Ultrasensitive determination of sulfathiazole using a molecularly imprinted electrochemical sensor with CuS microflowers as an electron transfer probe and Au@COF for signal amplification

Elevated temperature fabrication of copper sulfide nanosphere implemented boron carbide nanocomposite for hyper-sensitive detection of sulfadiazine in water and urine samples

This work introduces an innovative method for electrochemical sensing via the creation of copper sulfide-decorated boron carbide (B4C) nanocomposites (CuS@BC). The emphasis is on identifying sulfadiazine (SFZ), a commonly used antibiotic and environmental contaminant, often detected as a residue in water and human urine owing to its usage in beekeeping for treating bacterial infections. The existence of SFZ presents considerable hazards to vulnerable persons, highlighting the need for accurate detection techniques. The CuS was synthesized using hydrothermal technique, whereas the BC was created in a high-temperature tube furnace. This work utilizes the advanced CuS@BC nanocomposite-modified glassy carbon electrode (GCE) to examine the electrochemical detection of SFZ by differential pulse voltammetry (DPV). Thorough material characterization-incorporating Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). A charge transfer resistance of 370 Ω was found for the CuS@BC-modified electrode by electrochemical investigation. The modified GCE exhibits exceptional electrocatalytic efficacy for SFZ electro-oxidation at appropriate physiological circumstances (pH 7.0), displaying increased cathodic currents compared with the unmodified electrode. The CuS@BC sensor has an extensive detection range of 1-110 µM and an exceptionally low limit of detection of 0.086 µM, indicating outstanding sensitivity. Displaying higher cathodic currents related to the unmodified electrode, providing outstanding selectivity, high repeatability, great reproducibility, and strong functional durability. The CuS@BC-based sensor enhances SFZ detection and shows potential for wider applications in environmental and biological monitoring.

Progress in the application of functionalized covalent organic framework for bioanalysis

As a new type of crystalline porous polymer materials, covalent organic frameworks (COFs) with their unique features such as large surface area, tunable pore sizes, strong π-π stacking effect and size exclusion effects, have attracted wide attention in the analytical field. Due to the lack of catalytically active metal centers in bare COFs, functionalized COFs that are hybridized or modified with nanomaterials improve reactive activation and show better analytical performance for a variety of detection scenarios with complex analytes. Herein, we focused on the functionalized COFs used in bioanalysis ranging from nucleic acids, peptides, and proteins, to microorganisms, and discussed the functionalization strategy and unique structures and properties applied in the different stages of biosensing and advantages compared to other hybrid materials. Finally, challenges and future research directions of functionalized COFs in bioanalysis are discussed.

Advances and Challenges in Molecularly Imprinted Electrochemical Sensors for Application in Environmental, Biomedicine, and Food Safety

Molecularly imprinted electrochemical sensors (MIECSs) are a specialized class of sensors based on molecularly imprinted derivative materials (MIDPs), which have been extensively applied in environmental monitoring, biomedicine, and food safety, allowing for high selectivity and sensitivity in detecting target molecules. This review provides an in-depth exploration of the most innovative and successful nanomaterials employed for modifying imprinted polymers, highlighting their crucial role in enhancing sensor performance, including carbon-based nanomaterials, meal derivatives, magnetic nanomaterials, polymeric and composite nanomaterials. In addition to reviewing advances in derivative materials design, this article delves into the current challenges facing molecularly imprinted sensors, such as issues related to template removal, nonspecific binding, and fabrication reproducibility. These challenges limit the practical application of MIECSs, particularly in complex real-world environments. The review also discusses representative applications of these sensors, including environmental monitoring, biomedicine and food safety, which demonstrate their versatility and potential. Finally, the review outlines future research directions aimed at overcoming these challenges. This includes strategies for improving the stability and reusability of MIECSs, enhancing their selectivity and sensitivity, and developing novel imprinting techniques. By addressing these issues, researchers can pave the way for the next generation of electrochemical sensors, which will be more robust, reliable, and suitable for a wide range of industrial and clinical applications.

A novel electrochemical sensor for rapid detection of sulfathiazole by integrating [(4,4'-bipy/P2Mo17Co)n] modified electrode

In this study, we focused on the successful construction of [(4,4'-bipy/P2Mo17Co)6] modified electrodes using the layer-by-layer assembly method for the sensitive detection of sulfathiazole (ST). The redox reaction between ST and the metal ions in the modified layer leads to the transfer of electrons, resulting in the generation of the electrical signal. The introduction of 4,4'-bipyridine (4,4'-bipy) enhanced the molecular recognition of ST by the modified electrode. Under the combined effect of P2Mo17Co and 4,4'-bipy, the sensor exhibited good performance for ST detection (LOD: 0.5616 μM, linear ST concentration range: 0-50 μM). The spiked recoveries of the two groups were 84.4%-103.2% and 90.9%-109.4% for the determination of ST residues in large yellow croaker and South American white shrimp, respectively. In addition, the electrode showed excellent performance in terms of stability, reproducibility, and anti-interference ability.

Electrochemical measurement of morphine using a sensor fabricated from the CuS/g-C3N5/Ag nanocomposite

Morphine, as one of the most important narcotic drugs, significantly affects the nervous system and increases euphoria, which raises the likelihood of its misuse. Therefore, its measurement is of great importance. In this work, a new electrochemical sensor based on a nanocomposite of CuS/g-C3N5/AgNPs was developed for modifying Screen printed carbon electrodes (SPCEs) and used for the measurement of morphine through cyclic voltammetry and differential pulse voltammetry. Various analytical methods initially characterized the nanocomposite. The prepared sensor, which also has an extensive surface area, achieved a detection limit of 0.01 µM for morphine in a concentration range of 0.05-100 µM at pH 7. Besides its excellent capability in measuring morphine in real samples, the sensor exhibits good stability, reproducibility, and repeatability. The presence of CuS, due to its excellent high surface area alongside silver nanoparticles, leads to an increase in the conductivity of the g-C3N5 modified electrode, resulting in an increased oxidative current of morphine at the surface of the prepared sensor. Therefore, measuring low concentrations of morphine with this sensor was made possible. Additionally, measuring morphine without interference from various species is a strong point of the electrochemical sensor for morphine detection, and combined with the simplicity and ease of the method, it allows for morphine measurements to be conducted in the shortest possible time.

Hypersensitive electrochemical sensor based on thermally annealed gold-silver alloy nanoporous matrices for the simultaneous determination of sulfathiazole and sulfamethoxazole residues in food samples

In this study, we have developed a novel, hypersensitive, and ultraselective electrochemical sensor containing thermally annealed gold-silver alloy nanoporous matrices (TA-Au-Ag-ANpM) integrated with f-MWCNTs-CPE and poly(l-serine) nanocomposites for the simultaneous detection of sulfathiazole (SFT) and sulfamethoxazole (SFM) residues in honey, beef, and egg samples. TA-Au-Ag-ANpM/f-MWCNTs-CPE/poly(l-serine) was characterized using an extensive array of analytical (UV-Vis, FT-IR, XRD, SEM, and EDX), and electrochemical (EIS, CV and SWV) techniques. It exhibited outstanding performance over a wide linear range, from 4.0 pM to 490 μM for SFT and 4.0 pM to 520 μM for SFM, with picomolar detection and quantification limits (0.53 pM and 1.75 pM for SFT, 0.41 pM and 1.35 pM for SFM, respectively). The sensor demonstrated exceptional repeatability, reproducibility, and anti-interference capability, with percentage recovery of 95.6-102.4% in food samples and RSD below 5%. Therefore, the developed sensor is an ideal tool to address the current antibiotic residue crisis in food sources.

A novel molecularly imprinted electrochemical sensor based on quasi-three-dimensional nanomaterials Nb2CTx/AgNWs for specific detection of sulfadiazine

A novel molecularly imprinted electrochemical sensor (MIECS) was constructed for the specific detection of sulfadiazine (SDZ) in food. Niobium carbide (Nb2CTx) as a typical two-dimensional lamellar nanomaterial has good electrical conductivity and unique structure, which was assembled with one-dimensional silver nanowires (AgNWs) to form quasi-three-dimensional composite nanomaterials (Nb2CTx/AgNWs). As spacer material, AgNWs prevented the aggregation of Nb2CTx and the collapse of Nb2CTx layers. At the same time, a fast electron transport channel was constructed through the synergistic effect between nanomaterials the two. The Nb2CTx/AgNWs realized the enhancement of electrical signals. Molecularly imprinted polymers (MIPs) endowed the sensor with selectivity, achieving the specific detection of sulfadiazine. Under the optimal experimental conditions, the method has a wide linear range (1 × 10-8-1 × 10-4 mol L-1) and a low limit of detection (1.30 × 10-9 mol L-1). The sensor was used to detect sulfadiazine in pork, chicken, and feed samples, and the recovery was 82.61-94.87%. The results were in good agreement with the HPLC results, which proved the accuracy and practicability of the method.

A Critical Review on Detection of Foodborne Pathogens Using Electrochemical Biosensors

An outbreak of foodborne pathogens would cause severe consequences. Detecting and diagnosing foodborne diseases is crucial for food safety, and it is increasingly important to develop fast, sensitive, and cost-effective methods for detecting foodborne pathogens. In contrast to traditional methods, such as medium-based culture, nucleic acid amplification test, and enzyme-linked immunosorbent assay, electrochemical biosensors possess the advantages of simplicity, rapidity, high sensitivity, miniaturization, and low cost, making them ideal for developing pathogen-sensing devices. The biorecognition layer, consisting of recognition elements, such as aptamers, antibodies and bacteriophages, and other biomolecules or polymers, is the most critical component to determine the selectivity, specificity, reproducibility, and lifetime of a biosensor when detecting pathogens in a biosample. Furthermore, nanomaterials have been frequently used to improve electrochemical biosensors for sensitively detecting foodborne pathogens due to their high conductivity, surface-to-volume ratio, and electrocatalytic activity. In this review, we survey the characteristics of biorecognition elements and nanomaterials in constructing electrochemical biosensors applicable for detecting foodborne pathogens during the past five years. As well as the challenges and opportunities of electrochemical biosensors in the application of foodborne pathogen detection are discussed.

Not Only Graphene Two-Dimensional Nanomaterials: Recent Trends in Electrochemical (Bio)sensing Area for Biomedical and Healthcare Applications

Two-dimensional (2D) nanomaterials (e.g., graphene) have attracted growing attention in the (bio)sensing area and, in particular, for biomedical applications because of their unique mechanical and physicochemical properties, such as their high thermal and electrical conductivity, biocompatibility, and large surface area. Graphene (G) and its derivatives represent the most common 2D nanomaterials applied to electrochemical (bio)sensors for healthcare applications. This review will pay particular attention to other 2D nanomaterials, such as transition metal dichalcogenides (TMDs), metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXenes, applied to the electrochemical biomedical (bio)sensing area, considering the literature of the last five years (2018-2022). An overview of 2D nanostructures focusing on the synthetic approach, the integration with electrodic materials, including other nanomaterials, and with different biorecognition elements such as antibodies, nucleic acids, enzymes, and aptamers, will be provided. Next, significant examples of applications in the clinical field will be reported and discussed together with the role of nanomaterials, the type of (bio)sensor, and the adopted electrochemical technique. Finally, challenges related to future developments of these nanomaterials to design portable sensing systems will be shortly discussed.

Recent Progress of Covalent Organic Frameworks Applied in Electrochemical Sensors

As an emerging porous crystalline organic material, the covalent organic frameworks (COFs) are given more and more attention in many fields, such as gas storage and separation, catalysis, energy storage and conversion, luminescent devices, drug delivery, pollutant adsorption and removal, analysis and detection due to their special advantages of high crystallinity, flexible designability, controllable porosities and topologies, intrinsic chemical and thermal stability. In recent years, the COFs are applied in analytical chemistry, for instance, chromatography, solid-phase microextraction, luminescent and colorimetric sensing, surface-enhanced Raman scattering and electroanalytical chemistry. The COFs decorated electrodes show high performance for detecting trace substances with remarkable selectivity and sensitivity, such as heavy metal ions, glucose, hydrogen peroxide, drugs, antibiotics, explosives, phenolic compounds, pesticides, disease metabolites and so on. This review mainly summarized the application of COF based electrochemical sensor according to different target analytes.

Rapid and Sensitive Detection of Sulfamethizole Using a Reusable Molecularly Imprinted Electrochemical Sensor

Efficient methods for monitoring sulfonamides (SAs) in water and animal-source foods are of great importance to achieve environmental safety and protect human health. Here, we demonstrate a reusable and label-free electrochemical sensor for the rapid and sensitive detection of sulfamethizole based on an electropolymerized molecularly imprinted polymer (MIP) film as the recognition layer. To achieve effective recognition, monomer screening among four kinds of 3-substituted thiophenes was performed by computational simulation and subsequent experimental evaluation, and 3-thiopheneethanol was finally selected. MIP synthesis is very fast and green, and can be in situ fabricated on the transducer surface within 30 min in an aqueous solution. The preparation process of the MIP was characterized by electrochemical techniques. Various parameters affecting MIP fabrication and its recognition response were investigated in detail. Under optimized experimental conditions, good linearity in the range of 0.001-10 μM and a low determination limit of 0.18 nM were achieved for sulfamethizole. The sensor showed excellent selectivity, which can distinguish between structurally similar SAs. In addition, the sensor displayed good reusability and stability. Even after 7 days of storage, or being reused 7 times, higher than 90% of the initial determination signals were retained. The practical applicability of the sensor was also demonstrated in spiked water and milk samples at the nM determination level with satisfactory recoveries. Compared to relevant methods for SAs, this sensor is more convenient, rapid, economical, and eco-friendly, and had comparable or even higher sensitivity, which offered a simple and efficient method for SA detection.

Simulated adsorption of iodine by an amino-metal-organic framework modified with covalent bonds

Radioactive iodine in nuclear waste is increasingly harmful to the human body and the environment because of its strong radioactivity, high fluidity, easy solubility in water, and long half-life. It is very important to find clean and economical materials to recover and fix radioactive iodine. In this paper, the amino-metal-organic framework was covalently modified to obtain composite materials to improve the recycling of iodine in the environment. These adsorbents are used to adsorb iodine in water, showing outstanding adsorption performance. The adsorption data are in good agreement with the Langmuir isothermal adsorption model and pseudo-second-order kinetic model, indicating that the adsorption process is mainly monolayer adsorption and chemical adsorption. The two materials showed selective adsorption capacity for iodine in the solution containing multiple competing ions. The adsorption capacity of the covalently modified composite increased from 949.52 to 2157.44 mg/g. Compared with the amino-metal-organic framework, the modified composite contains more electron-rich groups as active sites, and forms charge transfer compounds with iodine to realize chemical adsorption. Through the simulated adsorption of ultra-high-pressure micro-jet, the material has certain working ability under high pressure, which provides a theoretical basis for the future recovery and utilization of iodine under high pressure.

A Sensitive and Selective Colorimetric Method Based on the Acetylcholinesterase-like Activity of Zeolitic Imidazolate Framework-8 and Its Applications

In this study, a simple colorimetric method was established to detect copper ion (Cu²⁺), sulfathiazole (ST), and glucose based on the acetylcholinesterase (AChE)-like activity of zeolitic imidazolate framework-8 (ZIF-8). The AChE-like activity of ZIF-8 can hydrolyze acetylthiocholine chloride (ATCh) to thiocholine (TCh), which will further react with 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB) to generate 2-nitro-5-thiobenzoic acid (TNB) that has a maximum absorption peak at 405 nm. The effects of different reaction conditions (buffer pH, the volume of ZIF-8, reaction temperature and time, and ATCh concentration) were investigated. Under the optimized conditions, the value of the Michaelis-Menten constant (K_m) is measured to be 0.83 mM, which shows a high affinity toward the substrate (ATCh). Meanwhile, the ZIF-8 has good storage stability, which can maintain more than 80.0% of its initial activity after 30 days of storage at room temperature, and the relative standard deviation (RSD) of batch-to-batch (n = 3) is 5.1%. The linear dependences are obtained based on the AChE-like activity of ZIF-8 for the detection of Cu²⁺, ST, and glucose in the ranges of 0.021–1.34 and 5.38–689.66 µM, 43.10–517.24 µM, and 0.0054–1.40 mM, respectively. The limit of detections (LODs) are calculated to be 20.00 nM, 9.25 µM, and 5.24 µM, respectively. Moreover, the sample spiked recoveries of Cu²⁺ in lake water, ST in milk, and glucose in strawberry samples were measured, and the results are in the range of 98.4–115.4% with the RSD (n = 3) lower than 3.3%. In addition, the method shows high selectivity in the real sample analysis.

Electrochemical (Bio)Sensors Based on Covalent Organic Frameworks (COFs)

Covalent organic frameworks (COFs) are defined as crystalline organic polymers with programmable topological architectures using properly predesigned building blocks precursors. Since the development of the first COF in 2005, many works are emerging using this kind of material for different applications, such as the development of electrochemical sensors and biosensors. COF shows superb characteristics, such as tuneable pore size and structure, permanent porosity, high surface area, thermal stability, and low density. Apart from these special properties, COF’s electrochemical behaviour can be modulated using electroactive building blocks. Furthermore, the great variety of functional groups that can be inserted in their structures makes them interesting materials to be conjugated with biological recognition elements, such as antibodies, enzymes, DNA probe, aptamer, etc. Moreover, the possibility of linking them with other special nanomaterials opens a wide range of possibilities to develop new electrochemical sensors and biosensors.

Construction of bifunctional electrochemical biosensors for the sensitive detection of the SARS-CoV-2 N-gene based on porphyrin porous organic polymers

In this study, a novel porphyrin-based porous organic polymer (POP) was constructed using 5,10,15,20-tetramine (4-aminophenyl) porphyrin (TAPP) and 5,5'-diformyl-2,2'-bipyridine (DPDD) as organic ligands via a solvothermal method (represented as TAPP-DPDD-POP). Then, it was utilized as a bifunctional scaffold for constructing a sensitive sensing strategy toward the nucleocapsid phosphoprotein (N-gene) of SARS-CoV-2. The obtained TAPP-DPDD-POP is composed of nanospheres with a size of 100-300 nm and possesses a highly conjugated and π-π stacking network. The coexistence of the porphyrin and bipyridine moieties of TAPP-DPDD-POP afforded considerable electrochemical activity and a strong binding interaction toward the SARS-CoV-2 N-gene-targeted antibody and targeted the aptamer strands of the N-gene. The TAPP-DPDD-POP-based aptasensor and immunosensor were manufactured for the sensitive analysis of SARS-CoV-2 N-gene, and exhibited the limit of detection (LOD) of 0.59 fg mL^-1 and 0.17 fg mL^-1, respectively, within the range of 0.1 fg mL^-1 to 1 ng mL^-1 of N-gene. The sensing performances of both the TAPP-DPDD-POP-based aptasensor and immunosensor were better than those of existing electrochemical biosensors for analyzing the N-gene, accompanied with excellent stability, high selectivity and reproducibility. The TAPP-DPDD-POP-based aptasensor and immunosensor were then employed to detect the N-gene from various environments, including human serum, river water, and seafoods. This work provides a new method of using an electrochemically active POP to sensitively and selectively analyze SARS-CoV-2 in diverse environments.

A SiO2@MIP electrochemical sensor based on MWCNTs and AuNPs for highly sensitive and selective recognition and detection of dibutyl phthalate

A molecularly imprinted sensor for highly sensitive and selective determination of dibutyl phthalate (DBP) was fabricated by combining multi-walled carbon nanotubes (MWCNTs) and Au nanoparticles (AuNPs) with surface molecularly imprinted polymer (SMIPs). The MWCNTs and AuNPs were designed to modify the electrode surface to accelerate the electron transfer rate and enhance the chemical stability. SMIPs were synthesized using SiO₂ microspheres as carriers. By loading SMIPs capable of identifying DBP on the surface of modified electrodes of MWCNTs and AuNPs, an electrochemical sensor for detecting DBP was successfully constructed. After optimizing the experimental conditions, the modified electrode SiO₂-COOH@MIP/AuNPs/MWCNTs/GCE can recognize DBP in the range of 10^-7g L^-1 to 10^-2g L^-1, and the detection limit achieved to 5.09 × 10^-9 g L^-1 (S/N = 3). The results demonstrate that the proposed MIP electrochemical sensor may be a promising candidate electrochemical strategy for detecting DBP in complex samples.

共价有机框架分子印迹聚合物复合材料的制备及其用于牛奶中痕量诺氟沙星的选择性富集

诺氟沙星(NFX)作为一种常见的喹诺酮类兽药,被广泛应用于畜牧业中,但其会残留在动物体内,进而对人体健康造成危害,为此有许多国家和组织均对NFX残留量进行了严格限制。为实现对复杂体系中痕量NFX残留的准确与可靠分析,该文制备了一种以共价有机框架(COFs)为载体的分子印迹聚合物(MIPs)。首先,在室温条件下,以金属三氟酸盐为催化剂,对苯二甲醛和3,3'-二氨基联苯为原料快速合成了“席夫碱”型共价有机框架(DP-COF)。然后将NFX、甲基丙烯酸、乙二醇二甲基丙烯酸酯与DP-COF混合,利用偶氮二异丁腈引发聚合反应,即可得到DP-COF@MIPs。整个制备过程条件温和,耗时仅5 h。采用场发射扫描电镜、傅里叶红外光谱、X射线衍射仪、BET比表面积测试仪等对其进行了表征。结果证实成功制备出了DP-COF@MIPs,该材料表面粗糙,拥有介孔范围的孔径(17.79 nm)。通过吸附实验、重复使用性实验对材料性能进行评估,结果表明该材料表观吸附容量高达41.57 mg/g,对NFX具有良好的特异性和选择性识别能力,且重复使用率令人满意。结合HPLC-UV-Vis,实现对牛奶样品中痕量NFX的检测。在3个加标水平下(0.03、0.1、0.3 mg/L),平均回收率为88.8%~92.9%,相对标准偏差小于1.7%。结果表明,该方法可以实现在复杂基质中对兽药残留高选择性、高灵敏度及准确性的检测。

A versatile and ultrasensitive molecularly imprinted electrochemiluminescence sensor with HRP-encapsulated liposome labeled by light-triggered click reaction for pesticide residues

A novel approach for trace detection of fipronil with a molecularly imprinted electrochemiluminescence sensor (MIECLS) is proposed. The sensitivity is significantly improved via signal amplification of the enzymatic reaction of horseradish peroxidase (HRP) released from encapsulated liposomes which linked onto the template molecules after rebinding. The molecularly imprinted polymer membrane was prepared through the electropolymerization of monomers with fipronil as a template. After the elution of the template molecules, the analyte fipronil was reabsorbed into the cavities. HRP-encapsulated liposomes were linked to the target molecules by light-triggered click reaction. The higher the concentration of the target was, the more HRP-encapsulated liposomes were present on the molecularly imprinted polymer (MIP) sensor. Then, HRP was liberated from liposomes, and the catalytic degradation of hydrogen peroxide (H₂O₂) by HRP occurs, which changed the electrochemiluminescence intensity of luminol significantly. The change of the ∆ECL intensity was linearly proportional to the logarithm of the fipronil concentration ranging from 1.00 × 10^-14 to 1.00 × 10^-9 mol/L, and the detection limit was 7.77 × 10^-16 mol/L. The recoveries obtained ranged from 95.7 to 105.8% with RSD < 5%. The sensitivity of the detection was significantly improved, and the analysis process was simplified in that the incubation step required in the conventional method was avoided. The sensor proposed provides a feasible platform for ultra-trace amount determination.

Extremely Sensitive Molecularly Imprinted ECL Sensor with Multiple Probes Released from Liposomes Immobilized by a Light-Triggered Click Reaction

A molecularly imprinted electrochemiluminescence sensor was prepared for sensitive and selective determination of aminotriazole via a novel strategy of multiple Ru(bpy)₃Cl₂ probes released from liposomes immobilized by a light-triggered click reaction. This sensing strategy provides a platform for trace detection of amino-containing pesticides. The target on the molecularly imprinted membrane connected to the Ru(bpy)₃Cl₂-encapsulated liposomes via the click reaction. After the destabilizing agent Triton X-100 was added, numerous Ru(bpy)₃Cl₂ molecules were released by liposomes on the molecularly imprinted polymer electrode. The ECL response of the sensor was linearly proportional to the logarithm of the aminotriazole concentration ranging from 5.00 × 10^-18 to 1.00 × 10^-12 mol/L, and the detection limit was 1.15 × 10^-18 mol/L. The sensitivity of the detection was significantly improved, and the analysis process was simplified.

Molecularly Imprinted Polymers Combined with Electrochemical Sensors for Food Contaminants Analysis

Detection of relevant contaminants using screening approaches is a key issue to ensure food safety and respect for the regulatory limits established. Electrochemical sensors present several advantages such as rapidity; ease of use; possibility of on-site analysis and low cost. The lack of selectivity for electrochemical sensors working in complex samples as food may be overcome by coupling them with molecularly imprinted polymers (MIPs). MIPs are synthetic materials that mimic biological receptors and are produced by the polymerization of functional monomers in presence of a target analyte. This paper critically reviews and discusses the recent progress in MIP-based electrochemical sensors for food safety. A brief introduction on MIPs and electrochemical sensors is given; followed by a discussion of the recent achievements for various MIPs-based electrochemical sensors for food contaminants analysis. Both electropolymerization and chemical synthesis of MIP-based electrochemical sensing are discussed as well as the relevant applications of MIPs used in sample preparation and then coupled to electrochemical analysis. Future perspectives and challenges have been eventually given.

Determination of chloropropanol with an imprinted electrochemical sensor based on multi-walled carbon nanotubes/metal-organic framework composites

In this paper, a composite composed of carboxylated multi-wall carbon nanotubes (cMWCNT) incorporated in a metal–organic framework (MOF-199) has been synthesized using 1,3,5-benzoic acid as a ligand through a simple solvothermal method. The synthesized cMWCNT/MOF-199 composite was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD). The cMWCNT/MOF-199 hybrids were modified on the surface of glassy carbon electrodes (GCE) to prepare a molecularly imprinted electrochemical sensor (MIECS) for specific recognition of 3-chloro-1,2-propanediol (3-MCPD). The electrodes were characterized by differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Under optimal conditions, the electrochemical sensor exhibited an excellent sensitivity and high selectivity with a good linear response range from 1.0 × 10⁻⁹ to 1.0 × 10⁻⁵ mol L⁻¹ and an estimated detection limit of 4.3 × 10⁻¹⁰ mol L⁻¹. Furthermore, this method has been successfully applied to the detection of 3-MCPD in soy sauce, and the recovery ranged from 96% to 108%, with RSD lower than 5.5% (n = 3), showing great potential for the selective analysis of 3-MCPD in foodstuffs.

In this study, cMWCNT/MOF-199 composites were used as the modified electrodes, and a MIECS having specific recognition of 3-MCPD was prepared by electrochemical polymerization for selective analysis of 3-MCPD in foodstuffs.

Covalent organic nanospheres modified magnetic nanoparticles for extraction of blood lipid regulators in water samples

Covalent organic nanospheres are new kind of nanospherical polymer with large specific surface area, uniform morphology, and excellent chemical and thermal stability. This material can be fabricated by a facile and rapid room temperature solution-phase strategy. In this work, magnetic nanoparticles were attached to the surface of covalent organic nanospheres, and the obtained composites were used for the extraction of blood lipid regulators such as clofibrate and fenofibrate. These composites were characterized with Fourier-transformed infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Several parameters that might affect the extraction efficiency including acetonitrile content, pH value, extraction time, and sample volume were investigated. Under optimum conditions, the proposed analytical method showed high extraction efficiency toward clofibrate and fenofibrate with enrichment factors between 60 and 83. This method exhibited outstanding analytical performance with wide linear range and excellent reproducibility and had low limits of detection in the range of 0.02-0.03 ng/mL. This method was also applied to the detection of clofibrate and fenofibrate in lake water samples, and good recoveries in the range of 92.6-112.6% was obtained.