Current trends and challenges in the synthesis and applications of chitosan-based nanocomposites for plants: A review

Mechanical and antibacterial properties of ZnO/chitosan bio-composite films

In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method. Two different ZnO powders, micrometer (d50 ≅ 1.5 μm) and nanometer sized (d50 ≅ 100 nm), were used to investigate the effect of ZnO particle size and concentration (0, 2, and 8% w/w of chitosan) on the mechanical and antibacterial properties of the ZnO/chitosan bio-composite films. The incorporation of the ZnO powders into the chitosan film resulted in an increase in the tensile strength (TS) and a decrease in the elongation at break (EB) values. Mechanical test results revealed that TS and EB properties were considerably affected (p < 0.05) by the concentration and particle size of the ZnO reinforcement. Disc diffusion method demonstrated good antibacterial activities of bio-composite films containing high amount of ZnO (8% w/w of chitosan) against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Bacillus subtilis. The growth-limiting effect of the films was more pronounced for S. aureus and K. pneumoniae. Due to enhanced TS and imparted antibacterial activity of the produced ZnO/chitosan bio-composite films, these materials are promising candidates for applications such as food packaging, wound dressing, and antibacterial coatings for various surfaces.

DEAE-chitosan nanoparticles as a pneumococcus-biomimetic material for the development of antipneumococcal therapeutics

Advanced biomaterials provide an interesting and versatile platform to implement new and more effective strategies to fight bacterial infections. Chitosan is one of these biopolymers and possesses relevant features for biomedical applications. Here we synthesized nanoparticles of chitosan derivatized with diethylaminoethyl groups (ChiDENPs) to emulate the choline residues in the pneumococcal cell wall and act as ligands for choline-binding proteins (CBPs). Firstly, we assessed the ability of diethylaminoethyl (DEAE) to sequester the CBPs present in the bacterial surface, thus promoting chain formation. Secondly, the CBP-binding ability of ChiDENPs was purposed to encapsulate a bio-active molecule, the antimicrobial enzyme Cpl-711 (ChiDENPs-711), with improved stability over non-derivatized chitosan. The enzyme-loaded system released more than 90% of the active enzybiotic in ≈ 2 h, above the usual in vivo half-life of this kind of enzymes. Therefore, ChiDENPs provide a promising platform for the controlled release of CBP-enzybiotics in biological contexts.

Smart nanomaterial and nanocomposite with advanced agrochemical activities

Conventional agriculture solely depends upon highly chemical compounds that have negatively ill-affected the health of every living being and the entire ecosystem. Thus, the smart delivery of desired components in a sustainable manner to crop plants is the primary need to maintain soil health in the upcoming years. The premature loss of growth-promoting ingredients and their extended degradation in the soil increases the demand for reliable novel techniques. In this regard, nanotechnology has offered to revolutionize the agrotechnological area that has the imminent potential over conventional agriculture and helps to reform resilient cropping systems withholding prominent food security for the ever-growing world population. Further, in-depth investigation on plant-nanoparticles interactions creates new avenues toward crop improvement via enhanced crop yield, disease resistance, and efficient nutrient utilization. The incorporation of nanomaterial with smart agrochemical activities and establishing a new framework relevant to enhance efficacy ultimately help to address the social acceptance, potential hazards, and management issues in the future. Here, we highlight the role of nanomaterial or nanocomposite as a sustainable as well stable alternative in crop protection and production. Additionally, the information on the controlled released system, role in interaction with soil and microbiome, the promising role of nanocomposite as nanopesticide, nanoherbicide, nanofertilizer, and their limitations in agrochemical activities are discussed in the present review.

Chitosan-Phenylalanine Nanoparticles (Cs-Phe Nps) Extend the Postharvest Life of Persimmon (Diospyros kaki) Fruits under Chilling Stress

There are high levels of damage imposed on persimmon fruit postharvest, especially after storing it in cold storage, which causes chilling injury (CI). To reduce this stress on the fruit, the conventional way is to use chemical treatments. Since there is a limitation in the use of chemical materials, it is necessary to apply non-harmful treatments to decrease chilling injury and maintain the quality of persimmon in cold storage. The aim of this study is to investigate the effects of chitosan-loaded phenylalanine nanoparticles (Cs-Phe NPs) (2.5 and 5 mM) on physiochemical and quality factors of persimmon (Diospyros kaki) during 45 days of storage at 4 °C (38 °F) and evaluate the impact of Cs-Phe NPs on the preserving quality in order to reduce the chilling injury of this fruit. The experiment was conducted using a completely randomized design with three replications. Treatments were applied at 15, 30, and 45 days after storage at 4 °C with ≥90% relative humidity. The size of Cs-Phe NPs was less than 100 nm, approximately. The results showed that application of 5 mM of Cs-Phe NPs delayed the negative effects of chilling stress and enhanced antioxidant capacity, firmness, and total soluble solids of persimmon fruit. Lower H2O2 and malonaldehyde (MDA) accumulation along with higher soluble tannin and total carotenoid accumulation in persimmon fruit treated with 5 mM Cs-Phe NPs was also observed. Fruit coated using Cs-Phe NPs in both concentrations (2.5 and 5 mM) showed the highest antioxidant enzyme activity for superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) and the lowest for polyphenol oxidase (PPO) and chilling injury during storage. According to our results, 5 mM of Cs-Phe NPs could be considered as the best treatment under chilling-stress conditions.

The Potential of Using Chitosan on Cereal Crops in the Face of Climate Change

This review presents the main findings from measurements carried out on cereals using chitosan, its derivatives, and nanoparticles. Research into the use of chitosan in agriculture is growing in popularity. Since 2000, 188 original scientific articles indexed in Web of Science, Scopus, and Google Scholar databases have been published on this topic. These have focused mainly on wheat (34.3%), maize (26.3%), and rice (24.2%). It was shown that research on other cereals such as millets and sorghum is scarce and should be expanded to better understand the impact of chitosan use. This review demonstrates that this chitosan is highly effective against the most dangerous diseases and pathogens for cereals. Furthermore, it also contributes to improving yield and chlorophyll content, as well as some plant growth parameters. Additionally, it induces excellent resistance to drought, salt, and low temperature stress and reduces their negative impact on cereals. However, further studies are needed to demonstrate the full field efficacy of chitosan.

Sustainable Agriculture Systems in Vegetable Production Using Chitin and Chitosan as Plant Biostimulants

Chitin and chitosan are natural compounds that are biodegradable and nontoxic and have gained noticeable attention due to their effective contribution to increased yield and agro-environmental sustainability. Several effects have been reported for chitosan application in plants. Particularly, it can be used in plant defense systems against biological and environmental stress conditions and as a plant growth promoter—it can increase stomatal conductance and reduce transpiration or be applied as a coating material in seeds. Moreover, it can be effective in promoting chitinolytic microorganisms and prolonging storage life through post-harvest treatments, or benefit nutrient delivery to plants since it may prevent leaching and improve slow release of nutrients in fertilizers. Finally, it can remediate polluted soils through the removal of cationic and anionic heavy metals and the improvement of soil properties. On the other hand, chitin also has many beneficial effects such as plant growth promotion, improved plant nutrition and ability to modulate and improve plants’ resistance to abiotic and biotic stressors. The present review presents a literature overview regarding the effects of chitin, chitosan and derivatives on horticultural crops, highlighting their important role in modern sustainable crop production; the main limitations as well as the future prospects of applications of this particular biostimulant category are also presented.