Synthesis of Silver Nanoparticles Mediated by Fungi: A Review

Biogenically proficient synthesis and characterization of silver nanoparticles employing marine procured fungi Aspergillus brunneoviolaceus along with their antibacterial and antioxidative potency

OBJECTIVES

To assess the extracellular synthesis of silver nanoparticles using marine derived fungi Aspergillus brunneoviolaceus with their antibacterial and antioxidant activities.

RESULTS

The biosynthesis of silver nanoparticles was estimated by the change in color from light yellow to dark brown within 36 h as the reaction progressed. UV-Visible spectroscopy exhibited its stability at 411 nm; ATR-FTIR spectroscopy depicted the functional group responsible for its production; X-Ray Diffraction denoted its crystalline FCC structure resembling the peaks in XRD pattern, corresponding to [111], [200], [220], [311] and [222] planes; TEM imaging revealed its spherical morphology with the particle size ranging from 0.72 to 15.21 nm and Tauc's plot analysis that disclosed its band gap energy as 2.44 eV that manifested the potential of AgNPs to be semiconductors. The characterization data henceforth, confirmed the efficient production of silver nanoparticles. The biosynthesized AgNPs expressed strong antibacterial activity against two Gram-positive and three Gram-negative bacteria. They also proved to possess higher antioxidative potentials by showing their potent radical scavenging activity against DPPH (2, 2-diphenyl-1-picrylhydrazyl).

CONCLUSIONS

The study unfolds the prospect for further utilization of this mycogenically synthesized AgNPs as antibacterial, antioxidative and anticancer agents.

Mycogenic Metal Nanoparticles for the Treatment of Mycobacterioses

Mycobacterial infections are a resurgent and increasingly relevant problem. Within these, tuberculosis (TB) is particularly worrying as it is one of the top ten causes of death in the world and is the infectious disease that causes the highest number of deaths. A further concern is the on-going emergence of antimicrobial resistance, which seriously limits treatment. The COVID-19 pandemic has worsened current circumstances and future infections will be more incident. It is urgent to plan, draw solutions, and act to mitigate these issues, namely by exploring new approaches. The aims of this review are to showcase the extensive research and application of silver nanoparticles (AgNPs) and other metal nanoparticles (MNPs) as antimicrobial agents. We highlight the advantages of mycogenic synthesis, and report on their underexplored potential as agents in the fight against all mycobacterioses (non-tuberculous mycobacterial infections as well as TB). We propose further exploration of this field.

Synthesis and characterization of microbial mediated cadmium oxide nanoparticles

Microbial mediated synthesis of metallic nanoparticles constitutes as effective and promising approach for the development of antibacterial materials in the field of bioengineering and biomedicine. We prepared Cadmium oxide nanoaprticles (CdO NPs) utilizing Penicillium oxalicum, and cadmium acetate solution via coprecipitate method. The elemental composition and morphology of these synthesized CdO NPs were examined through X-ray diffraction (XRD), UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy dispersive spectroscopy (EDS). Furthermore, we evaluated the bactericidal potential of prepared CdO NPs using Escherichia coli (E.coli), Staphylococcus aureus (S.aureus), Bacillus cereus (B.cereus), and Pseudomonas aeruginosa (P. aeruginosa). Dimethyl sulfoxide was used as negative control while erythromycin was used as positive control. The XRD spectrum revealed cubic crystalline nanoparticles with 22.94 nm size and UV showed absorbance peak at 297 nm with 2.5 eV band gap energy. FTIR depicted O─H and carboxylic groups along with CdO stretching vibration. EDS showed the presence of organic compounds on Cd and O over NPs surface. SEM results revealed the spherical shape of the CdO NPs. The synthesized NPs exhibited highly potent bactericidal activity against selected strains and demonstrated less optical density of 0.086 after 24 hr. Owing to the significant antibacterial activity of CdO NPs, the broad application prospects of these nanoparticles CdO NPs in extensive biomedical applications is indicated.

In-vitro anticancer activity against Caco-2 cell line of colloidal nano silver synthesized using aqueous extract of Eucalyptus Camaldulensis leaves

In the current study, we investigated the anticancer potential against human colon cells (Caco-2) of colloidal nanosilver (CN-Ag) produced in Syria using bioactive compounds in the aqueous extract of Eucalyptus camaldulensis leaves (AEECL). The formation of AgNPs was confirmed by UV-visible spectroscopy analysis with surface plasmon peak at 449 nm and their average size was found to be 12, 10, 23 nm by SEM, DLS and NTA respectively. This small size has confirmed the effective role of AEECL as capping agent. Further morphological characterization was done by EDS showed the presence of metallic silver. Zeta potential value (-23 mV) indicated the repulsion among the particles and stability of the formulation nanosilver. The anticancer effect of synthesized CN-Ag against Caco-2 has been tested. The cytotoxicity assay showed a dose-dependent and a time-dependent effect of CN-Ag. The high cytotoxicity of CN-Ag at low concentration (5μ/mL) open new prospects for the development of novel therapeutic approaches against human colon cancer Caco-2.

Evaluation of biosynthesis parameters, stability and biological activities of silver nanoparticles synthesized by Cornus Officinalis extract under 365 nm UV radiation

Since silver nanoparticles (AgNPs) synthesized by using plant extracts revealed varied biological activities, the green synthesis of AgNPs has attracted considerable attention. Although the green synthesis of AgNPs have been accomplished by using the extracts of Cornus Officinalis, which is a traditional Chinese medicine and exhibits a wide spectrum of phytochemicals. The effects of biosynthesis parameters on reducing reaction, stability and more broad biological activities of so-prepared AgNPs did not been evaluated. In this paper, we firstly assessed the effects of UV radiation, pH, material proportion and radiation times on the green synthesis of AgNPs under 365 nm UV radiation by UV-visible spectrum and dynamic light scattering (DLS) analysis. The results showed that UV radiation could accelerate the formation of AgNPs and influence the average size below pH 7.0, and the size of so-prepared AgNPs were sensitive to the pH and material proportion, but no obvious changes to UV radiation times, offering a size-controlled synthetic method for AgNPs. The further X-ray diffraction (XRD), transmission electron microscopy (TEM) and DLS studies showed AgNPs synthesized at pH 7.0, extract: AgNO₃ = 1 : 1 and after 4 h UV radiation were a face-centered cubic (fcc) structure and both spherical and polygonal in shape with average particle size of 64.5 ± 0.3 nm existed in a monodispersed form. Subsquently, the stability of AgNPs was analyzed by zeta potential (-24.8 mV) and the average size measurement after 30 days storage (63.3 ± 0.4 nm), revealing a high degree of stability. Lastly, the investigation of biological activities showed that the biosynthesized AgNPs had potent antioxidant activity, antimicrobial activity against both S. aureus and E. coli as well as anticancer activity against HCT116 and HepG2 cell lines but negligible cytotoxicity against SW620. And the internalization of biosynthesized AgNPs inside the bacterial cell was evaluated by flow cytometric analysis, where the SSC values have significant increase after treating with nanoparticles. These results confirmed that the biosynthesis parameters on the green synthesis of AgNPs by using Cornus Officinalis extract also played pivotal roles and so-prepared AgNPs would be useful for the development of new alternative antioxidant, antimicrobial and anticancer agents in biomedicine.

Advancements in Plant and Microbe-Based Synthesis of Metallic Nanoparticles and Their Antimicrobial Activity against Plant Pathogens

A large number of metallic nanoparticles have been successfully synthesized by using different plant extracts and microbes including bacteria, fungi viruses and microalgae. Some of these metallic nanoparticles showed strong antimicrobial activities against phytopathogens. Here, we summarized these green-synthesized nanoparticles from plants and microbes and their applications in the control of plant pathogens. We also discussed the potential deleterious effects of the metallic nanoparticles on plants and beneficial microbial communities associated with plants. Overall, this review calls for attention regarding the use of green-synthesized metallic nanoparticles in controlling plant diseases and clarification of the risks to plants, plant-associated microbial communities, and environments before using them in agriculture.

Skirmishing MDR strain of Candida albicans by effective antifungal CeO2 nanostructures using Aspergillus terreus and Talaromyces purpurogenus

Emerging antibiotics resistance fungal infectionsis a major global health problem and new antifungal formulations are direly needed to fight drug resistant Candida albicans strains. This study is aimed to synthesize effective antifungal nanostructures of cerium oxide (CeO2) using culture filtrates of two common fungal strains Aspergillus terreus and Talaromyces pupureogenus. The fungal strains used in the synthesis were identified by 18S rRNA gene sequencing and deposited to NCBI GenBank with the accession number of MN099077 and MN121629, respectively. The biofabricated CeO2 NPs were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Pure CeO2 nanoparticles (NPs) synthesized using Aspergillus terreus culture filtrate were depicted spherical morphology with average size of 28.5 nm. The CeO2NPs synthesized using Talaromyces pupureogenus revealed the presence of nanosponges with average size of 21.4 nm. Gas chromatography mass spectrometry of culture filtrates of respective strains indicated the presence of ethanol, 1-propanol and tri-chloromethane in culture filtrate of Aspergillus terreus and with addition of palmitic acid in Talaromyces pupureogenus culture filtrate which may have a function as bio reducers and capping agents. Dose dependent anticandidal activity of CeO2 NPs using various different concentrations (100, 200, 300, 600 μg ml−1) synthesized by both fungal strains was observed by disc diffusion assay against Candida albicansas evidenced by increase in size of zone of inhibitions with increasing concentration of CeO2NPs. Further in-vitro and in-vivo experiments are required to access the potential of CeO2 NPs for controlling Candida albicans strains.

Omics-Based Mechanistic Insight Into the Role of Bioengineered Nanoparticles for Biotic Stress Amelioration by Modulating Plant Metabolic Pathways

Bioengineered silver nanoparticles can emerge as a facile approach to combat plant pathogen, reducing the use of pesticides in an eco-friendly manner. The plants' response during tripartite interaction of plant, pathogen, and nanoparticles remains largely unknown. This study demonstrated the use of bioengineered silver nanoparticles in combating black spot disease caused by necrotrophic fungus Alternaria brassicicola in Arabidopsis thaliana via foliar spray. The particles reduced disease severity by 70-80% at 5 μg/ml without showing phytotoxicity. It elicited plant immunity by a significant reduction in reactive oxygen species (ROS), decreases in stress enzymes by 0.6-19.8-fold, and emergence of autophagy. Comparative plant proteomics revealed 599 proteins expressed during the interaction, where 117 differential proteins were identified. Among different categories, proteins involved in bioenergy and metabolism were most abundant (44%), followed by proteins involved in plant defense (20%). Metabolic profiling by gas chromatography-mass spectroscopy yielded 39 metabolite derivatives in non-polar fraction and 25 in the polar fraction of plant extracts. It was observed that proteins involved in protein biogenesis and early plant defense were overexpressed to produce abundant antimicrobial metabolites and minimize ROS production. Bioengineered silver nanoparticles performed dual functions to combat pathogen attack by killing plant pathogen and eliciting immunity by altering plant defense proteome and metabolome.

Green Chemistry Synthesis of Silver Nanoparticles and Their Potential Anticancer Effects

Nanobiotechnology has grown rapidly and become an integral part of modern disease diagnosis and treatment. Biosynthesized silver nanoparticles (AgNPs) are a class of eco-friendly, cost-effective and biocompatible agents that have attracted attention for their possible biomedical and bioengineering applications. Like many other inorganic and organic nanoparticles, such as AuNPs, iron oxide and quantum dots, AgNPs have also been widely studied as components of advanced anticancer agents in order to better manage cancer in the clinic. AgNPs are typically produced by the action of reducing reagents on silver ions. In addition to numerous laboratory-based methods for reduction of silver ions, living organisms and natural products can be effective and superior source for synthesis of AgNPs precursors. Currently, plants, bacteria and fungi can afford biogenic AgNPs precursors with diverse geometries and surface properties. In this review, we summarized the recent progress and achievements in biogenic AgNPs synthesis and their potential uses as anticancer agents.

Biogenic Metal Nanoparticles: A New Approach to Detect Life on Mars?

Metal nanoparticles (MNPs) have been extensively studied. They can be produced via different methods (physical, chemical, or biogenic), but biogenic synthesis has become more relevant, mainly for being referred by many as eco-friendly and more advantageous than others. Biogenic MNPs have been largely used in a wide variety of applications, from industry, to agriculture, to health sectors, among others. Even though they are increasingly researched and used, there is still space for exploring further applications and increasing their functionality and our understanding of their synthesis process. Here, we provide an overview of MNPs and biogenic MNPs, and we analyze the potential application of their formation process to astrobiology and the detection of life on Mars and other worlds. According to current knowledge, we suggest that they can be used as potential biosignatures in extra-terrestrial samples. We present the advantages and disadvantages of this approach, suggest further research, and propose its potential use for the search for life in future space exploration.

Nanoparticles as Anti-Microbial, Anti-Inflammatory, and Remineralizing Agents in Oral Care Cosmetics: A Review of the Current Situation

Many investigations have pointed out widespread use of medical nanosystems in various domains of dentistry such as prevention, prognosis, care, tissue regeneration, and restoration. The progress of oral medicine nanosystems for individual prophylaxis is significant for ensuring bacterial symbiosis and high-quality oral health. Nanomaterials in oral cosmetics are used in toothpaste and other mouthwash to improve oral healthcare performance. These processes cover nanoparticles and nanoparticle-based materials, especially domains of application related to biofilm management in cariology and periodontology. Likewise, nanoparticles have been integrated in diverse cosmetic produces for the care of enamel remineralization and dental hypersensitivity. This review summarizes the indications and applications of several widely employed nanoparticles in oral cosmetics, and describes the potential clinical implementation of nanoparticles as anti-microbial, anti-inflammatory, and remineralizing agents in the prevention of dental caries, hypersensitivity, and periodontitis.