Nitrate reductase-mediated synthesis of silver nanoparticles from AgNO3

Enhanced anti-cancer potency of sustainably synthesized anisotropic silver nanoparticles as compared with L-asparaginase

Acute lymphoblastic leukemia (ALL), a hematologic cancer that involves the production of abnormal lymphoid precursor cells, primarily affects children aged 2 to 10 years. The bacterial enzyme L-asparaginase produced from Escherichia coli is utilised as first-line therapy, despite the fact that 30 % of patients have a treatment-limiting hypersensitivity reaction. The current study elucidates the biosynthesis of extremely stable, water-dispersible, anisotropic silver nanoparticles (ANI Ag NPs) at room temperature and investigation of its anti-tumor potency in comparison to L-asparaginase. The optical, morphological, compositional, and structural properties of synthesized nanoparticles were evaluated using UV-Vis-NIR spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy, and X-ray Diffractometer. The UV-Vis-NIR spectra revealed the typical Surface Plasmon Resonance (SPR) at 423 nm along with additional NIR absorption at 962 nm and 1153 nm, while TEM images show different shapes and sizes of Ag nanoparticles ranging from 6.81 nm to 46 nm, together confirming their anisotropic nature. Further, the MTT assay demonstrated promising anticancer effects of ANI Ag NPs with an IC50 value of ∼7 μg/mL against HuT-78 cells. These sustainable anisotropic silver nanoparticles exhibited approximately four times better cytotoxic ability (at and above 10 μg/mL concentrations) than L-asparaginase against HuT-78 cells (a human T lymphoma cell line). Apoptosis analysis by Wright-Geimsa, Annexin-V, and DAPI staining indicated the role of apoptosis in ANI Ag NPs-mediated cell death. The measurement of NO, and Bcl2 and cleaved caspase-3 levels by colorimetric method and immunoblotting, respectively suggested their involvement in ANI Ag NPs-elicited apoptosis. The findings indicate that the biogenic approach proposed herein holds tremendous promise for the rapid and straightforward design of novel multifunctional nanoparticles for the treatment of T cell malignancies.

Biosynthesis and biocompatibility evaluation of zinc oxide nanoparticles prepared using Priestia megaterium bacteria

The current study aimed to find an effective, simple, ecological, and nontoxic method for bacterial green synthesis of zinc oxide nanoparticles (ZnONPs) using the bacterial strain Priestia megaterium BASMA 2022 (OP572246). The biosynthesis was confirmed by the change in color of the cell-free supernatant added to the zinc nitrate from yellow to pale brown. The Priestia megaterium zinc oxide nanoparticles (Pm/ZnONPs) were characterized using UV-Vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and zeta potential. The Pm/ZnONPs characterization showed that they have a size ranging between 5.77 and 13.9 nm with a semi-sphere shape that is coated with a protein-carbohydrate complex. An EDX analysis of the Pm/ZnONPs revealed the presence of the shield matrix, which was composed of carbon, nitrogen, oxygen, chlorine, potassium, sodium, aluminum, sulfur, and zinc. The results of the FTIR analysis showed that the reduction and stabilization of the zinc salt solution were caused by the presence of O-H alcohols and phenols, O=C=O stretching of carbon dioxide, N=C=S stretching of isothiocyanate, and N-H bending of amine functional groups. The produced ZnONPs had good stability with a charge of - 16.2 mV, as evidenced by zeta potential analysis. The MTT assay revealed IC50 values of 8.42% and 200%, respectively, for the human A375 skin melanoma and human bone marrow 2M-302 cell lines. These findings revealed that the obtained Pm/ZnONPs have the biocompatibility to be applied in the pharmaceutical and biomedical sectors.

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.

The Origin of the Intracellular Silver in Bacteria: A Comprehensive Study using Targeting Gold-Silver Alloy Nanoparticles

The bactericidal effects of silver nanoparticles (Ag NPs) against infectious strains of multiresistant bacteria is a well-studied phenomenon, highly relevant for many researchers and clinicians battling bacterial infections. However, little is known about the uptake of the Ag NPs into the bacteria, the related uptake mechanisms, and how they are connected to antimicrobial activity. Even less information is available on AgAu alloy NPs uptake. In this work, the interactions between colloidal silver-gold alloy nanoparticles (AgAu NPs) and Staphylococcus aureus (S. aureus) using advanced electron microscopy methods are studied. The localization of the nanoparticles is monitored on the membrane and inside the bacterial cells and the elemental compositions of intra- and extracellular nanoparticle species. The findings reveal the formation of pure silver nanoparticles with diameters smaller than 10 nm inside the bacteria, even though those particles are not present in the original colloid. This finding is explained by a local RElease PEnetration Reduction (REPER) mechanism of silver cations emitted from the AgAu nanoparticles, emphasized by the localization of the AgAu nanoparticles on the bacterial membrane by aptamer targeting ligands. These findings can deepen the understanding of the antimicrobial effect of nanosilver, where the microbes are defusing the attacking silver ions via their reduction, and aid in the development of suitable therapeutic approaches.

Microbial impact to environmental toxicants Ni(II) and Co(II): Joint toxicity and cellular response in Paramecium

Cobalt (Co) and Nickel (Ni) are increasingly found in our environment. We analysed their combined toxicity and uptake mechanisms in the early food chain by studying bacteria and the bacterivorous ciliate Paramecium as a primary consumer. We exposed both species to these metals to measure the toxicity, uptake and transfer of metals from bacteria to Paramecium. We found that Ni is more toxic than Co, and that toxicity increases for both metals when (i) food bacteria are absent and (ii) both metals are applied in combination. The cellular content in bacteria after exposure shows a concentration dependent bias for either Ni or Co. Comparing single treatment and joint exposure, bacteria show increased levels of both metals when these are both exposed. To imitate the basic level of the food chain, we fed these bacteria to paramecia. The cellular content shows a similar ratio of Nickel and Cobalt as in food bacteria. This is different to the direct application of both metals to paramecia, where Cobalt is enriched over Nickel. This indicates that bacteria can selectively pre-accumulate metals for introduction into the food chain. We also analysed the transcriptomic response of Paramecium to sublethal doses of Nickel and Cobalt to gain insight into their toxicity mechanisms. Gene ontology (GO) analysis indicates common deregulated pathways, such as ammonium transmembrane transport and ubiquitine-associated protein degradation. Many redox-related genes also show deregulation of gene expression, indicating cellular adaptation to increased RONS stress. This suggests that both metals may also target the same cellular pathways and this is consistent with the increased toxicity of both metals when used together. Our data reveal complex ecotoxicological pathways for these metals and highlights the different parameters for their fate in the ecosystem, in the food chain and their ecotoxicological risk after environmental contamination.

Bacterial MgSe complex nanoparticle synthesis and electrical characterization of fabricated Ag/MgSe/p-Si hetero-structure under dark and illumination

The Pseudomonas aeruginosa OG1 strain was used in the bacterial synthesis of MgSe compound nanoparticles. The obtained samples were subsequently shaped into nanocrystalline MgSe films, and their optical, structural, morphological, and electrical properties were assessed on glass and p-Si substrates. Structural and morphological characterizations showed that the fabricated thin film samples have a polycrystalline structure with high quality and uniform grain sizes. The MgSe films produced on glass substrates exhibit a direct spectral band gap of 2.53 eV, according to optical measurements. The Ag/MgSe/p-Si layered diode structure was fabricated using the produced MgSe nanoparticles and then characterized by electrical properties. Electrical measurements were carried out under these two conditions to assess the effects of dark and illumination conditions on the band dynamics of the heterostructure devices. Under illumination, the barrier height decreased while the interface density states distribution increased. These measurements showed that using bacterial-assisted grown MgSe nanocrystalline films, the developed Ag/MgSe/p-Si device structure exhibited a remarkable photoresponse and stable rectifying property. Green synthesis methods for the production of these nanocrystalline materials have the potential to offer low-cost alternatives for photosensitive applications.

First identification of potato tuber rot caused by Penicillium solitum, its silver nanoparticles synthesis, characterization and use against harmful pathogens

Potato is one of the highly consumed vegetable crop grown in different regions across Pakistan that is affected by fungal diseases. The current research was conducted to identify fungal pathogen causing mold-like disease of potato in Khyber Pakhtunkhwa (KP), Pakistan. For molecular identification and characterization of the fungal disease; potato tuber samples were collected followed by culturing on potato dextrose agar (PDA). Based on morphological features, the pathogen was identified as a Penicillium species. This result was obtained in 45 different isolates from potato tubers. Molecular identification was done using β-tubulin primers and ITS5 sequencing of 13 different isolates that releveled 98% homology with BLAST (GenBank accession no. KX958076) as Penicillium solitum (GenBank accession nos. ON307317; ON307475 and ON310801). Phylogenetic tree was constructed that showed Penicillium solitum prevalence along with Penicillium polonicum and Penicillium citrinum on potato tubers. Based on this, Penicillium solitum based silver nanoparticles (Ag NPs) were synthesized and characterized using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) and field emission scanning electron microscopy (FE SEM). UV-analysis showed a characteristic peak at 410 nm confirming synthesis of Penicillium solitum based Ag NPs. This was further confirmed by XRD followed by EDX and SEM that showed face cubic crystal structure with Ag as major constituent of 18 nm formed spherical Ag NPs. FTIR showed band stretching of O-H, N-O and C-H of biological origin. Similarly, Penicillium solitum based Ag NPs presented strong anti-bacterial and anti-fungal activity at 0.5 level of significance LSD. According to our knowledge, this is the first report of Penicillium solitum identification in Pakistan, its Ag NPs synthesis and characterization to be used against pathogens of agricultural significance.

Bacterial mediated green synthesis of silver nanoparticles and their antibacterial and antifungal activities against drug-resistant pathogens

In the healthcare sector, the production of bioactive silver nanoparticles (AgNPs) with antimicrobial properties is of great importance. In this study, a novel bacterial strain, Paenibacillus sp. MAHUQ-63, was identified as a potential candidate for facile and rapid biosynthesis of AgNPs. The synthesized AgNPs were used to control the growth of human pathogens, Salmonella Enteritidis and Candida albicans. The bacterial culture supernatant was used to synthesize the nanoparticles (NPs). Field emission transmission electron microscope examination showed spherical-shaped NPs with 15-55 nm in size. Fourier transform-infrared analysis identified various functional groups. The synthesized AgNPs demonstrated remarkable activity against S. Enteritidis and C. albicans. The zones of inhibition for 100 µl (0.5 mg ml-1) of AgNPs against S. Enteritidis and C. albicans were 18.0 ± 1.0 and 19.5 ± 1.3 mm, respectively. The minimum inhibitory concentrations were 25.0 and 12.5 µg ml-1 against S. Enteritidis and C. albicans, respectively. Additionally, the minimum bactericidal concentrations were 25.0 µg ml-1 against both pathogenic microbes. The field emission scanning electron microscopy analysis showed that the treatment of AgNPs caused morphological and structural damage to both S. Enteritidis and C. albicans. Therefore, these AgNPs can be used as a new and effective antimicrobial agent.

Bacteria-derived topologies of Cu2O nanozymes exert a variable antibacterial effect

The ability of bacteria to facilitate fabrication of nanomaterials has been adapted towards bacterial sensing applications. In this work, we fabricate spherical, cubic and truncated octahedron topologies of Cu2O nanoparticles via E. coli-facilitated redox reaction in an electrochemical setup. The Cu2O nanoparticles exhibit cytochrome c oxidase-like activity with the spherical topology displaying higher catalytic rate compared to the other geometries. The topology-dependent catalytic behavior of Cu2O nanoparticles has not been reported previously. The Cu2O nanozymes also display E. coli killing activity in a topology-correlated manner. The E. coli mediated redox reaction in an electrochemical setup is being reported for the first time for synthesis of different topologies of Cu2O which also exert a variable antibacterial effect.

Antifungal potentiality of mycogenic silver nanoparticles capped with chitosan produced by endophytic Amesia atrobrunnea

This research reports the fabrication of silver nanoparticles (AgNPs) from endophytic fungus, Amesia atrobrunnea isolated from Ziziphus spina-christi (L.). Influencing factors for instance, thermal degree of incubation, media, pH, and silver nitrate (AgNO3) molarity were optimized. Then, the AgNPs were encapsulated with chitosan (Ch-AgNPs) under microwave heating at 650 W for 90 s. Characterization of nanoparticles was performed via UV-visible (UV-vis) spectrophotometer, Fourier-transform infrared spectrophotometer (FTIR), zeta potential using dynamic-light scattering (DLS), and field-emission-scanning electron microscope (FE-SEM). Anti-fungal activity of Ch-AgNPs at (50, 25, 12.5, 6.25 mg/L) was tested against Fusarium oxysporum, Curvularia lunata, and Aspergillus niger using the mycelial growth inhibition method (MGI). Results indicated that Czapek-dox broth (CDB) with 1 mM AgNO3, an acidic pH, and a temperature of 25-30 °C were the optimum for AgNPs synthesis. (UV-vis) showed the highest peak at 435 nm, whereas Ch-AgNPs showed one peak for AgNPs at 405 nm and another peak for chitosan at 230 nm. FTIR analysis confirmed that the capping agent chitosan was successfully incorporated and interacted with the AgNPs through amide functionalities. Z-potential was -19.7 mV for AgNPs and 38.9 mV for Ch-AgNPs, which confirmed the significant stability enhancement after capping. FES-SEM showed spherical AgNPs and a reduction in the nanoparticle size to 44.65 nm after capping with chitosan. The highest mycelial growth reduction using fabricated Ch-AgNPs was 93% for C. lunata followed by 77% for A. niger and 66% F. oxysporum at (50 mg/L). Biosynthesis of AgNPs using A. atrobrunnea cell-free extract was successful. Capping with chitosan exhibited antifungal activity against fungal pathogens.

Advances in therapeutic applications of silver nanoparticles

Nanotechnology is one of the most appealing area for developing new applications in biotechnology and medicine. For decades, nanoparticles have been extensively studied for a variety of biomedical applications. Silver has evolved into a potent antibacterial agent that can be used in a variety of nanostructured materials of various shapes and sizes. Silver nanoparticles (AgNP) based antimicrobial compounds are employed in a wide range of applications, including medicinal uses, surface treatment and coatings, the chemical and food industries, and agricultural productivity. When designing formulations for specific applications, the size, shape, and surface area of AgNPs are all crucial structural aspects to consider. Different methods for producing AgNPs with varying sizes and forms that are less harmful have been devised. The anticancer, anti-inflammatory, antibacterial, antiviral, and anti-angiogenic properties of AgNPs have been addressed in this review, as well as their generation and processes. Herein, we have reviewed the advances in therapeutic applications of AgNPs, as well as their limitations and barriers for future applications.

Biosynthesis of silver nanoparticles using nitrate reductase from Aspergillus terreus N4 and their potential use as a non-alcoholic disinfectant

Green technology has been developed for the quick production of stabilized silver nanoparticles (AgNPs), with the assistance of nitrate reductase from an isolated culture of Aspergillus terreus N4. The organism's intracellular and periplasmic fractions contained nitrate reductase, with the former demonstrating the highest activity of 0.20 IU/g of mycelium. When the fungus was cultivated in a medium comprising 1.056% glucose, 1.836% peptone, 0.3386% yeast extract, and 0.025% KNO3, the greatest nitrate reductase productivity of 0.3268 IU/g was achieved. Statistical modeling via response surface methodology was used to optimize the enzyme production. The periplasmic and intracellular enzyme fractions were found to convert Ag+ to Ag0, initiating synthesis within 20 min, with predominant nanoparticle sizes between 25 and 30 nm. By normalizing the effects of temperature, pH, AgNO3 concentration, and mycelium age with a variable shaking period for enzyme release, the production of AgNPs with the periplasmic fraction was optimized. The synthesis of nanoparticles occurred at temperatures of 30, 40, and 50 °C, with the highest yield observed at 40 and 50 °C during shorter incubation periods. Similarly, the nanoparticles were synthesized at pH levels of 7.0, 8.0, and 9.0, with the greatest production observed at pH 8.0 and 9.0 at lower incubation periods. The antimicrobial activity of AgNPs was demonstrated against common foodborne pathogens, including Staphylococcus aureus and Salmonella typhimurium, indicating their potential as non-alcoholic disinfectants.

Fungi-mediated synthesis of nanoparticles: characterization process and agricultural applications

In the field of nanotechnology, the use of biologically active products from fungi for the reduction and synthesis of nanoparticles as an alternative to toxic chemicals has received extensive attention, due to their production of large quantities of proteins, high yields, easy handling, and the low toxicity of the residues. Fungi have become valuable tools for the manufacture of nanoparticles in comparison with other biological systems because of their enhanced growth control and diversity of metabolites, including enzymes, proteins, peptides, polysaccharides, and other macro-molecules. The ability to use different species of fungi and to perform the synthesis under different conditions enables the production of nanoparticles with different physicochemical characteristics. Fungal nanotechnology has been used to develop and offer products and services in the agricultural, medicinal, and industrial sectors. Agriculturally, it has found applications in plant disease management, crop improvement, biosensing, and the production of environmentally friendly, non-toxic pesticides and fertilizers to enhance agricultural production in general. The subject of this review is the application of fungi in the synthesis of inorganic nanoparticles, characterization, and possible applications of fungal nanoparticles in the diverse agricultural sector. The literature shows potential uses of fungi in biogenic synthesis, enabling the production of nanoparticles with different physiognomies. © 2023 Society of Chemical Industry.

Mycosynthesis of silver nanoparticles: a review

Metallic nanoparticles currently show multiple applications in the industrial, clinical and environmental fields due to their particular physicochemical characteristics. Conventional approaches for the synthesis of silver nanoparticles (AgNPs) are based on physicochemical processes which, although they show advantages such as high productivity and good monodispersity of the nanoparticles obtained, have disadvantages such as the high energy cost of the process and the use of harmful radiation or toxic chemical reagents that can generate highly polluting residues. Given the current concern about the environment and the potential cytotoxic effects of AgNPs, once they are released into the environment, a new green chemistry approach to obtain these nanoparticles called biosynthesis has emerged. This new alternative process counteracts some limitations of conventional synthesis methods, using the metabolic capabilities of living beings to manufacture nanomaterials, which have proven to be more biocompatible than their counterparts obtained by traditional methods. Among the organisms used, fungi are outstanding and are therefore being explored as potential nanofactories in an area of research known as mycosynthesis. For all the above, this paper aims to illustrate the advances in state of the art in the mycosynthesis of AgNPs, outlining the two possible mechanisms involved in the process, as well as the AgNPs stabilizing substances produced by fungi, the variables that can affect mycosynthesis at the in vitro level, the applications of AgNPs obtained by mycosynthesis, the patents generated to date in this field, and the limitations encountered by researchers in the area.

Nanobiotechnological approaches in antinociceptive therapy: Animal-based evidence for analgesic nanotherapeutics of bioengineered silver and gold nanomaterials

Pain management is a major challenge in healthcare systems worldwide. Owing to undesirable side effects of current analgesic medications, there is an exceeding need to develop the effective alternative therapeutics. Nowadays, the application of nanomaterials is being highly considered, as their exceptional properties arising from the nanoscale dimensions are undeniable. With the increasing use of metal NPs, more biocompatible and costly methods of synthesis have been developed in which different biological rescores including microorganisms, plants and algae are employed. Nanobiotechnology-based synthesis of nanosized particles is an ecological approach offering safe production of nanoparticles (NPs) by biological resources eliminating the toxicity attributed to the conventional routes. This review provides an assessment of biosynthesized silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) as antinociceptive agents in recent studies. Living animal models (mice and rats) have been used for analyzing the effect of biogenic NPs on decreasing the nociceptive pain utilizing different methods such as acetic acid-induced writhing test, hot plate test, and formalin test. Potent analgesic activity exhibited by green fabricated AgNPs and AuNPs represents the bright future of nanotechnology in the management of pain and other social and medicinal issues followed by this unpleasant sensation. Moreover, there NPs showed a protective effects on liver, kidney, and body weight in animal models that make them attractive for clinical studies. However, further research is required to fully address the harmless antinociceptive effect of NPs for clinical usage.

Biogenic Zinc Oxide Nanoparticles and Their Biomedical Applications: A Review

Nanotechnology has inscribed novel perception into the material science and one of the most extensively used nanomaterials is Zinc oxide nanoparticles (ZnO NPs) with healthcare and biomedical applications. Because of its outstanding biocompatibility, low toxicity, and low cost, ZnO NPs have become one of the most prominent metal oxide NPs in biological applications. This review highlights the different aspects of ZnO NPs, like their green synthesis as a substitute of conventional route due to avoidance of threat of hazardous, costly precursors and subsequent mostly therapeutic applications. Due to their wide bandwidth and high excitation binding energy, ZnO NPs have undergone extensive research. In addition to their potential applications as antibiotics, antioxidants, anti-diabetics, and cytotoxic agents, ZnO NPs also hold a promising future as an antiviral treatment for SARS-CoV-2. Zn has antiviral properties and may be effective against a variety of respiratory virus species, particularly SARS-CoV-2. This review includes a variety of topics, including the virus's structural properties, an overview of infection mechanism, and current COVID-19 treatments. Nanotechnology-based techniques for the prevention, diagnosis, and treatment of COVID-19 are also discussed in this review.

Environmentally Benign Nanoparticles for the Photocatalytic Degradation of Pharmaceutical Drugs

A rapid rise in industrialization has led to the release of pharmaceutical pollutants into water bodies, rendering water inappropriate for consumption by humans and animals, challenging our efforts to achieve the clean water sustainable development goal. These pharmaceutical pollutants include antibiotics, anticancer drugs, antidepressants, etc., which are highly stable and persistent in water, in addition to being harmful to life. At times, the secondary pollutant that is formed after degradation is more potent than the parent drug. Conventional water purification methods cannot completely remove these pollutants. Hence, efficient and robust methods are required to degrade pharmaceutical waste. Photocatalytic degradation of drugs is deemed an efficient and effective method for environmental remediation, along with recovery of photocatalysts, which are important for recycling and sustainable use. Herein, we present the synthesis of nanoparticles (NPs) and their application for photocatalytic degradation of pharmaceutical waste as a preferred water treatment method. Additionally, green synthesis of photocatalytic nanomaterials offers the benefit of avoiding secondary pollution. The green synthesis of NPs is employed by using plant extracts that offer a number of metabolites as reducing agents or capping agents, as well as the use of microbes as green nanofactories to tackle the issue of water cleanliness with respect to pharmaceutical waste. Despite regulations concerning drug disposal, some underdeveloped countries do not enforce and practice these guidelines in letter and spirit. Hence, the current work presenting a promising water cleanliness method is expected to contribute to the assurance of strict policy compliance and enforcement, resulting in the resolution of the health concerns with respect to hazardous pharmaceutical waste disposal in water bodies.

Cell-free synthesis of silver nanoparticles in spent media of different Aspergillus species

The recovery and valorization of metals and rare earth metals from wastewater are of great importance to prevent environmental pollution and recover valuable resources. Certain bacterial and fungal species are capable of removing metal ions from the environment by facilitating their reduction and precipitation. Even though the phenomenon is well documented, little is known about the mechanism. Therefore, we systematically investigated the influence of nitrogen sources, cultivation time, biomass, and protein concentration on silver reduction capacities of cell-free cultivation media (spent media) of Aspergillus niger, A. terreus, and A. oryzae. The spent medium of A. niger showed the highest silver reduction capacities with up to 15 μmol per milliliter spent medium when ammonium was used as the sole N-source. Silver ion reduction in the spent medium was not driven by enzymes and did not correlate with biomass concentration. Nearly full reduction capacity was reached after 2 days of incubation, long before the cessation of growth and onset of the stationary phase. The size of silver nanoparticles formed in the spent medium of A. niger was influenced by the nitrogen source, with silver nanoparticles formed in nitrate or ammonium-containing medium having an average diameter of 32 and 6 nm, respectively.

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.

Colorimetric Detection of Metals Using CdS-NPs Synthesized by an Organic Extract of Aspergillus niger

The use of cadmium sulfide nanoparticles (CdS-NPs) synthesized by fungi presents highly stable chemical and optical characteristics; this makes them a promising alternative for development of colorimetric methods for metal detection. Moreover, application of CdS-NPs is challenging due to the biological material used to carry out synthesis and coating is highly diverse; therefore, it is necessary to evaluate if such components are present in the biological material. Thus, the objective of this work was to detect metallic ions in synthetic water samples using CdS-NPs synthesized by the extract of Aspergillus niger. The conditions to produce fungal extracts were determined through a factorial design 2³; additionally, biomolecules involved in metallic ions detection, synthesis, and coating of CdS-NPs were quantified; the studied biomolecules are NADH, sulfhydryl groups, proteins, and ferric reducing antioxidants (FRAP). CdS-NPs synthesized in this study were characterized by spectrophotometry, zeta potential, and high-resolution transmission electron microscopy (HRTEM). Finally, detection capacity of metallic ions in synthetic water samples was evaluated. It was proved that the methanolic extract of Aspergillus niger obtained under established conditions has the necessary components for both synthesis and coating of CdS-NPs, as well as detection of metallic ions because it was possible to synthesize CdS-NPs with a hexagonal crystalline structure with a length of 2.56 ± 0.50 nm which were able to detect Pb²⁺, Cr⁶⁺, and Fe³⁺ at pH 4 and Co²⁺ at pH 8.

Evaluation of Sclerotinia sclerotiorum MTCC 8785 as a biological agent for the synthesis of silver nanoparticles and assessment of their antifungal potential against Trichoderma harzianum MTCC 801

INTRODUCTION

Owing to loads of industrial development and advancements, there is an unmet need for green-ecosystem support as well as safe technologies. For cost-cutting and eco-friendly applications, biosynthetic pathways for nanoparticle synthesis from microbes like bacteria, and fungi have attracted the global attention of researchers.

METHODS

In the present research work, silver nanoparticles (AgNPs) from fungus (mycogenic) were extracellularly synthesized with cell-free filtrates of fungal phytopathogen Sclerotinia sclerotiorum MTCC 8785 harvested from broth culture in Potato dextrose broth (CFF-PDB) and Amylase production media (CFF-AMP). The synthesis was carried out at pH 7, 28 °C under dark conditions. The synthesized AgNPs were characterized using UV spectrophotometer and transmission electron microscopy (TEM). Furthermore, the antifungal efficacy of AgNPs was evaluated against the Trichoderma harzianum MTCC 801 strain by radial inhibition assay.

RESULTS

Primarily, the process of biosynthesis was inferred by the characteristic change of color and spectral peak at 420 nm recorded with UV spectrophotometer further approved the nano silver production in CFF-AMP which approves the role of amylases in reduction mediated capping process. TEM analysis revealed that the AgNPs synthesized using S. sclerotiorum MTCC 8785 grown in PDB were spherical with variable size ranges from 10 to 50 nm in diameter whereas, the AgNPs synthesized using S. sclerotiorum MTCC 8785 grown in APM were in the size ranges from 40 to 50 nm.

CONCLUSIONS

This is the first investigatory concern where nano-silver from fungal phytopathogen S. sclerotiorum MTCC 8785 has been prospected as new age antifungal alternatives against evolving threats from T. harzianum strain.

Extracellular biosynthesis, OVAT/statistical optimization, and characterization of silver nanoparticles (AgNPs) using Leclercia adecarboxylata THHM and its antimicrobial activity

BACKGROUND

The biosynthesis of silver nanoparticles (AgNPs) is an area of interest for researchers due to its eco-friendly approach. The use of biological approaches provides a clean and promising alternative process for the synthesis of AgNPs. We used for the first time the supernatant of Leclercia adecarboxylata THHM under optimal conditions to produce AgNPs with an acceptable antimicrobial activity against important clinical pathogens.

RESULTS

In this study, soil bacteria from different locations were isolated and screened for their potential to form AgNPs. The selected isolate, which was found to have the ability to biosynthesize AgNPs, was identified by molecular methods as Leclercia adecarboxylata THHM and its 16S rRNA gene was deposited in GenBank under the accession number OK605882. Different conditions were screened for the maximum production of AgNPs by the selected bacteria. Five independent variables were investigated through optimizations using one variable at a time (OVAT) and the Plackett-Burman experimental design (PBD). The overall optimal parameters for enhancing the biosynthesis of AgNPs using the supernatant of Leclercia adecarboxylata THHM as a novel organism were at an incubation time of 72.0 h, a concentration of 1.5 mM silver nitrate, a temperature of 40.0 °C, a pH of 7.0, and a supernatant concentration of 30% (v/v) under illumination conditions. The biosynthesized AgNPs have been characterized by UV-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The biosynthesized AgNPs showed an absorption peak at 423 nm, spherical shape, and an average particle size of 17.43 nm. FTIR shows the bands at 3321.50, 2160.15, and 1636.33 cm^-1 corresponding to the binding vibrations of amine, alkyne nitrile, and primary amine bands, respectively. The biosynthesized AgNPs showed antimicrobial activity against a variety of microbial pathogens of medical importance. Using resazurin-based microtiter dilution, the minimum inhibitory concentration (MIC) values for AgNPs were 500 µg/mL for all microbial pathogens except for Klebsiella pneumoniae ATCC13883, which has a higher MIC value of 1000 µg/mL.

CONCLUSIONS

The obtained data revealed the successful green production of AgNPs using the supernatant of Leclercia adecarboxylata THHM that can be effectively used as an antimicrobial agent against most human pathogenic microbes.

New aspects of lipopeptide-incorporated nanoparticle synthesis and recent advancements in biomedical and environmental sciences: a review

The toxicity of metal nanoparticles has introduced promising research in the current scenario since an enormous number of people have been potentially facing this problem in the world. The extensive attention on green nanoparticle synthesis has been focussed on as a vital step in bio-nanotechnology to improve biocompatibility, biodegradability, eco-friendliness, and huge potential utilization in various environmental and clinical assessments. Inherent influence on the study of green nanoparticles plays a key role to synthesize the controlled and surface-influenced molecule by altering the physical, chemical, and biological assets with the provision of various precursors, templating/co-templating agents, and supporting solvents. However, in this article, the dominant characteristics of several kinds of lipopeptide biosurfactants are discussed to execute a critical study of factors affecting synthesis procedure and applications. The recent approaches of metal, metal oxide, and composite nanomaterial synthesis have been deliberated as well as the elucidation of the reaction mechanism. Furthermore, this approach shows remarkable boosts in the production of nanoparticles with the very less employed harsh and hazardous processes as compared to chemical or physical method-based nanoparticle synthesis. This study also shows that the advances in strain selection for green nanoparticle production could be a worthwhile and strong economical approach in futuristic medical science research.

Synthesis and characterization of plant extracted silver nanoparticles and advances in dental implant applications

Dental implantology has always emphasized silver nanoparticles (AgNPs) for various applications due to their biocompatibility, antibacterial activity, and increased surface volume ratio offered by these particles. It is utilized to a large extent in the dental implant industry as a surface modification, biocompatible constituent and composite material. AgNPs may be produced inexpensively, sustainably, and environmentally responsibly by utilizing technologies that extract the plant material. The phytochemical components that are contained in plants make them a better, non-toxic, and more cost-effective alternative to both physical and chemical approaches. Because the size and shape of AgNP depend on their synthesis method and technique, and because the efficacy and toxicity of AgNP depend on both size and shape, synthesis methods and techniques have recently become the focus of a significant amount of research attention. In this review, we discussed Plant Extracted Ag-NP's whose sizes range up to 100nm. This review also focuses on recent research advancements in the Plant Extracted synthesis of AgNPs, as well as their characterization methodologies, current obstacles, future possibilities, and applications in dental implantology.

Bacillus sp. extract used to fabricate ZnO nanoparticles for their antagonist effect against phytopathogens

In order to achieve the food demand of a growing population, agricultural productivity needs to be increased by employing safe strategies. In the present study we have evaluated ZnONPs that were synthesized from the culture supernatant of Bacillus subtilis. Bio mimetically synthesized ZnONPs showed a surface resonance peak of 355 nm corresponding to NPs formation. Further, NPs were examined for their size, shape and element confirmation by DLS, AFM, SEM, TEM and EDAX, which confirmed the synthesized NPs were nearly spherical in size with average diameter of 32 nm by TEM. Surface charge of + 34.3 mV was observed for NPs with a low poly-dispersity index of 0.21. In vitro efficacy studies against fungi Colletotrichum capsici, Sclerotium rolfsii, Alternaria solani and Fusarium oxysporum f. sp. cicero showed up to 99% mycelial growth inhibition at 0.125% ZnONPs. Further, in-vitro disk-diffusion assay showed inhibition zones of 23 ± 0.4 mm and 12.67 ± 0.24 mm for Xanthomonas axonopodis pv. punicae (Xap) and Xanthomonas oryzae pv. oryzae (Xoo) bacterial cultures. Plant toxicity study was observed that ≤ 0.14% NPs concentration was safe under greenhouse conditions. Overall, the present study emphasizes the potential effect of ZnONPs against agricultural pathogens which play an important role in agriculture production.

Mycosynthesis of Metal-Containing Nanoparticles-Fungal Metal Resistance and Mechanisms of Synthesis

In the 21st century, nanomaterials play an increasingly important role in our lives with applications in many sectors, including agriculture, biomedicine, and biosensors. Over the last two decades, extensive research has been conducted to find ways to synthesise nanoparticles (NPs) via mediation with fungi or fungal extracts. Mycosynthesis can potentially be an energy-efficient, highly adjustable, environmentally benign alternative to conventional physico-chemical procedures. This review investigates the role of metal toxicity in fungi on cell growth and biochemical levels, and how their strategies of resistance, i.e., metal chelation, biomineral formation, biosorption, bioaccumulation, compartmentalisation, and efflux of metals from cells, contribute to the synthesis of metal-containing NPs used in different applications, e.g., biomedical, antimicrobial, catalytic, biosensing, and precision agriculture. The role of different synthesis conditions, including that of fungal biomolecules serving as nucleation centres or templates for NP synthesis, reducing agents, or capping agents in the synthesis process, is also discussed. The authors believe that future studies need to focus on the mechanism of NP synthesis, as well as on the influence of such conditions as pH, temperature, biomass, the concentration of the precursors, and volume of the fungal extracts on the efficiency of the mycosynthesis of NPs.

Mycosynthesis of highly fluorescent selenium nanoparticles from Fusarium oxysporum, their antifungal activity against black fungus Aspergillus niger, and in-vivo biodistribution studies

In the past few years, photo-luminescent inorganic materials have been studied extensively as fluorescent sensors, and diagnostic and bioimaging tools. The assessment of photoluminescence (PL) properties of selenium nanoparticles (Se NPs), especially mycosynthesized Se NPs, is still in its infancy. Herein, we have biosynthesized highly dispersed fluorescent Se NPs (42 nm) using endophytic fungus Fusarium oxysporum, and fully characterized them using sophisticated instruments like TEM, XRD, UV–Vis spectrophotometer, FTIR, and PL spectrometer. To determine the therapeutic efficacy and side effect profiles, these crystalline Se NPs were radiolabeled with technetium-99m (^99mTc) and their biodistribution and renal clearance times were investigated in the normal Wister rat. The results showed that these Se NPs may be useful for targeting the lungs and liver dysfunction as significant accumulation of these NPs was observed in the liver (approx. 19.47 ± 4%) and lungs (at 6 ± 1%) after 10 min of post-injection. Quick circulation and the presence of Se NPs in kidney (3.8 ± 2%) also suggested the easy excretion of these NPs from the body through urinary tract. Furthermore, the antioxidant activity of Se NPs (IC₅₀, 159.5 μg/mL) has been investigated using DPPH free radical scavenging assay with scavenging efficacy of 80.4% where ascorbic acid (IC₅₀, 5.6 μg/mL) was used as a positive control. Additionally, the microscopic study of the inhibition zone encircled around Se NPs confirmed their strong antifungal and antisporulant activity against the black fungus Aspergillus niger.

Green synthesis of metal-based nanoparticles for sustainable agriculture

The large-scale use of conventional pesticides and fertilizers has put tremendous pressure on agriculture and the environment. In recent years, nanoparticles (NPs) have become the focus of many fields due to their cost-effectiveness, environmental friendliness and high performance, especially in sustainable agriculture. Traditional NPs manufacturing methods are energy-intensive and harmful to environment. In contrast, synthesizing metal-based NPs using plants is similar to chemical synthesis, except the biological extracts replace the chemical reducing agent. This not only greatly reduces the used of traditional chemicals, but also produces NPs that are more economical, efficient, less toxic, and less polluting. Therefore, green synthesized metal nanoparticles (GS-MNPs) are widely used in agriculture to improve yields and quality. This review provides a comprehensive and detailed discussion of GS-MNPs for agriculture, highlights the importance of green synthesis, compares the performance of conventional NPs with GS-MNPs, and highlights the advantages of GS-MNPs in agriculture. The wide applications of these GS-MNPs in agriculture, including plant growth promotion, plant disease control, and heavy metal stress mitigation under various exposure pathways, are summarized. Finally, the shortcomings and prospects of GS-MNPs in agricultural applications are highlighted to provide guidance to nanotechnology for sustainable agriculture.

Insights into the mapping of green synthesis conditions for ZnO nanoparticles and their toxicokinetics

Research on ZnO nanoparticles (NPs) has broad medical applications. However, the green synthesis of ZnO NPs involves a wide range of properties requiring optimization. ZnO NPs show toxicity at lower doses. This toxicity is a function of NP properties and pharmacokinetics. Moreover, NP toxicity and pharmacokinetics are affected by the species type and age of the animals tested. Physiologically based pharmacokinetic (PBPK) modeling offers a mechanistic platform to scrutinize the colligative effect of the interplay between these factors, which reduces the need for in vivo studies. This review provides a guide to choosing green synthesis conditions that result in minimal toxicity using a mechanistic tool, namely PBPK modeling.

Multidrug-Resistant Bacterial Pathogens and Public Health: The Antimicrobial Effect of Cyanobacterial-Biosynthesized Silver Nanoparticles

Background: Cyanobacteria are considered as green nano-factories. Manipulation of the size of biogenic silver nanoparticles is needed to produce particles that suit the different applications such as the use as antibacterial agents. The present study attempts to manipulate the size of biosynthesized silver nanoparticles produced by cyanobacteria and to test the different-sized nanoparticles against pathogenic clinical bacteria. Methods: Cyanothece-like. coccoid unicellular cyanobacterium was tested for its ability to biosynthesize nanosilver particles of different sizes. A stock solution of silver nitrate was prepared from which three different concentrations were added to cyanobacterial culture. UV-visible spectroscopy and FTIR were conducted to characterize the silver nanoparticles produced in the cell free filtrate. Dynamic Light Scattering (DLS) was performed to determine the size of the nanoparticles produced at each concentration. The antimicrobial bioassays were conducted on broad host methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus sp., was conducted to detect the nanoparticle size that was most efficient as an antimicrobial agent. Results. The UV-Visible spectra showed excellent congruence of the plasmon peak characteristic of nanosilver at 450 nm for all three different concentrations, varying peak heights were recorded according to the concentration used. The FTIR of the three solutions revealed the absence of characteristic functional groups in the solution. All three concentrations showed spectra at 1636 and 2050–2290 nm indicating uniformity of composition. Moreover, DLS analysis revealed that the silver nanoparticles produced with lowest concentration of precursor AgNO₃ had smallest size followed by those resulting from the higher precursor concentration. The nanoparticles resulting from highest concentration of precursor AgNO₃ were the biggest in size and tending to agglomerate when their size was above 100 nm. The three types of differently-sized silver nanoparticles were used against two bacterial pathogenic strains with broad host range; MRSA-(Methicillin-resistant Staphylococcus aureus) and Streptococcus sp. The three types of nanoparticles showed antimicrobial effects with the smallest nanoparticles being the most efficient in inhibiting bacterial growth. Discussion: Nanosilver particles biosynthesized by Cyanothece-like cyanobacterium can serve as antibacterial agent against pathogens including multi-drug resistant strains. The most appropriate nanoparticle size for efficient antimicrobial activity had to be identified. Hence, size-manipulation experiment was conducted to find the most effective size of nanosilver particles. This size manipulation was achieved by controlling the amount of starting precursor. Excessive precursor material resulted in the agglomeration of the silver nanoparticles to a size greater than 100 nm. Thereby decreasing their ability to penetrate into the inner vicinity of microbial cells and consequently decreasing their antibacterial potency. Conclusion: Antibacterial nanosilver particles can be biosynthesized and their size manipulated by green synthesis. The use of biogenic nanosilver particles as small as possible is recommended to obtain effective antibacterial agents.

Biological Synthesis of Silver Nanoparticles and Prospects in Plant Disease Management

Exploration of nanoparticles (NPs) for various biological and environmental applications has become one of the most important attributes of nanotechnology. Due to remarkable physicochemical properties, silver nanoparticles (AgNPs) are the most explored and used NPs in wide-ranging applications. Also, they have proven to be of high commercial use since they possess great chemical stability, conductivity, catalytic activity, and antimicrobial potential. Though several methods including chemical and physical methods have been devised, biological approaches using organisms such as bacteria, fungi, and plants have emerged as economical, safe, and effective alternatives for the biosynthesis of AgNPs. Recent studies highlight the potential of AgNPs in modern agricultural practices to control the growth and spread of infectious pathogenic microorganisms since the introduction of AgNPs effectively reduces plant diseases caused by a spectrum of bacteria and fungi. In this review, we highlight the biosynthesis of AgNPs and discuss their applications in plant disease management with recent examples. It is proposed that AgNPs are prospective NPs for the successful inhibition of pathogen growth and plant disease management. This review gives a better understanding of new biological approaches for AgNP synthesis and modes of their optimized applications that could contribute to sustainable agriculture.

Fungal Mushrooms: A Natural Compound With Therapeutic Applications

Fungi are extremely diverse in terms of morphology, ecology, metabolism, and phylogeny. Approximately, 130 medicinal activities like antitumor, immunomodulation, antioxidant, radical scavenging, cardioprotective and antiviral actions are assumed to be produced by the various varieties of medicinal mushrooms. The polysaccharides, present in mushrooms like β-glucans, micronutrients, antioxidants like glycoproteins, triterpenoids, flavonoids, and ergosterols can help establish natural resistance against infections and toxins.. Clinical trials have been performed on mushrooms like Agaricus blazei Murrill Kyowa for their anticancer effect, A. blazei Murrill for its antihypertensive and cardioprotective effects, and some other mushrooms had also been evaluated for their neurological effects. The human evaluation dose studies had been also performed and the toxicity dose was evaluated from the literature for number of mushrooms. All the mushrooms were found to be safe at a dose of 2000 mg/kg but some with mild side effects. The safety and therapeutic effectiveness of the fungal mushrooms had shifted the interest of biotechnologists toward fungal nanobiotechnology as the drug delivery system due to the vast advantages of nanotechnology systems. In complement to the vital nutritional significance of medicinal mushrooms, numerous species have been identified as sources of bioactive chemicals. Moreover, there are unanswered queries regarding its safety, efficacy, critical issues that affect the future mushroom medicine development, that could jeopardize its usage in the twenty-first century.

On Recent Developments in Biosynthesis and Application of Au and Ag Nanoparticles from Biological Systems

Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) are extensively studied nanoparticles (NPs) and are known to have profound applications in medicine. The researcher made continuous efforts for the environmental-friendly and economical methods, such as biogenic methods known as green synthesis. There are many strategies for separating and applying gold (Au) and silver (Ag) nanoparticles, of which biological routes have emerged as efficient, low-cost, and environmentally friendly techniques. This review focuses on recent developments of green synthesized AuNPs and AgNPs using biogenic sources such as algae, animals, plants, microbes, bacteria, fungi, and so on. Hence, it discusses their numerous biomedical applications and separating Au and Ag nanoparticles from plants, bacteria, fungi, and algae.

Green synthesis and characterization of silver nanoparticles using Eugenia roxburghii DC. extract and activity against biofilm-producing bacteria

The green synthesis of silver nanoparticles (AgNPs) and their applications have attracted many researchers as the AgNPs are used effectively in targeting specific tissues and pathogenic microorganisms. The purpose of this study is to synthesize and characterize silver nanoparticles from fully expanded leaves of Eugenia roxburghii DC., as well as to test their effectiveness in inhibiting biofilm production. In this study, at 0.1 mM concentration of silver nitrate (AgNO3), stable AgNPs were synthesized and authenticated by monitoring the color change of the solution from yellow to brown, which was confirmed with spectrophotometric detection of optical density. The crystalline nature of these AgNPs was detected through an X-Ray Diffraction (XRD) pattern. AgNPs were characterized through a high-resolution transmission electron microscope (HR-TEM) to study the morphology and size of the nanoparticles (NPs). A new biological approach was undertaken through the Congo Red Agar (CRA) plate assay by using the synthesized AgNPs against biofilm production. The AgNPs effectively inhibit biofilm formation and the biofilm-producing bacterial colonies. This could be a significant achievement in contending with many dynamic pathogens.

Trichoderma: An Eco-Friendly Source of Nanomaterials for Sustainable Agroecosystems

Traditional nanoparticle (NP) synthesis methods are expensive and generate hazardous products. It is essential to limit the risk of toxicity in the environment from the chemicals as high temperature and pressure is employed in chemical and physical procedures. One of the green strategies used for sustainable manufacturing is microbial nanoparticle synthesis, which connects microbiology with nanotechnology. Employing biocontrol agents Trichoderma and Hypocrea (Teleomorphs), an ecofriendly and rapid technique of nanoparticle biosynthesis has been reported in several studies which may potentially overcome the constraints of the chemical and physical methods of nanoparticle biosynthesis. The emphasis of this review is on the mycosynthesis of several metal nanoparticles from Trichoderma species for use in agri-food applications. The fungal-cell or cell-extract-derived NPs (mycogenic NPs) can be applied as nanofertilizers, nanofungicides, plant growth stimulators, nano-coatings, and so on. Further, Trichoderma-mediated NPs have also been utilized in environmental remediation approaches such as pollutant removal and the detection of pollutants, including heavy metals contaminants. The plausible benefits and pitfalls associated with the development of useful products and approaches to trichogenic NPs are also discussed.

Recent Advances and Mechanistic Insights into Antibacterial Activity, Antibiofilm Activity, and Cytotoxicity of Silver Nanoparticles

The substantial increase in multidrug-resistant (MDR) pathogenic bacteria is a major threat to global health. Recently, the Centers for Disease Control and Prevention reported possibilities of greater deaths due to bacterial infections than cancer. Nanomaterials, especially small-sized (size ≤10 nm) silver nanoparticles (AgNPs), can be employed to combat these deadly bacterial diseases. However, high reactivity, instability, susceptibility to fast oxidation, and cytotoxicity remain crucial shortcomings for their uptake and clinical application. In this review, we discuss various AgNPs-based approaches to eradicate bacterial infections and provide comprehensive mechanistic insights and recent advances in antibacterial activity, antibiofilm activity, and cytotoxicity (both in vitro and in vivo) of AgNPs. The mechanistic of antimicrobial activity involves four steps: (i) adhesion of AgNPs to cell wall/membrane and its disruption; (ii) intracellular penetration and damage; (iii) oxidative stress; and (iv) modulation of signal transduction pathways. Numerous factors affecting the bactericidal activity of AgNPs such as shape, size, crystallinity, pH, and surface coating/charge have also been described in detail. The review also sheds light on antimicrobial photodynamic therapy and the role of AgNPs versus Ag⁺ ions release in bactericidal activities. In addition, different methods of synthesis of AgNPs have been discussed in brief.

Plant-Mediated Green Synthesis of Ag NPs and Their Possible Applications: A Critical Review

The potential applications of Ag NPs are exciting and beneficial in a variety of fields; however, there is less awareness of the new risks posed by inappropriate disposal of Ag NPs. The Ag NPs have medicinal, plasmonic, and catalytic properties. The Ag NPs can be prepared via physical, chemical, or biological routes, and the selection of any specific route depends largely on the end-use. The downside of a physical and chemical approach is that it requires a wide space, high temperature, high temperature for a longer time to preserve the thermal stability of synthesized Ag NPs, and the use of toxic chemicals. Although these methods produce nanoparticles with high purity and well-defined morphology, it is critical to develop cost-effective, energy-efficient, and facile route, such as green synthesis; it suggests the desirable use of renewable resources by avoiding the use of additional solvents and toxic reagents in order to achieve the ultimate goal. However, each method has its pros and cons. The synthesized Ag NPs obtained using the green approach have larger biocompatibility and are less toxic towards the biotic systems. However, identifying the phytoconstituents that are responsible for nanoparticle synthesis is difficult and has been reported as a suitable candidate for biological application. The concentration of the effective bioreducing phytoconstituents plays a crucial role in deciding the morphology of the nanoparticle. Besides these reaction times, temperature, pH, and concentration of silver salt are some of the key factors that determine the morphology. Hence, careful optimization in the methodology is required as different morphologies have different properties and usage. It is due to which the development of methods to prepare nanoparticles effectively using various plant extracts is gaining rapid momentum in recent days. To make sense of what involves in the bioreduction of silver salt and to isolate the secondary metabolites from plants are yet challenging. This review focuses on the contribution of plant-mediated Ag NPs in different applications and their toxicity in the aquatic system.

A New Strategy for Microbial Taxonomic Identification through Micro-Biosynthetic Gold Nanoparticles and Machine Learning

Microorganisms can serve as biological factories for the synthesis of inorganic nanomaterials that can become useful as nanocatalysts, energy-harvesting-storage components, antibacterial agents, and biomedical materials. Herein, the development of biosynthesis of inorganic nanomaterials into a simple, stable, and accurate strategy for distinguishing microorganisms from multiple classification levels (i.e., kingdom, order, genus, and species) without gene amplification, biochemical testing, or target recognition is reported. Gold nanoparticles (AuNPs) biosynthesized by different microorganisms differ in color of the solution, and their features can be characterized, including the particle size, the surface plasmon resonance (SPR) spectrum, and the surface potential. The inter-relation between the features of micro-biosynthetic AuNPs and the classification of microorganisms are exploited at different levels through machine learning to establish a taxonomic model. This model agrees well with traditional classification methods that offers a new strategy for microbial taxonomic identification. The underlying mechanism of this strategy is related to the biomolecules produced by different microorganisms including glucose, glutathione, and nicotinamide adenine dinucleotide phosphate-dependent reductase that regulate the features of micro-biosynthetic AuNPs. This work broadens the application of biosynthesis of inorganic materials through micro-biosynthetic AuNPs and machine learning, which holds great promise as a tool for biomedical research.

Trichogenic Silver-Based Nanoparticles for Suppression of Fungi Involved in Damping-Off of Cotton Seedlings

Mycogenic silver nanoparticles (AgNPs) produced by some biocontrol agents have shown the ability to inhibit the growth of numerous plant pathogenic fungi, which may be a unique method of disease management. This study describes the extracellular production of AgNPs by Trichoderma harzianum. The size, shape, charge, and composition of the AgNPs were subsequently studied by UV-visible spectroscopy, DLS, zeta potential, TEM, SEM, and EDX, among other methods. The AgNPs had sizes ranging from 6 to 15 nm. The antifungal activities of bio-synthesized AgNPs and two commercial fungicides (Moncut and Maxim XL) were tested against three soil-borne diseases (Fusarium fujikuroi, Rhizoctonia solani, and Macrophomina phaseolina). Cotton seedling illnesses were significantly reduced under greenhouse settings after significant in vitro antifungal activity was documented for the control of plant pathogenic fungi. The use of biocontrol agents such as T. harzianum, for example, may be a safe strategy for synthesizing AgNPs and using them to combat fungus in Egyptian cotton.

Activity of Fusarium oxysporum-Based Silver Nanoparticles on Candida spp. Oral Isolates

Candida spp. resistant to commercially available antifungals are often isolated from patients with oral candidiasis, a situation that points to the need for the development of new therapies. Thus, we evaluated the activity of Fusarium oxysporum-based silver nanoparticles (AgNPs) on Candida spp. isolated from denture stomatitis lesions. Candida isolates were molecularly identified and submitted to susceptibility assays using AgNPs and commercial fungicides. The interference on biofilm formation and the mechanisms of action of AgNPs on Candida spp. were also investigated. Scanning electron microscopy was used to evaluate the morphology of AgNP-treated Candida. Candida albicans was the most frequent species isolated from denture stomatitis cases. All Candida spp. were susceptible to AgNPs at low concentrations, except Candida parapsilosis. AgNPs caused surface damage, cell disruption, and biofilm formation inhibition. The ergosterol supplementation protected C. albicans against the AgNP action. AgNPs are effective against Candida spp. and can be faced as a promising new therapeutic agent against oral candidiasis.

Streptomyces chiangmaiensis SSUT88A mediated green synthesis of silver nanoparticles: characterization and evaluation of antibacterial action against clinical drug-resistant strains

This study involved the characterization of AgNPs synthesized from soil isolate Streptomyces sp. SSUT88A and their antimicrobial activities. The strain SSUT88A revealed 98.8% similarity of the 16s rRNA gene to Streptomyces chiangmaiensis TA4-1T. The AgNPs were synthesized by mixing either intracellular or extracellular cell-free supernatant of strain SSUT88A with AgNO3. The synthesized AgNPs from intracellular cell-free supernatant and extracellular cell-free supernatant were designated as IS-AgNPs and ES-AgNPs, respectively. The IS-AgNPs showed maximum absorbance of UV-vis spectra at 418 nm, while ES-AgNPs revealed maximum absorbance at 422 nm. The TEM observation of synthesized AgNPs revealed a spherical shape with an average diameter of 13.57 nm for IS-AgNPs and 30.47 nm for ES-AgNPs. The XRD and XANES spectrum profile of both synthesized AgNPs exhibited similar spectrum energy, which corresponded to AgNPs. The IS-AgNPs revealed antimicrobial activity against clinical isolate drug-resistant bacteria (Acinetobacter baumannii, Escherichia coli 8465, Klebsiella pneumoniae 1617, and Pseudomonas aeruginosa N90PS), while ES-AgNPs had no antimicrobial activity. When compared to commercial AgNPs, IS-AgNPs exhibited antibacterial efficacy against all clinical isolate bacteria including A. baumannii, one of the most threatening multi-drug resistant strains, while commercial AgNPs did not. Thus, IS-AgNPs has potential to be further developed as an antimicrobial agent against drug-resistant bacteria.

Characterization of Talaromyces islandicus-mediated silver nanoparticles and evaluation of their antibacterial and anticancer potential

The biosynthesized silver nanoparticles (AgNPs) have been reported to possess several therapeutic applications. Silver is one of the important metals known for its bioactive properties not only as macromolecule but also as nanoparticle (NP). The current research focused on the eco-friendly synthesis of Talaromyces islandicus VSGF1(Lab code) -mediated AgNPs. The aqueous culture filtrate of T. islandicus VSGF1 was used as a reducing agent. The formation of AgNPs was confirmed by observing the color change from colorless to colloidal earthy-colored and a sharp absorption peak of ultraviolet-visible (UV-vis) spectroscopy at 400 nm. Fourier-transform infrared spectroscopy revealed the involvement of various functional groups for the formation and stabilization of AgNPs. The structure, size, and shape of mycosynthesized AgNPs were identified by X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy (AFM) analysis. The XRD analysis exhibited crystalline nature of NPs whereas AFM analysis revealed the spherical shape of AgNP with average size range between 13 and 66 nm. The antibacterial activity of AgNPs (50 μg/ml) investigated against gram-positive and gram-negative bacteria revealed maximum zone of inhibition (ZOI) against drug-resistant Enterococcus faecalis MTCC439 (18.66 ± 0.57 mm) and Pseudomonas aeruginosa MTCC96 (16 ± 0 mm) followed by Staphylococcus aureus MTCC96 (15.33 ± 0.57 mm), Bacillus subtilis MTCC441 (14.66 ± 0.57 mm), and Escherichia coli MTCC45 (14.66 ± 0.57 mm). Further, the AgNPs evaluated for antitumor activity against human hepatocellular carcinoma (HepG2) cell line exhibited promising result with half-maximal inhibitory concentration (MIC) value at 38.17 μg/ml concentration through MTT (methylthiazolyl tetrazolium assay) assay. Apparently, this is the first report from T. islandicus to the best of our knowledge.

Uptake, translocation, and transformation of silver nanoparticles in plants

This article reviews the plant uptake of silver nanoparticles (AgNPs) that occurred in soil systems and the in planta fate of Ag.

Myco-remediation: A mechanistic understanding of contaminants alleviation from natural environment and future prospect

Industrialization and modernization of agricultural systems contaminated lithosphere, hydrosphere, and biosphere of the Earth. Sustainable remediation of contamination is essential for environmental sustainability. Myco-remediation is proposed to be a green, economical, and efficient technology over conventional remediation technologies to combat escalating pollution problems at a global scale. Fungi can perform remediation of pollutants through several mechanisms like biosorption, precipitation, biotransformation, and sequestration. Myco-remediation significantly removes or degrades metal metals, persistent organic pollutants, and other emerging pollutants. The current review highlights the species-specific remediation potential, influencing factors, genetic and molecular control mechanism, applicability merits to enhance the bioremediation efficiency. Structure and composition of fungal cell wall is crucial for immobilization of toxic pollutants and a subtle change on fungal cell wall structure may significantly affect the immobilization efficiency. The utilization protocol and applicability of enzyme engineering and myco-nanotechnology to enhance the bioremediation efficiency of any potential fungus was proposed. It is advocated that the association of hyper-accumulator plants with plant growth-promoting fungi could help in an effective cleanup strategy for the alleviation of persistent soil pollutants. The functions, activity, and regulation of fungal enzymes in myco-remediation practices required further research to enhance the myco-remediation potential. Study of the biotransformation mechanisms and risk assessment of the products formed are required to minimize environmental pollution. Recent advancements in molecular "Omic techniques"and biotechnological tools can further upgrade myco-remediation efficiency in polluted soils and water.

Diversity of Microbial Metal Sulfide Biomineralization

Since the emergence of life on Earth, microorganisms have contributed to biogeochemical cycles. Sulfate-reducing bacteria are an example of widespread microorganisms that participate in the metal and sulfur cycles by biomineralization of biogenic metal sulfides. In this work, we review the microbial biomineralization of metal sulfide particles and summarize distinctive features from exemplary cases. We highlight that metal sulfide biomineralization is highly metal- and organism-specific. The properties of metal sulfide biominerals depend on the degree of cellular control and on environmental factors, such as pH, temperature, and concentration of metals. Moreover, biogenic macromolecules, including peptides and proteins, help cells control their extracellular and intracellular environments that regulate biomineralization. Accordingly, metal sulfide biominerals exhibit unique features when compared to abiotic minerals or biominerals produced by dead cell debris.

Marine Macroalgae Display Bioreductant Efficacy for Fabricating Metallic Nanoparticles: Intra/Extracellular Mechanism and Potential Biomedical Applications

The application of hazardous chemicals during nanoparticle (NP) synthesis has raised alarming concerns pertaining to their biocompatibility and equally to the environmental harmlessness. In the recent decade, nanotechnological research has made a gigantic shift in order to include the natural resources to produce biogenic NPs. Within this approach, researchers have utilized marine resources such as macroalgae and microalgae, land plants, bacteria, fungi, yeast, actinomycetes, and viruses to synthesize NPs. Marine macroalgae (brown, red, and green) are rich in polysaccharides including alginates, fucose-containing sulfated polysaccharides (FCSPs), galactans, agars or carrageenans, semicrystalline cellulose, ulvans, and hemicelluloses. Phytochemicals are abundant in phenols, tannins, alkaloids, terpenoids, and vitamins. However, microorganisms have an abundance of active compounds ranging from sugar molecules, enzymes, canonical membrane proteins, reductase enzymes (NADH and NADPH), membrane proteins to many more. The prime reason for using the aforesaid entities in the metallic NPs synthesis is based on their intrinsic properties to act as bioreductants, having the capability to reduce and cap the metal ions into stabilized NPs. Several green NPs have been verified for their biocompatibility in human cells. Bioactive constituents from the above resources have been found on the green metallic NPs, which has demonstrated their efficacies as prospective antibiotics and anti-cancer agents against a range of human pathogens and cancer cells. Moreover, these NPs can be characterized for the size, shapes, functional groups, surface properties, porosity, hydrodynamic stability, and surface charge using different characterization techniques. The novelty and originality of this review is that we provide recent research compilations on green synthesis of NPs by marine macroalgae and other biological sources (plant, bacteria, fungi, actinomycetes, yeast, and virus). Besides, we elaborated on the detailed intra- and extracellular mechanisms of NPs synthesis by marine macroalgae. The application of green NPs as anti-bacterial, anti-cancer, and popular methods of NPs characterization techniques has also been critically reviewed.

Extraction of Fucoidan from Turbinaria decurrens and the Synthesis of Fucoidan-Coated AgNPs for Anticoagulant Application

Brown seaweeds usually contain alginate as a major polymer. The second major sulfated polymer in brown seaweeds is fucoidan, which has huge potential in medicinal applications. In this study, the photosynthetic pigments from Turbinaria decurrens were first extracted using chloroform/methanol in the ratio of 1:1 (v/v), followed by fucoidan extraction with yields of 5.58% (crude) and 1.28% (purified fucoidan) from the dry weight of seaweed, whereas alginate was extracted with a yield of 14.7% DW of seaweed. The isolated fucoidan possessing anticoagulation property was identified and characterized as (1-3)-α-l-fucopyranosyl residues with sulfate groups primarily at the C4 position and to a lesser extent at the C2 position, whereas in the case of galactose, at the C3 and C6 positions. The AgNPs synthesized using isolated fucoidan exhibit strong anticoagulant activity and possess a good antibacterial property against Gram-negative clinical bacteria. Functional groups such as O-H, C-H, and S=O associated with sugar residues in sulfated fucoidan are involved in the synthesis of the nanoparticles with a spherical shape, size ranging from 10 to 60 nm, and showing polydispersity. From this study, we conclude that fucoidan-coated anionic AgNPs synthesized from T. decurrens have tremendous potential in drug development.

Bionanofactories for Green Synthesis of Silver Nanoparticles: Toward Antimicrobial Applications

Among the various types of nanoparticles and their strategy for synthesis, the green synthesis of silver nanoparticles has gained much attention in the biomedical, cellular imaging, cosmetics, drug delivery, food, and agrochemical industries due to their unique physicochemical and biological properties. The green synthesis strategies incorporate the use of plant extracts, living organisms, or biomolecules as bioreducing and biocapping agents, also known as bionanofactories for the synthesis of nanoparticles. The use of green chemistry is ecofriendly, biocompatible, nontoxic, and cost-effective. We shed light on the recent advances in green synthesis and physicochemical properties of green silver nanoparticles by considering the outcomes from recent studies applying SEM, TEM, AFM, UV/Vis spectrophotometry, FTIR, and XRD techniques. Furthermore, we cover the antibacterial, antifungal, and antiparasitic activities of silver nanoparticles.