New oligochitosan-nanosilica hybrid materials: preparation and application on chili plants for resistance to anthracnose disease and growth enhancement

Multifactorial role of nanoparticles in alleviating environmental stresses for sustainable crop production and protection

In the era of dire environmental fluctuations, plants undergo several stressors during their life span, which severely impact their development and overall growth in negative aspects. Abiotic stress factors, especially moisture stress i.e shortage (drought) or excess (flooding), salinity, temperature divergence (i.e. heat and cold stress), heavy metal toxicity, etc. create osmotic and ionic imbalance inside the plant cells, which ultimately lead to devastating crop yield, sometimes crop failure. Apart from the array of abiotic stresses, various biotic stress caused by pathogens, insects, and nematodes also affect production. Therefore, to combat these major challenges in order to increase production, several novel strategies have been adapted, among which the use of nanoparticles (NPs) i.e. nanotechnology is becoming an emerging tool in various facets of the current agriculture system, nowadays. This present review will elaborately depict the deployment and mechanisms of different NPs to withstand these biotic and abiotic stresses, along with a brief overview and indication of the future research works to be oriented based on the steps provided for future research in advance NPs application through the sustainable way.

Silicon nanoparticles: Synthesis, uptake and their role in mitigation of biotic stress

In the current scenario of global warming and climate change, plants face many biotic stresses, which restrain growth, development and productivity. Nanotechnology is gaining precedence over other means to deal with biotic and abiotic constraints for sustainable agriculture. One of nature's most beneficial metalloids, silicon (Si) shows ameliorative effect against environmental challenges. Silicon/Silica nanoparticles (Si/SiO₂NPs) have gained special attention due to their significant chemical and optoelectronic capabilities. Its mesoporous nature, easy availability and least biological toxicity has made it very attractive to researchers. Si/SiO₂NPs can be synthesised by chemical, physical and biological methods and supplied to plants by foliar, soil, or seed priming. Upon uptake and translocation, Si/SiO₂NPs reach their destined cells and cause optimum growth, development and tolerance against environmental stresses as well as pest attack and pathogen infection. Using Si/SiO₂NPs as a supplement can be an eco-friendly and cost-effective option for sustainable agriculture as they facilitate the delivery of nutrients, assist plants to mitigate biotic stress and enhances plant resistance. This review aims to present an overview of the methods of formulation of Si/SiO₂NPs, their application, uptake, translocation and emphasize the role of Si/SiO₂NPs in boosting growth and development of plants as well as their conventional advantage as fertilizers with special consideration on their mitigating effects towards biotic stress.

Natural sourced and non-toxic hybrid materials for boosting the growth of lettuce in a hydroponic system

Nanostructured hybrid materials, fabricated by combining nanosilica (n-S) obtained from rice husk and oligochitosan (OC) obtained from the shrimp shell, are environmentally friendly substances that can applied in green agriculture. In this study, 50 mg/L of nanostructured hybrid materials were applied on lettuce (Lactuca sativa L. var. longifolia) at different stages of its growth. Most of the hybrid-material-treated lettuce plants showed better growth than that of the control. The most suitable ages for applying the hybrid material to the lettuce are the ages of three weeks (H3W1) and four weeks (H4W1) to stimulate their growth. The longest leaf of the H3W1-treated lettuce increased by 7.14%, its fresh weight by 8.51%, the numbers of leaves by 4.67%, and the content of total chlorophyll by 24.89% compared with those of the control lettuce. The longest leaf of H4W1 increased by 9.52%, its fresh weight by 26.27%, the number of leaves by 9.52%, and the total chlorophyll content by 52.87% compared with those of the control lettuce. Hence, the hybrid material could be used as a green agrochemical with a great potential in modern agriculture. It can help replace and reduce the use of toxic chemical fertilizers and plant-protection products currently used on the market.

Chitosan/silica: A hybrid formulation to mitigate phytopathogens

Long-term and indiscriminate use of synthetic pesticides to mitigate plant pathogens have created serious issues of water health, soil contamination, non-target organisms, resistant species, and unpredictable environmental and human health hazards. These constraints have forced scientists to develop alternative plant disease management strategies to reduce synthetic chemical' dependency. During the last 20 years, biological agents and resistance elicitors have been the most important used alternatives. Silica-based materials/chitosan with a dual mode of action have been proposed as promising alternatives to prevent plant diseases through direct and indirect mechanisms. Moreover, the combined application of nano-silica and chitosan, due to their controllable morphology, high loading capacity, low toxicity, and efficient encapsulation, act as suitable carriers for biological agents, pesticides, and essential oils, making them proper candidates for mitigation of phytopathogens. Based on this potential, this literature study reviewed the silica and chitosan properties and their function in the plant. It also assessed their role in the fighting against soil and aerial phytopathogens, directly and indirectly, as novel hybrid formulations in future managing platforms.

Column optimization of adsorption and evaluation of bed parameters-based on removal of arsenite ion using rice husk

The objective of this study deals with column optimization of adsorption-based on removal of arsenite ion using rice husk. The parameters affecting the column adsorption study, i.e., influent-concentration, bed depth, and flow rate, were optimized. The range of parameters, i.e., influent-concentration (15-50 mg/L), flow rate (20, 35, 45, and 60 mL/min), and bed depth (15-60 mm), were studied experimentally. Kinetics models Bohart-Adams and Hutchins were studied to measure the amount adsorbed, depth of mass transfer zone, saturated concentration, and time observed at 10% & 90% breakthrough. The percentage amount adsorbed q_m enhanced with enhancement in bed depth but got reduced with influent ions concentration and volumetric flow rate. Established model Bohart-Adams and Hutchins equations were used for calculation of mass transfer zone which came out to be 51 mm. An adsorption capacity (q_m) of 4.5 mg/g for arsenite ions was achieved at optimum parameter values of 60 mm of bed depth, 20 mL/min volumetric flow rate, and 50 mg/L of influent ions concentration. The adsorption bed parameters were also evaluated using Hutchins and Michaels equations. The column study proved rice husk to be a potential adsorbent for the adsorption of arsenite.

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.

Role of Silica Nanoparticles in Abiotic and Biotic Stress Tolerance in Plants: A Review

The demand for agricultural crops continues to escalate with the rapid growth of the population. However, extreme climates, pests and diseases, and environmental pollution pose a huge threat to agricultural food production. Silica nanoparticles (SNPs) are beneficial for plant growth and production and can be used as nanopesticides, nanoherbicides, and nanofertilizers in agriculture. This article provides a review of the absorption and transportation of SNPs in plants, as well as their role and mechanisms in promoting plant growth and enhancing plant resistance against biotic and abiotic stresses. In general, SNPs induce plant resistance against stress factors by strengthening the physical barrier, improving plant photosynthesis, activating defensive enzyme activity, increasing anti-stress compounds, and activating the expression of defense-related genes. The effect of SNPs on plants stress is related to the physical and chemical properties (e.g., particle size and surface charge) of SNPs, soil, and stress type. Future research needs to focus on the “SNPs–plant–soil–microorganism” system by using omics and the in-depth study of the molecular mechanisms of SNPs-mediated plant resistance.

Highly Functional Materials Based on Nano-Lignin, Lignin, and Lignin/Silica Hybrid Capped Silver Nanoparticles with Antibacterial Activities

Rice husk is one of the most abundant biomass resources in the world, yet it is not effectively used. This study focuses on the sustainably rice-husk-extracted lignin, nano-lignin (n-Lignin), lignin-capped silver nanoparticles (LCSN), n-Lignin-capped silver nanoparticles (n-LCSN), and lignin-capped silica-silver nanoparticles (LCSSN), and using them for antibacterial activities. The final n-Lignin-based products had a sphere-like structure, of which the size varied between 50 and 80 nm. We found that while n-Lignin and lignin were less effective against Escherichia coli than against Staphylococcus aureus, n-Lignin/lignin-based hybrid materials, i.e., n-LCSN, LCSN, and LCSSN, were better against E. coli than against S. aureus. Interestingly, the antimicrobial behaviors of n-LCSNs could be further improved by decreasing the size of n-Lignin. Considering the facile, sustainable, and eco-friendly method that we have developed here, it is promising to use n-Lignin/lignin-based materials as highly efficient antimicrobials without environmental concerns.

Preparation and Effect of Selenium Nanoparticles/Oligochitosan on the White Blood Cell Recovery of Mice Exposed to Gamma-Ray Radiation

Owing to their excellent bioavailability, high bioactivity, and low toxicity, selenium nanoparticles (SeNPs) are emerging nanomaterials. In this study, SeNPs with a size of ∼41.8 nm were synthesised by γ-irradiation using oligochitosan (OCS) as the stabiliser. As-synthesized SeNPs/OCS were characterised by UV-Vis spectroscopy, transmission electron microscopy, and energy-dispersive X-ray (EDX) analysis. Results revealed that the as-obtained SeNP/OCS powder exhibits high purity. The SeNP/OCS solution’s stability test results indicated that the SeNP/OCS solution stored at 4°C exhibits good stability for 60 days. The SeNP/OCS solution was unstable at ambient temperature, and SeNP/OCS exhibited agglomeration after about 15 days. SeNP/OCS products recovered the total white blood cells of γ-ray irradiated mice. The SeNP/OCS product, which was synthesised by a green approach, with high purity and efficient recuperation of white blood cells, can be used potentially as a functional supplement to assist cancer radiotherapy patients.

R, P. R, Kalia A, Bhardwaj K, Bhardwaj P, Abd-Elsalam KA, Valis M, Kuca K. Nanohybrid Antifungals for Control of Plant Diseases: Current Status and Future Perspectives

The changing climatic conditions have led to the concurrent emergence of virulent microbial pathogens that attack crop plants and exhibit yield and quality deterring impacts on the affected crop. To counteract, the widespread infections of fungal pathogens and post-harvest diseases it is highly warranted to develop sustainable techniques and tools bypassing traditional agriculture practices. Nanotechnology offers a solution to the problems in disease management in a simple lucid way. These technologies are revolutionizing the scientific/industrial sectors. Likewise, in agriculture, the nano-based tools are of great promise particularly for the development of potent formulations ensuring proper delivery of agrochemicals, nutrients, pesticides/insecticides, and even growth regulators for enhanced use efficiency. The development of novel nanocomposites for improved management of fungal diseases can mitigate the emergence of resilient and persistent fungal pathogens and the loss of crop produce due to diseases they cause. Therefore, in this review, we collectively manifest the role of nanocomposites for the management of fungal diseases.

Nanosilica facilitates silica uptake, growth and stress tolerance in plants

Nanobiotechnology has gained considerable momentum in the field of plant sciences in the last few years. Nanomaterials of various metal oxides has been utilized for enhancing growth, productivity and in crop protection strategies. Among them, nanosilica has emerged as a key player in orchestrating plant growth and conferring tolerance to various abiotic and biotic stresses. Nanosilica has increased absorptivity that accounts for an increased uptake of silica, although the exact mechanism is not fully understood. Nanosilica uptake in the roots and leaves reduces the accumulation of reactive oxygen species (ROS) and membrane lipid peroxidation. It is known to restrict the entry of sodium ions and other heavy metals in plants. Concurrently, nanosilica deposition in the leaf tissue enhances the plant defense against pathogens. The present review attempts to provide a novel insight into its uptake mechanism and nanosilica mediated abiotic and biotic stress tolerance in plants. This review will also shed light on the prospects and challenges related to application of nanosilica based fertilizers.

Pristine and modified chitosan as solid catalysts for catalysis and biodiesel production: A minireview

Chitosan is one of the readily available polymers with relatively high abundance, biodegradable and sustainable materials with divergent functional groups that are employed in broad range of applications. Chitosan is widely used in many fields like adsorption, drug carrier for therapeutic activity, environmental remediation, drug formulation and among others. One of the unique features of chitosan is that it can be transformed to other forms like beads, films, flakes, sponges and fibres depending upon the applications. This review is aimed at showing the potential applications of chitosan and its modified solids in organic transformations. The number of existing articles is organized based on the nature of materials and subsequently with the types of reactions. After a brief description on the structural features of chitosan, properties, characterization methods including various analytical/microscopic techniques and some of the best practices to be followed in catalysis are also discussed. The next section of this review describes the catalytic activity of native chitosan without any modifications while the subsequent sections provide the catalytic activity of chitosan derivatives, chitosan covalently modified with metal complexes/salts through linkers and chitosan as support for metal nanoparticles (NPs). These sections discuss number of organic reactions that include Knoevenagel condensation, oxidation, reduction, heterocycles synthesis, cross-coupling reactions and pollutant degradation among others. A separate section provides the catalytic applications of chitosan and its modified forms for the production of fatty acid methyl esters (FAME) through esterification/transesterification reactions. The final section summarizes our views on the future directions of this field in the coming years.

Chitosan as a Wound Dressing Starting Material: Antimicrobial Properties and Mode of Action

Fighting bacterial resistance is one of the concerns in modern days, as antibiotics remain the main resource of bacterial control. Data shows that for every antibiotic developed, there is a microorganism that becomes resistant to it. Natural polymers, as the source of antibacterial agents, offer a new way to fight bacterial infection. The advantage over conventional synthetic antibiotics is that natural antimicrobial agents are biocompatible, non-toxic, and inexpensive. Chitosan is one of the natural polymers that represent a very promising source for the development of antimicrobial agents. In addition, chitosan is biodegradable, non-toxic, and most importantly, promotes wound healing, features that makes it suitable as a starting material for wound dressings. This paper reviews the antimicrobial properties of chitosan and describes the mechanisms of action toward microbial cells as well as the interactions with mammalian cells in terms of wound healing process. Finally, the applications of chitosan as a wound-dressing material are discussed along with the current status of chitosan-based wound dressings existing on the market.

Functional Nanostructured Oligochitosan⁻Silica/ Carboxymethyl Cellulose Hybrid Materials: Synthesis and Investigation of Their Antifungal Abilities

Functional hybrid materials were successfully synthesized from low-cost waste products, such as oligochitosan (OCS) obtained from chitosan (one of the main components in crab shells) and nanosilica (nSiO₂) obtained from rice husk, in a 1:1 ratio (w/w), and their dispersion in the presence of carboxymethyl cellulose at pH 7 was stable for over one month without aggregation. The molecular weights, chemical structures, morphologies, and crystallinities of the obtained materials were characterized by GPC, FTIR, TEM, and XRD, respectively. The antifungal effects of OCS, nSiO₂, and the OCS/nSiO₂ hybrid materials were investigated via a disk-diffusion method. The results showed that the nanohybrid materials had better resistance to Phytophthora infestans fungus than the individual components, and a concentration of the OCS2/nSiO₂ hybrid material of 800 mg L⁻¹ was the lowest concentration where the material completely inhibited Phytophthora infestans growth, as measured via an agar dilution method. This study not only creates a novel environmentally friendly material with unique synergistic effects that can replace current toxic agrochemicals but also can be considered a new platform for further research in green agricultural applications.