Lemon-Fruit-Based Green Synthesis of Zinc Oxide Nanoparticles and Titanium Dioxide Nanoparticles against Soft Rot Bacterial Pathogen Dickeya dadantii

Advances in bioinspired nanomaterials managing microbial biofilms and virulence: A critical analysis

Microbial virulence and biofilm formation stand as a big concern against the goal of achieving a green and sustainable future. Microbial pathogenesis is the process by which the microbes (bacterial, fungal, and viral) cause illness in their respective host organism. 'Nanotechnology' is a state-of-art discipline to address this problem. The use of conventional techniques against microbial proliferation has been challenging against the environment. To tackle this problem, there has been a revolution in this multi-disciplinary field, to address the aspect of bioinspired nanomaterials in the antibiofilm and antimicrobial sector. Bioinspired nanomaterials prove to be a potential antibiofilm and antimicrobial agent as they are non-hazardous to the environment and mostly synthesized using a single-step reduction protocol. They exhibit synergistic effects against bacterial, fungal, and viral pathogens and thereby, control the virulence. In this literature review, we have elucidated the potential of bioinspired nanoparticles as well as nanomaterials as a promising anti-microbial treatment pedagogy and throw light on the advancements in how smart photo-switchable platforms have been designed to exhibit both bacterial releasing as well as bacterial-killing properties. Certain limitations and possible outcomes of these bio-based nanomaterials have been discussed in the hope of achieving a green and sustainable ecosystem.

Preparation and characterization of pectin/hydroxyethyl cellulose/clay/TiO2 bionanocomposite films for microbial pathogen removal from contaminated water

Some of conventional wastewater disinfectants can have a harmful influence on the environment as well as human health. The aim of this investigation was synthesis and characterizes ecofriendly pectin/hydroxyethyl cellulose (HEC)/clay and pectin/HEC/clay incorporated with titanium dioxide nanoparticles (TiO2NPs) and use the prepared bionanocomposite as microbial disinfectants for real wastewater. Pectin/HEC/clay and pectin/HEC/clay/TiO2 bionanocomposite were characterized by various methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA). Mechanical properties and water vapor permeability (WVP) were carried out. The results of SEM showed that, the prepared bionanocomposite had a smooth surface. Additionally, TiO2 nanoparticles to the pectin/HEC/clay composites may lead to changes in the FTIR spectrum. The intensity of XRD peaks indicated that, TiO2NPs was small size crystallite. TGA illustrated that pectin has moderate thermal stability, while HEC generally exhibits good thermal stability. The TEM showed that, TiO2 nanoparticles have diameters <25 nm. On the other hand, antimicrobial activities of pectin/HEC/clay against Escherichia coli (E. coli), Staphylococcus aureus and Candida albicans have been enhanced by adding TiO2NPs. The minimum inhibitory concentration (MIC) of pectin/HEC/clay/TiO2 against E. coli was 200 mg/mL. Moreover, complete eradication of E. coli, Salmonella and Candida spp. from real wastewater was observed by using pectin/HEC/clay/TiO2 bionanocomposite. Finally, it can be concluded that, the synthesized bionanocomposite is environmentally friendly and considered an excellent disinfectant matter for removal of the microbial pathogens from wastewater to safely reuse.

Interaction of plants and metal nanoparticles: Exploring its molecular mechanisms for sustainable agriculture and crop improvement

Metal nanoparticles offer promising prospects in agriculture, enhancing plant growth and ensuring food security. Silver, gold, copper, and zinc nanoparticles possess unique properties making them attractive for plant applications. Understanding molecular interactions between metal nanoparticles and plants is crucial for unlocking their potential to boost crop productivity and sustainability. This review explores metal nanoparticles in agriculture, emphasizing the need to understand these interactions. By elucidating mechanisms, it highlights the potential for enhancing crop productivity, stress tolerance, and nutrient-use efficiency, contributing to sustainable agriculture and food security. Quantifying benefits and risks reveal significant advantages. Metal nanoparticles enhance crop productivity by 20% on average and reduce disease incidence by up to 50% when used as antimicrobial agents. They also reduce nutrient leaching by 30% and enhance soil carbon sequestration by 15%, but concerns about toxicity, adverse effects on non-target organisms, and nanoparticle accumulation in the food chain must be addressed. Metal nanoparticles influence cellular processes including sensing, signaling, transcription, translation, and post-translational modifications. They act as signaling molecules, activate stress-responsive genes, enhance defense mechanisms, and improve nutrient uptake. The review explores their catalytic role in nutrient management, disease control, precision agriculture, nano-fertilizers, and nano-remediation. A bibliometric analysis offers insights into the current research landscape, highlighting trends, gaps, and future directions. In conclusion, metal nanoparticles hold potential for revolutionizing agriculture, enhancing productivity, mitigating environmental stressors, and promoting sustainability. Addressing risks and gaps is crucial for their safe integration into agricultural practices.

Biologically inspired nanoformulations for the control of bacterial canker pathogens Clavibacter michiganensis subsp. michiganensis and subsp. capsici

Clavibacter michiganensis subsp. michiganensis (Cmm) and C. michiganensis subsp. capsici (Cmc) are phytopathogenic bacteria that cause bacterial canker disease in tomatoes and peppers, respectively. Bacterial canker disease poses serious challenges to solanaceous crops, causing significant yield losses and economic costs. Effective management necessitates the development of sustainable control strategies employing nanobiotechnology. In this study, the antibacterial effects of four Aspergillus sojae-mediated nanoformulations, including cobalt oxide nanoparticles (Co3O4 NPs), zinc oxide nanoparticles (ZnO NPs), cobalt ferrite nanoparticles (CoFe2O4 NPs), and CoFe2O4/functionalized multi-walled carbon nanotube (fMWCNT) bionanocomposite, were evaluated against Cmm and Cmc. The diameters of the zone of inhibition of A. sojae-mediated Co3O4 NPs, ZnO NPs, CoFe2O4 NPs, and CoFe2O4/fMWCNT bionanocomposite against Cmm and Cmc were 23.60mm, 22.09mm, 27.65mm, 22.51mm, and 19.33mm, 17.66mm, 21.64mm, 18.77mm, respectively. The broth microdilution assay was conducted to determine the minimal inhibitory and bactericidal concentrations. The MICs of Co3O4 NPs, ZnO NPs, CoFe2O4 NPs, and CoFe2O4/fMWCNT bionanocomposite against Cmm were 2.50mg/mL, 1.25mg/mL, 2.50mg/mL, and 2.50mg/mL, respectively. While, their respective MBCs against Cmm were 5.00mg/mL, 2.50mg/mL, 5.00mg/mL, and 5.00mg/mL. The respective MICs of Co3O4 NPs, ZnO NPs, CoFe2O4 NPs, and CoFe2O4/fMWCNT bionanocomposite against Cmc were 2.50mg/mL, 1.25mg/mL, 5.00mg/mL, and 5.00mg/mL. While, their respective MBCs against Cmc were 5.00mg/mL, 2.50mg/mL, 10.00mg/mL, and 10.00mg/mL. The morphological and ultrastructural changes of Cmm and Cmc cells were observed using field-emission scanning and transmission electron microscopy before and after treatment with sub-minimal inhibitory concentrations of the nanoformulations. Nanoformulation-treated bacterial cells became deformed and disrupted, displaying pits, deep cavities, and groove-like structures. The cell membrane detached from the bacterial cell wall, electron-dense particles accumulated in the cytoplasm, cellular components disintegrated, and the cells were lysed. Direct physical interactions between the prepared nanoformulations with Cmm and Cmc cells might be the major mechanism for their antibacterial potency. Further research is required for the in vivo application of the mycosynthesized nanoformulations as countermeasures to combat bacterial phytopathogens.

Nano zinc oxide mediated resuscitation of aged Cajanus cajan via modulating aquaporin, cell cycle regulatory genes and hormonal responses

KEY MESSAGE

Nanoparticle pretreatment improved the health of aged Cajanus cajan seeds viz., regulation of redox status, gene expression, and restoration of hormonal homeostasis. Ageing deteriorates the quality of seeds by lowering their vigor and viability, and terminating with loss of germination. These days, nanotechnology has been seen to revolutionize the agricultural sectors, and particularly nano zinc oxide (nZnO) has gained considerable interests due to its distinctive properties. The aim of the present work was to decipher the possibilities of using nZnO to rejuvenate accelerated aged (AA) seeds of Cajanus cajan. Both chemically (CnZnO) and green (GnZnO; synthesized using Moringa oleifera) fabricated nZnOs were characterized via standard techniques to interpret their purity, size, and shape. Experimental results revealed erratic germination with a decline in viability and membrane stability as outcomes of reactive oxygen intermediate (ROI) buildup in AA seeds. Application of nZnO substantially rebated the accrual of ROI, along with enhanced production of antioxidants, α-amylase activity, total sugar, protein and DNA content. Higher level of zinc was assessed qualitatively/ histologically and quantitatively in nZnO pulsed AA seeds, supporting germination without inducing toxicity. Meantime, augmentation in the gibberellic acid with a simultaneous reduction in the abscisic acid level were noted in nZnO invigorated seeds than that determined in the AA seeds, suggesting possible involvement of ROI in hormonal signalling. Furthermore, nZnO-subjected AA seeds unveiled differential expression of aquaporins and cell cycle regulatory genes. Summarizing, among CnZnO and GnZnO, later one holds better potential for a revival of AA seeds of Cajanus cajan by providing considerable tolerance against ageing-associated deterioration via recouping the cellular redox homeostasis, hormonal signaling, and alteration in expression patterns of aquaporin and cell cycle regulatory genes.

Green waste immobilized Ag/Cu feather like Bi-matrix on garment dye decomposes and their bio-efficacy

This paper describes a simple phyto-remediation of feather-like silver/copper bi-matrix (BMs) was constructed by employing pommagrant waste peel (PWP) extract as crucial role of reducing agent and chelating agents. Numerous strategies, including UV-Visible, XRD, SEM-EDX, and TEM and BET isotherm were used to analysis the optical, structural, surface area and functional properties. Ag/Cu BPNMs of TEM characterization shows feather-like architectural features with constrained size and shape. The Ag/Cu co-catalytic nanoparticles have a particle size of 34-64 nm. The photocatalytic efficiency of Ag/Cu BMs was investigated using a garment dye, Congo red (CR), at successive time intervals under halogen lamp exposure. For Ag/Cu bimetallic nanoparticles, the photocatalytic degradation rate was recorded to be 100% after 40 min which is caused by adsorption of Congo red dye molecules on Ag/Cu and their degradation by reactive oxygen species (ROS). ROS are free hydroxyl radicals such as •OH and O2• ions that have high oxidizing capacity. The developed Ag/Cu BMs shown effective bacteriostatic action against many infections.

Biogenic synthesis of ZnO and Al2O3 nanoparticles using Camellia sinensis and Origanum vulgare L. leaves extract for spectroscopic estimation of ofloxacin and ciprofloxacin in commercial formulations

The current study describes the biogenic synthesis of two metal oxides zinc oxide (ZnO), aluminum oxide (Al2O3) nanoparticles using Camellia sinensis, and Origanum vulgare L. leaves extract, respectively. The synthesized metal oxide nanoparticles were investigated using spectroscopic and microscopic techniques to confirm the formation of their nanostructures. Accurate and precise spectrofluorometric probes were proposed for the quantification of Ofloxacin (OFX) and Ciprofloxacin (CPFX) in their bulk and commercial formulations. The extraordinary properties of Zinc oxide and aluminum oxide nanoparticles (ZnONPs and Al2O3NPs) enhance the fluorescence intensity in the presence of 0.5 mL and 1.0 mL of sodium dodecyl sulfate (SDS, 1.0% w/v) as organizing agent for the detection of OFX and CPFX, respectively. The optical detection of both drugs at λex/em range 250-700 nm displayed linearity with a main correlation coefficient >0.999 at 1-300 (OFX-SDS-ZnONPs) and 0.5-100 (OFX-SDS-Al2O3NPs) ng mL-1,10-400 (CPFX-SDS-ZnONPs) and 0.1-50 (CPFX-SDS-Al2O3NPs) ng mL-1. The detection and quantification limits were found to be 0.04, 0.03, and 0.02, 0.04 ng mL-1, 0.13, 0.10, and 7.24, 0.09 ng mL-1 for the above-mentioned fluorescence systems, respectively. The suggested spectrofluorometric probes were validated and potentially applied for the estimation of OFX and CPFX in their bulk and commercial formulations.

Biofilm-Forming Ability of Phytopathogenic Bacteria: A Review of its Involvement in Plant Stress

Phytopathogenic bacteria not only affect crop yield and quality but also the environment. Understanding the mechanisms involved in their survival is essential to develop new strategies to control plant disease. One such mechanism is the formation of biofilms; i.e., microbial communities within a three-dimensional structure that offers adaptive advantages, such as protection against unfavorable environmental conditions. Biofilm-producing phytopathogenic bacteria are difficult to manage. They colonize the intercellular spaces and the vascular system of the host plants and cause a wide range of symptoms such as necrosis, wilting, leaf spots, blight, soft rot, and hyperplasia. This review summarizes up-to-date information about saline and drought stress in plants (abiotic stress) and then goes on to focus on the biotic stress produced by biofilm-forming phytopathogenic bacteria, which are responsible for serious disease in many crops. Their characteristics, pathogenesis, virulence factors, systems of cellular communication, and the molecules implicated in the regulation of these processes are all covered.

One-pot biogenic synthesis of C. limon/TiO2 with dual applications as an advance photocatalyst and antimicrobial agent

The present study portrays a facile, cost effective and environmental benign way for preparation of TiO₂ nanoparticles utilizing C. limon extract which possesses phytochemicals as reducing and stabilizing agents. Structural characterization by XRD reveals that C. limon/TiO₂ NPs exhibits anatase-type tetragonal crystallinity. An average crystallite-size is calculated using Debye Scherrer's method (3.79 nm), Williamson-Hall plot (3.60 nm), and Modified Debye Scherrer plot (3.68 nm) which are very much intercorrelated. The absorption peak at 274 nm (UV-Visible spectrum) corresponds to the bandgap (E_g) value of3.8 eV. The existence of different phytochemicals containing organic groups like N-H, C=O, O-H, has been elucidated from FTIR along with Ti-O bond stretching at wavenumber 780 cm^-1. Micro-structural investigations of TiO₂ NPs using FESEM and TEM display different geometrical configurations involving spherical, pentagons, hexagons, heptagons and capsule like structures. BET and BJH analysis show mesoporous characteristics of synthesized nanoparticles with specific surface-area (97.6 m² g^-1), pore-volume (0.018322 cm³ g^-1), and mean pore-diameter (∼7.5 nm) values. In adsorption studies, the influence of reaction parameters i.e., catalyst dosage and contact-time for removal of Reactive Green dye is explored along with Langmuir and Freundlich models. The highest adsorption capability is ∼219 mg g^-1 for green dye. TiO₂ displays an excellent photocatalytic efficiency of ∼96% towards the degradation of reactive green dye within 180 min and excellent reusable performance. C. limon/TiO₂ is found to have an outstanding performance with quantum yield value of 4.68 × 10^-5 molecules photon^-1 for Reactive Green dye degradation. Additionally, synthesized nanoparticles have exhibited antimicrobial activity against Gram-positive Staphylococcus aureus (S. aureus) and gram-negative Pseudomonas aeruginosa (P. aeruginosa) bacteria.

Recent Advances and Perspectives of Nanomaterials in Agricultural Management and Associated Environmental Risk: A Review

The advancement in nanotechnology has enabled a significant expansion in agricultural production. Agri-nanotechnology is an emerging discipline where nanotechnological methods provide diverse nanomaterials (NMs) such as nanopesticides, nanoherbicides, nanofertilizers and different nanoforms of agrochemicals for agricultural management. Applications of nanofabricated products can potentially improve the shelf life, stability, bioavailability, safety and environmental sustainability of active ingredients for sustained release. Nanoscale modification of bulk or surface properties bears tremendous potential for effective enhancement of agricultural productivity. As NMs improve the tolerance mechanisms of the plants under stressful conditions, they are considered as effective and promising tools to overcome the constraints in sustainable agricultural production. For their exceptional qualities and usages, nano-enabled products are developed and enforced, along with agriculture, in diverse sectors. The rampant usage of NMs increases their release into the environment. Once incorporated into the environment, NMs may threaten the stability and function of biological systems. Nanotechnology is a newly emerging technology, so the evaluation of the associated environmental risk is pivotal. This review emphasizes the current approach to NMs synthesis, their application in agriculture, interaction with plant-soil microbes and environmental challenges to address future applications in maintaining a sustainable environment.

Synergistic Action of Biosynthesized Silver Nanoparticles and Culture Supernatant of Bacillus amyloliquefacience against the Soft Rot Pathogen Dickeya dadantii

Nanomaterials are increasingly being used for crop growth, especially as a new paradigm for plant disease management. Among the other nanomaterials, silver nanoparticles (AgNPs) draw a great deal of attention because of their unique features and multiple usages. Rapid expansion in nanotechnology and utilization of AgNPs in a large range of areas resulted in the substantial release of these nanoparticles into the soil and water environment, causing concern for the safety of ecosystems and phytosanitary. In an attempt to find an effective control measure for sweet potato soft rot disease, the pathogen Dickeya dadantii was exposed to AgNPs, the cell-free culture supernatant (CFCS) of Bacillus amyloliquefaciens alone, and both in combination. AgNPs were synthesized using CFCS of Bacillus amyloliquefaciens strain A3. The green synthesized AgNPs exhibited a characteristic surface plasmon resonance peak at 410-420 nm. Electron microscopy and X-ray diffraction spectroscopy determined the nanocrystalline nature and 20-100 nm diameters of AgNPs. Release of metal Ag⁺ ion from biosynthesized AgNPs increases with time. AgNPs and CFCS of B. amyloliquefaciens alone exhibited antibacterial activity against the growth, biofilm formation, swimming motility, and virulence of strain A3. The antibacterial activities elevated with the elevation in AgNPs and CFCS concentration. Similar antibacterial activities against D. dadantii were obtained with AgNPs at 50 µg·mL^-1, 50% CFCS alone, and the combination of AgNPs at 12 µg·mL^-1 and 12% CFCS of B. amyloliquefaciens. In planta experiments indicated that all the treatments reduced D. dadantii infection and increased plant growth. These findings suggest that AgNPs along with CFCS of B. amyloliquefaciens can be applied to minimize this bacterial disease by controlling pathogen-contaminated sweet potato tuber with minimum Ag nano-pollutant in the environment.

Green synthesis and antimicrobial mechanism of nanoparticles: applications in agricultural and agrifood safety

The growing demand for food and its safety are a challenge for agriculture and agrifood. This has led to the incorporation of alternatives such as organic agriculture, the use of biocontrollers, the development of transgenic plants resistant to pathogens and the incorporation of nanotechnology. In this sense, agrochemicals based on nanoparticles (NPs) have been developed. Recently, the green synthesis of NPs has grown rapidly and, for this reason, molecules, microorganisms, fungi and plants are used. Synthesis from plant extracts offers a broad spectrum and, despite the fact that NPs are usually dispersed in size and shape, extensive antimicrobial effectiveness has been demonstrated at nanomolar concentrations. It has been shown that the mechanism of action can be through the dissipation of the driving force of the protons, the alteration of cellular permeability, the formation of bonds with the thiol group of the proteins, the generation of reactive species of oxygen, and the hyperoxidation of DNA, RNA and even the cell membrane. To improve the efficiency of NPs, modifications have been made such as coating with other metals, the addition of antibiotics, detergents and surfactants, as well as the acidification of the solution. Consequently, NPs are considered as a promising method for achieving safety in the agricultural and agrifood area. However, it is necessary to investigate the side effects of NPs, when applied in agroecological systems, on the textural, nutriment and sensory properties of food, as well as the impact on human health. © 2022 Society of Chemical Industry.

Current trends in management of bacterial pathogens infecting plants

Plants are continuously challenged by different pathogenic microbes that reduce the quality and quantity of produce and therefore pose a serious threat to food security. Among them bacterial pathogens are known to cause disease outbreaks with devastating economic losses in temperate, tropical and subtropical regions throughout the world. Bacteria are structurally simple prokaryotic microorganisms and are diverse from a metabolic standpoint. Bacterial infection process mainly involves successful attachment or penetration by using extracellular enzymes, type secretion systems, toxins, growth regulators and by exploiting different molecules that modulate plant defence resulting in successful colonization. Theses bacterial pathogens are extremely difficult to control as they develop resistance to antibiotics. Therefore, attempts are made to search for innovative methods of disease management by the targeting bacterial virulence and manipulating the genes in host plants by exploiting genome editing methods. Here, we review the recent developments in bacterial disease management including the bioactive antimicrobial compounds, bacteriophage therapy, quorum-quenching mediated control, nanoparticles and CRISPR/Cas based genome editing techniques for bacterial disease management. Future research should focus on implementation of smart delivery systems and consumer acceptance of these innovative methods for sustainable disease management.

Polyindole Embedded Nickel/Zinc Oxide Nanocomposites for High-Performance Energy Storage Applications

Conducting polymers integrated with metal oxides create opportunities for hybrid capacitive electrodes. In this work, we report a one-pot oxidative polymerization for the synthesis of integrated conductive polyindole/nickel oxide (PIn/NiO), polyindole/zinc oxide (PIn/ZnO), and polyindole/nickel oxide/zinc oxide (PNZ). The polymers were analyzed thoroughly for their composition and physical as well as chemical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and thermogravimetric analysis (TGA). The PIn and its composites were processed into electrodes, and their use in symmetrical supercapacitors in two- and three-electrode setups was evaluated by cyclic voltammetry (CV), galvanostatic discharge (GCD), and electrochemical impedance spectroscopy (EIS). The best electrochemical charge storage capability was found for the ternary PNZ composite. The high performance directly correlates with its uniformly shaped nanofibrous structure and high crystallinity. For instance, the symmetrical supercapacitor fabricated with PNZ hybrid electrodes shows a high specific capacitance of 310.9 F g^-1 at 0.5 A g^-1 with an energy density of 42.1 Wh kg^-1, a power density of 13.2 kW kg^-1, and a good cycling stability of 78.5% after 5000 cycles. This report presents new electrode materials for advanced supercapacitor technology based on these results.

Strategic nanoparticle-mediated plant disease resistance

Nanotechnology is a promising means for development of sustainable agriculture while the study of nanoparticle-mediated plant disease resistance is still in its primary stage. Nanotechnology has shown great promise in regulating: the content of secondary metabolites, inducing disease resistance genes, delivering hormones, delivering biomolecules (such as: nucleotides, proteins, and activators), and obtaining transgenic plants to resist plant diseases. In this review, we conclude its versatility and applicability in disease management strategies and diagnostics and as molecular tools. With the advent of new biotechnologies (e.g. de novo regeneration, CRISPR/Cas9, and GRF4-GIF1 fusion protein), we discuss the potential of nanoparticles as an optimal platform to deliver biomolecules to plants for genetic engineering. In order to ensure the safe use and social acceptance of plant nanoparticle technology, its adverse effects are discussed, including the risk of transferring nanoparticles through the food chain.

Comprehensive Study on Lemon Juice-Based Green Synthesis and Catalytic Activity of Bismuth Nanoparticles

Bismuth nanoparticles have gained considerable interest in catalysis because of their small size, large surface-to-volume ratio, and low toxicity. In spite of these advantages, the toxic reagents and solvents used in the synthetic process are significant limitations to their development and utilization. In this study, a green approach employing easily accessible lemon juice was applied for the synthesis of bismuth nanoparticles (BiNPs) as a green alternative to conventional chemical ones. This study clarified the formation and growing process of green-synthesized BiNPs using lemon juice as a reducing and capping agent. The reaction time and amounts of lemon juice significantly affect the growth, morphology, and stability of BiNPs, as confirmed from XRD, DLS, SEM, and TEM analyses. The synthesized BiNPs effectively catalyzed the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH₄, and the reduction was significantly accelerated by sunlight and the removal of the fibrous coating layer around BiNPs. Moreover, the synthesized BiNPs also show excellent catalytic efficacy toward the reduction of organic dyes, namely, methyl orange, methylene blue, and rhodamine B. All catalytic reductions followed the pseudo-first-order kinetics, and the rate constants are in the order of k _MB > k _RhB > k _MO > k _4-NP. The stated biogenic synthetic route paves the way for the green industrial fabrication of BiNPs and their uses in catalysis for wastewater treatment.

Biosynthesized metal oxide nanoparticles for sustainable agriculture: next-generation nanotechnology for crop production, protection and management

The current agricultural sector is not only in its most vulnerable state but is also becoming a threat to our environment due to expanding population and growing food demands along with worsening climatic conditions. In addition, numerous agrochemicals presently being used as fertilizers and pesticides have low efficiency and high toxicity. However, the rapid growth of nanotechnology has shown great promise to tackle these issues replacing conventional agriculture industries. Since the last decade, nanomaterials especially metal oxide nanoparticles (MONPs) have been attractive for improving agricultural outcomes due to their large surface area, higher chemical/thermal stability and tunable unique physicochemical characteristics. Further, to achieve sustainability, researchers have been extensively working on ecological and cost-effective biological approaches to synthesize MONPs. Hereby, we have elaborated on recent successful biosynthesis methods using various plants/microbes. Furthermore, we have elucidated different mechanisms for the interaction of MONPs with plants, including their uptake/translocation/internalization, photosynthesis, antioxidant activity, and gene alteration, which could revolutionize crop productivity/yield through increased nutrient amount, photosynthesis rate, antioxidative enzyme level, and gene upregulations. Besides, we have briefly discussed about functionalization of MONPs and their application in agricultural-waste-management. We have further illuminated recent developments of various MONPs (Fe₂O₃/ZnO/CuO/Al₂O₃/TiO₂/MnO₂) as nanofertilizers, nanopesticides and antimicrobial agents and their implications for enhanced plant growth and pest/disease management. Moreover, the potential use of MONPs as nanobiosensors for detecting nutrients/pathogens/toxins and safeguarding plant/soil health is also illuminated. Overall, this review attempts to provide a clear insight into the latest advances in biosynthesized MONPs for sustainable crop production, protection and management and their scope in the upcoming future of eco-friendly agricultural nanotechnology.

The emergence of metal oxide nanoparticles (NPs) as a phytomedicine: A two-facet role in plant growth, nano-toxicity and anti-phyto-microbial activity

Anti-microbial resistance (AMR) has recently emerged as an area of high interest owing to the rapid surge of AMR phenotypes. Metal oxide NPs (MeONPs) have been identified as novel phytomedicine and have recently peaked a lot of interest due to their potential applications in combating phytopathogens, besides enhancing plant growth and yields. Numerous MeONPs (Ti₂O, MgO, CuO, Ag₂O, SiO₂, ZnO, and CaO) have been synthesized and tested to validate their antimicrobial roles without causing toxicity to the cells. This review discusses the application of the MeONPs with special emphasis on anti-microbial activities in agriculture and enlists how cellular toxicity caused through reactive oxygen species (ROS) production affects plant growth, morphology, and viability. This review further highlights the two-facet role of silver and copper oxide NPs including their anti-microbial applications and toxicities. Furthermore, the factor modulating nanotoxicity and immunomodulation for cytokine production has also been discussed. Thus, this article will not only provide the researchers with the potential bottlenecks but also emphasizes a comprehensive outline of breakthroughs in the applicability of MeONPs in agriculture.

Green synthesis of titanium dioxide nanoparticles using plant biomass and their applications- A review

Biosynthesized nanoparticles have sparked a lot of interest as rapidly growing classes of materials for different applications. Plants are considered to be one of the most suitable sources for Green synthesis (GS) as they follow the environment-friendly route of biosynthesis of nanoparticles (NPs). This article focuses on the excavation of Titanium dioxide (TiO₂) NP from different parts of plants belonging to a distinct classification of taxonomic groups. During the process of biological synthesis of titanium NPs from plants, the extract derived from plant sources such as from root, stem, leaves, seeds, flowers, and latex possesses phytocompounds that tend to serve as both capping as well as reducing agents. TiO₂NP is one of the most commonly used engineered nanomaterials in nanotechnology-based consumer products. This article will provide an overview of the GS and characterization of TiO₂NPs from plant extracts of different taxonomic groups. Lastly, this review summarizes the current applications of TiO₂NPs.

Potential Applications of Engineered Nanoparticles in Plant Disease Management: A Critical Update

Plant diseases caused by pathogenic entities pose severe issues to global food security. Effective sensory applications and tools for the effective determination of plant diseases become crucial to the assurance of food supply and agricultural sustainability. Antibody-mediated molecular assays and nucleic acid are gold-standard approaches for plant disease diagnosis, but the evaluating methodologies are liable, complex, and laborious. With the rise in global food demand, escalating the food production in threats of diverse pathogen ranges, and climate change is a major challenge. Engineered nanoparticles (NPs) have been inserted into conventional laboratory sequence technologies or molecular assays that provide a remarkable increment in selectivity and sensitivity. In the present scenario, they are useful in plant disease management as well as in plant health monitoring. The use of NPs could sustainably mitigate numerous food security issues and or threats in disease management by decreasing the risk of chemical inputs and alleviating supra detection of pathogens. Overall, this review paper discusses the role of NPs in plant diseases management, available commercial products. Additionally, the future directions and their regulatory laws in the usage of the nano-diagnostic approach for plant health monitoring have been explained.

Facile Green Synthesis of Titanium Dioxide Nanoparticles by Upcycling Mangosteen (Garcinia mangostana) Pericarp Extract

In the present report, green synthesis of titanium dioxide nanoparticles (TiO₂ NPs) was performed by upcycling mangosteen (Garcinia mangostana) pericarp extract (methanol and ethyl acetate extracts). Field emission scanning electron microscopy images revealed an aggregated structure with a highly porous network of TiO₂ NPs. TiO₂ NPs synthesized with ethyl acetate extract (EtOAc-TiO₂ NPs) exhibited more monodispersity and possessed smoother surfaces than the control TiO₂ NPs (Con-TiO₂ NPs) and TiO₂ NPs synthesized with methanol extract (MeOH-TiO₂ NPs). High-resolution X-ray diffraction patterns clearly confirmed that TiO₂ NPs had a crystalline nature. A mixture of anatase and rutile was observed in Con-TiO₂ NPs and MeOH-TiO₂ NPs, while EtOAc-TiO₂ NPs had only anatase with the smallest size (12.50 ± 1.81 nm). Ethyl acetate extract contained the highest amount of α-mangostin; thus, the surface of TiO₂ NPs was functionalized with ethyl acetate extract. The functionalized TiO₂ NPs synthesized with ethyl acetate extract (EtOAc-TiO₂-αm) showed the highest 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) radical scavenging activity. In vitro cell viability on mouse fibroblast cells (NIH3T3) indicated that the newly synthesized TiO₂ NPs did not show any significant cytotoxicity. Therefore, the TiO₂ NPs in the present report have the potential to be used in cosmetic applications such as sunscreens.

Titanium and Zinc Based Nanomaterials in Agriculture: A Promising Approach to Deal with (A)biotic Stresses?

Abiotic stresses, such as those induced by climatic factors or contaminants, and biotic stresses prompted by phytopathogens and pests inflict tremendous losses in agriculture and are major threats to worldwide food security. In addition, climate changes will exacerbate these factors as well as their negative impact on crops. Drought, salinity, heavy metals, pesticides, and drugs are major environmental problems that need deep attention, and effective and sustainable strategies to mitigate their effects on the environment need to be developed. Besides, sustainable solutions for agrocontrol must be developed as alternatives to conventional agrochemicals. In this sense, nanotechnology offers promising solutions to mitigate environmental stress effects on plants, increasing plant tolerance to the stressor, for the remediation of environmental contaminants, and to protect plants against pathogens. In this review, nano-sized TiO₂ (nTiO₂) and ZnO (nZnO) are scrutinized, and their potential to ameliorate drought, salinity, and xenobiotics effects in plants are emphasized, in addition to their antimicrobial potential for plant disease management. Understanding the level of stress alleviation in plants by these nanomaterials (NM) and relating them with the application conditions/methods is imperative to define the most sustainable and effective approaches to be adopted. Although broad-spectrum reviews exist, this article provides focused information on nTiO₂ and nZnO for improving our understanding of the ameliorative potential that these NM show, addressing the gaps in the literature.

Rhamnella gilgitica functionalized green synthesis of ZnONPs and their multiple therapeutic properties

In the recent years, green synthesis of zinc oxide nanoparticles (ZnONPs) using plant extracts and phytochemicals has gained significant attention. In present research study, facile, green, and tunable ZnONPs were biosynthesized from Rhamnella gilgitica leaf aqueous extract as a strong reducing and stabilizing agents. The prepared ZnONPs@Rhamnella were characterized and validated using common nanotechnology techniques (UV-Vis, XRD, EDX, FT-IR, SEM, TEM, DLS, and Raman) and revealed spherical morphology with particle size ~21 nm. The asynthesized ZnONPs were further evaluated for different biological applications. Strong antimicrobial efficacies were reported for ZnONPs using disc-diffusion method and were capable of rendering significant antimicrobial potential. ZnONPs were evaluated against HepG2 (IC₅₀ : 18.40 μg/ml) and HUH7 (IC₅₀ : 20.59 μg/ml) cancer cell lines and revealed strong anticancer properties. Dose-dependent MTT cytotoxicity assay was confirmed using Leishmania tropica "KWH23 strain" (promastigote: IC₅₀ : 26.78 μg/ml and amastigote: IC₅₀ : 29.57 μg/ml). Antioxidant activities (DPPH: 93.36%, TAC: 72.43%) were performed to evaluate their antioxidant potentials. Further, protein kinase and α-amylase inhibition assays were determined. Biocompatibility assays were done using human RBCs and macrophages thus revealed biosafe and non-toxic nature of ZnONPs@Rhamnella. In current experiment, we concluded that greenly orchestrated ZnONPs is an attractive, non-toxic and ecofriendly candidate and showed potential biological activities. In future, different clinical trials and in vivo studies are necessary for the confirmation of these remedial properties of ZnONPs using different animal models.

Synthesis, Characterization, and Assessment of Anti-Cancer Potential of ZnO Nanoparticles in an In Vitro Model of Breast Cancer

Advanced innovations for combating variants of aggressive breast cancer and overcoming drug resistance are desired. In cancer treatment, ZnO nanoparticles (NPs) have the capacity to specifically and compellingly activate apoptosis of cancer cells. There is also a pressing need to develop innovative anti-cancer therapeutics, and recent research suggests that ZnO nanoparticles hold great potential. Here, the in vitro chemical effectiveness of ZnO NPs has been tested. Zinc oxide (ZnO) nanoparticles were synthesized using Citrullus colocynthis (L.) Schrad by green methods approach. The generated ZnO was observed to have a hexagonal wurtzite crystal arrangement. The generated nanomaterials were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-visible spectroscopy. The crystallinity of ZnO was reported to be in the range 50–60 nm. The NPs morphology showed a strong absorbance at 374 nm with an estimated gap band of 3.20 eV to 3.32 eV. Microscopy analysis proved the morphology and distribution of the generated nanoparticles to be around 50 nm, with the elemental studies showing the elemental composition of ZnO and further confirming the purity of ZnO NPs. The cytotoxic effect of ZnO NPs was evaluated against wild-type and doxorubicin-resistant MCF-7 and MDA-MB-231 breast cancer cell lines. The results showed the ability of ZnO NPs to inhibit the prefoliation of MCF-7 and MDA-MB-231 prefoliation through the induction of apoptosis without significant differences in both wild-type and resistance to doxorubicin.

Plant-Based Green Synthesis of Nanoparticles: Production, Characterization and Applications

Nanotechnology is a fast-expanding and multidisciplinary field with many applications in science and technology [...].

Silicon Dioxide Nanoparticles Induce Innate Immune Responses and Activate Antioxidant Machinery in Wheat Against Rhizoctonia solani

The phytopathogenic basidiomycetous fungus, Rhizoctonia solani, has a wide range of host plants including members of the family Poaceae, causing damping-off and root rot diseases. In this study, we biosynthesized spherical-shaped silicon dioxide nanoparticles (SiO2 NPs; sized between 9.92 and 19.8 nm) using saffron extract and introduced them as a potential alternative therapeutic solution to protect wheat seedlings against R. solani. SiO2 NPs showed strong dose-dependent fungistatic activity on R. solani, and significantly reduced mycelial radial growth (up to 100% growth reduction), mycelium fresh and dry weight, and pre-, post-emergence damping-off, and root rot severities. Moreover, the impact of SiO2 NPs on the growth of wheat seedlings and their potential mechanism (s) for disease suppression was deciphered. SiO2 NPs application also improved the germination, vegetative growth, and vigor indexes of infected wheat seedlings which indicates no phytotoxicity on treated wheat seedlings. Moreover, SiO2 NPs enhanced the content of the photosynthetic pigments (chlorophylls and carotenoids), induced the accumulation of defense-related compounds (particularly salicylic acid), and alleviated the oxidative stress via stimulation of both enzymatic (POD, SOD, APX, CAT, and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machinery. Collectively, our findings demonstrated the potential therapeutic role of SiO2 NPs against R. solani infection via the simultaneous activation of a multilayered defense system to suppress the pathogen, neutralize the destructive effect of ROS, lipid peroxidation, and methylglyoxal, and maintain their homeostasis within R. solani-infected plants.

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.

Therapeutic Applications of Metal and Metal-Oxide Nanoparticles: Dermato-Cosmetic Perspectives

Invention of novel nanomaterials guaranteeing enhanced biomedical performance in diagnostics and therapeutics, is a perpetual initiative. In this regard, the upsurge and widespread usage of nanoparticles is a ubiquitous phenomenon, focusing predominantly on the application of submicroscopic (< 100 nm) particles. While this is facilitated attributing to their wide range of benefits, a major challenge is to create and maintain a balance, by alleviating the associated toxicity levels. In this minireview, we collate and discuss particularly recent advancements in therapeutic applications of metal and metal oxide nanoparticles in skin and cosmetic applications. On the one hand, we outline the dermatological intrusions, including applications in wound healing. On the other hand, we keep track of the recent trends in the development of cosmeceuticals via nanoparticle engrossments. The dermato-cosmetic applications of metal and metal oxide nanoparticles encompass diverse aspects, including targeted, controlled drug release, and conferring ultraviolet and antimicrobial protections to the skin. Additionally, we deliberate on the critical aspects in comprehending the advantage of rheological assessments, while characterizing the nanoparticulate systems. As an illustration, we single out psoriasis, to capture and comment on the nanodermatology-based curative standpoints. Finally, we lay a broad outlook and examine the imminent prospects.

ZnO nanoparticles as efficient sunlight driven photocatalyst prepared by solution combustion method involved lime juice as biofuel

We have prepared high purity Zinc oxide (ZnO) nanoparticles (NPs) by solution combustion synthesis (SCS) method with the aid of lime juice extract. From powder X-ray diffraction (XRD) spectra, it is observed that the ZnO NPs possess single phase, hexagonal wurzite structure with sharp intense peak at (101) plane, agrees with the planes of SAED pattern. Further, the crystallite size is found to be around 18 nm. UV-Vis analysis shows strong UV absorbance band at 381 nm and PL measurements reveals the presence of strong UV emission at 347 nm along with few weak visible emissions. Optical studies infer the existence of lower recombination rate of electron-hole pair, influence the photocatalytic activity of ZnO. From XPS measurements, presence of oxygen rich states on surface are also confirmed (O 1 s states). The degradation performance and reusability of four different dyes (methylene blue (MB), methyl orange (MO), rhodamine B (RhB), Pararosaniline (PRA)) under UV and sunlight irradiations are carried out to illustrate the photo-catalytic activity in presence of a catalyst like ZnO NPs. Comparatively, about 98.8% of PRA and MB dyes are photodegraded at 90 and 75 min of sunlight irradiation, respectively. Among these two, PRA dye shows maximum degradation performance with shorter irradiation time along with good stability, which can be extend very well to minimize the pollution issues happening in society especially, industrial wastes.

Contact lenses coated with hybrid multifunctional ternary nanocoatings (Phytomolecule-coated ZnO nanoparticles:Gallic Acid:Tobramycin) for the treatment of bacterial and fungal keratitis

Contact lenses are widely used for visual corrections. However, while wearing contact lenses, eyes typically face discomforts (itching, irritation, burning, etc.) due to foreign object sensation, lack of oxygen permeability, and tear film disruption as opposed to a lack of wetting agents. Eyes are also prone to ocular infections such as bacterial keratitis (BK) and fungal keratitis (FK) and inflammatory events such as contact lens-related acute red eye (CLARE), contact lens peripheral ulcer (CLPU), and infiltrative keratitis (IK) caused by pathogenic bacterial and fungal strains that contaminate contact lenses. Therefore, a good design of contact lenses should adequately address the need for wetting, the supply of antioxidants, and antifouling and antimicrobial efficacy. Here, we developed multifunctional gallic acid (GA), phytomolecules-coated zinc oxide nanoparticles (ZN), and phytomolecules-coated zinc oxide nanoparticles + gallic acid + tobramycin (ZGT)-coated contact lenses using a sonochemical technique. The coated contact lenses exhibited significant antibacterial (>log₁₀ 5.60), antifungal, and antibiofilm performance against BK-causing multidrug resistant bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia. coli) and FK-related pathogenic fungal strains (Candida albicans, Aspergillus fumigatus, and Fusarium solani). The gallic acid, tobramycin, and phytomolecules-coated zinc oxide nanoparticles have different functionalities (-OH, -NH₂, -COOH, -COH, etc.) that enhanced wettability of the coated contact lenses as compared to that of uncoated ones and further enabled them to exhibit remarkable antifouling property by prohibiting adhesion of platelets and proteins. The coated contact lenses also showed significant antioxidant activity by scavenging DPPH and good cytocompatibility to human corneal epithelial cells and keratinocytes cell lines. STATEMENT OF SIGNIFICANCE: • Multifunctional coated lenses were developed with an efficient sonochemical approach. • Lens surface was modified with nanocoatings of ZnO nanoparticles, gallic acid, and tobramycin. • This synergistic combination endowed the lenses with remarkable antimicrobial activity. • Coated lenses also showed noteworthy antifouling and biofilm inhibition activities. • Coated lenses showed good antioxidant, biocompatibility, and wettability characteristics.

The emerging role of nanotechnology in skincare

The role of cosmetic products is rapidly evolving in our society, with their use increasingly seen as an essential contribution to personal wellness. This suggests the necessity of a detailed elucidation of the use of nanoparticles (NPs) in cosmetics. The aim of the present work is to offer a critical and comprehensive review discussing the impact of exploiting nanomaterials in advanced cosmetic formulations, emphasizing the beneficial effects of their extensive use in next-generation products despite a persisting prejudice around the application of nanotechnology in cosmetics. The discussion here includes an interpretation of the data underlying generic information reported on the product labels of formulations already available in the marketplace, information that often lacks details identifying specific components of the product, especially when nanomaterials are employed. The emphasis of this review is mainly focused on skincare because it is believed to be the cosmetics market sector in which the impact of nanotechnology is being seen most significantly. To date, nanotechnology has been demonstrated to improve the performance of cosmetics in a number of different ways: 1) increasing both the entrapment efficiency and dermal penetration of the active ingredient, 2) controlling drug release, 3) enhancing physical stability, 4) improving moisturizing power, and 5) providing better UV protection. Specific attention is paid to the effect of nanoparticles contained in semisolid formulations on skin penetration issues. In light of the emerging concerns about nanoparticle toxicity, an entire section has been devoted to listing detailed examples of nanocosmetic products for which safety has been investigated.

Breast Cancer Inhibition by Biosynthesized Titanium Dioxide Nanoparticles Is Comparable to Free Doxorubicin but Appeared Safer in BALB/c Mice

Cancer remains a global health burden prompting affordable, target-oriented, and safe chemotherapeutic agents to reduce its incidence rate worldwide. In this study, a rapid, cost-effective, and green synthesis of titanium dioxide (TiO₂) nanoparticles (NPs) has been carried out; Ex vivo and in vivoevaluation of their safety and anti-tumor efficacy compared to doxorubicin (DOX), a highly efficient breast anti-cancer agent but limited by severe cardiotoxicity in many patients.Thereby,TiO₂ NPs were eco-friendly synthetized using aqueous leaf extract of the tropical medicinal shrub Zanthoxylum armatum as a reducing agent. Butanol was used as a unique template. TiO₂ NPs were physically characterized by ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray powder diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) as routine state-of-the art techniques. The synthesized TiO₂ NPs were then evaluated for their cytotoxicity (by MTT, FACS, and oxidative stress assays) in 4T1 breast tumor cells, and their hemocompatibility (by hemolysis assay). In vivo anti-tumor efficacy and safety of the TiO₂ NPs were further assessed using subcutaneous 4T1 breast BALB/c mouse tumor model.The greenly prepared TiO₂ NPs were small, spherical, and crystalline in nature. Interestingly, they were hemocompatible and elicited a strong DOX-like concentration-dependent cytotoxicity-induced apoptosis both ex vivo and in vivo (with a noticeable tumor volume reduction). The underlying molecular mechanism was, at least partially, mediated through reactive oxygen species (ROS) generation (lipid peroxidation). Unlike DOX (P < 0.05), it is important to mention that no cardiotoxicity or altered body weight were observed in both the TiO₂ NPs-treated tumor-bearing mouse group and the PBS-treated mouse group (P > 0.05). Taken together, Z. armatum-derived TiO₂ NPs are cost-effective, more efficient, and safer than DOX. The present findings shall prompt clinical trials using green TiO₂ NPs, at least as a possible alternative modality to DOX for effective breast cancer therapy.

Bioinspired Green Synthesis of Zinc Oxide Nanoparticles from a Native Bacillus cereus Strain RNT6: Characterization and Antibacterial Activity against Rice Panicle Blight Pathogens Burkholderia glumae and B. gladioli

Burkholderia glumae and B. gladioli are seed-borne rice pathogens that cause bacterial panicle blight (BPB) disease, resulting in huge rice yield losses worldwide. However, the excessive use of chemical pesticides in agriculture has led to an increase in environmental toxicity. Microbe-mediated nanoparticles (NPs) have recently gained significant attention owing to their promising application in plant disease control. In the current study, we biologically synthesize zinc oxide nanoparticles (ZnONPs) from a native Bacillus cereus RNT6 strain, which was taxonomically identified using 16S rRNA gene analysis. The biosynthesis of ZnONPs in the reaction mixture was confirmed by using UV-Vis spectroscopy. Moreover, XRD, FTIR, SEM-EDS, and TEM analysis revealed the functional groups, crystalline nature, and spherical shape of ZnONPs with sizes ranging from 21 to 35 nm, respectively. Biogenic ZnONPs showed significant antibacterial activity at 50 µg mL-1 against B. glumae and B. gladioli with a 2.83 cm and 2.18 cm zone of inhibition, respectively, while cell numbers (measured by OD600) of the two pathogens in broth culture were reduced by 71.2% and 68.1%, respectively. The ultrastructure studies revealed the morphological damage in ZnONPs-treated B. glumae and B. gladioli cells as compared to the corresponding control. The results of this study revealed that ZnONPs could be considered as promising nanopesticides to control BPB disease in rice.

Recent Advances in Zinc Oxide Nanostructures with Antimicrobial Activities

This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties.

Bioinspired Green Synthesis of Chitosan and Zinc Oxide Nanoparticles with Strong Antibacterial Activity against Rice Pathogen Xanthomonas oryzae pv. oryzae

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastating diseases, resulting in significant yield losses in rice. The extensive use of chemical antibacterial agents has led to an increase the environmental toxicity. Nanotechnology products are being developed as a promising alternative to control plant disease with low environmental impact. In the present study, we investigated the antibacterial activity of biosynthesized chitosan nanoparticles (CSNPs) and zinc oxide nanoparticles (ZnONPs) against rice pathogen Xoo. The formation of CSNPs and ZnONPs in the reaction mixture was confirmed by using UV-vis spectroscopy at 300-550 nm. Moreover, CSNPs and ZnONPs with strong antibacterial activity against Xoo were further characterized by scanning and transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Compared with the corresponding chitosan and ZnO alone, CSNPs and ZnONPs showed greater inhibition in the growth of Xoo, which may be mainly attributed to the reduction in biofilm formation and swimming, cell membrane damage, reactive oxygen species production, and apoptosis of bacterial cells. Overall, this study revealed that the two biosynthesized nanoparticles, particularly CSNPs, are a promising alternative to control rice bacterial disease.

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

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

Effect of Colloidal Metal Nanoparticles on Biomass, Polysaccharides, Flavonoids, and Melanin Accumulation in Medicinal Mushroom Inonotus obliquus (Ach.:Pers.) Pilát

The article explores effect of colloidal nanoparticles (NPs) of Ag, Fe, and Mg metals on the growth activity of the medicinal mushroom Inonotus obliquus (Ach.:Pers.) Pilát and the synthesis of biologically active compounds (polysaccharides, flavonoids, and melanins). It was found that all the studied NPs stimulated growth activity. AgNPs inhibited polysaccharide and flavonoid synthesis, and stimulated melanin synthesis by 140%. Using MgNPs was effective to increase the level of accumulation of endopolysaccharides, flavonoids, and melanin pigments. FeNPs significantly increased the yield of endopolysaccharides. This effect should be used for biosynthesis stimulation for polysaccharides, flavonoids, and melanins obtaining from I. obliquus cultivated in vitro. The results demonstrate the potential of the use of metal colloidal solutions NPs for the development of environmentally friendly and effective biotechnology to produce biologically active compounds by medicinal macromycete I. obliquus.