Highly Sensitive Detection of Carbaryl Pesticides Using Potentiometric Biosensor with Nanocomposite Ag/r-Graphene Oxide/Chitosan Immobilized Acetylcholinesterase Enzyme

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.

Development of Fluorescent Co (II)-Integrated Carbon Dots and Their Application as a Off-On Mesotrione Detection Sensor

A very simple mesotrione-sensing medium with enhanced sensitivity detection limits has been proposed. A renovated hydrothermal method was adopted for synthesizing fluorescent carbon dots from ethylenediamine and glucose using a Teflon-lined simple autoclave in a GC oven. The resultant carbon dots were characterized via TEM, FTIR, UV-vis, particle size distribution, and EDX and evaluated in a fluorimeter as the sensing medium for mesotrione detection. The binding approach of the Co (II)-integrated glucose-bound carbon dots toward mesotrione is selective, making them an effective sensor for the real sample applications, where majority of the coexisting substances showed insignificant interference effect. Formation of the metastable state due to the molecular interaction between carbon dots and Co (II) resulted in fluorescence quenching at 456 nm. Enhancement in the fluorescence intensity occurred when mesotrione was added in the concentration range of 0.2-5.0 μg mL-1, with a limit of detection, limit of quantification, standard deviation, and relative standard deviation of 0.054, 0.164, 0.00082 μg mL-1, and 0.682%, respectively. Mesotrione determination was demonstrated in soil, water, and tomato samples with recoveries in the range of 95.38-104.7%. The selectivity of the sensor was found to be good enough when checked for the complex tomato sample spiked with different pesticides of the triketone family having structural similarities to mesotrione.

Electrochemical biosensor based on cellulose nanofibers/graphene oxide and acetylcholinesterase for the detection of chlorpyrifos pesticide in water and fruit juice†

In this work, cellulose nanofibers and graphene oxide are used to fabricate a simple and reliable electrochemical biosensor, based on acetylcholinesterase (AChE) for the detection of highly dangerous organophosphates (OPs), utilizing chlorpyrifos as a representative sample. AChE is an enzyme that is essential for neurotransmission and catalyzes the conversion of acetylcholine (ATCh) into thiocholine and acetic acid. The pesticide used in this work, chlorpyrifos, inhibits the catalytic activity of AChE on ATCh, and this inhibition can be measured using square wave voltammetry (SWV). Utilizing a process of surface modification, layers of cellulose nanofibers, graphene oxide, a chitosan-graphene oxide composite, and acetylcholinesterase (AChE/CS-GO/GO/CNFs) were immobilized on a screen-printed carbon electrode (SPCE). The modified SPCE working electrode was characterized using scanning electron microscopy and graphene oxide trapped in the cellulose nanofibers was found to increase the sensitivity of the biosensor. The modified biosensor demonstrated good performance for detection of chlorpyrifos over a linear range of 25–1000 nM under optimum conditions, and the limits of detection and quantification were 2.2 nM and 73 nM, respectively. Our sophisticated technique might offer a more precise, straightforward, quick, and environmentally friendly way to assess chlorpyrifos contamination in water and juice samples.

Cellulose nanofibers and graphene oxide are used to fabricate an electrochemical biosensor based on acetylcholinesterase for detecting organophosphates. This biosensor is simple and reliable, and it utilizes chlorpyrifos as a representative sample of highly dangerous OPs.

Highly stable acetylcholinesterase electrochemical biosensor based on polymerized ionic liquids microgel for pesticides detection

A highly stable electrochemical biosensor for pesticide detection was developed. For the first time polymeric ionic liquids (PILs) were introduced to construct an acetylcholinesterase (AChE) biosensor . AChE was entrapped in PILs microspheres through an emulsion polymerization reaction, where negatively charged Au nanoparticles (Au NPs) can be immobilized by the positively charged PILs, leading to improved catalytic performance. The results suggest that the positively charged PILs not only provide a biocompatible microenvironment around the enzyme molecule, stabilizing its biological activity and preventing its leakage, but also act as a modifiable interface allowing other components with electron transport properties to be loaded onto the polymer substrate, thus providing an efficient electron transport channel for the entrapped enzyme. More notably, when AChE was immobilized in a positively charged environment, the active site is closer to the electrode, promoting faster electron transfer. The detection limits of the constructed electrochemical biosensor AChE@PILs@Au NPs/GCE toward carbaryl and dichlorvos (DDVP) were 5.0 × 10^-2 ng ml^-1 and 3.9 × 10^-2 ng ml^-1, in a wide linear range of 6.3 × 10^-2-8.8 × 10² ng ml^-1 and 1.3 × 10^-1-1.4 × 10³ ng ml^-1, respectively. More importantly, the biosensor has high thermal and storage stability, which facilitates rapid field analysis of fruits and vegetables in a variety of climates. In addition, the biosensor reported has good repeatability and selectivity and has high accuracy in the analysis of peaches, tap water, and other types of samples.