"Sign-on/off" sensing interface design and fabrication for propyl gallate recognition and sensitive detection

A simple molecularly imprinted electrochemical sensor for determination of propyl gallate in food samples

Propyl gallate (PG), a prevalent synthetic phenolic antioxidant found in food products, has generated considerable apprehension owing to its potential adverse impacts on human health. Therefore, as a result of the current inquiry, an innovative electrochemical sensor with improved sensitivity and selectivity for PG detection has been created. Under optimal conditions, the manufactured sensor exhibits the capability to identify PG within a broad range from 0.01 μM to 5 μM and from 5 μM to 1000 μM with a limit of detection (LOD) of 6 nM, demonstrating exceptional levels of reproducibility, repeatability, stability, and selectivity. The sensor demonstrated successful detection of PG in edible oils and mayonnaise, with good recoveries ranging from 98.44 % to 101.37 %.

Boric acid group-functional Tb-MOF as a fluorescent and captured probe for the highly sensitive and selective determination of propyl gallate in edible oils

This study reports the development of a Tb-metal-organic framework (Tb-MOF)-based fluorescent platform for the detection of propyl gallate (PG). The Tb-MOF using 5-boronoisophthalic acid (5-bop) as the ligand exhibited multiple emissions at 490, 543, 585, and 622 nm under an excitation wavelength of 256 nm. The fluorescence of Tb-MOF was selectively and significantly weakened in the presence of PG due to the special nucleophilic reaction between the boric acid of Tb-MOF and o-diphenol hydroxyl of PG, and the combined effect of static quenching and internal filtering. Furthermore, this sensor enabled the determination of PG within seconds in a wide linear range of 1-150 μg/mL, and with a low detection limit of 0.098 μg/mL, and high specificity against other phenolic antioxidants. This work provided a new route for the sensitive and selective determination of PG in soybean oil, thus was perspective to monitor and reduce the risk of PG overuse.

Bimetallic MOF synergy molecularly imprinted ratiometric electrochemical sensor based on MXene decorated with polythionine for ultra-sensitive sensing of catechol

Dual-signal ratiometric molecularly imprinted polymer (MIP) electrochemical sensors with bimetallic active sites and high-efficiency catalytic activity were fabricated for the sensing of catechol (CC) with high selectivity and sensitivity. The amino-functionalization bimetallic organic framework materials (Fe@Ti-MOF-NH₂), coupled with two-dimensional layered titanium carbide (MXene) co-modified glassy carbon electrode provides an expanded surface while amplifying the output signal through the electropolymerization immobilization of polythionine (pTHi) and MIP. The oxidation of CC and pTHi were presented as the response signal and the internal reference signal. The oxidation peak current at +0.42 V rose with increased concentration of CC, while the peak currents of pTHi at -0.20 V remained constant. Compared to the common single-signal sensing system, this one (MIP/pTHi/MXene/Fe@Ti-MOF-NH₂/GCE), a novel ratiometric MIP electrochemical sensor exhibited two segments wide dynamic range of 1.0-300 μM (R² = 0.9924) and 300-4000 μM (R² = 0.9912), as well as an ultralow detection limit of 0.54 μM (S/N = 3). Due to the specific recognition function of MIPs and the advantages of built-in correction of pTHi, the prepared surface imprinting sensor presented an excellent performance in selectivity and reproducibility. Besides, this sensor possessed superior anti-interference ability with ions and biomolecules, excellent reproducibility, repeatability, and acceptable stability. Furthermore, the proposed sensing system exhibits high specific recognition in the determination of environmental matrices and biological fluids in real samples with satisfactory results. Therefore, this signal-enhanced ratiometric MIP electrochemical sensing strategy can accurately and selectively analyze and detect other substances.

Colorimetric sensor array based on CoOOH nanoflakes for rapid discrimination of antioxidants in food

The identification of synthetic antioxidants has considerable significance in food safety. Here, we described the development of a colorimetric sensor array for rapid detection of eight antioxidants in food through the redox reaction between CoOOH and antioxidants in the presence of colorimetric signal indicators. The CoOOH nanoflakes exhibited high catalytic oxidation activity and can independently catalyze oxidation signal indicators showing different colors. The color reaction was inhibited to different degrees in the presence of antioxidants, which resulted in distinct signal response patterns for their discrimination. The method showed good linearity in the range from 50 to 1000 nM for butylated hydroxytoluene (BHT), butylhydroxyanisole (BHA), propyl gallate (PG) and tert-butyl hydroquinone (TBHQ). Moreover, different proportions of antioxidants were located in the middle pattern of each single antioxidant, and showed certain linear relationships among different concentration ratios. Finally, the proposed colorimetric sensor array was used for practical applications where TBHQ and BHT were detected in biscuits and sausages, and BHA and PG were detected in fried pork kebabs, respectively. The results were further confirmed by high-performance liquid chromatography, which demonstrated the great potential of the colorimetry sensor array for practical applications.

Transition metal copper composite ionic liquid self-built ratiometric sensor for the detection of paracetamol

In this paper, a MOF derivative Cu-PF₆-MOF composed of transition metal copper and ionic liquid [BMIM] PF₆ was used to construct a ratiometric electrochemical sensor for paracetamol detection. Cu-PF₆-MOF was synthesized by chemical bath method and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray Photoelectron Spectroscopy (XPS) and X-ray powder diffraction (XRD). Owing to the introduction of ionic liquid [BMIM] PF₆ and the synthetic effect on transition metal copper and ionic liquid [BMIM] PF₆, Cu-PF₆-MOF has the higher conductivity, larger electroactive surface area and better intrinsic catalytic properties of the skeletal transition metal, exhibiting enhanced electrocatalytic response to the reduction of paracetamol. The stable reduction peak at -104 mV was used as the ratiometric signal for analytical paracetamol detection using differential pulse voltammetry (DPV), with a linear range of 0.1-100 μM and a detection limit of 0.03 μM (S/N = 3). In addition, the constructed sensor showed good reproducibility, stability and interference resistance, as well as ideal recoveries (98.20%-104.40%) for the analysis of paracetamol in water samples.

Evaluation of Antioxidants Using Electrochemical Sensors: A Bibliometric Analysis

The imbalance of oxidation and antioxidant systems in the biological system can lead to oxidative stress, which is closely related to the pathogenesis of many diseases. Substances with antioxidant capacity can effectively resist the harmful damage of oxidative stress. How to measure the antioxidant capacity of antioxidants has essential application value in medicine and food. Techniques such as DPPH radical scavenging have been developed to measure antioxidant capacity. However, these traditional analytical techniques take time and require large instruments. It is a more convenient method to evaluate the antioxidant capacity of antioxidants based on their electrochemical oxidation and reduction behaviors. This review summarizes the evaluation of antioxidants using electrochemical sensors by bibliometrics. The development of this topic was described, and the research priorities at different stages were discussed. The topic was investigated in 1999 and became popular after 2010 and has remained popular ever since. A total of 758 papers were published during this period. In the early stages, electrochemical techniques were used only as quantitative techniques and other analytical techniques. Subsequently, cyclic voltammetry was used to directly study the electrochemical behavior of different antioxidants and evaluate antioxidant capacity. With methodological innovations and assistance from materials science, advanced electrochemical sensors have been fabricated to serve this purpose. In this review, we also cluster the keywords to analyze different investigation directions under the topic. Through co-citation of papers, important papers were analyzed as were how they have influenced the topic. In addition, the author’s country distribution and category distribution were also interpreted in detail. In the end, we also proposed perspectives for the future development of this topic.

Ratiometric Electrochemistry: Improving the Robustness, Reproducibility and Reliability of Biosensors

Electrochemical biosensors are an increasingly attractive option for the development of a novel analyte detection method, especially when integration within a point-of-use device is the overall objective. In this context, accuracy and sensitivity are not compromised when working with opaque samples as the electrical readout signal can be directly read by a device without the need for any signal transduction. However, electrochemical detection can be susceptible to substantial signal drift and increased signal error. This is most apparent when analysing complex mixtures and when using small, single-use, screen-printed electrodes. Over recent years, analytical scientists have taken inspiration from self-referencing ratiometric fluorescence methods to counteract these problems and have begun to develop ratiometric electrochemical protocols to improve sensor accuracy and reliability. This review will provide coverage of key developments in ratiometric electrochemical (bio)sensors, highlighting innovative assay design, and the experiments performed that challenge assay robustness and reliability.

MXene with Great Adsorption Ability toward Organic Dye: An Excellent Material for Constructing a Ratiometric Electrochemical Sensing Platform

Ratiometric electrochemical sensors coupled with an intrinsic built-in correction have received much attention in biochemical analysis, which can effectively avoid potential impacts from both intrinsic and extrinsic factors. However, the complex modification procedure and the unstable reference signal limit development and application of ratiometric sensing. To address these issues, we proposed a novel ratiometric electrochemical platform based on MXene. Introduction of built-in correction was realized via simple one-step incubation of MXene in solution containing the reference molecule methylene blue (MB), and their firm electrostatic interaction ensures the strong adsorption capability of MXene toward MB. Remarkable enhancement in repeatibility and stability compared with nonratio sensor was proved by detecting the model analyte piroxicam. Furthermore, compatibility of the ratio sensor was demonstrated by integrating copper nanoparticles (CuNPs) into the platform. It turned out that sensing performance of the hybrid electrochemical sensor was significantly improved owing to synergistic effect of MXene and CuNPs, where the former affords a large specific surface area as well as quick electron transport, and the latter possess decent electrical catalytic ability. In all, the proposed ratiometric sensor based on MXene features easy preparation, superb reproducibility, robustness, and broad applicability, affording the platform highly competitive and reliable in the determination of a wide range of substances.

Au-polythionine nanocomposites: a novel mediator for bisphenol A dual-signal assay based on imprinted electrochemical sensor

In this work, a novel electrochemical sensor was developed by the modification of poly(p-aminobenzene sulfonic acid) (pABSA), Au-polythionine (Au-pTH) nanowires, and molecularly imprinted polymer (MIP) on glassy carbon electrode surface for bisphenol A (BPA) detection. The results of characterizations including scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectra, and X-ray diffraction showed the successful synthesis of helical structural Au-pTH nanowires, which acted as an electro-active probe for BPA detection. Cyclic voltammetry results illustrated that the modified pABSA, Au-pTH, and MIP endowed the sensor with good electrocatalytic activity, the second current signal, and recognition ability, respectively. Since the imprinted cavities provided electron transfer channels for thionine (TH) redox, the peak current of TH can be found in a blank electrolyte. The added BPA molecules can be rebound in imprinted cavities, which are oxidized and then display its current. The rebound BPA molecules in turn blocked the electron transfer channels for TH redox, resulting in the decrease of TH current. A double signal defined, as the sum of the changes of TH current (∆i_TH|) and BPA current (|∆i_BPA|) (|∆i_TH|+|∆i_BPA|), was employed as the detected signal for BPA sensitive detection, which was linearly proportional to the logarithm of concentration of BPA ranging from 8.0 × 10^-8 to 1.0 × 10^-4 mol/L with a limit of detection of 3.8 × 10^-8 mol/L (S/N = 3) in a weakly acidic solution. Moreover, the natural recognition ability of MIP enabled the sensor to selectively detect BPA from its analogues. The proposed dual-signal strategy-based sensor provided a feasible tool for rapid, sensitive, and selective determination of BPA. Graphical abstract.

Molecularly Imprinted Poly(thionine)-Based Electrochemical Sensing Platform for Fast and Selective Ultratrace Determination of Patulin

An innovative approach based on a surface functional monomer-directing strategy for the construction of a sensitive and selective molecularly imprinted electrochemical sensor for patulin recognition is described. A patulin imprinted platinum nanoparticle (PtNP)-coated poly(thionine) film was grown on a preformed thionine tailed surface of PtNP-nitrogen-doped graphene (NGE) by electropolymerization, which provided high capacity and fast kinetics to uptake patulin molecules. Thionine acted not only as a functional monomer for molecularly imprinted polymer (MIP), but also as a signal indicator. Enhanced sensitivity was obtained by combining the excellent electric conductivity of PtNPs, NGE, and thionine with multisignal amplification. The designed sensor displayed excellent performance for patulin detection over the range of 0.002-2 ng mL^-1 (R² = 0.995) with a detection limit of 0.001 ng mL^-1 for patulin. In addition, the resulting sensor showed good stability and high repeatability and selectivity. Furthermore, the feasibility of its applications has also been demonstrated in the analysis of real samples, providing novel tactics for the rational design of MIP-based electrochemical sensors to detect a growing number of deleterious substances.

Determination of the antioxidant propyl gallate in meat by using a screen-printed electrode modified with CoSe2 nanoparticles and reduced graphene oxide

A voltammetric sensor is described for the quantitation of propyl gallate (PG). A screen-printed carbon electrode (SPCE) was modified with reduced graphene sheets that were decorated with cobalt diselenide nanoparticles (CoSe₂@rGO). The material was hydrothermally prepared and characterized by several spectroscopic techniques. The modified SPCE displays excellent electrocatalytic ability towards PG. Differential pulse voltammetry, with a peak voltage at 0.34 V (vs. Ag/AgCl) has a sensitivity of 12.84 μA·μM^-1·cm^-2 and a detection limit as low as 16 nM. The method is reproducible, selective, and practical. This method was applied to the determination of PG in spiked meat samples, and the result showed an adequate recovery. Graphical abstract Schematic of a new method for fast and sensitive electrochemical determination of the food additive propyl gallate in meat.

Highly specific and sensitive determination of propyl gallate in food by a novel fluorescence sensor

Propyl gallate (PG), one of the most widely used synthetic phenolic antioxidants in edible oil, cookies and fried food, has received extensive concern due to its possible toxic effects on human health. Herein, a novel fluorescence analytical method is firstly proposed to sensitively and selectively determine propyl gallate (PG) by utilizing the unique fluorescence quenching property of organic molybdate complex (OMC) formed by the specific reaction between MoO₄^2- and PG to g-C₃N₄ nanosheets. Under the optimum conditions, the developed fluorescence sensor allows highly sensitive detection of PG in a wide range from 0.5 to 200 μg mL^-1 with a detection limit of 0.11 μg mL^-1, and possesses excellent specificity and good recoveries. All the analytical results indicate the present method provides an effective approach for rapid detection of PG in common products, which is beneficial for monitoring and reducing the risk of overuse of PG.

A ratiometric strategy -based electrochemical sensing interface for the sensitive and reliable detection of imidacloprid

A ratiometric electrochemical sensor was developed for selective and sensitive detection of imidacloprid. Modified poly(thionine) provided a built-in correction to endow the sensor with good accuracy and stability.

Simple and effective label-free electrochemical immunoassay for carbohydrate antigen 19-9 based on polythionine-Au composites as enhanced sensing signals for detecting different clinical samples

Carbohydrate antigen 19-9 (CA19-9) is an important biomarker for the early diagnosis and clinical monitoring of pancreatic cancer. Reliable, simple, and accurate methods for the detection of CA19-9 are still urgently needed. In this study, polythionine-Au composites (AuNPs@ PThi) were designed and prepared through one-pot reaction using HAuCl₄ as the co-oxidant and raw material in thionine solution containing FeCl₃ as the oxidant. AuNPs@PThi-immobilized glassy carbon electrode was used as a sensitive redox probe for electrochemical interface. AuNPs@PThi not only favored the amplification of electrochemical signals but also facilitated excellent environmental friendliness for bioassay. Maximizing the electrochemical properties of AuNPs@PThi, an effective label-free electrochemical immunoassay for the ultrasensitive and reliable detection of CA19-9 was developed. Under optimal conditions, the linear range of the proposed immunosensor was estimated to range from 6.5 to 520 U/mL, with a detection limit of 0.26 U/mL at a signal-to-noise ratio of 3. The prepared immunosensor for CA19-9 detection showed high sensitivity, stability, and reproducibility. Furthermore, the fabricated immunosensor based on AuNPs@PThi can effectively detect and distinguish clinical serum samples of pancreatic cancer and normal control with accuracy and convenience.