Chemosensors, Volume 11, Issue 12 (December 2023) – 11 articles

In recent years, there has been a significant rise in the popularity of plant-based products due to various reasons, such as ethical concerns, environmental sustainability, and health benefits. Sensory analysis is a powerful tool for evaluating the human appreciation of food and drink products. To link the sensory evaluation to the chemical and textural compositions, further quantitative analyses are required. Unfortunately, due to the destructive nature of sensory analysis techniques, quantitative evaluation can only be performed on samples that are different from those ingested. The quantitative knowledge of the analytical parameters of the exact sample ingested would be far more informative. Coupling non-destructive techniques, such as near-infrared (NIR) and hyperspectral imaging (HSI) spectroscopy, to sensory evaluation presents several advantages. The intact sample can be analyzed before ingestion, providing in a short amount of time matrices of quantitative data of several parameters at once. In this review, NIR and imaging-based techniques coupled with chemometrics based on artificial intelligence and machine learning for sensory evaluation are documented. To date, no review article covering the application of these non-destructive techniques to sensory analysis following a reproducible protocol has been published. This paper provides an objective and comprehensive overview of the current applications of spectroscopic and sensory analyses based on the state-of-the-art literature from 2000 to 2023. Full article

Fipronil (FIP), a broad-spectrum phenylpyrazole insecticide, is highly toxic and threatens human health and ecological balance. Developing convenient, rapid, portable analytical technology for on-site and high-frequency testing of FIP is essential to reduce its damage. Herein, a monoclonal antibody (Clone F-3F6) against FIP, with high affinity and specificity, was produced using a novel immunogen, FIP-BSA, which was simply and directly synthesized by conjugating FIP with bovine serum albumin (BSA). Among the previously reported antibodies, F-3F6 acts more specifically against FIP. The FIP metabolites fipronil desulfinyl, fipronil sulfide, and fipronil sulfone showed lower cross-reactivity, and other pesticides were not recognized. To achieve high-frequency and on-site measurements of FIP, an evanescent wave fluorescence biosensor was built by integrating evanescent wave fluorescence technology, a functionalized fiber bioprobe, and a fluorescence-labeled F-3F6 antibody. The detection limit of FIP was 0.032 μg/L. The detection results of real milk and water samples showed that all the coefficients of variation were less than 10%, and the recovery ranged from 90 to 120%. The high reusability and stability of functionalized fiber bioprobe enables the accurate, cost-effective, high-frequency, and facile quantitative detection of FIP. This highly specific and reliable evanescent wave fluorescence biosensor will be well suited to the sensitive and high-frequency on-site analysis of only FIP in food. Full article

In the present study we report the development of an advantageous optical sensor for the speciation of Fe(III)/Fe(II). The sensor is based on the selective reaction of Fe(III) with a Desferal (Deferoxamine) reagent at pH = 2, while both Fe(III) and Fe(II) react with the reagent at pH = 5 using an acetate/glycine buffer. In this way, frequently used extra oxidation (H₂O₂) or reduction (ascorbic acid or hydroxylamine) steps are avoided. Both species can be determined in the range of 25 to 150 μM using a 96-well plate platform and the instrument-free detection of the colored complex with an overhead book scanner. The LOD is 4 μM, and an additional advantage is that a single calibration curve can be utilized for quantitation. The applicability of the sensor was demonstrated by analyzing commercially available pharmaceutical formulations for quality control purposes. Full article

This study describes the incorporation of bioengineered flagellin (4HIS) protein in conjunction with TiO₂ anatase nanoparticles into a chitosan (Chit) polymeric matrix as a highly sensitive electrode modifier for the determination of diclofenac sodium (DS) in wastewater. Two types of electrodes were prepared using a simple drop-casting method. The inner structure of the obtained modified electrode was characterized by scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy and isothermal titration calorimetry (ITC). The electrochemical and electroanalytical parameters of DS oxidation at the nanostructured interface of the modified electrode were obtained via cyclic voltammetry and square-wave voltammetry. The analytical parameters for diclofenac electro-detection showed a 50% decrease in LOD and LOQ at Chit + TiO₂ + 4HIS/GCE-modified electrode compared with the Chit + 4HIS/GCE-modified electrode. The obtained tools were successfully used for DS detection in drug tablets and wastewater samples. Thus, it was demonstrated that in the presence of a histidine-containing flagellin variant, the electrode has DS recognition capacity which increases in the presence of TiO₂ nanoparticles, and both induce excellent performances of the prepared tools, either in synthetic solution or in real samples. Full article

This work presents the electrochemical determination of cholecalciferol (Vitamin D₃) in water-organic mixtures using a glassy carbon electrode (GCE) and commercial screen-printed carbon electrodes (SPCEs). The electrocatalytic behavior of Vitamin D₃ on the surface of the working electrode produced a well-defined oxidation peak at +0.95 V (vs. Ag|AgCl, 3.0 mol L⁻¹) and +0.7 V (vs. Ag-SPCE pseudo-reference electrode) for the GCE and SPCE, respectively, in 0.1 M LiClO₄ prepared in 50% ethanol. The nature of the organic solvent needed for the solubilization of Vitamin D₃ was evaluated, together with the concentration of the supporting electrolyte, the ratio of the water-organic mixture, the voltametric parameters for the cyclic voltammetry (CV), and square-wave voltammetry (SWV) analyses. Under the optimized conditions, a linear correlation between the anodic peak current and the concentration of Vitamin D₃ was obtained over the range of 0.47 to 123 µmol L⁻¹ and 59.4 to 1651 µmol L⁻¹ for the GCE and SPCE, respectively. The determined limits of detection (LOD) were 0.17 (GCE) and 19.4 µmol L⁻¹ (SPCE). The methodology was successfully applied to commercial supplement tablets of Vitamin D₃. Additionally, this work shows the possibility of using non-modified GCE and SPCE for routine analysis of Vitamin D₃. Full article

Laser engraving is a convenient, fast, one-step, and environmentally friendly technique used to produce more conductive surfaces by local pyrolysis. The laser’s thermal treatment can also remove non-conductive materials from the electrode surfaces and improve electrochemical performance. The improvement was assessed by electrochemical tools such as cyclic voltammograms and electrochemical impedance spectroscopy using [Fe(CN)₆]^3−/4− and dopamine as redox probes. The electrochemical results observed showed that a treated surface showed an improvement in electron transfer and less resistance to charge transfer. To optimize the electrode performance, it was necessary to search for the most favorable graphite mines and optimize the parameters of the laser machine (laser power, scan rate, and output distance). The resultant material was adequately characterized by Raman spectroscopy and scanning electron microscopy (SEM), where an irregular surface composed of crystalline graphite particles was noticed. Furthermore, as a proof-of-concept, it was applied to detect indapamide (IND) in synthetic urine by flow injection analysis (FIA), a diuretic drug often used by athletes to alter urine composition to hide forbidden substance consumption in doping tests. Full article

The progression of Alzheimer’s disease (AD) is positively correlated with the phosphorylation damage of Tau-441 protein, which is the marker with the most potential for the early detection of AD. The low content of Tau-441 in human serum is a major difficulty for the realization of content detection. Herein, we prepared an electrochemical immunosensor modified with Poly(3,4-ethylene-dioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS)/Carboxylated multi-walled carbon nanotube (MWCNTs-COOH) nanocomposites based on electrochemical immunoassay technology for the low-concentration detection of Tau-441. The immunosensor based on the nanocomposite can take advantage of the characteristics of conductive polymers to achieve electrical signal amplification and use MWCNTs-COOH to increase the contact area of the active site and bond with the Tau-441 antibodies on the electrode. The physicochemical and electrical properties of PEDOT: PSS/MWCNTs-COOH were studied by in situ characterization techniques and electrochemical characterization methods, indicating that the immunosensor has high selectivity and sensitivity to the Tau-441 immune reaction. Under optimized optimal conditions, the electrochemical immunosensor detected a range of concentrations of Tau-441 to obtain a low detection of limit (0.0074 ng mL⁻¹) and demonstrated good detection performance through actual human serum sample testing experiments. Therefore, the study provides an effective reference value for the early diagnosis of AD. Full article

In this study, a novel highly sensitive and selective fluorescent optode membrane aimed at the determination of Pb(II) ion is proposed by incorporating N-(3-(1,4-dioxa-7,13-dithia-10-azacyclopentadecan-10-yl)propyl)-5-(dimethylamino)naphthalene-1-sulfonamide (L) as fluoroionophore in polyvinyl chloride (PVC) containing 2-nitrophenyl octylether (NPOE) as a plasticizer. In addition to high stability and reproducibility, the proposed optosensor showed a unique selectivity toward Pb(II) ion, with a wide linear range of molar concentrations (1.0 × 10⁻⁹–1.0 × 10⁻³ M) and a low detection limit of 7.5 × 10⁻¹⁰ M in solution at pH 5.0. The formation constants of the Pb(II) complexes with the fluoroionophore were evaluated by fitting the fluorescence data with a nonlinear least-squares curve-fitting program, and further information about the structures of the complexes were evaluated based on hybrid-DFT calculations. The optosensor exhibited a fast response time of less than three min, being easily regenerated by exposure to a solution of dithiothreitol. The sensor was applied to the determination of Pb(II) in real samples (canned tuna fish), and it provided satisfactory results comparable to those obtained via atomic absorption spectrometry (AAS). Full article

A novel ligand, namely, (N’,N’’’-((1E,2E)-1,2-diphenylethane-1,2-diylidene)bis(3-allyl-2-hydroxybenzohydrazide) (H2DBAZ), was designed and synthesized. This ligand demonstrated the ability to successfully interact with Tb(III) ions, resulting in the formation of a chemosensor that exhibited luminescent properties. The novel ligand was produced and subsequently subjected to characterization with several analytical techniques, including mass spectroscopy, elemental analysis, Fourier-transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance spectroscopy (¹H NMR). The postulated chemical structure of the Tb(III)–(DBAZ) complex was assessed utilizing a molar ratio approach. The chemosensor exhibited both selectivity and sensitivity towards malathion when compared to other nine organophosphorus pesticides that were investigated in methanol. The method was based on the phenomenon of luminescence static quenching shown by the complex subsequent to its interaction with the malathion pesticide. A linear Stern–Volmer plot was seen and, subsequently, utilized to generate the calibration curve. The observed linear range spanned from 0.39 to 60 µM, with a strong correlation coefficient of 0.999. Additionally, the limit of detection (LOD) was determined to be 0.118 µM. This methodology was successfully employed to measure the presence of malathion in various water samples. This particular complex exhibited promising potential for application in the development of a chemosensor utilizing the molecularly imprinted polymer approach. Full article

There is a pressing need to identify recent directions in the field of aptamer-based sensing. DNA aptamers that are synthetically generated by in vitro selection mechanisms using the SELEX technique are single-stranded oligonucleotides which are selected to bind to a target with favorable sensitivity and selectivity. These aptamers have attracted significant attention due to their high binding affinity and ability to be easily engineered and provide various detection modes in what are known as aptasensors. Our aim is to focus on specialized detection strategies that have gained less attention but are of vital importance, such as optical detection in live cells, fluorescence polarization sensing, multi-analyte detection, colorimetric bioassays, wavelength shifting, and electrochemical-based detection. This will provide us with a perspective to facilitate developments in aptasensor technology for various targets, promising a bright future for biological receptors in the field of biosensing. Full article