Applications of plant terpenoids in the synthesis of colloidal silver nanoparticles

The formation and antibacterial activity of Zn/ZnO nanoparticle produced in Pometia pinnata leaf extract solution using a laser ablation technique

The single-step green synthesis has been successfully established to prepare a bi-phase structure of Zn/ZnO nanoparticles using laser ablation in a liquid medium. Nd: YAG laser with the wavelength of 1064 nm was employed to perform the laser ablation in pure water and Pometia pinnata (P. pinnata) leaf extract, with the leaf, were extracted in pure water and some concentration of ethanol. ZnO nanoparticles can be obtained via laser ablation in pure water, while the usage of P. pinnata leaf extract as the solution has caused the appearance of the bi-phase Zn/ZnO nanostructure. X-ray diffraction (XRD) pattern indicates the appearance of Zn peaks alongside with ZnO peaks with the inclusion of P. pinnata leaf extract. Transmission electron microscope (TEM) images show the change of shape from the rod-like shape into a spherical shape and smaller size spherical shape of Zn/ZnO nanoparticles in comparison with ZnO. Noticeable change of UV-visible spectrum emerges as the water was substituted by P. pinnata leaf extract. The zeta potential of Zn/ZnO prepared with P. pinnata extracted in water, with the value of - 18.9 V, reduces down to - 43.5 and - 41.1 for 20-40% of ethanol concentration, respectively. The as-prepared ZnO and Zn/ZnO colloidal samples were evaluated for their antibacterial activities against two strains Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Zn/ZnO sample shows a more substantial antibacterial effect in comparison with pure ZnO, no bacteria alive after 12 and 24 h' treatment for E. coli and S. aureus, respectively.

Conifer-Derived Metallic Nanoparticles: Green Synthesis and Biological Applications

The use of metallic nanoparticles in engineering and biomedicine disciplines has gained considerable attention. Scientists are exploring new synthesis protocols of these substances considering their small size and lucrative antimicrobial potential. Among the most economical techniques of synthesis of metallic nanoparticles via chemical routes, which includes the use of chemicals as metal reducing agents, is considered to generate nanoparticles possessing toxicity and biological risk. This limitation of chemically synthesized nanoparticles has engendered the exploration for the ecofriendly synthesis process. Biological or green synthesis approaches have emerged as an effective solution to address the limitations of conventionally synthesized nanoparticles. Nanoparticles synthesized via biological entities obtained from plant extracts exhibit superior effect in comparison to chemical methods. Recently, conifer extracts have been found to be effective in synthesizing metallic nanoparticles through a highly regulated process. The current review highlights the importance of conifers and its extracts in synthesis of metallic nanoparticles. It also discusses the different applications of the conifer extract mediated metallic nanoparticles.

Silver Nanoparticles: Mechanism of Action and Probable Bio-Application

This review is devoted to the medical application of silver nanoparticles produced as a result of "green" synthesis using various living organisms (bacteria, fungi, plants). The proposed mechanisms of AgNPs synthesis and the action mechanisms on target cells are highlighted.

Nano zinc elicited biochemical characterization, nutritional assessment, antioxidant enzymes and fatty acid profiling of rapeseed

The use of nanomaterials in agriculture is a current need and could be helpful in overcoming food security risks. Brassica napus L. is the third most important crop for edible oil, having double low unsaturated fatty acids. In the present study, we investigated the effects of green synthesized Zn NPs on biochemical effects, antioxidant enzymes, nutritional quality parameters and on the fatty acid profile of rapeseed (B. napus). Plant-mediated synthesis of zinc nanoparticles (Zn NPs) was carried out using Mentha arvensis L. leaf extract followed by characterization through ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-Ray (EDX), and X-Ray diffraction (XRD). NPs exhibited irregular shapes ranging in size from 30-70 nm and EDX analysis confirmed 96.08% of Zn in the sample. The investigated biochemical characterization (protein content, proline content, total soluble sugar (TSS), total flavonoid content (TFC), and total phenolic content (TPC) showed a substantial change on exposure to Zn NPs. A dose-dependent gradual increase was observed in the antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Oil and moisture contents dropped significantly from the control level in the rapeseed (B. napus) varieties. However, different trends in nutritional (Zn, Na+, K+) and fatty acid profiling of B. napus have been noted. This study demonstrates that Zn NPs have the potential to improve the biochemical, nutritional, antioxidant enzymes, and fatty acid profile of B. napus varieties.

Platinum Nanoparticles: Green Synthesis and Biomedical Applications

Platinum nanoparticles (PtNPs) have superior physicochemical properties and great potential in biomedical applications. Eco-friendly and economic approaches for the synthesis of PtNPs have been developed to overcome the shortcomings of the traditional physical and chemical methods. Various biogenic entities have been utilized in the green synthesis of PtNPs, including mainly plant extracts, algae, fungi bacteria, and their biomedical effects were assessed. Other biological derivatives have been used in the synthesis of PtNPs such as egg yolk, sheep milk, honey, and bovine serum albumin protein. The green approaches for the synthesis of PtNPs have reduced the reaction time, the energy required, and offered ambient conditions of fabrication. This review highlights the state-of-the-art methods used for green synthesis of PtNPs, synthesis parameters, and their reported biomedical applications.

Variation in surface properties, metabolic capping, and antibacterial activity of biosynthesized silver nanoparticles: comparison of bio-fabrication potential in phytohormone-regulated cell cultures and naturally grown plants

We compared surface properties, metabolic capping and antibacterial activity of silver nanoparticles, synthesized through extracts of cell cultures of Fagonia indica and its naturally grown form. Extracts from cell cultures (produced with thidiazuron (TDZ) or melatonin (MLN)) were compared to the naturally grown whole plant extracts (WPEs) for their reducing potential, and their effects on physical and biochemical properties of the biosynthesized silver nanoparticles. UV-Vis spectroscopy revealed that the surface plasmon resonance peaked at λ = 415 nm for MLN-AgNPs, λ = 430 nm for TDZ-AgNPs and λ = 460-465 nm for WPE-AgNPs. Transmission electron microscopy and energy dispersive X-rays of AgNPs showed that compared to WPE-AgNPs (mean diameter = 22 nm), extracts from MLN- and TDZ-induced cell cultures produced particles with spherical shapes and smaller diameters (i.e. mean diameter = 15 nm and 19 nm, respectively). Size distribution analysis also showed that TDZ-AgNPs were nearer to a symmetric distribution in terms of diameter (skewness = 0.80) as compared to WPE-AgNPs (skewness = 0.9) and MLN-AgNPs (skewness = 1.4). Furthermore, MLN-induced cell culture extracts produced AgNPs in higher concentration (210 μg mL-1) compared to AgNPs from TDZ-induced cell culture extracts (160 μg mL-1) and WPE (138 μg mL-1). Two-way comparisons of LC-MS/MS profiles of TDZ-AgNPs, MLN-AgNPs, and WPE-AgNPs revealed differences in their secondary metabolite profiles, which might account for differences in their differential response in bio-fabrication, and size distribution. Activity against different pathogenic bacterial strains, Escherichia coli, Bacillus cereus, Xanthomonas citri, Agrobacterium tumefaciens, Streptomyces griseus, and Erwinia carotovora suggested that MLN-AgNPs were more effective compared to TDZ- and WPE-AgNPs. These results indicated that phytohormones induced cell cultures can enhance the production, physical and biochemical properties of AgNPs.

Biogenic fabrication of nanomaterials from flower-based chemical compounds, characterization and their various applications: A review

Nanotechnology is evolving as a significant discipline of research with various applications. It includes the materials and their applications having one dimension in the range of 1-100 nm. Many chemical and physical protocol have been utilized for the nanoparticles (NPs) fabrication. These protocols are costly, hazardous and consumes high energy. Thus, researchers are inclined towards biological synthesis of NPs using plant and or herbal extract as these methods are simple, sustainable, ecofriendly and cost-effective. Flower is an important part of plants, and contained several phytochemicals such as flavonoids, terpenoids, coumarins, sterol and xanthones which acts as an important precursor for NPs synthesis. These compounds acted as reducing as well as stablishing agent during fabrication processes. They have been thoroughly characterized by various techniques. The fabricated NPs have shown potential antimicrobial activity against bacterial and fungal infections. They have been also used as potential therapeutic agent for human breast cancer, gastric adenocarcinoma cell, colorectal adenocarcinoma cell and pancreas ductal adenocarcinoma cells. Overall, the aim of this review article to facilitates the recent understanding of flower-mediated NPs fabrication (a sustainable and ecofriendly resource), their application in different disciplines and challenges.

Biosynthesized Silver Nanoparticles by Aqueous Stem Extract of Entada spiralis and Screening of Their Biomedical Activity

Silver nanoparticles (Ag-NPs) have been established as antibacterial nanoparticles and have been innovatively developed to overcome the occurrence of antibiotic resistance in the environment. In this study, an environmentally friendly and easy method of the biosynthesis of Ag-NPs plants, mediated by aqueous extract stem extract of Entada spiralis (E. spiralis), was successfully developed. The E. spiralis/Ag-NPs samples were characterized using spectroscopy and the microscopic technique of UV-visible (UV-vis), X-ray Diffraction (XRD), Field Emission Transmission Electron Microscope (FETEM), zeta potential, and Fourier Transform Infrared (FTIR) analyses. Surface Plasmon Resonance (SPR) absorption at 400-450 nm in the UV-vis spectra established the formation of E. spiralis/Ag-NPs. The crystalline structure of E. spiralis/Ag-NPs was displayed in the XRD analysis. The small size, around 18.49 ± 4.23 nm, and spherical shape of Ag-NPs with good distribution was observed in the FETEM image. The best physicochemical parameters on Ag-NPs biosynthesis using E. spiralis extract occurred at a moderate temperature (~52.0°C), 0.100 M of silver nitrate, 2.50 g of E. spiralis dosage and 600 min of stirring reaction time. The antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Proteus vulgaris using an antibacterial disk diffusion assay. Based on the results, it is evident that E. spiralis/Ag-NPs are susceptible to all the bacteria and has promising potential to be applied in both the industry and medical fields.

Comparison of biogenic silver nanoparticles formed by Momordica charantia and Psidium guajava leaf extract and antifungal evaluation

Exploiting plant extracts to form metallic nanoparticles has been becoming the promising alternative routes of chemical and physical methods owing to environmentally friendly and abundantly renewable resources. In this study, Momordica charantia and Psidium guajava leaf extract (MC.broth and PG.broth) are exploited to fabricate two kinds of biogenic silver nanoparticles (MC.AgNPs and PG.AgNPs). Phytoconstituent screening is performed to identify the categories of natural compounds in MC.broth and PG.broth. Both extracts contain wealthy polyphenols which play a role of reducing agent to turn silver (I) ions into silver nuclei. Trace alkaloids, rich saponins and other oxygen-containing compounds creating the organic corona surrounding nanoparticles act as stabilizing agents. MC.AgNPs and PG.AgNPs are characterized by UV-vis and FTIR spectrophotometry, EDS and TEM techniques. FTIR spectra indicate the presence of O-H, C = O, C-O-C and C = C groups on the surface of silver nanoparticles which is corresponded with three elements of C, O and Ag found in EDS analysis. TEM micrographs show the spherical morphology of MC.AgNPs and PG.AgNPs. MC.AgNPs were 17.0 nm distributed in narrow range of 5–29 nm, while the average size of PG.AgNPs were 25.7 nm in the range of 5–53 nm. Further, MC.AgNPs and PG.AgNPs exhibit their effectively inhibitory ability against A. niger, A. flavus and F. oxysporum as dose-dependence. Altogether, MC.AgNPs and PG.AgNPs will have much potential in scaled up production and become the promising fungicides for agricultural applications.

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

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

Green synthesis of silver nanoparticles for application in cosmetics

In this work, we analyzed the advantages of using silver nanoparticles (AgNPs) synthesized with natural extracts in ultraviolet-visible spectroscopy (UV-Vis) protective cream. The photodegradation properties of the new UV-Vis protective milk show an increase in its absorption band compared to AgNP-free cream. Previous to the study of the AgNPs mixed within the body milk, we studied the optical UV-Vis properties of extracts at different collection times, as they can influence the spectral range of UV-Vis absorption of the hybrid compound (AgNPs + natural extract). Shape and size of the AgNPs differs from the type of reducing agent as well as the concentration of silver nitrate used. We also compared the cytotoxicity in cell lines and the antibacterial effect of the AgNPs without and with organic coating. All these studies showed that we obtained hybrid sun-protective body milk with a high degree of solar protection and with low cytotoxicity at a cellular level, thus improving its protective properties. The synthetized hybrid compound could be a possible cost-affordable alternative for the market.

Silver nanoparticles: Synthesis, medical applications and biosafety

Silver nanoparticles (AgNPs) have been one of the most attractive nanomaterials in biomedicine due to their unique physicochemical properties. In this paper, we review the state-of-the-art advances of AgNPs in the synthesis methods, medical applications and biosafety of AgNPs. The synthesis methods of AgNPs include physical, chemical and biological routes. AgNPs are mainly used for antimicrobial and anticancer therapy, and also applied in the promotion of wound repair and bone healing, or as the vaccine adjuvant, anti-diabetic agent and biosensors. This review also summarizes the biological action mechanisms of AgNPs, which mainly involve the release of silver ions (Ag+), generation of reactive oxygen species (ROS), destruction of membrane structure. Despite these therapeutic benefits, their biological safety problems such as potential toxicity on cells, tissue, and organs should be paid enough attention. Besides, we briefly introduce a new type of Ag particles smaller than AgNPs, silver Ångstrom (Å, 1 Å = 0.1 nm) particles (AgÅPs), which exhibit better biological activity and lower toxicity compared with AgNPs. Finally, we conclude the current challenges and point out the future development direction of AgNPs.

Photocatalytic dye degradation and antimicrobial activities of Pure and Ag-doped ZnO using Cannabis sativa leaf extract

A facile green route has been employed for the synthesis of ZnO and Ag-doped ZnO using Cannabis sativa as a reducing and stabilizing agent. The as-synthesized nanoparticles were characterized and tested for photocatalytic dye degradation and antimicrobial activity. The results suggested that nanoparticles have shown antimicrobial activity against different human pathogenic bacteria (Escherichia coli, Klebsiella pneumonia, MRSA, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus) and fungal strains (Fusarium spp. and Rosellinia necatrix). Ag-doped nanoparticles comparatively have shown better removal Congo red and methyl orange under visible light. Therefore, green synthesized nanoparticles could have beneficial applications in environmental science and biological field.

Eco-friendly green synthesis of clove buds extract functionalized silver nanoparticles and evaluation of antibacterial and antidiatom activity

Biological fouling has caused a lot of concern in marine industries due to the attachment of microorganisms on marine surfaces. Silver nanoparticles (AgNPs) have a great potential to inhibit and hold strong toxicity against microorganisms on artificial surfaces immersed in seawater. In this study, AgNPs are synthesized using extract of clove buds (CE) plant as a reducing and stabilizing agent by biological synthesis method. The obtained CE-AgNPs product was characterized by using different techniques. Ultraviolet-visible spectroscopy (UV-Vis) results confirmed the formation of CE-AgNPs with its surface plasmon resonance peak range. Fourier-transform infrared spectroscopy (FTIR) study showed the formation of functional groups responsible for the reduction of Ag⁺ into Ag^o. X-Ray Diffraction (XRD) results revealed face-centered cubic (fcc) silver crystals having four different diffraction peaks at 38.08, 44.21, 64.42 and 77.32 with corresponding lattice plane value recorded at (111), (200), (220) and (311), respectively. Structural characterization using scanning electron microscopy equipped with energy dispersive X-Ray Analyzer (SEM-EDX), Transmission electron microscopy (TEM) and atomic force microscopy (AFM) also confirmed the successful formation of CE-AgNPs with fcc structure. The histogram of particle size distribution through TEM image showed an average size of 9.42 nm of the synthesized product. Finally, the antibacterial and antidiatom activity of the synthesized product was analyzed. The CE-AgNPs synthesized using CE possesses good inhibitory activity against the marine bacterium community and Nitzschia closterium diatom. These results indicate that CE-AgNPs can be used as a novel material for antibacterial and antidiatoms means to inhibit the biofouling on marine surfaces.

Flower-Based Green Synthesis of Metallic Nanoparticles: Applications beyond Fragrance

Green synthesis has gained wide attention as a sustainable, reliable, and eco-friendly approach to the synthesis of a variety of nanomaterials, including hybrid materials, metal/metal oxide nanoparticles, and bioinspired materials. Plant flowers contain diverse secondary compounds, including pigments, volatile substances contributing to fragrance, and other phenolics that have a profound ethnobotanical relevance, particularly in relation to the curing of diseases by 'Pushpa Ayurveda' or floral therapy. These compounds can be utilized as potent reducing agents for the synthesis of a variety of metal/metal oxide nanoparticles (NPs), such as gold, silver, copper, zinc, iron, and cadmium. Phytochemicals from flowers can act both as reducing and stabilizing agents, besides having a role as precursor molecules for the formation of NPs. Furthermore, the synthesis is mostly performed at ambient room temperatures and is eco-friendly, as no toxic derivatives are formed. The NPs obtained exhibit unique and diverse properties, which can be harnessed for a variety of applications in different fields. This review reports the use of a variety of flower extracts for the green synthesis of several types of metallic nanoparticles and their applications. This review shows that flower extract was mainly used to design gold and silver nanoparticles, while other metals and metal oxides were less explored in relation to this synthesis. Flower-derived silver nanoparticles show good antibacterial, antioxidant, and insecticidal activities and can be used in different applications.

Biogenic platinum nanoparticles using black cumin seed and their potential usage as antimicrobial and anticancer agent

Herein, the biogenic platinum nanoparticles (Pt NPs) were synthesized by using black cumin seed (Nigella sativa L.) extract as a reducing agent. The biogenic platinum nanoparticles synthesized by black cumin seed extract was characterized in detail by Transmission Electron Microscopy (TEM), UV-vis spectrophotometer, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). According to TEM analysis, Pt nanoparticles have spherical shapes and sizes between 1-6 nm. Moreover, the biogenic Pt NPs was assessed for its cytotoxicity effect on MDA-MB-231 breast and HeLa cervical cancer lines and their antibacterial effect against selected strains of gram-positive and negative bacteria. The cytotoxicity and bacterial tests showed the effectiveness of biogenic Pt nanoparticles. Dose-dependent toxicity effects were shown in the MDA-MB-231 breast and HeLa cervical cancer lines (IC50: 36.86 μg/mL and 19.83 μg/mL, respectively). In addition, Pt NPs showed high zone diameters against gram-positive and gram-negative bacteria at concentrations of 100 and 500 μg/ml. These results contribute to the development of the pharmaceutical industry as a potential antibacterial and anticancer agent.

Plant-based gold nanoparticles; a comprehensive review of the decade-long research on synthesis, mechanistic aspects and diverse applications

The worldwide focus on research in the field of green nanotechnology has resulted in the environmentally and biologically safe applications of a diversity of nanomaterials. Nanotechnology, in general, implies the production of nanoparticles having different but regular shapes, sizes, and properties. A lot of studies have been conducted on the synthesis of metal nanoparticles through biological, chemical, and physical methods. Owing to its safety, both environmental and in vivo, as well as the ease of synthesis, biogenic routes especially the plant-based synthesis of metal nanoparticles has been preferred as the best strategy. Among the metal nanoparticles, gold nanoparticles are recognized as the most potent, biocompatible and environment-friendly. A decade of research work has attempted the production of gold nanoparticles mediated by different parts of various plants. Further, these nanoparticles have been engineered through modification in the sizes and shapes for attaining enhanced activity and optimal performance in many different applications including biomedical, antimicrobial, diagnostics and environmental applications. This article reviews the fabrication strategies for gold nanoparticles via plant-based routes and highlights the diversity of the applications of these materials in bio-nanotechnology. The review article also highlights the recent developments in the synthesis and optical properties of gold nanoparticles.

Electrochemical Detection of Gallic Acid-Capped Gold Nanoparticles Using a Multiwalled Carbon Nanotube-Reduced Graphene Oxide Nanocomposite Electrode

Recently, a plethora of ecofriendly methods have been developed for the synthesis of AuNPs using a multitude of biogenic agents. Polyphenols from plants are particularly attractive for producing AuNPs because in addition to helping with the synthesis of AuNPs, the polyphenol capping of the NPs can be used as a platform for versatile applications. Polyphenol-capped AuNPs could also make the detection of AuNPs possible, should they be released into the environment. Because polyphenols are redox-active, they can be used as a probe to detect AuNPs using electrochemical techniques. In this work, we have developed an MWCNT-rGO nanocomposite electrode for the sensitive detection of AuNPs capped with gallic acid (GA, a green-tea-derived polyphenol) using differential pulse voltammetry (DPV). The reduction of gallic acid-capped AuNPs was used as the quantification signal, and the calibration curve displayed a detection limit of 2.57 pM. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), we have shown that the modification of the electrode surface with an MWCNT-rGO hybrid nanocomposite resulted in a 10-fold increase in current response leading to the sensitive detection of GA-AuNPs compared to unmodified electrodes. We have also demonstrated the applicability of the electrochemical sensor in detecting GA-AuNPs in various analytical matrixes such as human serum and natural creek water (Highland Creek, ON) with good recovery.

Essential Oils and Isolated Terpenes in Nanosystems Designed for Topical Administration: A Review

Essential oils are natural products with a complex composition. Terpenes are the most common class of chemical compounds present in essential oils. Terpenes and the essential oils containing them are widely used and investigated by their pharmacological properties and permeation-enhancing ability. However, many terpenes and essential oils are sensitive to environmental conditions, undergoing volatilization and chemical degradation. In order to overcome the chemical instability of some isolated terpenes and essential oils, the encapsulation of these compounds in nanostructured systems (polymeric, lipidic, or molecular complexes) has been employed. In addition, nanoencapsulation can be of interest for pharmaceutical applications due to its capacity to improve the bioavailability and allow the controlled release of drugs. Topical drug administration is a convenient and non-invasive administration route for both local and systemic drug delivery. The present review focuses on describing the current status of research concerning nanostructured delivery systems containing isolated terpenes and/or essential oils designed for topical administration and on discussing the use of terpenes and essential oils either for their biological activities or as permeation enhancers in pharmaceutic formulations.

Methylene blue dye removal on silver nanoparticles reduced by Kyllinga brevifolia

Silver nanoparticles (AgNPs) were prepared by reacting Kyllinga brevifolia extract (KBE) with AgNO₃ aqueous solution at room temperature (22 ± 3 °C). The phytochemical constituents in KBE responsible for the reduction process were identified as carbohydrate, protein, and plant sterols (stigmasterol and campesterol). KBE was also found to function as a capping agent for stabilization of AgNPs. The AgNPs were stable at room temperature and had a quasi-spherical shape with an average particle size 22.3 nm. The use of KBE offers not only eco-friendly and non-pathogenic path for AgNPs formation, it also induced rapid formation of the AgNPs. Methylene blue (MB) removal was then done on the AgNPs in the presence of either KBE or NaBH₄. Ninety-three percent removal of MB was achieved with a rate of reaction 0.2663 min^-1 in the solution with KBE+AgNPs (pH 2). However, in NaBH₄+AgNPs system, 100% MB removal was achieved at pH 8-10. The reaction rate was 2.5715 min^-1 indicating a fast removal rate of MB dye. The process of reduction occurs via electron relay effect whereas in KBE+AgNPs system, sedimentation occurred along with the reduction process. Nevertheless, the use of KBE+AgNPs system is preferred as the reducing agent is more benign to the environment.

In vivo biosynthesis and spatial distribution of Ag nanoparticles in maize (Zea mays L.)

Nanoparticles (NPs), especially biosynthesised in living plants by absorbing soluble salts and reducing metal ions, are extensively used in various fields. This work aimed at investigating the in vivo biosynthesis of silver NPs (Ag-NPs) in maize and the spatial distribution of the NPs and some important nutrient elements in the plant. The content of silver in plant was examined by inductively coupled plasma-atomic emission spectrometer showing that Ag can be absorbed by plant as soluble salts. The NPs in different parts of maize plant were detected and analysed by transmission electron microscopy, demonstrating the synthesis of NPs and their transport from the root to the shoots. Two-dimensional proton induced X-ray emission of silver, chlorine and several nutrient elements elucidated the possible relationship between synthesis of NPs and several nutrient elements in plant tissues. To their knowledge, this is the first report of possibility of synthesis of Ag-NPs in living plants maize (Zea mays L.). This study presents direct evidence for synthesis of NPs and distribution of related nutrient elements in maize, which has great significance for studying synthetic application of NPs in crop plants.

Silver nanoparticles as antimicrobial therapeutics: current perspectives and future challenges

Utility of silver metal in antimicrobial therapy is an accepted practice since ages that faded with time because of the identification of a few silver resistant strains in the contemporary era. A successive development of antibiotics soon followed. However, due to an indiscriminate and unregulated use coupled with poor legal control measures and a dearth of expertise in handling the critical episodes, the antibiotics era has already seen a steep decline in the past decades due to the evolution of multi-drug resistant 'superbugs' which pose a sizeable challenge to manage with. Due to limited options in the pipeline and no clear strategy in the forefront, the aspirations for novel, MDR focused drug discovery to target the 'superbugs' arose which once again led to the rise of AgNPs in antimicrobial research. In this review, we have focused on the green routes for the synthesis of AgNPs, the mode of microbial inhibition by AgNPs, synergistic effect of AgNPs with antibiotics and future challenges for the development of nano-silver-based therapeutics.

Glutamic acid assisted phyto-management of silver-contaminated soils through sunflower; physiological and biochemical response

Phytoremediation is a cost-effective and eco-friendly technique for the removal of heavy metal-contaminated soils and water. The less availability and mobility of heavy metals in medium decreased the efficiency of this technique. The mobility and availability of these metals in the medium can be enhanced by the addition of organic chelators. The present study was conducted to investigate the possibility of glutamic acid (GA) in improving silver (Ag) phytoextraction by sunflower (Helianthus annuus L.). Different concentrations of Ag and GA were supplied in solution form in different combinations after defined intervals. Results depicted that increasing concentration of Ag significantly reduced the plant biomass, photosynthetic pigments, and antioxidant enzyme activities (like catalase, peroxidase, ascorbate, peroxidase, superoxide dismutase). Furthermore, Ag stress increased the Ag concentration and the production of reactive oxygen species (ROS) in sunflower plants. The addition of GA alleviated the Ag-induced toxicity in plants and enhanced Ag concentration and accumulation in sunflower. The addition of GA enhanced Ag accumulation in sunflower roots by 70, 79, 58, and 66% at 0-, 100-, 250-, and 500-μM Ag treatments, respectively, as compared to control plants. In conclusion, the results showed that Ag significantly reduced the physiological and biochemical attributes in term of reduced growth of sunflower and the addition of GA alleviated the Ag induced toxicity and enhanced Ag uptake. The results suggested that sunflower can be used as hyper-accumulator plant for the removal of Ag under GA. Further studies are required to understand the role of GA at gene and microscopic level in plants.

Biogenic synthesis of Au, Ag and Au–Ag alloy nanoparticles using Cannabis sativa leaf extract

Biogenic synthesis of gold (Au), silver (Ag) and bimetallic alloy Au–Ag nanoparticles (NPs) from aqueous solutions using Cannabis sativa as reducing and stabilising agent has been presented in this report. Formation of NPs was monitored using UV–visible spectroscopy. Morphology of the synthesised metallic and bimetallic NPs was investigated using X‐ray diffraction and scanning electron microscopy. Elemental composition and the surface chemical state of NPs were confirmed by energy dispersive X‐ray spectroscopy analysis. Fourier transform‐infrared spectroscopy was utilised to identify the possible biomolecules responsible for the reduction and stabilisation of the NPs. Biological applicability of biosynthesised NPs was tested against five bacterial strains namely Klebsiella pneumonia , Bacillus subtilis (B. subtilis ), Escherichia coli , Staphylococcus aureus and Pseudomonas aeruginosa (P. aeruginosa ) and Leishmania major promastigotes. The results showed considerable antibacterial and anti‐leishmanial activity. The Au–Ag bimetallic NPs showed improved antibacterial activity against B. subtilis and P. aeruginosa as compared to Au and Ag alone, while maximum anti‐leishmanial activity was observed at 250 μg ml−1 NP concentration. These results suggest that biosynthesised NPs can be used as potent antibiotic and anti‐leishmanial agents.

Synthesis Approaches of Zinc Oxide Nanoparticles: The Dilemma of Ecotoxicity

Human’s quest for innovation, finding solutions of problems, and upgrading the industrial yield with energy efficient and cost-effective materials has opened the avenues of nanotechnology. Among a variety of nanoparticles, zinc oxide nanoparticles (ZnO) have advantages because of the extraordinary physical and chemical properties. It is one of the cheap materials in cosmetic industry, nanofertilizers, and electrical devices and also a suitable agent for bioimaging and targeted drug and gene delivery and an excellent sensor for detecting ecological pollutants and environmental remediation. Despite inherent toxicity of nanoparticles, synthetic routes are making use of large amount of chemical and stringent reactions conditions that are contributing as environmental contaminants in the form of high energy consumption, heat generation, water consumption, and chemical waste. Further, it is also adding to the innate toxicity of nanoparticles (NPs) that is either entirely ignored or poorly investigated. The current review illustrates a comparison between pollutants and hazards spawned from chemical, physical, and biological methods used for the synthesis of ZnO. Further, the emphasis is on devising eco-friendly techniques for the synthesis of ZnO especially biological methods which are comparatively less hazardous and need to be optimized by controlling the reaction conditions in order to get desired yield and characteristics.

Green synthesis of silver nanoparticles via plant extracts: beginning a new era in cancer theranostics

With the development of the latest technologies, scientists are looking to design novel strategies for the treatment and diagnosis of cancer. Advances in medicinal plant research and nanotechnology have attracted many researchers to the green synthesis of metallic nanoparticles due to its several advantages over conventional synthesis (simple, fast, energy efficient, one pot processes, safer, economical and biocompatibility). Medicinally active plants have proven to be the best reservoirs of diverse phytochemicals for the synthesis of biogenic silver nanoparticles (AgNPs). In this review, we discuss mechanistic advances in the synthesis and optimization of AgNPs from plant extracts. Moreover, we have thoroughly discussed the recent developments and milestones achieved in the use of biogenic AgNPs as cancer theranostic agents and their proposed mechanism of action. Anticipating all of the challenges, we hope that biogenic AgNPs may become a potential cancer theranostic agent in the near future.