Electrostatic wrapping of eupatorium-based botanical herbicide with chitosan derivatives for controlled release

Chitosan nanoplatforms in agriculture for multi-potential applications - Adsorption/removal, sustained release, sensing of pollutants & delivering their alternatives - A comprehensive review

An increase in the global population has led to an increment in the food consumption, which has demanded high food production. To meet the production demands, different techniques and technologies are adopted in agriculture the past 70 years, where utilization of the industry-manufactured/synthetic pesticides (SPTCs - e.g., herbicides, insecticides, fungicides, bactericides, nematicides, acaricides, avicides, and so on) is one of them. However, it has been later revealed that the usage of SPTCs has negatively impacted the environment - especially water and soil, and also agricultural products - mainly foods. Though preventive measures are taken by government agencies, still the utilization rate of SPTCs is high, and consequently, their maximum residual limit (MRL) levels in food are above tolerance, which further results in serious health concerns in humans. So, there is an immediate need for decreasing the utilization of the SPTCs by delivering them effectively at reduced levels in agriculture but with the required efficacy. Apart from that, it is mandatory to detect/sense and also to remove them to lessen the environmental pollution, while developing effective alternative techniques/technologies. Among many suitable materials that are developed/idenified, chitosan, a bio-polymer has gained great attention and is comprehensively implemented in all the above-mentioned applications - sensing, delivery and removal, due to their excellent and required properties. Though many works are available, in this work, a special attention is given to chitosan and its derivatives (i.e., chitosan nanoparticles (CNPs))based removal, controlled release and sensing of the SPTCs - specifically herbicides and insecticides. Moreover, the chitosan/CNPs-based protective effects on the in vivo models during/after their exposure to the SPTCs, and the current technologies like clustered regularly interspaced short palindromic repeats (CRISPR) as alternatives for SPTCs are also reviewed.

Recent advances in stimuli-response mechanisms of nano-enabled controlled-release fertilizers and pesticides

Nanotechnology-enabled fertilizers and pesticides, especially those capable of releasing plant nutrients or pesticide active ingredients (AIs) in a controlled manner, can effectively enhance crop nutrition and protection while minimizing the environmental impacts of agricultural activities. Herein, we review the fundamentals and recent advances in nanofertilizers and nanopesticides with controlled-release properties, enabled by nanocarriers responsive to environmental and biological stimuli, including pH change, temperature, light, redox conditions, and the presence of enzymes. For pH-responsive nanocarriers, pH change can induce structural changes or degradation of the nanocarriers or cleave the bonding between nutrients/pesticide AIs and the nanocarriers. Similarly, temperature response typically involves structural changes in nanocarriers, and higher temperatures can accelerate the release by diffusion promoting or bond breaking. Photothermal materials enable responses to infrared light, and photolabile moieties (e.g., o-nitrobenzyl and azobenzene) are required for achieving ultraviolet light responses. Redox-responsive nanocarriers contain disulfide bonds or ferric iron, whereas enzyme-responsive nanocarriers typically contain the enzyme's substrate as a building block. For fabricating nanofertilizers, pH-responsive nanocarriers have been well explored, but only a few studies have reported temperature- and enzyme-responsive nanocarriers. In comparison, there have been more reports on nanopesticides, which are responsive to a range of stimuli, including many with dual- or triple-responsiveness. Nano-enabled controlled-release fertilizers and pesticides show tremendous potential for enhancing the utilization efficiency of nutrients and pesticide AIs. However, to expand their practical applications, future research should focus on optimizing their performance under realistic conditions, lowering costs, and addressing regulatory and public concerns over environmental and safety risks.

Research Progress of a Pesticide Polymer-Controlled Release System Based on Polysaccharides

In recent years, with the development of the nanomaterials discipline, many new pesticide drug-carrying systems-such as pesticide nano-metal particles, nano-metal oxides, and other drug-carrying materials-had been developed and applied to pesticide formulations. Although these new drug-loading systems are relatively friendly to the environment, the direct exposure of many metal nanoparticles to the environment will inevitably lead to potential effects. In response to these problems, organic nanomaterials have been rapidly developed due to their high-quality biodegradation and biocompatibility. Most of these organic nanomaterials were mainly polysaccharide materials, such as chitosan, carboxymethyl chitosan, sodium alginate, β-cyclodextrin, cellulose, starch, guar gum, etc. Some of these materials could be used to carry inorganic materials to develop a temperature- or pH-sensitive pesticide drug delivery system. Herein, the pesticide drug-carrying system developed based on polysaccharide materials, such as chitosan, was referred to as the pesticide polymer drug-carrying system based on polysaccharide materials. This kind of drug-loading system could be used to protect the pesticide molecules from harsh environments, such as pH, light, temperature, etc., and was used to develop the function of a sustained release, targeted release of pesticides in the intestine of insects, and achieve the goal of precise application, reduction, and efficiency of pesticides. In this review, the recent progress in the field of polysaccharide-based polymer drug delivery systems for pesticides has been discussed, and suggestions for future development were proposed based on the current situation.

Preparation, characterization and antimicrobial activities of cyclic substituted chitosan derivatives

Six cyclic substituted chitosan derivatives were synthesized, and their structures were characterized by FTIR, ¹³C NMR and elemental analyses. Additionally, their antimicrobial properties were studied. The synthesized derivatives showed significantly greater zones of inhibition compared with chitosan. The zone of inhibition values produced by C₂-2-naphthylamine formamide-C₆-2-naphthylamine formyl ester-polymer chitosan against Sarcina sp., Staphylococcus aureus and Escherichia coli were 24 mm, 21 mm and 21 mm, respectively, whereas those of C₂-cyclohexylamine formamide-C₆-cyclohexylamine formyl ester-low chitosan against Fusarium equiseti and Verticillium dahliae were 14 mm and 15 mm, respectively. The antibacterial abilities of chitosan and its derivatives against the Gram-positive bacteria Sarcina sp. and Staphylococcus aureus were stronger than those against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. In addition, all of the high and low molecular weight chitosan derivatives showed greater bacteriostatic activities than antifungal activities. The results provided a useful reference for the development of chitosan and its derivatives used as new pesticides.