus-NP bionanoconjugate to remediate dye pollutants in wastewaters and land contaminated with the effluent of textile industries.

Antimicrobial activity of biosynthesised silver nanoparticles against multidrug-resistant microbes isolated from cancer patients with bacteraemia and candidaemia

Background

In the past years, saprophytic bacteria and candida have been emerging as potential human pathogens causing life-threatening infections in patients with cancer. This study was designed to determine the bacteria and candida species, causing bloodstream infections in cancer patients and the assessment of their susceptibility to antibiotics and biosynthesised silver nanoparticles.

Materials and Methods

Ninety-seven microbial pathogens recovered from blood samples of cancer patients were included in the present study. The microbial isolates were collected in a duration period extending from December 2016 to July 2018 at National Cancer Institute, Cairo, Egypt. The clinical samples were collected using microbiological methods and were cultivated on MacConkey agar, blood agar media and Sabouraud dextrose agar media. The microbial isolates were identified using both standard microbiological methods and VITEK 2 compact automated system. The antibiotic resistance pattern was determined by the VITEK 2 compact automatic system and disk diffusion method, according to the Clinical and Laboratory Standards Institute. The characterisation of nanoparticles was carried out using ultraviolet spectroscopy and electron microscope. The antimicrobial activity of bio (AgNPs) was evaluated.

Results

A total of 97 microbial isolates recovered from collected blood samples from cancer patients were included in the study. Pathogenic bacteria and Candida were represented by 74 isolates (76.22%) and 23 isolates (23.69), respectively. Among the 74 bacterial isolates, Escherichia coli constituted (27.81%), Klebsiella pneumoniae (24.72%), Acinetobacter baummannii (11.33%), Pseudomonas aeruginosa (4.12%), Enterobacter spp. (3.09%) and) Staphylococcus aureus (2.06%). Cedecea davisae (1.03%), Burkholderia cepacia (1.03%) and Pantoea agglomerans (1.03%). Among the 23 Candida isolates, Candida tropicalis constituted (9.27%), Candida albicans (5.15%), Candida glabrata (5.15%) and Candida krusei (4.12%) from the total microbial isolates. The antibiotic susceptibility results revealed that amikacin and gentamycin were the most effective antibiotics against Gram-negative bacteria, while vancomycin and linezolid were most effective against S. aureus. Caspofungin was the most effective against candida species. The obtained stable biosynthesised silver nanoparticles ranged in size from 10 nm to 100 nm and were mostly spherical in shape. These biosilver nanoparticles showed the highest antimicrobial activity against most of the microbial isolates (bacteria and Candida). The in vitro cytotoxicity of biosynthesised AgNPs on HeLa cell lines revealed a dose-dependent potential. The IC50 value of AgNPs was found 6 and 5.6 μg/ml, respectively.

Conclusion

The present study revealed a significant distribution of multidrug-resistant microbes, which may increase the burden of healthcare to prevent infections in cancer patients. Biosilver nanoparticles exhibit antimicrobial activity against multidrug-resistant microbes and could be considered as effective agents against these strains.

Central Composite Design for Optimizing the Biosynthesis of Silver Nanoparticles using Plantago major Extract and Investigating Antibacterial, Antifungal and Antioxidant Activity

Central composite design (CCD) was applied to optimize the synthesis condition of silver nanoparticles (AgNPs) using the extract of Plantago major (P. major) seeds via a low cost and single-step process. The aqueous seed extract was applied as both reducing element and capping reagent for green production of AgNPs. Five empirical factors of synthesis including temperature (Temp), pH, volume of P. major extract (Vex), volume of AgNO3 solution (VAg) and synthesis time were used as independent variables of model and peak intensity of Surface Plasmon Resonance (SPR) originated from NPs as the dependent variable. The predicted optimal conditions was determined to be: Temp = 55 °C, pH = 9.9,Vex = 1.5 mL, VAg = 30 mL, time = 60 min. The characterization of the prepared AgNPs at these optimum conditions was conducted by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) to determine the surface bio-functionalities. Bio-activity of these AgNPs against bacteria and fungi were evaluated based on its assay against Micrococcus luteus, Escherichia coli and Penicillium digitatum. Furthermore, antioxidant capacity of these NPs was checked using the ferric reducing antioxidant power (FRAP) assay.

Enhanced biodegradation of an endocrine disrupting micro-pollutant: Di (2-ethylhexyl) phthalate using biogenic self-assembled monolayer of silver nanoparticles

Di (2-ethylhexyl) phthalate (DEHP) is one of the predominant plasticizer and an endocrine disrupting chemical occurring almost in all partitions of the environment. Though DEHP occur at lower concentration, reluctance arises due to their ability to disrupt endocrine system even lower concentration. In the present study, DEHP was assessed for degradation at minimal level (1-100 μg L^-1) by a novel bacterial strain, Rhodococcus jostii PEVJ9. In the experimental design, significant variables were concentration of silver nitrate and DEHP, pH, temperature, time and agitation. Degradation without SAM-silver nanoparticles was 30-66% (predicted value = 30.8-66.8%, R² = 99.7%) while, degradation in the presence of SAM-silver nanoparticles onto bacterial cells was 100% (predicted value = 98.4-102.1%, R² = 99.6%) within 72 h. In short, this is the first report illustrating the experimental designs in biogenic synthesis of SAM-silver nanoparticles and enhanced degradation of DEHP at minimal level. The study overcomes poor bioavailability and assimilation of DEHP at lower concentration by the microbial population present in the environment. Thus, an efficient clean-up would prevent or minimize DEHP exposure at all trophic levels ranging from feminization of fishes to reproductive disorders in humans.

Synthesis and applications of various bimetallic nanomaterials in water and wastewater treatment

Bimetallic nanoparticles are the complex combination of two different metal constituents in nanoscale. Water and wastewater treatment utilizing bimetallic particles is an emerging research area. When two metals are combined, it can show not only the properties of its constituents but also new and enhanced properties derived by the synergy of the combination. These properties of bimetallic nanoparticles inevitably depend on the size, structure, and morphology of the particles. Thus the adopting synthesis strategy is very crucial to achieve desired results. Here in this review, the various bimetallic synthesis strategies are compared. The bimetallic nanoparticles decontaminate water through adsorption and/or catalysis mechanism. The various degradation pathways, specifically, adsorption, reduction, oxidation, and advanced oxidation processes are discussed in detail in this review.

Incorporated plant extract fabricated silver/poly-D,l-lactide-co-glycolide nanocomposites for antimicrobial based wound healing

Polymeric nanocomposites have gained extensive attention in modern nanotechnology by reason of its design, flexibility, sole applications and lower life cycle costs. Preparation of composites using spreading of inorganic metal nanoparticles in organic polymeric matrices has plenty of scope and applications in the biomedical field. Poly-D,l-lactide-co-glycolide (PLGA) is an appreciated polymer for composites preparation because of its non-toxic and promising biodistribution. The consideration of metal nanoparticles has extended rapidly with the presence of new nanocomposites into a range of products and technologies. Compared to bulk materials the synthesized metal nanoparticles have unique character and biomedical uses due to its shape, size, and huge surface to volume ratio. Among different inorganic metal nanoparticles, silver nanoparticles (Ag NPs) have dominated in the biomedical field owing to its diverse potential applications including imaging, sensor, diagnosis and disease treatment. Further, medicinal plant extract mediated Ag NPs shown superior advantages and its antimicrobial based wound healing prospective has been established. However, not much information on plant extract mediated Ag NPs integrated PLGA nanocomposites wound healing applications. In the present review, we discussed necessity, preparation, characterization and antimicrobial based wound healing mechanism of incorporated plant extract mediated silver/PLGA nanocomposites.

Pleiotropic Functions and Biological Potentials of Silver Nanoparticles Synthesized by an Endophytic Fungus

In recent years, the biological synthesis of silver nanoparticles (AgNPs) from microorganisms has become an emerging trend for developing biocompatible nanomaterials that finds applications in nano and biomedical sectors. In the present study, we demonstrated a facile, green and eco-friendly method for AgNPs synthesis using the endophytic fungi (Colletotrichum incarnatum DM16.3) isolated from medicinal plant Datura metel and its in vitro antithrombin and cytotoxic activity. At first, biosynthesis of colloidal AgNPs was predicted by visual observation of color change and UV-visible spectra demonstrated specific surface plasmon resonance peak at 420 nm which confirmed the presence of nanoparticles. Microscopic analyses revealed the structure of highly aggregated, spherical and crystalline AgNPs in the diameter range of 5–25 nm. Transform infrared spectroscopy (FT-IR) spectral analysis confirmed the presence of probable biomolecules required for the reduction of silver ions. In vitro evaluation of thrombin activity demonstrates that AgNPs could exert strong inhibition against both thrombin activity (87%) and thrombin generation (84%), respectively. Further, in silico based mechanistic analysis yielded a better insight in understanding the probable amino acids responsible for AgNPs binding with thrombin protein. Similarly, in vitro cytotoxicity of synthesized AgNPs on human epithelial cells using MTT assay did not produce any substantial effects after 24 h exposure which indicates excellent biocompatibility nature, whereas notable toxicity was observed on human cancerous (HeLa) cells at 50 μg/mL (IC₅₀ value). In addition, assessment of AgNPs at 10 μg/mL concentration via crystal violet method on biofilm forming Gram-positive (Vibrio cholerae) and Gram-negative bacteria (Bacillus cereus) revealed inhibition up to 85 and 46%, respectively. Overall, this study showed the possibility of microbially synthesized AgNPs as a potent inhibitor for managing acute thrombosis and highlighted their role for other biomedical applications.

Ammonia-controlled synthesis of monodispersed N-doped carbon nanoparticles

The presence of ammonia slowing down the acid-catalysed Schiff base formation as well as control the monodispersity through the separation of nucleation and growth stages.

Extracellular biosynthesis of biocompatible CdSe quantum dots

An extracellular biosynthesis method has been developed to prepare cadmium selenide (CdSe) quantum dots (QDs) with strong fluorescence emission by incubating cheap Cd and Se inorganic salts with Escherichia coli (E.coli) bacteria. Ultraviolet-visible absorption spectra, photoluminescence (PL) spectra, and high-resolution transmission electron microscopy analysis showed that the biosynthesised CdSe QDs have an average size of 3.1 nm, the excellent optical properties with fluorescence emission around 494 nm, and the good crystallinity. It was found that addition of 80 mg of mercaptosuccinic acid resulted in the formation of CdSe QDs with highest PL intensity. Furthermore, Fourier-transform infrared spectra of as-synthesised CdSe QDs confirmed the presence of a surface protein capping layer. The biosynthesised CdSe QDs were incorporated into the yeast cells as illustrated by laser confocal scanning microscopy images, showing a great potential in bio-imaging and bio-labelling application.

Antibacterial Activity of Ag-Hydroxyapatite Coating Against Hematogenous Infection by Methicillin-Resistant Staphylococcus aureus in the Rat Femur

Several antibacterial materials have been developed to prevent periprosthetic joint infection and thus prevent serious complications for patients and surgeons. However, no study has addressed the activity of antibacterial materials against hematogenous infection. The present study evaluated the antibacterial activity of a silver-containing hydroxyapatite-coated implant against methicillin-resistant Staphylococcus aureus (MRSA) hematogenous infection. Implants coated with hydroxyapatite and silver-hydroxyapatite were inserted into rats' right and left femurs, respectively, after which the animals were infected with S. aureus via a tail vessel. About 10⁷ colony-forming units was the optimal bacterial number for the establishment of S. aureus hematogenous infection. Bacterial loads and C-reactive protein in the blood were measured to confirm bacteremia and inflammation. Fourteen days after the infection, bacterial loads were statistically lower in the femurs containing silver-hydroxyapatite-coated implants than in those with hydroxyapatite-coated implants (p = 0.022). Thus, silver-hydroxyapatite-coated implants might provide antibacterial activity against MRSA hematogenous infection in the postoperative period. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2655-2660, 2019.

Green synthesis and structural classification of Acacia nilotica mediated-silver doped titanium oxide (Ag/TiO2) spherical nanoparticles: Assessment of its antimicrobial and anticancer activity

Current exanimation reports, green fabrication of silver doped TiO2 nanoparticles (Ag/TiO2) using aqueous extract of Acacia nilotica as bio-reductant and assess its potential as antimicrobial and anticancer agent. The obtained spherical Ag/TiO2 were characterized by various analytical techniques including FTIR, (XRD), (FE-SEM EDS), and (TEM). Synthesized Ag/TiO2 demonstrated broad spectrum antibacterial and anticandidal activity. The order of antimicrobial activity was found to be E. coli > C. albicans > MRSA > P. aeruginosa. In addition, cytotoxicity and oxidative stress of Ag/TiO2 nanoparticles in (MCF-7) cells was also investigated. Outcomes of MTT assay showed concentration dependent reduction in cell viability. Further, synthesized NPs reduced the level of glutathione, induced ROS generation and lipid peroxidation in the treated cells. Therefore, it is envisaged that these spherical nanoparticles may be exploited in drug delivery, pharmaceutical, and food industry.

Rod-shaped gold nanoparticles biosynthesized using Pb2+-induced fungus Aspergillus sp. WL-Au

Gold nanoparticles (AuNPs) attracted much attention owing to their distinguished characteristics and applications. In this study, rod-shaped AuNPs were biosynthesized using Pb²⁺-induced fungus Aspergillus sp. The synthesized AuNPs showed a UV-vis absorption peak at 534 nm. Scanning electron microscopy and transmission electron microscopy analyses showed that rod-shaped AuNPs were biosynthesized and attached on the mycelia surfaces. Energy-dispersive spectrometer analysis identified gold as the unique metallic composition of synthesized nanoparticles. X-ray powder diffraction analysis showed that the AuNPs were face-centered cubic crystalline structure. Furthermore, Fourier transform infrared spectroscopy analysis detected functional groups, including C = O, C-O-C, amine I and II which played active roles in AuNPs formation. In addition, the main shape of synthesized AuNPs changed from sphere to rod-shape with the increase of biomass and Pb²⁺ concentration. This study reports quite uniform rod-shaped AuNPs biosynthesized using Pb²⁺-induced fungus Aspergillus sp. WL-Au for the first time. This will provide a valid alternative for oriented biosynthesis of AuNPs.

Elemental Silver Nanoparticles: Biosynthesis and Bio Applications

The data on the specifics of synthesis of elemental silver nanoparticles (Ag-NP) having various geometric shapes (pseudo spherical, prismatic, cubic, trigonal-pyramidal, etc.), obtained by using various biological methods, and their use in biology and medicine have been systematized and generalized. The review covers mainly publications published in the current 21st century. Bibliography: 262 references.

Controllable Synthesis of Surface Pt-Rich Bimetallic AuPt Nanocatalysts for Selective Hydrogenation Reactions

Bimetallic nanocatalysts, with efficient and controllable catalytic performance, have a promising application in chemical production. In this study, surface Pt-rich bimetallic AuPt nanoparticles with different Pt/Au ratios were prepared and tested in selective hydrogenation reactions of substituted nitroaromatics. Au nanoparticles were first prepared with n-butyllithium as a rapid reducer, which were further used as seeds in the slow growth process of Pt atoms. Because of the employed sequential reduction method and the following atom diffusion, surface Pt-rich bimetallic AuPt nanoparticles were obtained. Compared with the uniform AuPt alloy nanocatalysts synthesized by the co-reduction method with n-butyllithium as the reducer and monometallic Pt nanocatalysts, the obtained surface Pt-rich AuPt bimetallic nanocatalysts presented an enhanced catalytic selectivity or activity. The performance enhancement is assigned to the optimized Au/Pt interaction in the surface Pt-rich bimetallic nanostructures. This work demonstrates that the optimization of the stoichiometry and construction of bimetallic materials is a feasible method to synthesize controllable and efficient nanocatalysts.

Metal nanoparticles fabricated by green chemistry using natural extracts: biosynthesis, mechanisms, and applications

Nanoparticles (NPs) are new inspiring clinical targets that have emerged from persistent efforts with unique properties and diverse applications. However, the main methods currently utilized in their production are not environmentally friendly. With the aim of promoting a green approach for the synthesis of NPs, this review describes eco-friendly methods for the preparation of biogenic NPs and the known mechanisms for their biosynthesis. Natural plant extracts contain many different secondary metabolites and biomolecules, including flavonoids, alkaloids, terpenoids, phenolic compounds and enzymes. Secondary metabolites can enable the reduction of metal ions to NPs in eco-friendly one-step synthetic processes. Moreover, the green synthesis of NPs using plant extracts often obviates the need for stabilizing and capping agents and yields biologically active shape- and size-dependent products. Herein, we review the formation of metallic NPs induced by natural extracts and list the plant extracts used in the synthesis of NPs. In addition, the use of bacterial and fungal extracts in the synthesis of NPs is highlighted, and the parameters that influence the rate of particle production, size, and morphology are discussed. Finally, the importance and uniqueness of NP-based products are illustrated, and their commercial applications in various fields are briefly featured.

Synthesis and Application of Silver Nanoparticles (Ag NPs) for the Prevention of Infection in Healthcare Workers

Silver is easily available and is known to have microbicidal effect; moreover, it does not impose any adverse effects on the human body. The microbicidal effect is mainly due to silver ions, which have a wide antibacterial spectrum. Furthermore, the development of multidrug-resistant bacteria, as in the case of antibiotics, is less likely. Silver ions bind to halide ions, such as chloride, and precipitate; therefore, when used directly, their microbicidal activity is shortened. To overcome this issue, silver nanoparticles (Ag NPs) have been recently synthesized and frequently used as microbicidal agents that release silver ions from particle surface. Depending on the specific surface area of the nanoparticles, silver ions are released with high efficiency. In addition to their bactericidal activity, small Ag NPs (<10 nm in diameter) affect viruses although the microbicidal effect of silver mass is weak. Because of their characteristics, Ag NPs are useful countermeasures against infectious diseases, which constitute a major issue in the medical field. Thus, medical tools coated with Ag NPs are being developed. This review outlines the synthesis and utilization of Ag NPs in the medical field, focusing on environment-friendly synthesis and the suppression of infections in healthcare workers (HCWs).

Biosynthesis of Silver Nanoparticles Mediated by Extracellular Pigment from Talaromyces purpurogenus and Their Biomedical Applications

In recent years, green syntheses have been researched comprehensively to develop inexpensive and eco-friendly approaches for the generation of nanoparticles. In this context, plant and microbial sources are being examined to discover potential reducing agents. This study aims to utilize an extracellular pigment produced by Talaromyces purpurogenus as a prospective reducing agent to synthesize silver nanoparticles (AgNPs). Biosynthesized AgNPs were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), electron probe micro analyser (EPMA), and zeta potential. The pigment functional groups involved in the generation of AgNPs were investigated using Fourier transform infrared spectroscopy. TEM images showed that the generated nanoparticles were spherical, hexagonal, rod-shaped, and triangular-shaped with a particle size distribution from 4 to 41 nm and exhibited a surface plasmon resonance at around 410 nm. DLS and zeta potential studies revealed that the particles were polydispersed and stable (−24.8 mV). EPMA confirmed the presence of elemental silver in the samples. Biosynthesized AgNPs exhibited minimum inhibitory concentrations of 32 and 4 μg/mL against E. coli and S. epidermidis, respectively. Further, cytotoxicity of the AgNPs was investigated against human cervical cancer (HeLa), human liver cancer (HepG2), and human embryonic kidney (HEK-293) cell lines using 5-fluorouracil as a positive control. A significant activity was recorded against HepG2 cell line with a half-maximal inhibitory concentration of 11.1 μg/mL.

Green nanotechnology: a review on green synthesis of silver nanoparticles - an ecofriendly approach

Background: Nanotechnology explores a variety of promising approaches in the area of material sciences on a molecular level, and silver nanoparticles (AgNPs) are of leading interest in the present scenario. This review is a comprehensive contribution in the field of green synthesis, characterization, and biological activities of AgNPs using different biological sources. Methods: Biosynthesis of AgNPs can be accomplished by physical, chemical, and green synthesis; however, synthesis via biological precursors has shown remarkable outcomes. In available reported data, these entities are used as reducing agents where the synthesized NPs are characterized by ultraviolet-visible and Fourier-transform infrared spectra and X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Results: Modulation of metals to a nanoscale drastically changes their chemical, physical, and optical properties, and is exploited further via antibacterial, antifungal, anticancer, antioxidant, and cardioprotective activities. Results showed excellent growth inhibition of the microorganism. Conclusion: Novel outcomes of green synthesis in the field of nanotechnology are appreciable where the synthesis and design of NPs have proven potential outcomes in diverse fields. The study of green synthesis can be extended to conduct the in silco and in vitro research to confirm these findings.