Aptamer-functionalized metal-organic frameworks (MOFs) for biosensing.

Heavy metal pollution has become more and more serious with industrial development and resource exploitation. Because heavy metal ions are difficult to be biodegraded, they accumulate in the human body and cause serious threat to human health. However, the conventional methods to detect heavy metal ions are more strictly to the requirements by detection equipment, sample pretreatment, experimental environment, etc. Aptasensor has the advantages of strong specificity, high sensitivity and simple preparation to detect small molecules, which provides a new direction platform in the detection of heavy metal ions. This paper reviews the selection of aptamers as target for heavy metal ions since the 21th century and aptasensors application for detection of heavy metal ions that were reported in the past five years. Firstly, the selection methods for aptamers with high specificity and high affinity are introduced. Construction methods and research progress on sensor based aptamers as recognition element are also introduced systematically. Finally, the challenges and future opportunities of aptasensors in detecting heavy metal ions are discussed.

/pdf/advances-in-aptamer-screening-and-aptasensors-detection-of-4xv0b5ty3a.pdf

Advances in aptamer screening and aptasensors' detection of heavy metal ions.

Fluorescence carbon nanomaterials-based sensors for accurate tracing of pesticides in environmental, food and biological samples have gained considerable interest in the past decade years to protect ecosystem, guarantee food safety and prevent disease, making it a trending hot-spot. This review focuses on recent advances and new trends of pesticides monitoring (including organophosphorus, neonicotinoids and carbamates pesticides) on the base of fluorescence carbon nanomaterials, with particular emphasis on zero-dimensional (0-D) carbon dots/graphene quantum dots, 2-D carbon nitride nanosheets and 3-D carbon-based metal/covalent organic frameworks. These fluorometric strategies are classified by several main recognition unit, including enzyme, antibody, aptamer and molecularly-imprinted polymers, offering great performance for pesticides with a limit of detection down to pg mL−1 level. Beyond performance comparison of these emerging sensors with other strategies, we discuss the existing hurdles and present challenges to practical sensor designs, followed by exploring future perspectives for breakthroughs in fluorescence carbon nanomaterials-based sensors.

Biosensors based on fluorescence carbon nanomaterials for detection of pesticides

For survival and quality of life, human society has sought more productive, precise, and sustainable agriculture. Agrochemistry, which solves farming issues in a chemical manner, is the core engine that drives the evolution of modern agriculture. To date, agrochemistry has utilized chemical technologies in the form of pesticides, fertilizers, veterinary drugs and various functional materials to meet fundamental demands from human society, while increasing the socio-ecological consequences due to inefficient use. Thus, more useful, precise, and designable scaffolding materials are required to support sustainable agrochemistry. Reticular chemistry, which weaves molecular units into frameworks, has been applied in many fields based on two cutting-edge porous framework materials, namely metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). With flexibility in composition, structure, and pore chemistry, MOFs and COFs have shown increasing functionalities associated with agrochemistry in the last decade, potentially introducing reticular chemistry as a highly accessible chemical toolbox into agrochemical technologies. In this critical review, we will demonstrate how reticular chemistry shapes the future of agrochemistry in the fields of farm sensing, agro-ecological preservation and reutilization, agrochemical formulations, smart indoor farming, agrobiotechnology, and beyond.

Introducing reticular chemistry into agrochemistry.

Agrochemicals, which are crucial to meet the world food qualitative and quantitative demand, are compounds used to kill pests (insects, fungi, rodents, or unwanted plants). Regrettably, there are some important issues associated with their widespread and extensive use (e.g., contamination, bioaccumulation, and development of pest resistance); thus, a reduced and more controlled use of agrochemicals and thorough detection in food, water, soil, and fields are necessary. In this regard, the development of new functional materials for the efficient application, detection, and removal of agrochemicals is a priority. Metal–organic frameworks (MOFs) with exceptional sorptive, recognition capabilities, and catalytical properties have very recently shown their potential in agriculture. This Review emphasizes the recent advances in the use of MOFs in agriculture through three main views: environmental remediation, controlled agrochemical release, and detection of agrochemicals.

https://pubs.acs.org/doi/pdf/10.1021/acsami.2c00615

Metal–Organic Frameworks in Agriculture

This study reports on a fluorescent aptasensor of chlorpyrifos (CPF) based on terbium(iii) based on metal-organic frameworks (Tb-MOFs) and PDDA-aggregated-gold nanoparticles (AuNPs). The dispersed AuNPs quench the emissions of the Tb-MOF, while the PDDA-aggregated AuNPs have little effect. The aptamer interacts with PDDA via electrostatic interaction to prevent the aggregation of the AuNPs, which protects the AuNPs from PDDA-induced aggregation and the fluorescence of the Tb-MOF is quenched by FRET between the Tb-MOF and the dispersed AuNPs. Upon the addition of CPF, aptamers are exhausted to form a CPF-aptamer complex, and the following PDDA causes the aggregation of AuNPs, accompanied by weak quenching of the fluorescence of the Tb-MOF. This unlabelled strategy sensitively detects CPF at a concentration of 3.8 nM with a linear range of 5-600 nM. The assay is selective for CPF over other interfering compounds. The method was successfully applied to the determination of CPF in (spiked) tap water and vegetables and fruits samples, indicating its potential applications in enlarging the target scope of luminescent-MOF-based detection for environmental and agricultural samples.

Fluorescent aptasensing of chlorpyrifos based on the assembly of cationic conjugated polymer-aggregated gold nanoparticles and luminescent metal–organic frameworks

The fabrication of a magnetically controlled colorimetric aptasensor for chlorpyrifos is reported. The aptasensor was fabricated by the attachment of the colorimetric labels onto the magnetic carrier due to the hybridization reaction between the complementary DNA and aptamer. Chlorpyrifos detection was realized by monitoring the color changes of the TMB/H2O2 solution before and after incubation of the aptasensor with chlorpyrifos via exposure to external magnetic force. The color change was monitored at 650 nm by UV-Vis spectrophotometer. Under the optimal conditions, this magnetically controlled Cu-MOF-based aptasensor showed a detection limit of 4.4 ng/mL with a linear range of 0–1250 ng/mL. The colorimetric aptasensor displayed high selectivity for chlorpyrifos toward other interfering pesticides. The aptasensor was successfully applied for the spiked test of chlorpyrifos in fruits and vegetable samples with good recovery, which were in agreement with data obtained by GC-MS analysis. This magnetically controlled Cu-MOF-based sensing strategy not only leads to development of efficient and facile phase separation, but also expands the MOF’s target scope from H2O2 or glucose to pesticides.

Magnetically controlled colorimetric aptasensor for chlorpyrifos based on copper-based metal-organic framework nanoparticles with peroxidase mimetic property.

A method is described for the determination of the pesticide chlorothalonil (CLT). It is based on the finding that citrate-capped gold nanoparticles (AuNPs) undergo aggregation on exposure to chlorothalonil. This is accompanied by a visually detectable color change from wine red to blue. The effect is due to the interaction of the cyano group of chlorothalonil with gold nanoparticles. The assay may also be performed by using a spectrometer. The ratio of absorbances at 700 nm and 520 nm (A700/A520) linearly drops in the 5 to 100 ng·mL−1 CLT concentration range, with a 3.6 ng·mL−1 detection limit. This is below the Chinese guideline value for cucumber. The method is rather simple and does not require any modification of the AuNPs or the utilization of antibody. It was successfully applied to the determination of CLT in (spiked) cucumber samples. Recoveries ranged from 80.4 to 97.4%, and the analytical results compared well with those obtained by HPLC.

Colorimetric determination of the pesticide chlorothalonil based on the aggregation of gold nanoparticles.

A method based on QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for determining 43 pesticide residues in strawberries. The clean-up sorbents were optimized, with 50 mg PSA + 50 mg C18 + 150 mg MgSO4 showing the best performance in d-SPE. The effect of injection volume on matrix effect (ME) was investigated. The proposed method had a linear range of 0.001–0.1 mg kg−1, and determination coefficients (R2) were greater than 0.995. Recoveries of the selected pesticides were 70.1–119.6% with relative standard deviations (RSD) at three concentrations (0.01, 0.05, and 0.1 mg kg−1) lower than 20%. The limit of quantification (LOQ) of the 43 pesticides was ≤ 0.005 mg kg−1. This method was applied to 80 strawberry samples collected from 8 villages in Beijing suburbs, and 12 pesticide residues were quantitatively detected with the concentrations ranging from 0.02 to 2.5 mg kg−1.

Determination of Pesticide Residues in Strawberries by Ultra-performance Liquid Chromatography-Tandem Mass Spectrometry

Currently known rapid determination of fungicides usually relies on antibody-based immunoassay. This paper reports a simple antibody-free colorimetric assay for chlorothalonil via the inhibition of an enzyme-triggered reaction. The enzymatic activity of glyceraldehyde-3-phosphate dehydrogenase was significantly inhibited by chlorothalonil, and the color change of NBT-PMS system induced from NADH formation was suppressed, which could be used indirectly to assay chlorothalonil. The limit of detection (LOD) was 0.05 μM with a linear range from 0.5 to 10 μM, and the detection of 1 μM chlorothalonil in solution was achieved with a naked-eye readout. In addition, the colorimetric measurement results of the cucumber samples showed a good recovery rate, although the sensitivity was less effective than the instrumental method. Nevertheless, the results demonstrates that the chlorometric method provides potential opportunities for reliable, cost-effective quantitative detection for chlorothalonil residues in vegetables.

/pdf/antibody-free-colorimetric-detection-of-chlorothalonil-in-10mdnf42mo.pdf

Antibody-free colorimetric detection of chlorothalonil in cucumberviathe inhibition of an enzyme-triggered reaction

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