On-site rapid and simultaneous detection of acetamiprid and fipronil using a dual-fluorescence lab-on-fiber biosensor

Spherical fluorinated covalent organic polymer for highly efficient and selective extraction of fipronil and its metabolites in soil

Covalent organic polymers (COPs) have garnered considerable attention as promising adsorbents of online solid phase extraction (online SPE). Morphology modulation provides an appealing solution to enhance adsorption efficiency and reduce back-pressure in the absorbent. However, the synthesis of COPs with regular geometric shapes and specific adsorption selectivity remains challenging. In this study, a uniform spherical fluorinated COP (F-sCOP, average diameter: 2.14 μm) was successfully synthesized by Schiff base reaction of 1,3,5-triformylphoroglucinol (TP) and 2,2'-bis(trifluoromethyl)benzidine (TFMB). The F-sCOP had a large surface area (BET: 346.2 m2 g-1), remarkable enrichment capacity (enrichment factors: 186-782), high selectivity toward fipronil and its metabolites (adsorption efficiency >93.1%), and admirable service life (>60 times). Based on the adsorbent, a novel μ-matrix cartridge extraction-online-μ-solid phase extraction-high performance liquid chromatography-mass spectrometry (μ-MCE-online-μ-SPE-HPLC-MS) method was constructed and used to track trace fipronil and its metabolites in soil. The proposed method exhibited a wide linear range (0.05-1000 ng g-1), low quantitation limits (LOQs: 0.0027-0.011 ng g-1), high recoveries (90.1-119.6%) and good repeatability (RSD ≤10.5%, n = 3) for fipronil analysis. This study paves the way for pesticide analysis in soil risk assessment.

Recent developments of (bio)-sensors for detection of main microbiological and non-biological pollutants in plastic bottled water samples: A critical review

The importance of water in all biological processes is undeniable. Ensuring access to clean and safe drinking water is crucial for maintaining sustainable water resources. To elaborate, the consumption of water of inadequate quality can have a repercussion on human health. Furthermore, according to the instability of tap water quality, the consumption rate of bottled water is increasing every day at the global level. Although most people believe bottled water is safe, it can also be contaminated by microbiological or chemical pollution, which can increase the risk of disease. Over the last decades, several conventional analytical tools applied to analyze the contamination of bottled water. On the other hand, some limitations restrict their application in this field. Therefore, biosensors, as emerging analytical method, attract tremendous attention for detection both microbial and chemical contamination of bottled water. Biosensors enjoy several facilities including selectivity, affordability, and sensitivity. In this review, the developed biosensors for analyzing contamination of bottled water were highlighted, as along with working strategies, pros and cons of studies. Challenges and prospects were also examined.

Porphyrin-based covalent organic framework as oxidase mimic for highly sensitive colorimetric detection of pesticides

A covalent organic framework-based strategy was designed for label-free colorimetric detection of pesticides. Covalent organic framework-based nanoenzyme with excellent oxidase-like catalytic activity was synthesized. Unlike other artificial enzymes, porphyrin-based covalent organic framework (p-COF) as the oxidase mimic showed highly catalytic chromogenic activity and good affinity toward TMB without the presence of H2O2, which can be used as substitute for peroxidase mimics and H2O2 system in the colorimetric reaction. Based on the fact that the pesticide-aptamer complex can inhibit the oxidase activity of p-COF and reduced the absorbance at 650 nm in UV-Vis spectrum, a label-free and facile colorimetric detection of pesticides was designed and fabricated. Under the optimized conditions, the COF-based colorimetric probe for pesticide detection displayed high sensitivity and selectivity. Taking fipronil for example the limit of detection was 2.7 ng/mL and the linear range was 5 -500,000 ng/mL. The strategy was successfully applied to the detection of pesticides with good recovery , which was in accordance with that of HPLC-MS/MS. The COF-based colorimetric detection was free of complicated modification H2O2, which guaranteed the accuracy and reliability of measurements. The COF-based sensing strategy is a potential candidate for the sensitive detection of pesticides of interests.

A low-background and wash-free signal amplification F-CRISPR biosensor for sensitive quantitative and visible qualitative detection of Salmonella Typhimurium

In traditional CRISPR-based biosensors, the cleavage-induced signal generation is insufficient because only a signals is generated at a CRISPR-induced cleavage. Herein, we developed an improved CRISPR/Cas12a-based biosensor with an enlarged signal generation which integrated the hybridization chain reaction (HCR) and low-background Förster Resonance Energy Transfer (FRET) signal output mode. The HCR with nucleic acid self-assembly capability was used as a signal carrier to load more signaling molecules. To get the best signal amplification, three different fluorescence signal output modes (fluorescence recovery, FRET and low-background FRET) generated by two fluoresceins, FAM and Cy5, were fully investigated and compared. The results indicated that the low-background FRET signal output mode with the strictest signal generation conditions yielded the highest signal-to-noise ratio (S/N) (19.17) and the most obvious fluorescence color change (from red to yellow). In optimal conditions, the proposed biosensor was successfully applied for Salmonella Typhimurium (S. Typhimurium) detection with 6 h (including 4 h for sample pre-treatment) from the initial target processing to the final detection result. The qualitative sensitivity, reliant on color changes, was 103 CFU/mL. The quantitative sensitivity, calculated by the fluorescence value, were 1.62 × 101 CFU/mL, 3.72 × 102 CFU/mL, and 8.71 × 102 CFU/mL in buffer solution, S. Typhimurium-spiked milk samples, and S.Typhimurium-spiked chicken samples, respectively. The excellent detection performance of the proposed biosensor endowed its great application potential in food and environment safety monitoring.

Colorimetric and ratiometric supramolecular AIE fluorescent probe for the on-site monitoring of fipronil

The overuse of fipronil (FPN, a broad-spectrum insecticide) in agriculture has brought great concerns for environmental pollution and food safety. The development of a rapid, reliable, and portable analytical method for the on-site monitoring of FPN is therefore of great significance but is full of challenge. Herein, a novel supramolecular probe using human serum albumin (HSA) as the host and an aggregation-induced emission-active fluorescence probe LIQ-TPA-TZ as the guest was developed for the colorimetric and ratiometric detection of FPN, displaying fast response (30 s), high sensitivity (LOD ∼ 0.05 μM), and good selectivity and anti-interference performance. Moreover, portable paper-based test strips could be facilely obtained and utilized for the determination of FPN, showing colorimetric changes from yellow to orange. This supramolecular probe also demonstrated great potential in real applications for choosing the best cleaning method to reduce the residue rate of FPN on apples. This study provides a versatile tool for the fast and real-time analysis of FPN, which greatly benefits the on-site determination of pesticides with the use of simple testing apparatus.

Recent Progress in Functional-Nucleic-Acid-Based Fluorescent Fiber-Optic Evanescent Wave Biosensors

Biosensors capable of onsite and continuous detection of environmental and food pollutants and biomarkers are highly desired, but only a few sensing platforms meet the "2-SAR" requirements (sensitivity, specificity, affordability, automation, rapidity, and reusability). A fiber optic evanescent wave (FOEW) sensor is an attractive type of portable device that has the advantages of high sensitivity, low cost, good reusability, and long-term stability. By utilizing functional nucleic acids (FNAs) such as aptamers, DNAzymes, and rational designed nucleic acid probes as specific recognition ligands, the FOEW sensor has been demonstrated to be a general sensing platform for the onsite and continuous detection of various targets ranging from small molecules and heavy metal ions to proteins, nucleic acids, and pathogens. In this review, we cover the progress of the fluorescent FNA-based FOEW biosensor since its first report in 1995. We focus on the chemical modification of the optical fiber and the sensing mechanisms for the five above-mentioned types of targets. The challenges and prospects on the isolation of high-quality aptamers, reagent-free detection, long-term stability under application conditions, and high throughput are also included in this review to highlight the future trends for the development of FOEW biosensors capable of onsite and continuous detection.