Extracellular synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 and their biological applications

Potentials of roots, stems, leaves, flowers, fruits, and seeds extract for the synthesis of silver nanoparticles

Silver nanoparticles (AgNPs) have gained significant attention in various applications due to their unique properties that differ from bulk or macro-sized counterparts. In the advancement of nanotechnology, a reliable, non-toxic, and eco-friendly green synthesis has widely been developed as an alternative method for the production of AgNPs, overcoming limitations associated with the traditional physical and chemical methods. Green synthesis of AgNPs involves the utilization of biological sources including plant extracts with silver salt as the precursor. The potential of phytochemicals in plant extracts serves as a reducing/capping and stabilizing agent to aid in the bio-reduction of Ag+ ions into a stable nanoform, Ag0. This review provides insights into the potentials of various plant parts like root, stem, leaf, flower, fruit, and seed extracts that have been extensively reported for the synthesis of AgNPs.

Nanomaterial in controlling biofilms and virulence of microbial pathogens

The escalating threat of antimicrobial resistance (AMR) poses a grave concern to global public health, exacerbated by the alarming shortage of effective antibiotics in the pipeline. Biofilms, intricate populations of bacteria encased in self-produced matrices, pose a significant challenge to treatment, as they enhance resistance to antibiotics and contribute to the persistence of organisms. Amid these challenges, nanotechnology emerges as a promising domain in the fight against biofilms. Nanomaterials, with their unique properties at the nanoscale, offer innovative antibacterial modalities not present in traditional defensive mechanisms. This comprehensive review focuses on the potential of nanotechnology in combating biofilms, focusing on green-synthesized nanoparticles and their associated anti-biofilm potential. The review encompasses various aspects of nanoparticle-mediated biofilm inhibition, including mechanisms of action. The diverse mechanisms of action of green-synthesized nanoparticles offer valuable insights into their potential applications in addressing AMR and improving treatment outcomes, highlighting novel strategies in the ongoing battle against infectious diseases.

A review of microbes mediated biosynthesis of silver nanoparticles and their enhanced antimicrobial activities

In recent decades, biosynthesis of metal and (or) metal oxide nanoparticles using microbes is accepted as one of the most sustainable, cost-effective, robust, and green processes as it does not encompass the usage of largely hazardous chemicals. Accordingly, numerous simple, inexpensive, and environmentally friendly approaches for the biosynthesis of silver nanoparticles (AgNPs) were reported using microbes avoiding conventional (chemical) methods. This comprehensive review detailed an advance made in recent years in the microbes-mediated biosynthesis of AgNPs and evaluation of their antimicrobial activities covering the literature from 2015-till date. It also aimed at elaborating the possible effect of the different phytochemicals, their concentrations, extraction temperature, extraction solvent, pH, reaction time, reaction temperature, and concentration of precursor on the shape, size, and stability of the synthesized AgNPs. In addition, while trying to understand the antimicrobial activities against targeted pathogenic microbes the probable mechanism of the interaction of produced AgNPs with the cell wall of targeted microbes that led to the cell's reputed and death have also been detailed. Lastly, this review detailed the shape and size-dependent antimicrobial activities of the microbes-mediated AgNPs and their enhanced antimicrobial activities by synergetic interaction with known commercially available antibiotic drugs.

Recent Advancements in Metallic Au- and Ag-Based Chitosan Nanocomposite Derivatives for Enhanced Anticancer Drug Delivery

The rapid advancements in nanotechnology in the field of nanomedicine have the potential to significantly enhance therapeutic strategies for cancer treatment. There is considerable promise for enhancing the efficacy of cancer therapy through the manufacture of innovative nanocomposite materials. Metallic nanoparticles have been found to enhance the release of anticancer medications that are loaded onto them, resulting in a sustained release, hence reducing the dosage required for drug administration and preventing their buildup in healthy cells. The combination of nanotechnology with biocompatible materials offers new prospects for the development of advanced therapies that exhibit enhanced selectivity, reduced adverse effects, and improved patient outcomes. Chitosan (CS), a polysaccharide possessing distinct physicochemical properties, exhibits favorable attributes for controlled drug delivery due to its biocompatibility and biodegradability. Chitosan nanocomposites exhibit heightened stability, improved biocompatibility, and prolonged release characteristics for anticancer medicines. The incorporation of gold (Au) nanoparticles into the chitosan nanocomposite results in the manifestation of photothermal characteristics, whereas the inclusion of silver (Ag) nanoparticles boosts the antibacterial capabilities of the synthesized nanocomposite. The objective of this review is to investigate the recent progress in the utilization of Ag and Au nanoparticles, or a combination thereof, within a chitosan matrix or its modified derivatives for the purpose of anticancer drug delivery. The research findings for the potential of a chitosan nanocomposite to deliver various anticancer drugs, such as doxorubicin, 5-Fluroacil, curcumin, paclitaxel, and 6-mercaptopurine, were investigated. Moreover, various modifications carried out on the chitosan matrix phase and the nanocomposite surfaces to enhance targeting selectivity, loading efficiency, and pH sensitivity were highlighted. In addition, challenges and perspectives that could motivate further research related to the applications of chitosan nanocomposites in cancer therapy were summarized.

Exploring the potential of a Ephedra alata leaf extract: Phytochemical analysis, antioxidant activity, antibacterial properties, and green synthesis of ZnO nanoparticles for photocatalytic degradation of methylene blue

Ephedra alata leaf extracts have therapeutic properties and contain various natural compounds known as phytochemicals. This study assessed the phytochemical content and antioxidant effects of a Ephedra alata leaf extract, as well as zinc oxide (ZnO) nanoparticle production. The extract contained phenolic acids, including vanillic acid, chlorogenic acid, gallic acid, p-coumaric acid, vanillin and rutin. Its total phenolic content and total flavonoid content were 48.7 ± 0.9 mg.g-1 and 1.7 ± 0.4 mg.g-1, respectively. The extract displayed a DPPH inhibition rate of 70.5%, total antioxidant activity of 49.5 ± 3.4 mg.g-1, and significant antimicrobial activity toward Gram-positive and negative bacteria. The synthesized ZnO nanoparticles had spherical shape, crystallite size of 25 nm, particle size between 5 and 30 nm, and bandgap energy of 3.3 eV. In specific conditions (90 min contact time, pH 7, and 25°C), these nanoparticles efficiently photodegraded 87% of methylene blue, suggesting potential applications for sustainable water treatment and pollution control.

Smart nanoparticles for cancer therapy

Smart nanoparticles, which can respond to biological cues or be guided by them, are emerging as a promising drug delivery platform for precise cancer treatment. The field of oncology, nanotechnology, and biomedicine has witnessed rapid progress, leading to innovative developments in smart nanoparticles for safer and more effective cancer therapy. In this review, we will highlight recent advancements in smart nanoparticles, including polymeric nanoparticles, dendrimers, micelles, liposomes, protein nanoparticles, cell membrane nanoparticles, mesoporous silica nanoparticles, gold nanoparticles, iron oxide nanoparticles, quantum dots, carbon nanotubes, black phosphorus, MOF nanoparticles, and others. We will focus on their classification, structures, synthesis, and intelligent features. These smart nanoparticles possess the ability to respond to various external and internal stimuli, such as enzymes, pH, temperature, optics, and magnetism, making them intelligent systems. Additionally, this review will explore the latest studies on tumor targeting by functionalizing the surfaces of smart nanoparticles with tumor-specific ligands like antibodies, peptides, transferrin, and folic acid. We will also summarize different types of drug delivery options, including small molecules, peptides, proteins, nucleic acids, and even living cells, for their potential use in cancer therapy. While the potential of smart nanoparticles is promising, we will also acknowledge the challenges and clinical prospects associated with their use. Finally, we will propose a blueprint that involves the use of artificial intelligence-powered nanoparticles in cancer treatment applications. By harnessing the potential of smart nanoparticles, this review aims to usher in a new era of precise and personalized cancer therapy, providing patients with individualized treatment options.

Evaluation of the biological responses of silver nanoparticles synthesized using Pelargonium x hortorum extract

Silver nanoparticles (AgNPs) are one of the widely studied nanomaterials for diverse biomedical applications, in particular, as antimicrobial agents to kill bacteria, fungi, and viruses. In this report, AgNPs were synthesized using a geranium (Pelargonium x hortorum) leaves extract and tested for their antimicrobial and cytotoxic activity and reactive oxygen species (ROS) production. Using green biosynthesis, the leaves extract was employed as a reducing and stabilizing agent. Synthesis parameters like reaction time and precursor (silver nitrate AgNO3) volume final were modified, and the products were tested against Streptococcus mutans. For the first time, the metabolomic analysis of extract, we have identified more than 50 metabolites. The UV-Vis analysis showed a peak ranging from 410-430 nm, and TEM confirmed their nearly spherical morphology for all NPs. The antimicrobial activity of the NPs revealed a minimum inhibitory concentration (MIC) of 10 μg mL-1. Concerning cytotoxicity, a dose-time-dependent effect was observed with a 50% cellular cytotoxicity concentration (CC50) of 4.51 μg mL-1 at 24 h. Interestingly, the cell nuclei were visualized using fluorescence microscopy, and no significant changes were observed. These results suggest that synthesized spherical AgNPs are promising potential candidates for medical applications.

Exploring the cytotoxicity on human lung cancer cells and DNA binding stratagem of camptothecin functionalised silver nanoparticles through multi-spectroscopic, and calorimetric approach

The influence of nanoparticles inside the human body and their interactions with biological macromolecules need to be explored/studied prior to specific applications. The objective of this study is to find the potential of camptothecin functionalised silver nanoparticles (CMT-AgNPs) in biomedical applications. This article primarily investigates the binding stratagem of CMT-AgNPs with calf thymus DNA (ctDNA) through a series of spectroscopic and calorimetric methods and then analyses the anticancer activity and cytotoxicity of CMT-AgNPs. The nanoparticles were synthesized using a simple one pot method and characterized using UV-Visible, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). The average size of CMT-AgNPs is 10 ± 2 nm. A group of experimental techniques such as UV-Visible spectrophotometry, fluorescence dye displacement assay, circular dichroism (CD) and viscosity analysis unravelled the typical groove binding mode of CMT-AgNPs with ctDNA. The CD measurement evidenced the minor conformational alterations of double helical structure of ctDNA in the presence of CMT-AgNPs. The information deduced from the isothermal titration calorimetry (ITC) experiment is that the binding was exothermic and spontaneous in nature. Moreover, all the thermodynamic binding parameters were extracted from the ITC data. The binding constants obtained from UV absorption experiments, fluorescence dye displacement studies and ITC were consistently in the order of 10⁴ Mol^-1. All these results validated the formation of CMT-AgNPs-ctDNA complex and the results unambiguously confirm the typical groove binding mode of CMT-AgNPs. An exhaustive in vitro MTT assay by CMT-AgNPs and CMT against A549, HT29, HeLa and L929 cell lines revealed the capability of CMT-AgNPs as a potential anticancer agent.

Nanovesicle and extracellular polymeric substance synthesis from the remediation of heavy metal ions from soil

Heavy metal toxicity affects aquatic plants and animals, disturbing biodiversity and ecological balance causing bioaccumulation of heavy metals. Industrialization and urbanization are inevitable in modern-day life, and control and detoxification methods need to be accorded to meet the hazardous environment. Microorganisms and plants have been widely used in the bioremediation of heavy metals. Sporosarcina pasteurii, a gram-positive bacterium that is widely known for its calcite precipitation property in bio-cementing applications has been explored in the study for its metal tolerance ability for the first time. S. pasteurii SRMNP1 (KF214757) can tolerate silver stress to form nanoparticles and can remediate multiple heavy metals to promote the growth of various plants. This astounding property of the isolate warranted extensive examinations to comprehend the physiological changes during an external heavy metal stress condition. The present study aimed to understand various physiological responses occurring in S. pasteuriiSRMNP1 during the metal tolerance phenomenon using electron microscopy. The isolate was subjected to heavy metal stress, and a transmission electron microscope examination was used to analyze the physiological changes in bacteria to evade the metal stress. S. pasteurii SRMNP1 was tolerant against a wide range of heavy metal ions and can withstand a broad pH range (5-9). Transmission Electron Microscopy (TEM) examination of S. pasteurii SRMNP1 followed by 5 mM nickel sulfate treatment revealed the presence of nanovesicles encapsulating nanosized particles in intra and extracellular spaces. This suggests that the bacteria evade the metal stress by converting the metal ions into nanosized particles and encapsulating them within nanovesicles to efflux them through the vesicle budding mechanism. Moreover, the TEM images revealed an excessive secretion of extracellular polymeric substances by the strain to discharge the metal particles outside the bacterial system. S. pasteurii can be foreseen as an effective bioremediation agent with the potential to produce nanosized particles, nanovesicles, and extracellular polymeric substances. This study provides physiological evidence that, besides calcium precipitation applications, S. pasteurii can further be explored for its multidimensional roles in the fields of drug delivery and environmental engineering.

Biosynthesis of Silver and Gold Nanoparticles and Their Efficacy Towards Antibacterial, Antibiofilm, Cytotoxicity, and Antioxidant Activities

The World Health Organization (WHO) reports that the emergence of multidrug-resistant and the slow advent of novel and more potent antitumor and antimicrobial chemotherapeutics continue to be of the highest concern for human health. Additionally, the stability, low solubility, and negative effects of existing drugs make them ineffective. Studies into alternative tactics to tackle such tenacious diseases was sparked by anticancer and antibacterial. Silver (Ag) and gold (Au) nanoparticles (NPs) were created from Trichoderma saturnisporum, the much more productive fungal strain. Functional fungal extracellular enzymes and proteins carried out the activities of synthesis and capping of the generated nano-metals. Characterization was done on the obtained Ag-NPs and Au-NPs through UV-vis, FTIR, XRD, TEM, and SEM. Additionally, versus methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Klebsiella pneumoniae, the antibacterial activities of Ag-NPs and Au-NPs were assessed. In particular, the Ag-NPs were more effective against pathogenic bacteria than Au-NPs. Furthermore, antibiofilm study that shown Au-NPs had activity more than Ag-NPs. Interestingly, applying the DPPH procedure, these noble metallic NPs had antioxidant activity, in which the IC₅₀ for Ag-NPs and Au-NPs was 73.5 μg/mL and 190.0 μg/mL, respectively. According to the cytotoxicity evaluation results, the alteration in the cells was shown as loss of their typical shape, partial or complete loss of monolayer, granulation, shrinking, or cell rounding with IC₅₀ for normal Vero cell were 693.68 μg/mL and 661.24 μg/mL, for Ag-NPs and Au-NPs, respectively. While IC₅₀ for cancer cell (Mcf7) was 370.56 μg/mL and 394.79 μg/mL for Ag-NPs and Au-NPs, respectively. Ag-NPs and Au-NPs produced via green synthesis have the potential to be employed in the medical industry as beneficial nanocompounds.

Synthesis of Trimetallic (Ni-Cu)@Ag Core@Shell Nanoparticles without Stabilizing Materials for Antibacterial Applications

We report a simple method to prepare colloidal trimetallic (Ni-Cu)@Ag core@shell nanoparticles (NPs) without stabilizing materials. Experimental evidence was found for the successful synthesis of these NPs using X-ray diffraction (XRD), optical spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The presence of core metals (Ni and Cu) was confirmed by elemental analysis using a total reflection X-ray fluorescence (TXRF) analysis. In addition, the absorption spectra of the prepared samples exhibited broad bands compared to the bands of the monometallic NPs, indicating the formation of a core-shell nanostructure. The antibacterial activity of the trimetallic NPs was evaluated against three Gram-negative (Pseudomonas aeruginosa, Escherichia coli, and Salmonella) and two Gram-positive (Streptococcus and Staphylococcus aureus) bacteria on Mueller-Hinton agar. These NPs showed high inhibition of bacterial growth at the low sample concentrations used in this study compared to other nanomaterials. One of the interesting results of the current study is that the inhibition zone of Pseudomonas aeruginosa as a resistant bacterium was high for most NPs. These results make the prepared samples promising candidates for antibiotic material applications.

Mechanistic and recent updates in nano-bioremediation for developing green technology to alleviate agricultural contaminants

The rise in environmental pollutant levels in recent years is mostly attributable to anthropogenic activities such as industrial, agricultural and other activities. Additionally, these activities may produce excessive levels of dangerous toxicants such as heavy metals, organic pollutants including pesticide and herbicide chemicals, and sewage discharges from residential and commercial sources. With a focus on environmentally friendly, sustainable technology, new technologies such as combined process of nanotechnology and bioremediation are urgently needed to accelerate the cost-effective remediation process to alleviate toxic contaminants than the conventional remediation methods. Numerous studies have shown that nanoparticles possess special qualities including improved catalysis and adsorption as well as increased reactivity. Currently, microorganisms and their extracts are being used as promising, environmentally friendly catalysts for engineered nanomaterial. In the long term, this combination of both technologies called nano-bioremediation may significantly alter the field of environmental remediation since it is more intelligent, safe, environmentally friendly, economical and green. This review provides an overview of soil and water remediation techniques as well as the use of nano-bioremediation, which is made from various living organisms. Additionally, current developments related to the mechanism, model and kinetic studies for remediation of agricultural contaminants have been discussed.

Comparing the Anticancer Activities of Green-Synthesized Ginsenoside and Transformed Ginsenoside Nanoconjugates (Ag, Au, and Pt)

Aim: To assess the anticancer activity of nanoparticles synthesized via a green method using American ginseng (AG). Methods: Stem-leaf saponins from AG (SAG) and heat-transformed stem-leaf saponins from AG (TSAG) were used to synthesize different SAG nanoparticles (SAG-NPs) and TSAG nanoparticles (TSAG-NPs). The NPs were characterized, and their anticancer activity was assessed in vitro. Results: The NPs, which differed in size (16.69 nm∼253.8 nm), were spherical or polyhedral with a low PDI and good stability. The TSAG-NPs inhibited cancer cells by inhibiting proliferation, promoting cancer cell apoptosis and directly leading cancer cells to necrosis. The small cell lung cancer cell line (SCLC) NCI-H446 was the most sensitive to the TSAG-AgNPs, with an IC50 value of 20.71±2.38 μg/mL, and the TSAG-AgNPs inhibited invasiveness and reduced the risk of metastasis. Conclusion: TSAG-AgNPs, selected from many SAG-NPs and TSAG-NPs, are sensitive to SCLC and provide a new approach to the currently limited treatment.

Green Chemistry Based Gold Nanoparticles Synthesis Using the Marine Bacterium Lysinibacillus odysseyi PBCW2 and Their Multitudinous Activities

Green chemistry has paved an 'avant-garde avenue' in the production and fabrication of eco-friendly stable nanoparticles employing the utilization of biological agents. In the present study we present the first report on the potential of the marine bacterium Lysinibacillus odysseyi PBCW2 for the extracellular production of gold nanoparticles (AuNPs). Utilizing a variety of methods, AuNPs in the cell-free supernatant of L. odysseyi (CFS-LBOE) were identified and their antioxidant, antibacterial, and dye-degrading properties were examined. The visual coloring of the reaction mixture to a ruby red hue showed the production of LBOE-AuNPs; validated by means of XRD, TEM, SEM, XRD, DLS, TGA, and FT-IR analysis. Additionally, the 2,2-diphenyl-1-picrylhydrazyl technique and the well diffusion assay were used to examine their dose-dependent antioxidant and antibacterial activity. These biogenic LBOE-AuNPs showed 91% dye degradation efficiency during catalytic reduction activity on BTB dye, demonstrating their versatility as options for heterogeneous catalysis.

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 antibacterial applications of gold and silver nanoparticles from Ligustrum vulgare berries

Increasing demand for green or biological nanoparticles has led to various green technologies and resources, which play a critical role in forming biocompatible or green nanoparticles. So far, numerous medicinal plants have been explored for this purpose, assuming that medicinal components from the plant's material will contribute to corona formation around nanoparticles and enhance their efficacy. Research is also extended to other green and waste resources to be utilized for this purpose. In the current study, we explored Ligustrum vulgare berries, also known as privet berries, to reduce gold and silver salts into nanoparticles. L. vulgare berries showed great potential to form these nanoparticles, as gold nanoparticles (LV-AuNPs) formed within 5 min at room temperature, and silver nanoparticles (LV-AgNPs) formed in 15 min at 90 °C. LV-AuNPs and LV-AgNPs were characterized by various analytical methods, including UV–Vis, SEM, EDX, TEM, DLS, sp-ICP-MS, TGA, FT-IR, and MALDI-TOF. The results demonstrate that the LV-AuNPs are polydisperse in appearance with a size range 50–200 nm. LV-AuNPs exhibit various shapes, including spherical, triangular, hexagonal, rod, cuboid, etc. In contrast, LV-AgNPs are quite monodisperse, 20–70 nm, and most of the population was spherical. The nanoparticles remain stable over long periods and exhibit high negative zeta potential values. The antimicrobial investigation of LV-AgNPs demonstrated that the nanoparticles exhibit antibacterial ability with an MBC value of 150 g/mL against P. aeruginosa and 100 g/mL against E. coli, as determined by plate assay, live and dead staining, and SEM cell morphology analysis.

Biogenic Silver Nanoparticles Strategically Combined With Origanum vulgare Derivatives: Antibacterial Mechanism of Action and Effect on Multidrug-Resistant Strains

Multidrug-resistant bacteria have become a public health problem worldwide, reducing treatment options against several pathogens. If we do not act against this problem, it is estimated that by 2050 superbugs will kill more people than the current COVID-19 pandemic. Among solutions to combat antibacterial resistance, there is increasing demand for new antimicrobials. The antibacterial activity of binary combinations containing bioAgNP (biogenically synthesized silver nanoparticles using Fusarium oxysporum), oregano essential oil (OEO), carvacrol (Car), and thymol (Thy) was evaluated: OEO plus bioAgNP, Car plus bioAgNP, Thy plus bioAgNP, and Car plus Thy. This study shows that the mechanism of action of Thy, bioAgNP, and Thy plus bioAgNP involves damaging the membrane and cell wall (surface blebbing and disruption seen with an electron microscope), causing cytoplasmic molecule leakage (ATP, DNA, RNA, and total proteins) and oxidative stress by enhancing intracellular reactive oxygen species and lipid peroxidation; a similar mechanism happens for OEO and Car, except for oxidative stress. The combination containing bioAgNP and oregano derivatives, especially thymol, shows strategic antibacterial mechanism; thymol disturbs the selective permeability of the cell membrane and consequently facilitates access of the nanoparticles to bacterial cytoplasm. BioAgNP-treated Escherichia coli developed resistance to nanosilver after 12 days of daily exposition. The combination of Thy and bioAgNP prevented the emergence of resistance to both antimicrobials; therefore, mixture of antimicrobials is a strategy to extend their life. For antimicrobials alone, minimal bactericidal concentration ranges were 0.3-2.38 mg/ml (OEO), 0.31-1.22 mg/ml (Car), 0.25-1 mg/ml (Thy), and 15.75-31.5 μg/ml (bioAgNP). The time-kill assays showed that the oregano derivatives acted very fast (at least 10 s), while the bioAgNP took at least 30 min to kill Gram-negative bacteria and 7 h to kill methicillin-resistant Staphylococcus aureus (MRSA). All the combinations resulted in additive antibacterial effect, reducing significantly minimal inhibitory concentration and acting faster than the bioAgNP alone; they also showed no cytotoxicity. This study describes for the first time the effect of Car and Thy combined with bioAgNP (produced with F. oxysporum components) against bacteria for which efficient antimicrobials are urgently needed, such as carbapenem-resistant strains (E. coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa) and MRSA.

Probiotic-Mediated Biosynthesis of Silver Nanoparticles and Their Antibacterial Applications against Pathogenic Strains of Escherichia coli O157:H7

The present study aimed to suggest a simple and environmentally friendly biosynthesis method of silver nanoparticles (AgNPs) using the strain Bacillus sonorensis MAHUQ-74 isolated from kimchi. Antibacterial activity and mechanisms of AgNPs against antibiotic-resistant pathogenic strains of Escherichia coli O157:H7 were investigated. The strain MAHUQ-74 had 99.93% relatedness to the B. sonorensis NBRC 101234^T strain. The biosynthesized AgNPs had a strong surface plasmon resonance (SPR) peak at 430 nm. The transmission electron microscope (TEM) image shows the spherical shape and size of the synthesized AgNPs is 13 to 50 nm. XRD analysis and SAED pattern revealed the crystal structure of biosynthesized AgNPs. Fourier transform infrared spectroscopy (FTIR) data showed various functional groups associated with the reduction of silver ions to AgNPs. The resultant AgNPs showed strong antibacterial activity against nine E. coli O157:H7 pathogens. Minimum inhibitory concentration (MIC) values of the AgNPs synthesized by strain MAHUQ-74 were 3.12 μg/mL for eight E. coli O157:H7 strains and 12.5 μg/mL for strain E. coli ATCC 25922. Minimum bactericidal concentrations (MBCs) were 25 μg/mL for E. coli O157:H7 ATCC 35150, E. coli O157:H7 ATCC 43895, E. coli O157:H7 ATCC 43890, E. coli O157:H7 ATCC 43889, and E. coli ATCC 25922; and 50 μg/mL for E. coli O157:H7 2257, E. coli O157: NM 3204-92, E. coli O157:H7 8624 and E. coli O157:H7 ATCC 43894. FE-SEM analysis demonstrated that the probiotic-mediated synthesized AgNPs produced structural and morphological changes and destroyed the membrane integrity of pathogenic E. coli O157:H7. Therefore, AgNPs synthesized by strain MAHUQ-74 may be potential antibacterial agents for the control of antibiotic-resistant pathogenic strains of E. coli O157:H7.

Binary Effects of Gynostemma Gold Nanoparticles on Obesity and Inflammation via Downregulation of PPARγ/CEPBα and TNF-α Gene Expression

Nanoscience is a multidisciplinary skill with elucidated nanoscale particles and their advantages in applications to various fields. Owing to their economical synthesis, biocompatible nature, and widespread biomedical and environmental applications, the green synthesis of metal nanoparticles using medicinal plants has become a potential research area in biomedical research and functional food formulations. Gynostemma pentaphyllum (GP) has been extensively used in traditional Chinese medicine to cure several diseases, including diabetes mellitus (DM). This is the first study in which we examined the efficacy of G. pentaphyllum gold nanoparticles (GP-AuNPs) against obesity and related inflammation. GP extract was used as a capping agent to reduce Au²⁺ to Au⁰ to form stable gold nanoparticles. The nanoparticles were characterized by using UV–VIS spectroscopy, and TEM images were used to analyze morphology. In contrast, the existence of the functional group was measured using FTIR, and size and shape were examined using XRD analysis. In vitro analysis on GP-AuNPs was nontoxic to RAW 264.7 cells and 3T3-L1 cells up to a specific concentration. It significantly decreased lipid accumulation in 3T3-L1 obese and reduced NO production in Raw 264.7 macrophage cells. The significant adipogenic genes PPARγ and CEPBα and a major pro-inflammatory cytokine TNF-α expression were quantified using RT-PCR. The GP-AuNPs decreased the face of these genes remarkably, revealing the antiadipogenic and anti-inflammatory activity of our synthesized GP-AuNPs. This study represents thorough research on the antiobesity effect of Gynostemma pentaphyllum gold nanoparticles synthesized using a green approach and the efficacy instead of related inflammatory responses.

Green Synthesis of Gold Nanoparticles: An Eco-Friendly Approach

By virtue of their unique physicochemical properties, gold nanoparticles (AuNPs) have gained significant interest in a broad range of biomedical applications such as sensors, diagnosis, and therapy. AuNPs are generally synthesized via different conventional physical and chemical methods, which often use harmful chemicals that induce health hazards and pollute the environment. To overcome these issues, green synthesis techniques have evolved as alternative and eco-friendly approaches to the synthesis of environmentally safe and less-expensive nanoparticles using naturally available metabolites from plants and microorganisms such as bacteria, fungi, and algae. This review provides an overview of the advances in the synthesis of AuNPs using different biological resources with examples, and their profound applications in biomedicine. A special focus on the biosynthesis of AuNPs using different medicinal plants and their multifunctional applications in antibacterial, anti-inflammatory, and immune responses are featured. Additionally, the applications of AuNPs in cancer theranostics, including contrast imaging, drug delivery, hyperthermia, and cancer therapeutics, are comprehensively discussed. Moreover, this review will shed light on the importance of the green synthesis approach, and discuss the advantages, challenges, and prospects in this field.

Antibacterial Effect of Silver Nanoparticles Is Stronger If the Production Host and the Targeted Pathogen Are Closely Related

Microbial resistance to antibiotics is one of the key challenges that lead to the search for alternate antimicrobial treatment approaches. Silver nanoparticles (AgNPs) are well known for their antimicrobial effects against a wide variety of drug-resistant microorganisms. AgNPs can be synthesized using microbial hosts, using a green and economical synthesis route, which produces extremely stable and highly active nanoparticles. Such green AgNPs are coated with a biological coating often referred to as a corona, originating from the production microorganism. In this study, we asked whether the composition of the biological corona might influence the antimicrobial activity of green AgNPs. To investigate this, we produced AgNPs in Pseudomonas putida KT2440 and Escherichia coli K12 MG1655, and tested them against pathogen species from the corresponding genera. AgNPs exhibited a size range of 15-40 nm for P. putida and 30-70 nm for E. coli, and both types of nanoparticles were surrounded by a thick biological corona layer, providing extreme stability. The nanoparticles remained stable over long periods and exhibited negative zeta potential values. P-AgNPs (obtained from P. putida) were tested against pathogenic Pseudomonas aeruginosa PAO1, and E-AgNPs (obtained from E. coli) were tested against pathogenic Escherichia coli UTI 89. Antimicrobial studies were conducted by Minimum bactericidal concentration (MBC), live/dead staining and SEM analysis. MBC of P-AgNPs against P. aeruginosa was 1 μg/mL, and MBC of E-AgNPs against E. coli UTI 89 was 8 μg/mL. In both cases, the MBC values were superior to those of green AgNPs produced in organisms unrelated to the target pathogens, available in the literature. Our results suggest that NPs produced in microorganisms closely related to the target pathogen may be more effective, indicating that the composition of the biological corona may play a crucial role in the antimicrobial mechanism of AgNPs.

Strong Antimicrobial Activity of Silver Nanoparticles Obtained by the Green Synthesis in Viridibacillus sp. Extracts

Recently, green silver nanoparticles (G-AgNPs) have gained much attention in medical science due to their extraordinary effects against multidrug-resistant microorganisms. The strong antimicrobial nature of G-AgNPs corresponds to their unique physicochemical properties such as size, shape, surface charge, and active surface groups available to interact with the pathogens. The current study demonstrates a simple, environmentally friendly, and economical method to produce G-AgNPs from an environmental isolate of Viridibacillus sp. The produced G-AgNPs were characterized by various analytical methods, including UV-Vis spectroscopy, single-particle inductively coupled plasma-mass spectrometry (sp-ICP-MS), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), elemental mapping, transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA). The reduction of Ag⁺ to Ag° was observed by UV-Vis spectroscopy, which demonstrated the formation of stable G-AgNPs with a Surface Plasmon Resonance (SPR) band at the maximum of 430 nm. TEM analysis demonstrated that the G-AgNPs were spherical with a 5–30 nm size range. The produced G-AgNPs were stable for more than 1 year in an aqueous solution at 4°C. Importantly, G-AgNPs showed remarkable antimicrobial activity against Gram-negative pathogens- E. coli and P. aeruginosa with MIC values of 0.1 and 4 μg/mL and MBC values of 1 and 8 μg/mL, respectively. This level of antimicrobial activity is superior to other AgNPs reported in the literature.

Exploring Dose-Dependent Cytotoxicity Profile of Gracilaria edulis-Mediated Green Synthesized Silver Nanoparticles against MDA-MB-231 Breast Carcinoma

Green-based synthesis of metal nanoparticles using marine seaweeds is a rapidly growing technology that is finding a variety of new applications. In the present study, the aqueous extract of a marine seaweed, Gracilaria edulis, was employed for the synthesis of metallic nanoparticles without using any reducing and stabilizing chemical agents. The visual color change and validation through UV-Vis spectroscopy provided an initial confirmation regarding the Gracilaria edulis-mediated green synthesized silver nanoparticles. The dynamic light scattering studies and high-resolution transmission electron microscopy pictographs exhibited that the synthesized Gracilaria edulis-derived silver nanoparticles were roughly spherical in shape having an average size of 62.72 ± 0.25 nm and surface zeta potential of -15.6 ± 6.73 mV. The structural motifs and chemically functional groups associated with the Gracilaria edulis-derived silver nanoparticles were observed through X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopy. Further, the synthesized nanoparticles were further screened for their antioxidant properties through DPPH, hydroxyl radical, ABTS, and nitric oxide radical scavenging assays. The phycosynthesized nanoparticles exhibited dose-dependent cytotoxicity against MDA-MB-231 breast carcinoma cells having IC50 value of 344.27 ± 2.56 μg/mL. Additionally, the nanoparticles also exhibited zone of inhibition against pathogenic strains of Bacillus licheniformis (MTCC 7425), Salmonella typhimurium (MTCC 3216), Vibrio cholerae (MTCC 3904), Escherichia coli (MTCC 1098), Staphylococcus epidermidis (MTCC 3615), and Shigella dysenteriae (MTCC9543). Hence, this investigation explores the reducing and stabilizing capabilities of marine sea weed Gracilaria edulis for synthesizing silver nanoparticles in a cost-effective approach with potential anticancer and antimicrobial activity. The nanoparticles synthesized through green method may be explored for their potential utility in food preservative film industry, biomedical, and pharmaceutical industries.

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

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

Synthesis, Characterization and Biomedical Application of Silver Nanoparticles

Silver nanoparticles (AgNPs) have been employed in various fields of biotechnology due to their proven properties as an antibacterial, antiviral and antifungal agent. AgNPs are generally synthesized through chemical, physical and biological approaches involving a myriad of methods. As each approach confers unique advantages and challenges, a trends analysis of literature for the AgNPs synthesis using different types of synthesis were also reviewed through a bibliometric approach. A sum of 10,278 publications were analyzed on the annual numbers of publication relating to AgNPs and biological, chemical or physical synthesis from 2010 to 2020 using Microsoft Excel applied to the Scopus publication database. Furthermore, another bibliometric clustering and mapping software were used to study the occurrences of author keywords on the biomedical applications of biosynthesized AgNPs and a total collection of 224 documents were found, sourced from articles, reviews, book chapters, conference papers and reviews. AgNPs provides an excellent, dependable, and effective solution for seven major concerns: as antibacterial, antiviral, anticancer, bone healing, bone cement, dental applications and wound healing. In recent years, AgNPs have been employed in biomedical sector due to their antibacterial, antiviral and anticancer properties. This review discussed on the types of synthesis, how AgNPs are characterized and their applications in biomedical field.

Rowan Berries: A Potential Source for Green Synthesis of Extremely Monodisperse Gold and Silver Nanoparticles and Their Antimicrobial Property

Rowanberries (Sorbus aucuparia) are omnipresent in Europe. The medicinal importance of rowanberries is widely known and corresponds to the active ingredients present in the fruits, mainly polyphenols, carotenoids, and organic acids. In the current study, we explored rowanberries for the reduction of gold and silver salts into nanoparticles. Rowanberries-mediated gold nanoparticles (RB-AuNPs) formed within 5 s at room temperature, and silver nanoparticles (RB-AgNPs) formed in 20 min at 90 °C. The produced nanoparticles were thoroughly characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), single-particle inductively coupled plasma–mass spectrometry (sp-ICP-MS), thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FT-IR) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF). The characterization confirmed that the nanoparticles are highly monodisperse, spherical, stable over long periods, and exhibit a high negative zeta potential values. The produced RB-AuNPs and RB-AgNPs were 90–100 nm and 20–30 nm in size with a thick biological corona layer surrounding them, providing extreme stability but lowering the antimicrobial activity. The antimicrobials study of RB-AgNPs revealed that the nanoparticles have antimicrobial potential with an MBC value of 100 µg/mL against P. aeruginosa and 200 µg/mL against E. coli.

β-1,3-Glucan binding protein-based silver nanoparticles enhance the wound healing potential and disease resistance in Oreochromis mossambicus against Aeromonas hydrophilla

Here we attempted to synthesize β-1,3-glucan binding protein-based silver nanoparticles (Phβ-GBP-AgNPs) and evaluate its wound healing and disease resistance prompting ability in Oreochromis mossambicus. Using a column chromatography technique, an immune molecule, Phβ-GBP was purified from the haemolymph of rice field crab, Paratelphusa hydrodromus. Phβ-GBP-AgNPs were synthesized and described through SDS-PAGE, UV-vis spectroscopy, HR-TEM, XRD and FTIR analysis. HR-TEM revealed that the synthesized Phβ-GBP-AgNPs were spherical with a 20-40 nm size range and the particles were not aggregated. Wound and infection were experimentally generated in O. mossambicus and treated with Phβ-GBP, chem-AgNPs and Phβ-GBP-AgNPs for 20 days. The immune parameters (peroxidase, lysozyme and protease) and antioxidant enzymes (SOD and catalase) were examined in the serum of experimental fish. Phβ-GBP-AgNPs elevated the immune and antioxidant enzymes during the healing process and enhanced the wound healing percentage in fish than Phβ-GBP and chem-AgNPs. The immune parameters and antioxidant enzymes were declined in the serum of fish (treated with Phβ-GBP-AgNPs) after the mid-period of wound healing. Compared to others, relative percentage survival was increased in experimentally wounded and infected fish treated with Phβ-GBP-AgNPs against Aeromonas hydrophila. Moreover, Phβ-GBP-AgNPs exhibited less toxicity towards Artemia salina than chem-AgNPs during 24 h exposure period. As a result, Phβ-GBP-AgNPs may act as an alternative to commercial antibiotics and be considered an effective immunostimulant in treating skin lesions in intensive farming.

Biological Synthesis of Nanocatalysts and Their Applications

Over the past few decades, the synthesis and potential applications of nanocatalysts have received great attention from the scientific community. Many well-established methods are extensively utilized for the synthesis of nanocatalysts. However, most conventional physical and chemical methods have some drawbacks, such as the toxicity of precursor materials, the requirement of high-temperature environments, and the high cost of synthesis, which ultimately hinder their fruitful applications in various fields. Bioinspired synthesis is eco-friendly, cost-effective, and requires a low energy/temperature ambient. Various microorganisms such as bacteria, fungi, and algae are used as nano-factories and can provide a novel method for the synthesis of different types of nanocatalysts. The synthesized nanocatalysts can be further utilized in various applications such as the removal of heavy metals, treatment of industrial effluents, fabrication of materials with unique properties, biomedical, and biosensors. This review focuses on the biogenic synthesis of nanocatalysts from various green sources that have been adopted in the past two decades, and their potential applications in different areas. This review is expected to provide a valuable guideline for the biogenic synthesis of nanocatalysts and their concomitant applications in various fields.

Phyto-fabricated Nanoparticles and Their Anti-biofilm Activity: Progress and Current Status

Biofilm is the self-synthesized, mucus-like extracellular polymeric matrix that acts as a key virulence factor in various pathogenic microorganisms, thereby posing a serious threat to human health. It has been estimated that around 80% of hospital-acquired infections are associated with biofilms which are found to be present on both biotic and abiotic surfaces. Antibiotics, the current mainstream treatment strategy for biofilms are often found to be futile in the eradication of these complex structures, and to date, there is no effective therapeutic strategy established against biofilm infections. In this regard, nanotechnology can provide a potential platform for the alleviation of this problem owing to its unique size-dependent properties. Accordingly, various novel strategies are being developed for the synthesis of different types of nanoparticles. Bio-nanotechnology is a division of nanotechnology which is gaining significant attention due to its ability to synthesize nanoparticles of various compositions and sizes using biotic sources. It utilizes the rich biodiversity of various biological components which are biocompatible for the synthesis of nanoparticles. Additionally, the biogenic nanoparticles are eco-friendly, cost-effective, and relatively less toxic when compared to chemically or physically synthesized alternatives. Biogenic synthesis of nanoparticles is a bottom-top methodology in which the nanoparticles are formed due to the presence of biological components (plant extract and microbial enzymes) which act as stabilizing and reducing agents. These biosynthesized nanoparticles exhibit anti-biofilm activity via various mechanisms such as ROS production, inhibiting quorum sensing, inhibiting EPS production, etc. This review will provide an insight into the application of various biogenic sources for nanoparticle synthesis. Furthermore, we have highlighted the potential of phytosynthesized nanoparticles as a promising antibiofilm agent as well as elucidated their antibacterial and antibiofilm mechanism.

Biosynthesis, Characterization and Antibacterial Application of Novel Silver Nanoparticles against Drug Resistant Pathogenic Klebsiella pneumoniae and Salmonella Enteritidis

The present study highlights the biosynthesis of silver nanoparticles (AgNPs) using culture supernatant of Massilia sp. MAHUQ-52 as well as the antimicrobial application of synthesized AgNPs against multi-drug resistant pathogenic Klebsiella pneumoniae and Salmonella Enteritidis. Well-defined AgNPs formation occurred from the reaction mixture of cell-free supernatant and silver nitrate (AgNO3) solution within 48 h of incubation. UV-visible spectroscopy analysis showed a strong peak at 435 nm, which corresponds to the surface plasmon resonance of AgNPs. The synthesized AgNPs were characterized by FE-TEM, EDX, XRD, DLS and FT-IR. From FE-TEM analysis, it was found that most of the particles were spherical shape, and the size of synthesized nanoparticles (NPs) was 15-55 nm. EDX spectrum revealed a strong silver signal at 3 keV. XRD analysis determined the crystalline, pure, face-centered cubic AgNPs. FT-IR analysis identified various functional molecules that may be involved with the synthesis and stabilization of AgNPs. The antimicrobial activity of Massilia sp. MAHUQ-52 mediated synthesized AgNPs was determined using the disk diffusion method against K. pneumoniae and S. Enteritidis. Biosynthesized AgNPs showed strong antimicrobial activity against both K. pneumoniae and S. Enteritidis. The MICs of synthesized AgNPs against K. pneumoniae and S. Enteritidis were 12.5 and 25.0 μg/mL, respectively. The MBC of biosynthesized AgNPs against both pathogens was 50.0 μg/mL. From FE-SEM analysis, it was found that the AgNPs-treated cells showed morphological changes with irregular and damaged cell walls that culminated in cell death.

A concise review on the role of selenium for bone cancer applications

Cancer is one of the most challenging health problems in the world. Several clinical treatments have been developed, but all presenting several limitations. Among different types of cancer, bone cancer is less common, and limited new clinical treatment strategies have been proposed. Recently, a range of advanced materials has been investigated and applied for bone cancer treatment applications. However, due to the unique physiological properties of the bone tissue (a load-bearing tissue), the selection of the right type of material or the combination of suitable functional materials and base materials are critical. Selenium has been reported to present specific targeting inhibition effects on bone cancer without affecting the surrounding healthy tissue, revealing a huge potential for the development of new bone cancer treatment strategies. This paper presents a concise review on the use of selenium for bone cancer applications, discussing main synthesis methods, biocompatibility, and cytotoxicity aspects and the combination of selenium with a wide range of ceramics, metals, and polymers. Future perspectives and the novel concept of a dual-functional scaffold for both cancer treatment and new bone regeneration are also discussed.

Bacterial metal nanoparticles to develop new weapons against bacterial biofilms and infections

The widespread use of antibiotics has resulted in the outbreak and spread of antibiotic-resistant pathogens. Bacterial antibiotic resistance may develop at cellular and community levels. In the latter case, it is based on tolerance which implicates the shift from a free-living form of life (i.e., planktonic) to a sessile multi-stratified community (i.e., biofilm). Metal nanoparticles (MNPs) have been shown to be promising candidates as antimicrobial agents. MNPs are able to interact with and penetrate bacterial biofilms, thus, resulting effective antibiofilm compounds. Another interesting aspect is the possibility of using plants, fungi, yeasts, and bacteria to obtain biogenic MNPs (BMNP). Bacteria are able to grow in presence of many different toxic heavy metal ions thanks to different metal resistance gene clusters that allow a variety of biochemical counters (formation of harmless complexes, efflux, precipitation, reduction, etc.). The formation of BMNPs by bacterial cells could be, in most cases, just a consequence of metal detoxification mechanisms. This review focuses on BMNPs from bacterial origin that may represent a good source of compounds with a broad spectrum of activity against common Gram-positive and Gram-negative pathogens and bacterial biofilms thereof. In particular, the state of art on BMNP synthesis by bacteria is presented and potential applications in the fight against biofilm-associated infections and resistant pathogens are highlighted. In addition, critical aspects on BMNP bacterial synthesis and utilization are commented.Key points• New antimicrobials to fight antibiotic-resistant pathogens are urgently needed.• Biogenic metal nanoparticles can efficiently hit biofilm-forming pathogens.• Metal-nanoparticle composition could confer specific antibiofilm activity.

Hydrogel with silver nanoparticles synthesized by Mimosa tenuiflora for second-degree burns treatment

In this work we use Mimosa tenuiflora (MtE) extracts as reducing agents to synthesize silver nanoparticles (AgMt NPs) which were characterized by DPPH and Total Polyphenols Assays, UV-visible, X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). AgMt NPs possess average sizes of 21 nm and fcc crystalline structure, it was also confirmed that the MtE is present in the AgMt NPs even after the cleaning protocol applied. Subsequently, carbopol hydrogels were made and the MtE and the synthesized AgMt NPs were dispersed in different gels (MtE-G and AgMt NPs-G, respectively) at 100 µg/g concentration. The gels were characterized by UV-Vis, IR, and rheology. Antimicrobial tests were performed using Staphylococcus aureus and Escherichia coli. Burn wound healing was evaluated in a second-degree burn injury on a Wistar rats model for 14 days and additional skin biopsies were examined with histopathological analysis. Gel with commercial silver nanoparticles (Ag NPs) was prepared and employed as a control on the biological assays. Hydrogel system containing silver nanoparticles synthesized with Mimosa tenuiflora (AgMt NPs-G) is a promising therapeutic strategy for burn wound healing, this due to bactericidal and anti-inflammatory effects, which promotes a more effective recovery (in percentage terms) by damaged area.

Bacterial Mediated Rapid and Facile Synthesis of Silver Nanoparticles and Their Antimicrobial Efficacy against Pathogenic Microorganisms

In the present study, silver nanoparticles (AgNPs), biosynthesized using culture supernatant of bacterial strain Paenarthrobacter nicotinovorans MAHUQ-43, were characterized and their antimicrobial activity was investigated against both Gram-positive Bacillus cereus and Gram-negative bacteria Pseudomonas aeruginosa. Bacterial-mediated synthesized AgNPs were characterized by UV-Visible (UV-Vis) spectrophotometer, field emission-transmission electron microscopy (FE-TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS) analysis. The UV-Vis spectral analysis showed the absorption maxima at 466 nm which assured the synthesis of AgNPs. The FE-TEM analysis revealed the spherical shape of nanoparticles with the size range from 13 to 27 nm. The EDX and XRD analysis ensured the crystalline nature of biosynthesized AgNPs. The FTIR analysis revealed the involvement of different biomolecules for the synthesis of AgNPs as reducing and capping agents. The bacterial-mediated synthesized AgNPs inhibited the growth of pathogenic strains B. cereus and P. aeruginosa and developed a clear zone of inhibition (ZOI). The MIC and MBC for both pathogens were 12.5 µg/mL and 25 µg/mL, respectively. Moreover, field emission scanning electron microscopy analysis revealed that the synthesized AgNPs can destroy the outer membrane and alter the cell morphology of treated pathogens, leading to the death of cells. This study concludes the eco-friendly, facile and rapid synthesis of AgNPs using P. nicotinovorans MAHUQ-43 and synthesized AgNPs showed excellent antimicrobial activity against both Gram-positive and Gram-negative pathogens.

Mechanism of Producing Metallic Nanoparticles, with an Emphasis on Silver and Gold Nanoparticles, Using Bottom-Up Methods

Bottom-up nanoparticle (NP) formation is assumed to begin with the reduction of the precursor metallic ions to form zero-valent atoms. Studies in which this assumption was made are reviewed. The standard reduction potential for the formation of aqueous metallic atoms-E0(Mn+aq/M0aq)-is significantly lower than the usual standard reduction potential for reducing metallic ions Mn+ in aqueous solution to a metal in solid state. E0(Mn+aq/M0solid). E0(Mn+aq/M0aq) values are negative for many typical metals, including Ag and Au, for which E0(Mn+aq/M0solid) is positive. Therefore, many common moderate reduction agents that do not have significantly high negative reduction standard potentials (e.g., hydrogen, carbon monoxide, citrate, hydroxylamine, formaldehyde, ascorbate, squartic acid, and BH4-), and cannot reduce the metallic cations to zero-valent atoms, indicating that the mechanism of NP production should be reconsidered. Both AgNP and AuNP formations were found to be multi-step processes that begin with the formation of clusters constructed from a skeleton of M+-M+ (M = Ag or Au) bonds that is followed by the reduction of a cation M+ in the cluster to M0, to form Mn0 via the formation of NPs. The plausibility of M+-M+ formation is reviewed. Studies that suggest a revised mechanism for the formation of AgNPs and AuNPs are also reviewed.

Green synthesis of metal nanoparticles using microorganisms and their application in the agrifood sector

The agricultural sector is currently facing many global challenges, such as climate change, and environmental problems such as the release of pesticides and fertilizers, which will be exacerbated in the face of population growth and food shortages. Therefore, the need to change traditional farming methods and replace them with new technologies is essential, and the application of nanotechnology, especially green technology offers considerable promise in alleviating these problems. Nanotechnology has led to changes and advances in many technologies and has the potential to transform various fields of the agricultural sector, including biosensors, pesticides, fertilizers, food packaging and other areas of the agricultural industry. Due to their unique properties, nanomaterials are considered as suitable carriers for stabilizing fertilizers and pesticides, as well as facilitating controlled nutrient transfer and increasing crop protection. The production of nanoparticles by physical and chemical methods requires the use of hazardous materials, advanced equipment, and has a negative impact on the environment. Thus, over the last decade, research activities in the context of nanotechnology have shifted towards environmentally friendly and economically viable 'green' synthesis to support the increasing use of nanoparticles in various industries. Green synthesis, as part of bio-inspired protocols, provides reliable and sustainable methods for the biosynthesis of nanoparticles by a wide range of microorganisms rather than current synthetic processes. Therefore, this field is developing rapidly and new methods in this field are constantly being invented to improve the properties of nanoparticles. In this review, we consider the latest advances and innovations in the production of metal nanoparticles using green synthesis by different groups of microorganisms and the application of these nanoparticles in various agricultural sectors to achieve food security, improve crop production and reduce the use of pesticides. In addition, the mechanism of synthesis of metal nanoparticles by different microorganisms and their advantages and disadvantages compared to other common methods are presented.

A review on biosynthesis of metal nanoparticles and its environmental applications

Nanotechnology has become one of the emerging multi-disciplinary fields receiving universal attention and playing a substantial role in agriculture, environment and pharmacology. In spite of various techniques employed for nanoparticle synthesis such as laser ablation, mechanical milling, spinning and chemical deposition, usage of hazardous chemicals and expensiveness of the process makes it unsuitable for the continuous production. Hence the necessity of sustainable, economic and environment friendly approach development have increased in recent years. Microbial synthesis of nanoparticles connecting microbiology and nanotechnology is one of the green techniques employed for sustainable production. Gold, silver and other metal nanoparticles like platinum, palladium, molybdenum nanoparticles biosynthesis by bacteria, fungi, yeast and algae have been reported in the present review. On account of microbial rich community, several microbes have been explored for the production of nanoparticles. Nanoparticles are also employed for environmental remediation processes such as pollutant removal and detection of contaminants. Lack of monodispersity and prolonged duration of synthesis are the limitations of bio-synthesis process which can be overcome by optimization of methods of microbial cultivation and its extraction techniques. The current review describes the different microbes involved in the synthesis of nanoparticles and its environmental applications.

Ecofriendly Synthesis of Silver Nanoparticles by Terrabacter humi sp. nov. and Their Antibacterial Application against Antibiotic-Resistant Pathogens

It is essential to develop and discover alternative eco-friendly antibacterial agents due to the emergence of multi-drug-resistant microorganisms. In this study, we isolated and characterized a novel bacterium named Terrabacter humi MAHUQ-38^T, utilized for the eco-friendly synthesis of silver nanoparticles (AgNPs) and the synthesized AgNPs were used to control multi-drug-resistant microorganisms. The novel strain was Gram stain positive, strictly aerobic, milky white colored, rod shaped and non-motile. The optimal growth temperature, pH and NaCl concentration were 30 °C, 6.5 and 0%, respectively. Based on 16S rRNA gene sequence, strain MAHUQ-38^T belongs to the genus Terrabacter and is most closely related to several Terrabacter type strains (98.2%-98.8%). Terrabacter humi MAHUQ-38^T had a genome of 5,156,829 bp long (19 contigs) with 4555 protein-coding genes, 48 tRNA and 5 rRNA genes. The culture supernatant of strain MAHUQ-38^T was used for the eco-friendly and facile synthesis of AgNPs. The transmission electron microscopy (TEM) image showed the spherical shape of AgNPs with a size of 6 to 24 nm, and the Fourier transform infrared (FTIR) analysis revealed the functional groups responsible for the synthesis of AgNPs. The synthesized AgNPs exhibited strong anti-bacterial activity against multi-drug-resistant pathogens, Escherichia coli and Pseudomonas aeruginosa. Minimal inhibitory/bactericidal concentrations against E. coli and P. aeruginosa were 6.25/50 and 12.5/50 μg/mL, respectively. The AgNPs altered the cell morphology and damaged the cell membrane of pathogens. This study encourages the use of Terrabacter humi for the ecofriendly synthesis of AgNPs to control multi-drug-resistant microorganisms.

Biologically rapid synthesis of silver nanoparticles by Sphingobium sp. MAH-11T and their antibacterial activity and mechanisms investigation against drug-resistant pathogenic microbes

The present study highlights the biological synthesis of silver nanoparticles (AgNPs) using Sphingobium sp. MAH-11 and also their antibacterial mechanisms against drug-resistant pathogenic microorganisms. The nanoparticle synthesis method used in this study was reliable, facile, rapid, cost-effective and ecofriendly. The AgNPs exhibited the highest absorbance at 423 nm. The TEM image expressed spherical shape of AgNPs and the size of synthesized AgNPs was 7-22 nm. The selected area diffraction (SAED) pattern and XRD spectrum revealed the crystalline structure of AgNPs. The results of FTIR analysis disclosed the functional groups responsible for the reduction of silver ion to metal nanoparticles. The biosynthesized AgNPs showed strong anti-microbial activity against drug-resistant pathogenic microorganisms. Moreover, Escherichia coli and Staphylococcus aureus were used to explore the antibacterial mechanisms of biosynthesized AgNPs. Minimal inhibitory concentrations (MICs) of E. coli and S. aureus were 6.25 μg/mL and 50 μg/mL, respectively and minimum bactericidal concentrations (MBCs) of E. coli and S. aureus were 25 μg/mL and 100 μg/mL, respectively. Results exhibited that biosynthesized AgNPs caused morphological changes and injured the membrane integrity of strains E. coli and S. aureus. The AgNPs synthesized by Sphingobium sp. MAH-11 may serve as a potent antimicrobial agent for many therapeutic applications.

Multifunctional Gold Nanoparticles: A Novel Nanomaterial for Various Medical Applications and Biological Activities

Nanotechnology has become a trending area in science and has made great advances with the development of functional, engineered nanoparticles. Various metal nanoparticles have been widely exploited for a wide range of medical applications. Among them, gold nanoparticles (AuNPs) are widely reported to guide an impressive resurgence and are highly remarkable. AuNPs, with their multiple, unique functional properties, and easy of synthesis, have attracted extensive attention. Their intrinsic features (optics, electronics, and physicochemical characteristics) can be altered by changing the characterization of the nanoparticles, such as shape, size and aspect ratio. They can be applied to a wide range of medical applications, including drug and gene delivery, photothermal therapy (PTT), photodynamic therapy (PDT) and radiation therapy (RT), diagnosis, X-ray imaging, computed tomography (CT) and other biological activities. However, to the best of our knowledge, there is no comprehensive review that summarized the applications of AuNPs in the medical field. Therefore, in this article we systematically review the methods of synthesis, the modification and characterization techniques of AuNPs, medical applications, and some biological activities of AuNPs, to provide a reference for future studies.

A Sustainable Approach for the Green Synthesis of Silver Nanoparticles from Solibacillus isronensis sp. and Their Application in Biofilm Inhibition

The use of bacteria as nanofactories for the green synthesis of nanoparticles is considered a sustainable approach, owing to the stability, biocompatibility, high yields and facile synthesis of nanoparticles. The green synthesis provides the coating or capping of biomolecules on nanoparticles surface, which confer their biological activity. In this study, we report green synthesis of silver nanoparticles (AgNPs) by an environmental isolate; named as AgNPs1, which showed 100% 16S rRNA sequence similarity with Solibacillus isronensis. UV/visible analysis (UV/Vis), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the synthesized nanoparticles. The stable nature of nanoparticles was studied by thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS). Further, these nanoparticles were tested for biofilm inhibition against Escherichia coli and Pseudomonas aeruginosa. The AgNPs showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 3.12 µg/mL and 6.25 µg/mL for E. coli, and 1.56 µg/mL and 3.12 µg/mL for P. aeruginosa, respectively.

Recent Advances in Metal Decorated Nanomaterials and Their Various Biological Applications: A Review

Nanoparticles (nanoparticles) have received much attention in biological application because of their unique physicochemical properties. The metal- and metal oxide-supported nanomaterials have shown significant therapeutic effect in medical science. The mechanisms related to the interaction of nanoparticles with animal and plant cells can be used to establish its significant role and to improve their activity in health and medical applications. Various attempts have been made to discuss the antibiotic resistance and antimicrobial activity of metal-supported nanoparticles. Despite all these developments, there is still a need to investigate their performance to overcome modern challenges. In this regard, the present review examines the role of various types of metal-supported nanomaterials in different areas such as antibacterial, antifungal, anticancer, and so on. Based on the significant ongoing research and applications, it is expected that metal-supported nanomaterials play an outstanding role not only in medical but also in other important areas.

Green Synthesis of Silver Nanoparticles Using Pseudoduganella eburnea MAHUQ-39 and Their Antimicrobial Mechanisms Investigation against Drug Resistant Human Pathogens

Silver nanoparticles (AgNPs) have shown great promise in biomedical applications. The exact mechanism and mode of action of AgNPs regarding antimicrobial activity are still not well known. Moreover, synthesis of nanoparticles by physical and chemical methods is expensive and not ecofriendly. This study highlights the green, rapid, facile, cost-effective and ecofriendly synthesis of AgNPs using Pseudoduganella eburnea MAHUQ-39 and also investigates their antibacterial mechanisms. The transmission electron microscopy (TEM) image revealed a spherical shape of the AgNPs. The size of the synthesized AgNPs was 8 to 24 nm. The elemental mapping and selected area electron diffraction (SAED) and X-ray diffraction (XRD) patterns revealed the crystalline structure of AgNPs. Fourier-transform infrared spectroscopy (FTIR) analysis identified the functional groups that are involved in the reduction of silver ion to AgNPs. The green synthesized AgNPs exhibited strong antimicrobial activity against multidrug-resistant pathogenic microbes. Minimal inhibitory concentrations (MICs) of Staphylococcus aureus and Pseudomonas aeruginosa were 100 μg/mL and 6.25 μg/mL, respectively, and the minimum bactericidal concentrations (MBCs) of S. aureus and P. aeruginosa were 200 μg/mL and 50 μg/mL, respectively. Our data demonstrated that synthesized AgNPs created structural changes of cells and destroyed the membrane integrity of strains S. aureus and P. aeruginosa. Therefore, AgNPs synthesized by strain MAHUQ-39 can be used as a powerful antimicrobial agent for various therapeutic applications.