Green synthesis and characterizations of silver and gold nanoparticles using leaf extract of Rosa rugosa

Plant-based synthesis, characterization approaches, applications and toxicity of silver nanoparticles: A comprehensive review

The development of an environmentally benign method for the synthesis of nanoparticles has been facilitated by green chemistry. "Green synthesis" uses a range of biological elements like microbes, plants, and other biodegradable materials to produce NPs. Active biomolecules that are secreted by natural strains and present in the plant extracts serve as both reducing and capping/stabilizing agents. Microorganisms' intracellular enzymes can reduce metal ions, which explains how NPs might potentially nucleate. Plant-based synthesis of nanomaterials is particularly promising owing to abundant resources, simplicity of synthesis, and low cost. Silver nanoparticles (AgNPs) are attracting great attention in the research community due to their wide variety of applications in chemistry, food technology, microbiology, and biomedicine. Recent years have seen a large amount of research on the bio-genic synthesis of AgNPs employing biomaterials like plant extract and bacteria as reducing agents. Herein we discuss a thorough overview of the plant-based synthesis of silver nanoparticles (AgNPs), characterization approaches, applications, and toxicity. The review covers the green chemistry and nanotechnology elements of producing AgNPs, including a thorough discussion of the plant extract mediated synthesis, detailed formation mechanism, and a well-balanced emphasis on hazards and advantages. Based on current developments, the optimisation strategies, applications, and interdisciplinary characteristics are also covered in detail.

Biosynthesis Optimization of Antibacterial-Magnetic Iron Oxide Nanoparticles from Bacillus megaterium

The occurrence of antibiotic resistance on common bacterial agents and the need to use new generations of antibiotics have led to the use of various strategies for production. Taking inspiration from nature, using bio-imitation patterns, in addition to the low cost of production, is advantageous and highly accurate. In this research, we were able to control the temperature, shake, and synthesis time of the synthesis conditions of Bacillus megaterium bacteria as a model for the synthesis of magnetic iron nanoparticles and optimize the ratio of reducing salt to bacterial regenerating agents as well as the concentration of salt to create iron oxide nanoparticles with more favorable properties and produced with more antibacterial properties. Bacterial growth was investigated by changing the incubation times of pre-culture and overnight culture in the range of the logarithmic phase. The synthesis time, salt ratio, and concentration were optimized to achieve the size, charge, colloidal stability, and magnetic and antibacterial properties of nanoparticles. The amount of the effective substance produced by the bacteria was selected by measuring the amount of the active substance synthesized using the free radical reduction (DPPH) method. With the help of DPPH, the duration of the synthesis was determined to be one week. Characterizations such as UV-vis spectroscopy, FTIR, FESEM, X-ray, and scattering optical dynamics were performed and showed that the nanoparticles synthesized with a salt concentration of 80 mM and a bacterial suspension to salt ratio of 2:1 are smaller in size and have a light scattering index, a PDI index close to 0.1, and a greater amount of reducing salt used in the reaction during one week compared to other samples. Moreover, they had more antibacterial properties than the concentration of 100 mM. As a result, better characteristics and more antibacterial properties than common antibiotics were created on E. coli and Bacillus cereus.

Green Synthesis of Gold Nanoparticles Using Liquiritin and Other Phenolics from Glycyrrhiza glabra and Their Anti-Inflammatory Activity

Phenolic compounds are the main phytochemical constituents of many higher plants. They play an important role in synthesizing metal nanoparticles using green technology due to their ability to reduce metal salts and stabilize them through physical interaction/conjugation to the metal surface. Six pure phenolic compounds were isolated from licorice (Glycyrrhiza glabra) and employed in synthesizing gold nanoparticles (AuNPs). The isolated compounds were identified as liquiritin (1), isoliquiritin (2), neoisoliquiritin (3), isoliquiritin apioside (4), liquiritin apioside (5), and glabridin (6). The synthesized AuNPs were characterized using UV, zeta sizer, HRTEM, and IR and tested for their stability in different biological media. The phenolic isolates and their corresponding synthesized NP conjugates were tested for their potential in vitro cytotoxicity. The anti-inflammatory effects were investigated in both normal and inflammation-induced settings, where inflammatory biomarkers were stimulated using lipopolysaccharides (LPSs) in the RAW 264.7 macrophage cell line. LPS, functioning as a mitogen, promotes cell growth by reducing apoptosis, potentially contributing to observed outcomes. Results indicated that all six pure phenolic isolates inhibited cell proliferation. The AuNP conjugates of all the phenolic isolates, except liquiritin apioside (5), inhibited cell viability. LPS initiates inflammatory markers by binding to cell receptors and setting off a cascade of events leading to inflammation. All the pure phenolic isolates, except isoliquiritin, neoisoliquiritin, and isoliquiritin apioside inhibited the inflammatory activity of RAW cells in vitro.

Bio-fabrication of silver nanoparticles using Commelina erecta, L.: a mechanistic approach on synthesis, optimization, antibacterial, and antioxidant potential

The ongoing exploration of economical, sustainable, and environment-friendly methods for synthesizing monodisperse colloidal metal nanoparticles is growing day by day due to their potential application in various fields. The use of plant derivatives in nanoparticle synthesis and their suitability as sustainable catalysts have emerged as significant areas of research. In this study, silver nanoparticles were synthesized using an aqueous extract obtained from the commonly found weed Commelina erecta, L. Extensive study is conducted to optimize various synthesis parameters such as pH, reducing agent concentration, silver nitrate concentration, and temperature. The plant extract utilized in the synthesis process contained variety of antioxidants, including malic acid, phenol, benzoic acid, and catechol, which played a crucial role in both reduction and capping during the synthesis process, thereby making them suitable for biomedical applications. The optimized synthesis process yielded silver nanoparticles with a particle size of 16.2 ± 3.1 nm. These nanoparticles exhibited excellent stability and demonstrated remarkable antibacterial activity compared to the standard antibacterial agent, streptomycin. In addition, the silver nanoparticles displayed promising antioxidant activity attributed to the presence of antioxidant functional groups on their surface. This study reports, for the first time, the synthesis of silver nanoparticles using antioxidant compounds present in C. erecta, L. plant extract. The antioxidant compounds identified through GC-MS belong to phenols, phenolic acids, and carboxylic acid groups. Furthermore, the exceptional antimicrobial and antioxidant properties exhibited by the synthesized silver nanoparticles offer new possibilities for their potential applications.

Biosynthesis, Characterization, and Biomedical Applications of Gold Nanoparticles with Cucurbita moschata Duchesne Ex Poiret Peel Aqueous Extracts

In this study, AuNPs were biosynthesized from Cucurbita moschata fruit peel extracts. Biosynthesized AuNPs exhibited maximum absorbance at a 555 nm wavelength, and XRD analysis indicated that the CM-AuNPs had a particle size of less than 100 nm and a cubic crystal structure. TEM scans revealed that the gold particles exhibited a spherical morphology, with an average size of 18.10 nm. FTIR analysis revealed strong peaks indicating the presence of functional groups involved in the reduction reactions. The surface charge of the biosynthesized AuNPs was determined to be -19.7 mV. The antibacterial and antifungal activities of AuNPs against pathogen strains were assessed by the minimum inhibitory concentration (MIC) method. The cytotoxic effects of CM-AuNPs on cancer cell lines (Sk-Ov-3, CaCo2, and A549) and healthy cell lines (HUVEC) were investigated using the MTT method. The findings indicated that AuNPs biosynthesized by the green synthesis method using C. moschata peel aqueous extract had high inhibition on the growth of pathogenic microorganisms and effective cytotoxic activity against cancerous cell lines at low doses. As a result, it can be concluded that CM-AuNPs will be eminently effective in the production of antibacterial and/or anticancer drugs in the pharmaceutical, food, and cosmetic industries.

Emerging Nanotechnology for the Treatment of Alzheimer's Disease

Nanotechnology is a great choice for medical research, and the green synthesis approach is a novel and better way to synthesize nanoparticles. Biological sources are cost-effective, environmentally friendly, and allow large-scale production of nanoparticles. Naturally obtained 3 β-hydroxy-urs- 12-en-28-oic acids reported for neuroprotective and dendritic structure are reported as solubility enhancers. Plants are free from toxic substances and act as natural capping agents. In this review, the pharmacological properties of ursolic acid (UA) and the structural properties of the dendritic structure are discussed. UA acid appears to have negligible toxicity and immunogenicity, as well as favorable biodistribution, according to the current study, and the dendritic structure improves drug solubility, prevents drug degradation, increases circulation time, and potentially targets by using different pathways with different routes of administration. Nanotechnology is a field in which materials are synthesized at the nanoscale. Nanotechnology could be the next frontier of humankind's technological advancement. Richard Feynman first used the term 'Nanotechnology' in his lecture, "There is Plenty of Room at the Bottom", on 29th December, 1959, and since then, interest has increased in the research on nanoparticles. Nanotechnology is capable of helping humanity by solving major challenges, particularly in neurological disorders like Alzheimer's disease (AD), the most prevalent type, which may account for 60-70% of cases. Other significant forms of dementia include vascular dementia, dementia with Lewy bodies (abnormal protein aggregates that form inside nerve cells), and a number of illnesses that exacerbate frontotemporal dementia. Dementia is an acquired loss of cognition in several cognitive domains that are severe enough to interfere with social or professional functioning. However, dementia frequently co-occurs with other neuropathologies, typically AD with cerebrovascular dysfunction. Clinical presentations show that neurodegenerative diseases are often incurable because patients permanently lose some neurons. A growing body of research suggests that they also advance our knowledge of the processes that are probably crucial for maintaining the health and functionality of the brain. Serious neurological impairment and neuronal death are the main features of neurodegenerative illnesses, which are also extremely crippling ailments. The most prevalent neurodegenerative disorders cause cognitive impairment and dementia, and as average life expectancy rises globally, their effects become more noticeable.

Synergistic action of sumatriptan delivery and targeting magnesium deficiency using green, pH-responsive MgO nanoparticles synthesized from mahua flower extracts

Magnesium oxide (MgO) nanoparticles were green synthesized using mahua (Madhuca longifolia) flower extracts by solvent evaporation and characterized by UV-visible spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and Energy dispersive X-ray analysis (EDX). The drug loading of sumatriptan succinate (SS), an anti-migraine drug, was optimized using MINITAB's response surface methodology (RSM) Box Behnken model (BBD) model. The investigation of drug adsorption and release kinetics was further conducted using the optimized set obtained through RSM. The optimized parameters consisted of 23.53 mg of nanoparticles, a loading time of 6 h, and a pH of 9, yielding the experimental drug loading efficiency ~47%. The primary objective of this study is to investigate the potential of utilizing these green synthesized MgO nanoparticles for a dual purpose. The primary objective of this study is to investigate the viability of utilizing MgO nanoparticles synthesized through green route for the delivery of an anti-migraine medication. Additionally, the study aims to examine the degradation of these nanoparticles at physiological pH levels, with the intention of potentially enhancing cellular absorption. The investigation involved the assessment of drug release kinetics using various mathematical models, with a focus on the release of SS from MgO nanoparticles. This evaluation was conducted at different pH levels, specifically pH 5, 7, and 9. It has been found that the SS release increases as pH decreases, which is attributed to the dissolution of MgO nanoparticles, which therefore exhibits varied behavior at different pHs. The confirmation of the degradation of the green synthesized MgO nanoparticles was achieved through the execution of a degradation study, followed by the analysis of the obtained samples using FESEM and EDS. At neutral, the release data obtained adhered to the Higuchi model, which suggests that the release of the drug is based on diffusion. This finding is particularly advantageous for the controlled release of an anti-migraine drug. The results obtained from the study indicate that MgO nanoparticles have the potential to serve as a significant component in drug delivery systems, specifically as drug carriers. Attachment of SS over MgO nanoparticles to form SS loaded MgO nanoparticles and its possible working mechanism.

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.

Bio-functionalized nickel-silica nanoparticles suppress bacterial leaf blight disease in rice (Oryza sativa L.)

Introduction

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastative diseases that threatens rice plants worldwide. Biosynthesized nanoparticle (NP) composite compounds have attracted attention as environmentally safe materials that possess antibacterial activity that could be used in managing plant diseases.

Methods

During this study, a nanocomposite of two important elements, nickel and silicon, was biosynthesized using extraction of saffron stigmas (Crocus sativus L.). Characterization of obtained nickel-silicon dioxide (Ni-SiO2) nanocomposite was investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission/Scanning electron microscopy (TEM/SEM), and energy-dispersive spectrum (EDS). Antibacterial activities of the biosynthesized Ni-SiO2 nanocomposite against Xoo were tested by measuring bacterial growth, biofilm formation, and dead Xoo cells.

Results and discussions

The bacterial growth (OD600) and biofilm formation (OD570) of Xoo treated with distilled water (control) was found to be 1.21 and 1.11, respectively. Treatment with Ni-SiO2 NPs composite, respectively, reduced the growth and biofilm formation by 89.07% and 80.40% at 200 μg/ml. The impact of obtained Ni-SiO2 nanocomposite at a concentration of 200 μg/ml was assayed on infected rice plants. Treatment of rice seedlings with Ni-SiO2 NPs composite only had a plant height of 64.8 cm while seedlings treated with distilled water reached a height of 45.20 cm. Notably, Xoo-infected seedlings treated with Ni-SiO2 NPs composite had a plant height of 57.10 cm. Furthermore, Ni-SiO2 NPs composite sprayed on inoculated seedlings had a decrease in disease leaf area from 43.83% in non-treated infected seedlings to 13.06% in treated seedlings. The FTIR spectra of biosynthesized Ni-SiO2 nanocomposite using saffron stigma extract showed different bands at 3,406, 1,643, 1,103, 600, and 470 cm-1. No impurities were found in the synthesized composite. Spherically shaped NPs were observed by using TEM and SEM. EDS revealed that Ni-SiO2 nanoparticles (NPs) have 13.26% Ni, 29.62% Si, and 57.11% O. Xoo treated with 200 µg/ml of Ni-SiO2 NPs composite drastically increased the apoptosis of bacterial cells to 99.61% in comparison with 2.23% recorded for the control.

Conclusions

The application of Ni-SiO2 NPs significantly improved the vitality of rice plants and reduced the severity of BLB.

Characterization and Biological Studies of Synthesized Titanium Dioxide Nanoparticles from Leaf Extract of Juniperus phoenicea (L.) Growing in Taif Region, Saudi Arabia

Green synthesis of metal nanoparticles in nanosized form has acquired great interest in the area of nanomedicine as an environmentally friendly and cost-effective alternative compared to other chemical and physical methods. This study deals with the eco-friendly green synthesis of titanium dioxide nanoparticles (TiO2 NPs) utilizing Juniperus phoenicea leaf extract and their characterization. The biosynthesis of TiO2 NPs was completed in 3 h and confirmed by UV-Vis spectroscopy, a strong band at 205.4 nm distinctly revealed the formation of NPs. Transmissions electron microscopy (TEM) analysis showed the synthesized TiO2 NPs are spherical in shape, with a diameter in a range of 10–30 nm. The XRD major peak at 27.1° congruent with the (110) lattice plane of tetragonal rutile TiO2 phase. Dynamic light scattering (DLS) analysis revealed synthesized TiO2 NPs average particle size (hydrodynamic diameter) of (74.8 ± 0.649) nm. Fourier transmission infrared (FTIR) revealed the bioactive components present in the leaf extract, which act as reducing and capping agents. The antimicrobial efficacy of synthesized TiO2NPs against, Staphylococcus aureus, and Bacillus subtilis (Gram-positive), Escherichia coli and Klebsiella pneumoniae (Gram-negative), Yeast strain (Saccharomyces cerevisiae) and fungi (Aspergillus niger, and Penicillium digitatum) assayed by a disc diffusion method. TiO2NPs inhibited all tested strains by mean inhibition zone (MIZ), which ranged from the lowest 15.7 ± 0.45 mm against K. pneumoniae to the highest 30.3 ± 0.25 against Aspergillus niger. The lowest minimum inhibitory concentration (MIC) and bactericidal (MBC) values were 20 μL/mL and 40 μL/mL of TiO2NPs were observed against Asp. niger. Moreover, it showed significant inhibitory activity against human ovarian adenocarcinoma cells with IC50 = 50.13 ± 1.65 µg/mL. The findings concluded that biosynthesized TiO2 NPs using Juniperus phoenicea leaf extract can be used in medicine as curative agents according to their in vitro antibacterial, antifungal, and cytotoxic activities.

Antimicrobial evaluation of silver nanoparticles using extracts of Crescentia cujete L

New natural reducing agents with a lower negative impact on the environment and with a high antimicrobial potential are required for the process of obtaining silver nanoparticles through the chemical reduction method. The use of plant extracts can be a fast track in the formation of nanoparticles. In this case, organic compounds such as terpenes, flavonoids, enzymes, proteins, and cofactors present in plants act as reducing agents for nanomaterials. This research evaluated the antimicrobial property of silver nanoparticles from extracts of Crescentia cujete L. The presence of quercetin (flavonoid) was determined by high-performance liquid chromatography (HPLC); the production of silver nanoparticles (AgNPs) was established by green synthesis; the size and morphology of the nanomaterials were evaluated by scanning electron microscope (SEM). The antimicrobial capacity was studied by two analysis methods: modified culture medium and surface seeding. The presence of quercetin (26.55 mg L-1) in the crude extract of Crescentia cujete L., identified by HPLC, was evidenced. Nanoparticle formation was spherical, with an average size of 250 ± 3 and 460 ± 6 nm. Microbiological cultures with treatment showed 94% microbial inhibition. It was concluded that the Crescentia cujete L., leaves shoed an acceptable concentration of quercetin to be used as a useful adjuvant to enhance the reduction of NPs synthesis. The nanoparticles produced by green synthesis proved to have a positive effect to combat pathogenic microorganisms.

Biologically Synthesized Rosa rugosa-Based Gold Nanoparticles Suppress Skin Inflammatory Responses via MAPK and NF-κB Signaling Pathway in TNF-α/IFN-γ-Induced HaCaT Keratinocytes

Nanotechnology-applied materials and related therapeutics have gained attention for treating inflammatory skin diseases. The beach rose (Rosa rugosa), belonging to the family Rosaceae, is a perennial, deciduous woody shrub endemic to northeastern Asia. In this study, R. rugosa-based gold nanoparticles (RR-AuNPs) were biologically synthesized under optimal conditions to explore their potential as anti-inflammatory agents for treating skin inflammation. The synthesized RR-AuNPs were analyzed using field emission-transmission electron microscopy, energy-dispersive X-ray spectrometry, selected-area electron diffraction, and X-ray diffraction. The uniformly well-structured AuNPs showed near-spherical and polygonal shapes. Cell viability evaluation and optical observation results showed that the RR-AuNPs were absorbed by human keratinocytes without causing cytotoxic effects. The effects of RR-AuNPs on the skin inflammatory response were investigated in human keratinocytes treated with tumor necrosis factor-α/interferon-γ (T + I). The results showed that T + I-stimulated increases in inflammatory mediators, including chemokines, interleukins, and reactive oxygen species, were significantly suppressed by RR-AuNP treatment in a concentration-dependent manner. The western blotting results indicated that the RR-AuNP-mediated anti-inflammatory effects were highly associated with the suppression of inflammatory signaling, mitogen-activated protein kinase, and nuclear factor-κB. These results demonstrate that plant extract-based AuNPs are novel anti-inflammatory candidates for topical application to treat skin inflammation.

Biogenic Synthesis of Copper-Based Nanomaterials Using Plant Extracts and Their Applications: Current and Future Directions

Plants have been used for multiple purposes over thousands of years in various applications such as traditional Chinese medicine and Ayurveda. More recently, the special properties of phytochemicals within plant extracts have spurred researchers to pursue interdisciplinary studies uniting nanotechnology and biotechnology. Plant-mediated green synthesis of nanomaterials utilises the phytochemicals in plant extracts to produce nanomaterials. Previous publications have demonstrated that diverse types of nanomaterials can be produced from extracts of numerous plant components. This review aims to cover in detail the use of plant extracts to produce copper (Cu)-based nanomaterials, along with their robust applications. The working principles of plant-mediated Cu-based nanomaterials in biomedical and environmental applications are also addressed. In addition, it discusses potential biotechnological solutions and new applications and research directions concerning plant-mediated Cu-based nanomaterials that are yet to be discovered so as to realise the full potential of the plant-mediated green synthesis of nanomaterials in industrial-scale production and wider applications. This review provides readers with comprehensive information, guidance, and future research directions concerning: (1) plant extraction, (2) plant-mediated synthesis of Cu-based nanomaterials, (3) the applications of plant-mediated Cu-based nanomaterials in biomedical and environmental remediation, and (4) future research directions in this area.

Green Synthesis of Silver Nanoparticles Using Artemisia vulgaris Extract and Its Application toward Catalytic and Metal-Sensing Activity

Nonessential heavy metals are toxic to human health. In this study, mercury, a hazardous metal, was detected by colorimetric analysis using Artemisia vulgaris-mediated silver nanoparticles (AgNP) without any modification in an aqueous solution. The UV–vis spectroscopy showed a characteristic SPR band of Ag0 at 418 nm, indicating the formation of AgNPs. The AgNPs were crystalline, with an average size of 7 nm, as calculated from the XRD data. The SEM images revealed the spherical and polycrystalline AgNPs within the agglomerated form. The FTIR spectra elucidated the functional group of the extract attached with the Ag0. The broad, strong peak at 3632 cm−1 indicated the involvement of the -OH group of compounds of extract in reducing silver ions. The peak of EDX spectra around 3 keV confirmed the silver in the nanostructure. A colorimetric method was employed for the heavy metal sensing in the aqueous medium without modification of AgNPs suspension. The obtained AgNPs were found to be selective and highly sensitive toward Hg2+ ions. The AgNPs suspension turned colorless after adding 380 µL of 1 mM Hg2+. The synthesized AgNPs showed the catalytic activity on reduction of 4-nitrophenol in the presence of NaBH4 within 8 min with a rate constant of 1.21 × 10−2 s−1. The outcome of these findings suggests that the application of Artemisia vulgaris influenced AgNPs for metal sensing and green catalysis.

Peroxidase-Mimicking Activity of Biogenic Gold Nanoparticles Produced from Prunus nepalensis Fruit Extract: Characterizations and Application for the Detection of Mycobacterium bovis

In the present study, a facile, eco-friendly, and controlled synthesis of gold nanoparticles (Au NPs) using Prunus nepalensis fruit extract is reported. The biogenically synthesized Au NPs possess ultra-active intrinsic peroxidase-like activity for the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. Chemical analysis of the fruit extract demonstrated the presence of various bioactive molecules such as amino acids (l-alanine and aspartic acids), organic acids (benzoic acid and citric acid), sugars (arabinose and glucose), phenolic acid, and bioflavonoids (niacin and myo-inositol), which likely attributed to the formation of stable biogenic Au NPs with excellent peroxidase-mimicking activity. In comparison with the natural horseradish peroxidase (HRP) enzyme, the biogenic Au NPs displayed a 9.64 times higher activity with regard to the reaction velocity at 6% (v/v) H2O2, presenting a higher affinity toward the TMB substrate. The Michaelis-Menten constant (KM) values for the biogenic Au NPs and HRP were found to be 6.9 × 10-2 and 7.9 × 10-2 mM, respectively, at the same concentration of 100 pM. To investigate its applicability for biosensing, a monoclonal antibody specific for Mycobacterium bovis (QUBMA-Bov) was directly conjugated to the surface of the biogenic Au NPs. The obtained results indicate that the biogenic Au NPs-QUBMA-Bov conjugates are capable of detecting M. bovis based on a colorimetric immunosensing method within a lower range of 100 to 102 cfu mL-1 with limits of detection of ∼53 and ∼71 cfu mL-1 in an artificial buffer solution and in a soft cheese spiked sample, respectively. This strategy demonstrates decent specificity in comparison with those of other bacterial and mycobacterial species. Considering these findings together, this study indicates the potential for the development of a cost-effective biosensing platform with high sensitivity and specificity for the detection of M. bovis using antibody-conjugated Au nanozymes.

Silver nanostructures prepared via novel green approach as an effective platform for biological and environmental applications

Silver nanoparticles play a significant role in biomedical sciences due to their unique properties allowing for their use as an effective sensing and remediation platform Herein, the green synthesis of silver nanostructures (Ag NSs), prepared via aqueous extract of waste Brassica oleracea leaves in the presence of silver nitrate solution (10-4 M), is reported. The Ag NSs are fully characterized and their efficacy with respect to 4-nitrophenol reduction, glucose sensing, and microbes is determined. Visually, the color of silver nitrate containing solution altered from colorless to yellowish, then reddish grey, confirming the formation of Ag NSs. HRTEM and SEAD studies revealed the Ag NSs to have different morphologies (triangular, rod-shaped, hexagonal, etc., within a size range of 20-40 nm) with face-centered cubic (fcc) crystal structure. The Ag NSs possess high efficacy for nitrophenol reduction (<11 min and degradation efficiency of 98.2%), glucose sensing (LOD: 5.83 µM), and antimicrobial activity (E. coli and B. subtilis with clearance zones of 18.3 and 14 mm, respectively). Thus, the current study alludes towards the development of a cost-effective, sustainable, and efficient three-in-one platform for biomedical and environmental applications.

Green synthesis of gold nanaoparticles using Delphinium Chitralense tuber extracts, their characterization and enzyme inhibitory potential

Green synthesis has been introduced as an alternative to chemical synthesis due to the serious consequences. Metal nanoparticles synthesized through green approach have different pharmaceutical, medical and agricultural applications. The present study followed a green and simple route for the preparation of potentially bioactive gold nanoparticles (Au NPs). Au NPs were prepared via green synthesis approach using crude basic alkaloidal portion of the tuber of Delphinium chitralense. The green synthesized Au NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) fourier transform infrared (FTIR), and UV-Visible spectrophotometer. Morphological analysis shows that Au NPs have cubic geometry with different sizes. UV-Vis spectroscopic analysis confirmed the synthesis of Au NPs while XRD proved their pure crystalline phase. The Au NPs showed promising dose dependent inhibition of both AChE and BChE as compared to the crude as well as standard drug.

Multifarious global flora fabricated phytosynthesis of silver nanoparticles: a green nanoweapon for antiviral approach including SARS-CoV-2

The progressive research into the nanoscale level upgrades the higher end modernized evolution with every field of science, engineering, and technology. Silver nanoparticles and their broader range of application from nanoelectronics to nano-drug delivery systems drive the futuristic direction of nanoengineering and technology in contemporary days. In this review, the green synthesis of silver nanoparticles is the cornerstone of interest over physical and chemical methods owing to its remarkable biocompatibility and idiosyncratic property engineering. The abundant primary and secondary plant metabolites collectively as multifarious phytochemicals which are more peculiar in the composition from root hair to aerial apex through various interspecies and intraspecies, capable of reduction, and capping with the synthesis of silver nanoparticles. Furthermore, the process by which intracellular, extracellular biological macromolecules of the microbiota reduce with the synthesis of silver nanoparticles from the precursor molecule is also discussed. Viruses are one of the predominant infectious agents that gets faster resistance to the antiviral therapies of traditional generations of medicine. We discuss the various stages of virus targeting of cells and viral target through drugs. Antiviral potential of silver nanoparticles against different classes and families of the past and their considerable candidate for up-to-the-minute need of complete addressing of the fulminant and opportunistic global pandemic of this millennium SARS-CoV2, illustrated through recent silver-based formulations under development and approval for countering the pandemic situation.

Graphical abstract

One step green synthesis of Cu nanoparticles by the aqueous extract of Juglans regia green husk: assessing its physicochemical, environmental and biological activities

Juglans regia (J. regia) green husk is an abundant agricultural waste. In this study, an economical, rapid and green synthetic route was introduced for the biosynthesis of copper nanoparticles (CuNPs) by applying the aqueous extract of J. regia green husk at the ambient conditions. Ultra Violet-Visible (UV-Visible) analysis revealed that the Surface Plasmon Resonance (SPR) of the CuNP was 212 nm. The average hydrodynamic and metallic core diameters of the CuNPs were about 53-28 nm, respectively. X-ray Diffraction (XRD) analysis presented that the CuNPs were amorphous. The CuNPs exhibited the highest free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging efficiency. These nanoparticles (NPs) showed antibacterial, antifungal and antibiofilm properties. They presented photocatalytic activity against Methyl Orange (MO). Besides, the potential of these NPs for the fast and precise colorimetric detection of Hg²⁺ was remarkable. The biosynthesized CuNPs are introduced as a multifunctional nanomaterial with various applications in medicine and environmental cases. The CuNPs were produced through an environmentally green process by the aqueous extract of dried J. regia green husk at the ambient condition. The CuNPs confirmed that this type of nanomaterial is a multifunctional agent with significant antibacterial, antifungal, antibiofilm, antioxidant, photocatalytic activities. Besides, it is a promising colorimetric sensor for the detection of Hg²⁺ in an aqueous complex media.

Biogenic Synthesis of Silver Nanoparticles, Characterization and Their Applications—A Review

With the growing awareness for the need of sustainable environment, the importance of synthesizing and the application of green nanoparticles has gained special focus. Among various metal nanoparticles, silver nanoparticles (AgNPs) have gain significant attention. AgNPs are synthesized conventionally by physical and chemical methods using chemicals such as reducing agents, which are hazardous to environment due to their toxic properties, provoking a serious concern to create and develop environment friendly methods. Thus, biological alternatives are emerging to fill gaps, such as green syntheses that use biological molecules taken from plant sources in the form of extracts, which have shown to be superior to chemical and physical approaches. These biological molecules derived from plants are assembled in a highly regulated manner to make them suitable for metal nanoparticle synthesis. The current review outlines the wide plant diversity that may be used to prepare a rapid and single-step procedure with a green path over the traditional ones, as well as their antifungal activity.

The antimicrobial activity of biogenic silver nanoparticles synthesized from extracts of Red and Green European pear cultivars

Green nanotechnology stands amongst the leading giants of innovation for the twenty first century technological advances. More interesting, is the use of natural products as reducing agents. These could be recyclable materials from fruits and vegetables to produce nanoparticles (NPs) with novel properties. In the current study, silver NPs (AgNPs) were synthesized using the water extracts from the peel and flesh of two Pyrus communis L. cultivars, namely, the Forelle (Red) Pears (RPE) and Packham Triumph (Green) Pears (GPE). The AgNPs were characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS), High Resolution Transmission Electron Microscopy (HRTEM) and Fourier Transform Infra-Red Spectroscopy (FTIR). The antibacterial activities of the AgNPs were evaluated using agar well diffusion and microdilution assays. The cytotoxicity of the AgNPs was investigated on a rat macrophage (RAW 264.7) cells using MTT assay. Both the RPE and GPE were capable of synthesizing the AgNPs at high temperatures (70 and 100 °C). The AgNPs exhibited antibacterial activity against the test strains, and also had low toxicity towards the RAW 264.7 cells. Thus, the synthesized AgNPs have a potentially viable use in bio-applications for treatment of bacterial infections.

Biogenic Silver Nanoparticles: Synthesis and Application as Antibacterial and Antifungal Agents

The importance and need for eco-oriented technologies has increased worldwide, which leads to an enhanced development of methods for the synthesis of nanoparticles using biological agents. This review de-scribes the current approaches to the preparation of biogenic silver nanoparticles, using plant extracts and filtrates of fungi and microorganisms. The peculiarities of the synthesis of particles depending on the source of biocomponents are considered as well as physico-morphological, antibacterial and antifungal properties of the resulting nanoparticles which are compared with such properties of silver nanoparticles obtained by chemical synthesis. Special attention is paid to the process of self-assembly of biogenic silver nanoparticles.

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.

An overview of the phytosynthesis of various metal nanoparticles

Nanotechnology is an emerging branch of science wherein various valuable molecules with altered properties can be synthesized and utilized for numerous technological applications. Nowadays, nanotechnology is the preferred tool for the agriculture, food, and medicine industries. However, consistent accumulation of toxic by-products during the synthesis of nanoparticles from the established physical and chemical methods imposes an unprecedented danger to the environment and human well-being. The biological route for the synthesis of nanoparticles offers a potential option over the conventional chemical synthesis process due to the involvement of non-toxic and environmentally friendly materials, such as plants, fungi, bacteria, etc. Phytosynthesis, a type of biological synthesis, utilizes various combinations of secondary metabolites from different plant parts (whole plant, leaves, fruit peel, root, bark, seeds, and stem) for non-toxic and environmentally friendly nanoparticles fabrication. Non-toxic and environmentally friendly secondary metabolites derived from plants are the sources of reducing and capping agents during the biosynthesis of nanoparticles which proceeds in a controlled manner with desired characteristics. Phytosynthesis of nanoparticles is also a simple, economic, durable, and reproducible process. The present article is a comprehensive depiction of the synthesis of different metal nanoparticles from diverse plant species.

A Simplistic Single-Step Method for Preparing Biomimetic Nanoparticles from Endogenous Biomaterials

Many works utilize products isolated from nature as capping agents to functionalize gold nanoparticles for targeting and therapeutic applications. Some of the most advanced of these strategies utilize complex multicomponent biomaterials, such as whole cell-membranes, for nanoparticle functionalization strategies for evading or initializing immune response as well as for targeting. Strategies like these, wherein whole cell membrane is utilized for functionalization, take advantage of the complexity of the protein-lipid content and organization, which cells normally use for communication and interaction (instilling these capacities to nanoparticle vectors). Many approaches for achieving this in functionalizing the surface of nanoparticles rely on multistep processes, which necessitate the addition and then removal of synthetic molecules, heating, or pH modifications. These processes can have deleterious modifying effects on the functionalizing biomolecules, resulting in loss of product and time during each purification step, as well as potentially changing the biomolecule functionality toward a nondesirable effect. Here, we describe methods for forming gold nanoparticles at room temperature in a single step, functionalized with proteins, using nicotinamide adenine dinucleotide (NADH). This process enables formation of nanoparticles that can be functionalized by individual proteins (demonstrated with FBS) or whole cells membrane (extracted from B16F10 cells). This work is derivative from observations found in the literature by us and others, that mammalian cells are capable of producing gold nanoparticles from ionic gold without the supplementation of chemical species. The products of this single-step synthesis described herein have been optimized to maintain biomolecule integrity and so that there are no further purification steps required. To characterize the nanoparticles in terms of their shape, size, surface functionality, and biomolecule integrity throughout development, we employed light-based spectroscopy techniques, molecular modeling, electron microscopy, light scattering, and gel electrophoresis techniques. In order to compare the optimized biomolecule-functionalized nanoparticles against current standards (which require synthetic linkers, heating, or pH manipulation), we employed metabolic and live/dead assays as well as light-based microscopy/spectroscopy in vitro. In comparing our synthetic process against others for forming gold nanoparticles functionalized with complex biomolecule components (whole-cell membrane), we found that this process had superior particle internalization. Our strategy has similar outlets for application to these other works, however, because this process is entirely reliant on endogenous biomaterials and has additional potential.

Phytoproduct, Arabic Gum and Opophytum forsskalii Seeds for Bio-Fabrication of Silver Nanoparticles: Antimicrobial and Cytotoxic Capabilities

The application of biological materials in synthesizing nanoparticles has become significant issue in nanotechnology. This research was designed to assess biogenic silver nanoparticles (AgNPs) fabricated using two aqueous extracts of Acacia arabica (Arabic Gum) (A-AgNPs) and Opophytum forsskalii (Samh) seed (O-AgNPs), which were used as reducing and capping agents in the NPs development, respectively. The current study is considered as the first report for AgNP preparation using Opophytum forsskalii extract. The dynamic light scattering, transmission electron microscopy, and scanning electron microscopy were employed to analyze the size and morphology of the biogenic AgNPs. Fourier transform infrared (FTIR) spectroscopy and chromatography/mass spectrometry (GC-MS) techniques were used to identify the possible phyto-components of plant extracts. The phyto-fabricated NPs were assessed for their antibacterial activity and also when combined with some antibiotics against Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa and Escherichia coli (Gram-negative) and their anticandidal ability against Candida albicans using an agar well diffusion test. Furthermore, cytotoxicity against LoVo cancer cell lines was studied. The results demonstrated the capability of the investigated plant extracts to change Ag+ ions into spherical AgNPs with average size diameters of 91 nm for the prepared O-AgNPs and 75 nm for A-AgNPs. The phyto-fabricated AgNPs presented substantial antimicrobial capabilities with a zone diameter in the range of 10-29.3 mm. Synergistic effects against all tested strains were observed when the antibiotic and phyto-fabricated AgNPs were combined and assessed. The IC50 of the fabricated O-AgNPs against LoVo cancer cell lines was 28.32 μg/mL. Ten and four chemical components were identified in Acacia arabica (Arabic Gum) and Opophytum forsskalii seed extracts, respectively, by GC-MS that are expected as NPs reducing and capping agents. Current results could lead to options for further research, such as investigating the internal mechanism of AgNPs in bacteria, Candida spp., and LoVo cancer cell lines as well as identifying specific molecules with a substantial impact as metal-reducing agents and biological activities.

The exploitation of rice husk biomass for the bio-inspired synthesis of gold nanoparticles as a multifunctional material for various biological and photocatalytic applications

We report an efficient and facile approach to biosynthesis of gold nanoparticles (AuNPs) using the extract of an agro-waste rice husk generated from rice production. The biosynthesized NPs produced were characterized by UV-Visible absorption, TEM, XRD, EDX, and FTIR methods. The impact of temperature and pH on the stability of the synthesized AuNPs was also studied. The TEM imaging revealed the formation of monodispersed spherical NPs with an average size of ~ 15 nm. The absorption spectrum of AuNPs demonstrated the formation of Surface Plasmon Resonance (SPR) peak at 530 nm. The XRD pattern suggested the formation of face-centered cubic (FCC) lattice structure of AuNPs. The FTIR analysis displayed characteristic peaks related to various phytochemicals in the plant extract responsible for reducing and stabilizing NPs. In addition, AuNPs showed thermal stability when subjected to various temperature scales. The AuNPs exhibited an efficiency against the pathogenic bacteria Staphylococcus aureus and pathogenic fungi Candida albicans. The AuNPs 18.5% DPPH free scavenging activity, indicating the antioxidant potential for AuNPs. In addition, the AuNPs showed anticancer activity against the colorectal adenocarcinoma carcinoma cell line. Furthermore, AuNPs displayed significant enhancement in photocatalytic degradation of Methylene Blue and 4-Nitrophenol dyes. The results obtained reveal the possible usage of AuNPs produced using rice husk in several biomedical applications.

A semi-quantitative risk ranking of potential human exposure to engineered nanoparticles (ENPs) in Europe

Large quantities of engineered nanoparticles (ENPs) have emerged on the European market with the rapid development of nanotechnology, however knowledge of potential health risks to humans remains in its infancy. The ENP safety issue is of pressing concern as their novel physicochemical characteristics have been illustrated compared to other bulk-form counterparts. Therefore, it is critical to carry out a comprehensive risk assessment for ENPs to guide risk management in industrial sectors. Based on current data availability, a risk ranking model is developed in accordance with the European Chemicals Agency (ECHA) advice for ENP risk assessment. In this study a Quantity, Exposure, Hazard (QEH) risk scoring model was adopted for characterizing both quantitative and qualitative data, including potential exposure pathways and hazard information. Scores were assigned to quantities of ENPs used in consumer products, intake likelihoods (oral, inhalation, and dermal intake), and hazard potential. Exposure through environmental routes and through consumer products are regarded as significant potential exposure routes. This model prioritized ENPs used in Europe according to human health risk potential. Nano-titanium dioxide (TiO₂) ranked the highest, resulting from exposure through consumer products. Silver nanoparticles (AgNP), as the second most critical ENP, is of most concern in terms of the risk from environmental sinks. Regarding the compartmentalization of total ENP risks to humans, the consumption of consumer products with nano-ingredients, especially nano-TiO₂, nano-silicon dioxide (SiO₂), and AgNP, constitutes the majority of the QEH risk index. The inadequacy of ENP risk management procedures is highlighted, not only during manufacturing, but also during nanomaterial waste disposal processes from marketplace through to the environment. Current risk assessments are based upon recent knowledge of the ENP class as novel pollutants, highlighting the need for further quantification of underlying risks as data emerges.

Metabolite and Elastase Activity Changes in Beach Rose (Rosa rugosa) Fruit and Seeds at Various Stages of Ripeness

Rose hips are the fruits of the beach rose (Rosa rugosa). To determine the optimal harvest time and to obtain the maximum functional compounds, rose hips at various stages of ripeness (immature, early, mid, and late) were harvested, and the flesh tissue and seeds were separated. The rose hip flesh showed the highest total phenolic content at the mid-ripeness stage (8.45 ± 0.62 mg/g gallic acid equivalent concentration (dry weight)). The early-, mid-, and late-ripeness stages of rose hip flesh did not show significantly different 2,2-diphenyl-1-picrylhydrazyl antioxidant capacities. The elastase inhibitory activity of the 95% ethanol extract from the rose hip seeds was highest at the mid-ripeness stage; however, the elastase inhibitory activity of the rose hip tissue was not significantly different from that of the seeds. Pathway analysis using MetaboAnalyst showed that sucrose, fructose, and glucose gradually increased as the fruit ripened. Ursolic acid was detected in the seeds but not in the flesh. Of the fatty acids, linoleic acid concentrations were highest in rose hip seeds, followed by linolenic acid, oleic acid, and palmitic acid. Fatty acids and ursolic acid might be the active compounds responsible for elastase inhibitory activity and can be utilized as a functional cosmetic material.

Facile and Novel Synthesis of Spiky Gold Nanoparticles as an Efficient Antimicrobial Agent against Pseudomonas Aeruginosa

AIMS

The study aims to develop advanced antibacterial agents as nanoparticles instead of antibiotics due to the emergence of antimicrobial resistance.

BACKGROUND

Pseudomonas aeruginosa is capable of causing many diseases, including severe bacterial pneumonia. There is a need for an efficient antibacterial agent to kill these pathogens.

OBJECTIVE

The objective of the study is to synthesize advanced antibacterial agents as nanoparticles for biomedical applications that can play a vital role in killing Gram-negative bacteria (Pseudomonas aeruginosa).

METHOD

A novel fabricated growth of hydrophilic spiky gold nanoparticles (SGNPs) via reduction method is reported.

RESULTS

The surface plasmon resonance peak of the synthesized SGNPs was tuned under the near-infrared range. The SGNPs have anisotropic and spiky morphology with 68 nm size and -58 mV surface charge. They are pure, possessing adsorption similar to the organic material. Pseudomonas aeruginosa treated with synthesized SGNPs showed 60% bacterial death at the concentration of 100 μM.

CONCLUSION

This work consists of the novel synthesis of SGNPs via a safe and simple reduction method. The synthesized SGNPs exhibit strong antibacterial activity against the Gram-negative bacteria Pseudomonas aeruginosa measured using a microplate assay test. The result showed that these SGNPs are ideal for biomedical applications.

Mechanochemistry as an Alternative Method of Green Synthesis of Silver Nanoparticles with Antibacterial Activity: A Comparative Study

This study shows mechanochemical synthesis as an alternative method to the traditional green synthesis of silver nanoparticles in a comparative manner by comparing the products obtained using both methodologies and different characterization methods. As a silver precursor, the most commonly used silver nitrate was applied and the easily accessible lavender (Lavandula angustofolia L.) plant was used as a reducing agent. Both syntheses were performed using 7 different lavender:AgNO₃ mass ratios. The synthesis time was limited to 8 and 15 min in the case of green and mechanochemical synthesis, respectively, although a significant amount of unreacted silver nitrate was detected in both crude reaction mixtures at low lavender:AgNO₃ ratios. This finding is of particular interest mainly for green synthesis, as the potential presence of silver nitrate in the produced nanosuspension is often overlooked. Unreacted AgNO₃ has been removed from the mechanochemically synthesized samples by washing. The nanocrystalline character of the products has been confirmed by both X-ray diffraction (Rietveld refinement) and transmission electron microscopy. The latter has shown bimodal size distribution with larger particles in tens of nanometers and the smaller ones below 10 nm in size. In the case of green synthesis, the used lavender:AgNO₃ ratio was found to have a decisive role on the crystallite size. Silver chloride has been detected as a side-product, mainly at high lavender:AgNO₃ ratios. Both products have shown a strong antibacterial activity, being higher in the case of green synthesis, but this can be ascribed to the presence of unreacted AgNO₃. Thus, one-step mechanochemical synthesis (without the need to prepare extract and performing the synthesis as separate steps) can be applied as a sustainable alternative to the traditional green synthesis of Ag nanoparticles using plants.

Effect of various synthesis parameters on the stability of size controlled green synthesis of silver nanoparticles

In this study, we have focused on the green method using Litchi Chinensis Leaf Extract (LCLE) for the synthesis of silver nanoparticles (AgNPs). Here, the experimental control parameters (reducing/stabilizing agent quantity, reaction time and temperature, silver ion concentrations) were studied during the size controlled synthesis of silver nanoparticles and their physicochemical properties have been studied. For biological studies, the stability of AgNPs at physiological pH is of vital importance; hence, post-synthesis solution stability of AgNPs was examined at various pH conditions. Stable AgNPs are formed by treating the aqueous solution of AgNO3 with LCLE. Formation of AgNPs was observed visually by the change in the color and further characterized by the surface Plasmon resonance (SPR) peak observed at 436 nm by UV–vis spectroscopy. The synthesized AgNPs were also characterized for their size distribution by Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), Transmission electron microscope (TEM), crystalline nature by X-Ray Diffraction (XRD) and Fourier Transform infrared (FITR) for the functional groups present. The size of AgNPs was in the range of 40–50 nm, spherical in with face centered cubic (FCC) structure. The biomolecules (epicatechin) present in LCLE were responsible for reduction, capping, and stabilizing agent of AgNPs. Post- synthesis, the stability of AgNPs has been studied by changes in the SPR peaks at various pH (2–11) conditions using UV–vis spectroscopy. This size controlled nanoparticles are very stable at physiological pH and retain their intrinsic SPR property.

Biogenic Synthesis of Silver Nanoparticles with High Antimicrobial and Catalytic Activities using Sheng Di Huang (Rehmannia glutinosa)

Silver nanoparticles (AgNPs) are widely sought after for a variety of biomedical and environmental applications due to their antimicrobial and catalytic properties. We present here a green and simple synthesis of AgNPs utilizing traditional Chinese medicinal herbs. The screening of 20 aqueous herb extracts shows that Sheng Di Huang (Rehmannia glutinosa) had the most promising potential in producing AgNPs of 30±6 nm, with narrow size distribution and high crystallinity. The antimicrobial activities of these AgNPs conducted on E. coli cells were found to be superior in comparison to poly(vinylpyrrolidone)-capped AgNPs synthesized using common chemical method. Additionally, the AgNPs obtained possess excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol. We compared the phytochemical and FTIR spectral analyses of the herb extract before and after synthesis, in order to elucidate the phytochemicals responsible for the reduction of Ag⁺ ions and the capping of the AgNPs produced.

Application of biosynthesized metal nanoparticles in electrochemical sensors

Recently, the development of eco-friendly, cost-effective and reliable methods for synthesis of metal nanoparticles has drawn a considerable attention. The so-called green synthesis, using mild reaction conditions and natural resources as plant extracts and microorganisms, has established as a convenient, sustainable, cheap and environmentally safe approach for synthesis of a wide range of nanomaterials. Over the past decade, biosynthesis is regarded as an important tool for reducing the harmful effects of traditional nanoparticle synthesis methods commonly used in laboratories and industry. This review emphasizes the significance of biosynthesized metal nanoparticles in the field of electrochemical sensing. There is increasing evidence that green synthesis of nanoparticles provides a new direction in designing of cost-effective, highly sensitive and selective electrode-catalysts applicable in food, clinical and environmental analysis. The article is based on 157 references and provided a detailed overview on the main approaches for green synthesis of metal nanoparticles and their applications in designing of electrochemical sensor devices. Important operational characteristics including sensitivity, dynamic range, limit of detection, as well as data on stability and reproducibility of sensors have also been covered.

Critical analysis of biophysicochemical parameters for qualitative improvement of phytogenic nanoparticles

Conventional chemical approaches for synthesizing nanoparticles (NPs) may restrict their applicability as they are not eco-friendly, energetically efficient and often involve toxic reducing/capping agents; but phytonanotechnology enabled the synthesis of safe, inexpensive, highly biocompatible NPs. In this regard, thorough understanding of green components and the modulatory effects of different reaction conditions on the physicochemical parameters of green synthesized NPs would be a prerequisite, which is not depicted elsewhere. This review critically analyzes the relevant reaction conditions from their mechanistic viewpoints in plant-based synthesis of NPs arising fundamental issues which need to be determined carefully. The size, stability and surface chemistry of phytogenic NPs may be fabricated as a function of multiple interconnected reaction parameters and the plant species used. The therapeutic potential of phytogenic NPs may depend on the plant species used; and so the meticulous understanding of physicochemical parameters and the family wise shorting of elite plant species may potentially benefit the theranostic future of plant-based NPs.

Effect of silver nanoparticles and Bacillus cereus LPR2 on the growth of Zea mays

The effect of Plant Growth Promoting Rhizobacteria (Bacillus sp.) and silver nanoparticles on Zea mays was evaluated. The silver nanoparticles were synthesized from Tagetes erecta (Marigold) leaf and flower extracts, whereas PGPR isolated from spinach rhizosphere. The silver nanoparticles (AgNPs) were purified using ultra centrifugation and were characterized using UV-Vis spectroscopy at gradient wavelength and also by High Resolution Transmission Electron microscopy (HRTEM). The average particles size of AgNPs was recorded approximately 60 nm. Almost all potential isolates were able to produce Indole Acetic Acid (IAA), ammonia and Hydrogen cyanide (HCN), solubilized tricalcium phosphate and inhibited the growth of Macrophomina phaseolina in vitro but the isolate LPR2 was found the best among all. On the basis of 16S rRNA gene sequence, the isolate LPR2 was characterized as Bacillus cereus LPR2. The maize seeds bacterized with LPR2 and AgNPs individually showed a significant increase in germination (87.5%) followed by LPR2 + AgNPs (75%). But the maximum growth of root and shoot of maize plant was observed in seeds coated with LPR2 followed by AgNPs and a combination of both. Bacillus cereus LPR2 and silver nanoparticles enhanced the plant growth and LPR2 strongly inhibited the growth of deleterious fungal pathogen. Therefore, LPR2 and AgNPs could be utilized as bioinoculant and growth stimulator, respectively for maize.

Towards plant-mediated chemistry - Au nanoparticles obtained using aqueous extract of Rosa damascena and their biological activity in vitro

An eco-friendly, efficient, and controlled synthesis of gold nanoparticles with application of the aqueous extract of Rosa damascena (Au@RD NPs) without using any other reducing agents was studied. Au@RD NPs of narrow size distribution were characterized by UV-vis and FT-IR spectroscopies, transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, particle size analysis, and zeta potential measurements. In vitro stability experiments revealed that the Au@RD NPs were stable for over a year (pH ~ 3.5), proving a significant stabilizing potential of the aqueous RD extract. The high total content of polyphenols, flavonoids, and reducing sugars along with the powerful antioxidant activity of the RD extract was determined by spectroscopic and analytical methods. Colloids prepared from the purified and lyophilized Au@RD NPs (electrokinetic potential of ca. -33 mV) were stable for at least 24 h under terms similar to physiological conditions (pH = 7.4, PBS). The in vitro cytotoxicity of Au@RD NPs was investigated against peripheral blood mononuclear lymphocytes (PBML), acute promyelocytic leukemia (HL60), and human lung adenocarcinoma (A549). Selective cytotoxicity of Au@RD NPs towards cancer cells (HL60, A549) over normal cells (PBML) in vitro was explicitly demonstrated by viability assays. Comet assay revealed a higher level of DNA damages in cancer cells when compared with normal ones. Apoptotic death in cancer cells was proved by measuring caspases activity. Thus, the developed Au@RD NPs, obtained by the plant-mediated green synthesis, are attractive hybrid materials for the medical applications combining two active components - metal nanoparticles platform and plant-derived metabolites.