Waveguide-Based Fluorescent Immunosensor for the Simultaneous Detection of Carbofuran and 3-Hydroxy-Carbofuran

Recent progress in biosensor regeneration techniques

Biosensors are widely used in various applications, from medical diagnostics to environmental monitoring. Their widespread and continuous use necessitates regeneration methods to ensure cost-effectiveness and sustainability. In the realm of advancing human-centric bioelectronics for continuous monitoring, employing these sensors for real-time, in situ detection of biomarkers presents a considerable challenge. This mini-review examines diverse strategies utilized for the regeneration of biosensors, categorizing them based on their underlying mechanisms and discussing representative works. We explore methods ranging from surface engineering/re-functionalization, chemical treatments, allosteric regulation of bioreceptors, to manipulations of electric/magnetic fields, highlighting their working principles and exemplary studies. The advantages of each method, such as simplicity, high regeneration efficiency, and versatility, are discussed alongside their challenges, including degradation over cycles, limited applicability, and potential damage to sensors. As the demand for continuous and real-time biosensing escalates, the development of efficient and reliable regeneration strategies becomes essential. This mini-review offers an overview of the current landscape of biosensor regeneration, aiming to guide future research and innovations in this area.

Deep eutectic solvent-based dispersive liquid-liquid microextraction followed by smartphone digital image colorimetry for the determination of carbofuran in water samples

A detection method of carbofuran (CBF) in water samples was reported using deep eutectic solvent (DES)-based dispersive liquid-liquid microextraction (DLLME) combined with digital image colorimetry (DIC), which was environmentally friendly, solvent-saving, rapid, and convenient. Under alkaline conditions, the green and multifunctional extractant DESs dissociated into linalool and heptanoic acid, and CBF was hydrolyzed to 2,3-dihydro-2,2-dimethyl-7-benzofuranol and further coupled with fast blue BB salt to form an azo derivative. Heptanoic acid led to the dispersion of linalool to extract the orange-red azo derivative; DIC was used for quantitative analysis using a smartphone with its associated ease of data-acquisition. This experiment optimized the types, molar ratios, and volumes of DESs and the amounts of sodium carbonate and sodium chloride. Under optimal conditions, the limits of detection (LOD) and quantitation (LOQ) were 0.024-0.032 mg L^-1 and 0.081-0.108 mg L^-1, respectively. The extraction recoveries in real samples (tap, pond, and river water) were 92.4-101.0% with a relative standard deviation below 4.6%. This method has successfully analyzed CBF in different water samples and shows prospects for the monitoring and control of CBF residues in other environmental samples.

Production and Selection of Antibody–Antigen Pairs for the Development of Immunoenzyme Assay and Lateral Flow Immunoassay Methods for Carbofuran and Its Analogues

To produce a sensitive monoclonal antibody (mAb) for the simultaneous detection of carbofuran, benfuracarb, carbosulfan and 3-hydroxy-carbofuran, 2,3-dihydro-2,2-dimethyl-7-benzofuranmethanamine (DDB) was conjugated to bovine serum albumin (BSA) to prepare the immunogen DDB-BSA and mice were immunized. Coating antigens were prepared by conjugating DDB and 5-methoxy-2,3-dihydrobenzofuran-3-acetic acid (MDA) to BSA and ovalbumin (OVA), respectively. Furthermore, the effect of different antibody–antigen pairs on the sensitivity of ELISA and LFIA methods for the detection of carbofuran was investigated. After the immunization, a high-affinity mAb 13C8 was obtained. The ability of the coating antigen to compete with carbofuran for binding antibodies was found to be significantly different between ELISA and LFIA methods. With the antibody–antigen pair 13C8-MDA-OVA, the IC₅₀ values of the ELISA and QD-LFIA methods for carbofuran were 0.18 ng/mL and 0.67 ng/mL, respectively. The cross-reactivity (CR) values of the two methods for benfuracarb, carbosulfan and 3-hydroxy-carbofuran ranged from 72.0% to 83.7%, while, for other carbamate pesticides, the CR values were less than 1%. The spiked recoveries of carbofuran in vegetables by the QD-LFIA method were 83–111%, with a coefficient of variation below 10%, and the test results of the actual samples were consistent with the HPLC-MS method. Overall, this study provides key materials for the development of immunoassays for carbofuran and its analogues, and the antibody–antigen pair selection strategy established in this study provides useful insights for the development of sensitive immunoassays for other compounds.

Novel Dual-Color Immunochromatographic Assay Based on Chrysanthemum-like Au@polydopamine and Colloidal Gold for Simultaneous Sensitive Detection of Paclobutrazol and Carbofuran in Fruits and Vegetables

To ensure food safety and prevent the toxic effects of paclobutrazol (PBZ) and carbofuran (CAR) on humans, a sensitive and rapid method for the detection of PBZ and CAR in fruits and vegetables is required. Herein, a highly sensitive PBZ monoclonal antibody (PBZ mAb) and CAR monoclonal antibody (CAR mAb) with half-inhibitory concentrations (IC₅₀) at 0.77 and 0.82 ng mL⁻¹ were prepared, respectively. We proposed a novel dual-color immunochromatographic assay (ICA) with two test lines (T₁ and T₂) and an independent control line (C) based on chrysanthemum-like Au@Polydopamine (AuNC@PDA) and colloidal gold (AuNPs) for the simultaneous and sensitive detection of PBZ and CAR with naked-eye detection limits of 10 and 5 μg kg⁻¹, respectively. The limits of detection (LOD) for PBZ and CAR were 0.117 and 0.087 μg kg⁻¹ in orange, 0.109 and 0.056 μg kg⁻¹ in grape, and 0.131 and 0.094 μg kg⁻¹ in cabbage mustard, respectively. The average recoveries of PBZ and CAR in orange, grape, and cabbage mustard were 97.86−102.83%, with coefficients of variation from 8.94 to 11.05. The detection results of this method for 30 samples (orange, grapes, and cabbage mustard) agreed well with those of liquid chromatography–tandem mass spectrometry. The novel dual-color ICA was sensitive, rapid, and accurate for the simultaneous detection of PBZ and CAR in real samples.

Modern and Dedicated Methods for Producing Molecularly Imprinted Polymer Layers in Sensing Applications

Molecular imprinting (MI) is the most available and known method to produce artificial recognition sites, similar to antibodies, inside or at the surface of a polymeric material. For this reason, scholars all over the world have found MI appealing, thus developing, in this past period, various types of molecularly imprinted polymers (MIPs) that can be applied to a wide range of applications, including catalysis, separation sciences and monitoring/diagnostic devices for chemicals, biochemicals and pharmaceuticals. For instance, the advantages brought by the use of MIPs in the sensing and analytics field refer to higher selectivity, sensitivity and low detection limits, but also to higher chemical and thermal stability as well as reusability. In light of recent literature findings, this review presents both modern and dedicated methods applied to produce MIP layers that can be integrated with existent detection systems. In this respect, the following MI methods to produce sensing layers are presented and discussed: surface polymerization, electropolymerization, sol–gel derived techniques, phase inversionand deposition of electroactive pastes/inks that include MIP particles.