NiO@Ni-MOF nanoarrays modified Ti mesh as ultrasensitive electrochemical sensing platform for luteolin detection

Proton-capture strategy for stable redox potential in luteolin detection using SnO2-ZIF-67 electrodes

Variations in H⁺ concentration significantly impact the redox potential of luteolin during electrochemical sensor detection, leading to indeterminate electrochemical signals and hindering accurate identification of luteolin. In this study, we developed a proton-capture strategy for electrochemical sensing by synthesizing a ZIF-67-modified SnO2 (SnO2-ZIF-67) composite, enabling constant peak potential detection across a range of pH environments. We demonstrated through both experimental methods and density functional theory (DFT) that ZIF-67 induces a high density of oxygen vacancies within the SnO₂ crystal, which capture protons dissociated from luteolin, thereby preventing potential shifts during electrochemical detection. We proved that the reaction of luteolin on the SnO₂-ZIF-67 modified electrode involves the transfer of two electrons and two protons, with a charge transfer coefficient of 0.58. The SnO2-ZIF-67 modified sensing electrode exhibits a record-high sensitivity of 218.7 μA μM⁻1 for luteolin detection, with an ultra-low detection limit of 0.12 nM. Furthermore, the sensor shows excellent selectivity for luteolin, with common coexisting ions and compounds causing no significant interference. The sensing electrode also demonstrates exceptional stability, retaining 94.5 % of its initial signal after four weeks of exposure to air, and it accurately detects luteolin in real samples, highlighting its great potential for practical applications.

Monitoring of Specific Phytoestrogens by Dedicated Electrochemical Sensors: A Review

Phytoestrogens are non-steroidal estrogens produced from plants that can bind with the human body's estrogenic receptor site and be used as a substitute for maintaining hormonal balance. They are mainly classified as flavonoids, phenolic acids, lignans, stilbenes, and coumestans; some are resocyclic acids of lactones, which are mycotoxins and not natural phytoestrogen. Phytoestrogens have many beneficial medicinal properties, making them an important part of the daily diet. Electrochemical sensors are widely used analytical tools for analysing various pharmaceuticals, chemicals, pollutants and food items. Electrochemical sensors provide an extensive platform for highly sensitive and rapid analysis. Several reviews have been published on the importance of the biological and medicinal properties of phytoestrogens. However, this review provides an overview of recent work performed through electrochemical measurements with electrochemical sensors and biosensors for all the classes of phytoestrogens done so far since 2019.

Recent advances on metal-organic framework-based electrochemical sensors for determination of organic small molecules

Metal-organic frameworks (MOFs) are an extraordinarily versatile class of porous materials renowned for their intricate three-dimensional skeletal architectures and exceptional chemical properties. These extraordinary attributes have pushed MOFs into the vanguard of diverse disciplines such as microporous conduction, catalysis, separation, biomedical engineering, and electrochemical sensing. The focus of this review is to offer a comprehensive summary of recent advancements in designing MOF-based electrochemical sensors for detecting organic small molecules. offer a comprehensive survey of the recent progress in the methodologies adopted for the construction of MOF composites, covering template-assisted synthesis, Modification in synthesis, and post-synthesis modification. In addition, we discuss the practical application of MOF-based electrochemical sensors in the detection of organic small molecules. Our findings highlight the superior electrochemical sensing capabilities of these novel composites compared to those of their pristine counterparts. In conclusion, we provide a condensed perspective on the potential future trajectories in this domain, underscoring the impetus for continued enquiry and enhancement of MOF composite assemblies. With sustained investigation, the horizon appears bright for electrochemical sensing of small organic molecules and their myriad applications.

A novel electrochemical sensor for detection of luteolin in food based on 3D networked electrically interconnected SiO2@GO/MXene composite

Luteolin (Lu), a compound with various biochemical and pharmacological activities beneficial to human health, has attracted researchers' attention. This study proposes an efficient and scalable method using ultrasound to intercalate graphene oxide (GO)-coated silica spheres (SiO2) into MXenes, resulting in a 3D conductive interconnected structural composite material. Characterization of the composite material was conducted using SEM, TEM, XRD, XPS, and Raman spectroscopy. MXenes exhibit excellent electrical conductivity, and the SiO2@GO surface with abundant hydroxyl and silanol groups provides high-binding active sites that facilitate Lu molecule enrichment. The formation of the 3D conductive interconnected structural composites enhances charge transport, significantly improving sensor sensitivity. Consequently, the sensor demonstrates excellent detection capabilities (detection range 0.03-7000 nM, detection limit 12 pM). Furthermore, the sensor can be applied to quantitative determination of Lu in real samples, including chrysanthemums, Jiaduobao, honeysuckle, purple perilla, and peanut shells, achieving recoveries between 98.2 and 104.7%.

Expanded interlayer spacing of SnO2 QDs-Decorated MXene for highly selective luteolin detection with Ultra-Low limit of detection

Although there have been advancements in electrochemical catalysts for luteolin detection, their practical use is constrained by low sensitivity, inadequate selectivity, and unsatisfactory limit of detection. MXene, a class of 2D materials, possesses exceptional physical-chemical properties that make it highly suitable for electrochemical detection. Nevertheless, the self-stacking and limited interlayer spacing of MXene impede its extensive application in electrochemical detection. Herein, a SnO2 QDs-MXene composite is synthesized for selective electrochemical detection of luteolin. Inserting SnO2 QDs between tightly stacked MXene layers expands the d-spacing of MXene, enhancing the specific surface area and enabling abundant active sites for redox reactions. The inclusion of MXene in the modified SnO2 QDs-MXene/GCE electrode significantly enhances electron transfer. As a result, the electrode demonstrates exceptional luteolin detection capabilities, including a wide linear range (0.1-1200 nM), high sensitivity (12.4 μA μM-1), and an ultra-low limit of detection (0.14 nM). Additionally, the SnO2 QDs-MXene/GCE electrode exhibits good repeatability, excellent reproducibility, remarkable stability, and high selectivity, making it suitable for practical sample analysis. This research contributes to advancing ultra-low limit of detection sensors for accurate luteolin detection.

Rapid quantitative detection of luteolin using an electrochemical sensor based on electrospinning of carbon nanofibers doped with single-walled carbon nanoangles

In this study, single-walled carbon nanoangles/carbon nanofibers (SWCNHs/CNFs) were synthesized by electrospinning, followed by annealing in a N₂ atmosphere. The synthesized composite was structurally characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical sensor was fabricated by modifying a glassy carbon electrode (GCE) for luteolin detection, and its electrochemical characteristics were investigated using differential pulse voltammetry, cyclic voltammetry, and chronocoulometry. Under optimized conditions, the response range of the electrochemical sensor to luteolin was 0.01-50 μM, and the detection limit was 3.714 nM (S/N = 3). The SWCNHs/CNFs/GCE sensor showed excellent selectivity, repeatability, and reproducibility, thus enabling the development of an economical and practical electrochemical method for the detection of luteolin.

A novel electrochemical sensor based on gold nanobipyramids and poly-L-cysteine for the sensitive determination of trilobatin

Trilobatin is a flavonoid that has wide application prospects due to its various pharmacological effects, such as anti-inflammation and anti-oxidation. In this work, a novel electrochemical sensor based on gold nanobipyramids (AuNBs) and L-cysteine (L-cys) was constructed for the sensitive and selective determination of trilobatin. The AuNBs, which were prepared by a seed-mediated growth method, had large specific surface areas and excellent electrical conductivity. A layer of L-cys film, which provided more active sites through the amino and hydroxyl groups, was modified on the surface of the AuNBs by electropolymerization. Significantly, the Au-S bond between the L-cys film and AuNBs could improve the stability of the sensor and it exhibited satisfactory electrocatalytic oxidation activity for trilobatin. Under optimized conditions, the sensor based on poly-L-cys/AuNBs/GCE was used to determine trilobatin by differential pulse voltammetry (DPV). Two wide linear ranges between the current peak and the concentration of trilobatin were obtained in the range from 5 to 100 μM and 100 to 1000 μM, and the low detection limit (LOD) was up to 2.55 μM (S/N = 3). The sensor demonstrated desirable reproducibility, stability, and selectivity and was applied to detect real trilobatin samples extracted from Lithocarpus polystachyus Rehd.'s leaves, showing recoveries of 98.36%-104.96%, with satisfactory results.

An electrochemical sensor for purine base detection with ZIF-8-derived hollow N-doped carbon dodecahedron and AuNPs as electrocatalysts

In this paper, a novel electrochemical sensor was constructed for the detection of purine bases. Ultrafine carbide nanocrystals confined within porous nitrogen-doped carbon dodecahedrons (PNCD) were synthesized by adding molybdate to ZIF-8 followed by annealing. With MoC-based PNCDs (MC-PNCDs) as the carrier, gold nanoparticles (AuNPs) were deposited on the electrode surface via potentiostatic deposition as the promoter of electron transfer, forming a AuNPs/MC-PNCDs/activated glassy carbon electrode (AGCE) sensor. MC-PNCDs had a large specific surface area, which combined with the excellent electrocatalytic activity of AuNPs, synergistically improved the electrocatalytic activity. The morphology and structure of the electrode surface modifier were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray photoelectron spectroscopy, infrared spectroscopy, X-ray diffraction, nitrogen adsorption-desorption analysis, and electrochemical characterization. Under the optimal conditions, the linear detection range of guanine (G) and adenine (A) was 0.5-160.0 μM, and the detection limits (S/N=3) were 72.1 and 69.6 nM, respectively. AuNPs/MC-PNCDs/AGCE was successfully constructed, and was used to simultaneously detect G and A with high sensitivity and selectivity. Moreover, the sensor was successfully used to detect G and A in herring sperm DNA samples.

Recent Progress in Electrochemical Nano-Biosensors for Detection of Pesticides and Mycotoxins in Foods

Pesticide and mycotoxin residues in food are concerning as they are harmful to human health. Traditional methods, such as high-performance liquid chromatography (HPLC) for such detection lack sensitivity and operation convenience. Efficient, accurate detection approaches are needed. With the recent development of nanotechnology, electrochemical biosensors based on nanomaterials have shown solid ability to detect trace pesticides and mycotoxins quickly and accurately. In this review, English articles about electrochemical biosensors in the past 11 years (2011-2022) were collected from PubMed database, and various nanomaterials are discussed, including noble metal nanomaterials, magnetic metal nanoparticles, metal-organic frameworks, carbon nanotubes, as well as graphene and its derivatives. Three main roles of such nanomaterials in the detection process are summarized, including biomolecule immobilization, signal generation, and signal amplification. The detection targets involve two types of pesticides (organophosphorus and carbamate) and six types of mycotoxins (aflatoxin, deoxynivalenol, zearalenone, fumonisin, ochratoxin A, and patulin). Although significant achievements have been made in the evolution of electrochemical nano-biosensors, many challenges remain to be overcome.

Recent advances in the electrochemical applications of Ni-based metal organic frameworks (Ni-MOFs) and their derivatives

Nickel-based metal-organic skeletal materials (Ni-MOFs) are a new class of inorganic materials that have aroused attention of investigators during past couple of years. They offer advantages such as high specific surface area, structural diversity, tunable framework etc. This assorted class of materials exhibited catalytic activity and electrochemical properties and display wide range of applications in the fields of electrochemical sensing, electrical energy storage and electrocatalysis. In this context, the presented review focuses on strategies to improve the electrochemical performance and stability of Ni-MOFs through the optimization of synthesis conditions, the construction of composite materials, and the preparation of derivatives of precursors. The review also presents the applications of Ni-MOFs and their derivatives as electrochemical sensors, energy storage devices, and electrocatalysts. In addition, the challenges and further electrochemical development prospects of Ni-MOFs have been discussed.

Hydrothermal Evaluation of Vernacular Housing: Comparing Case Studies of Waste PET Bottles, Stone, and Adobe Houses

This work shows the humidity and thermal evaluation of different case studies of houses. The analyses focused on room prototypes and houses built in different regions of Querétaro, México. Three different climatic zones were included with the evaluations of houses and prototypes. The assessments of internal and external parameters in residential buildings are also shown. The internal parameter measurements were done with hydro-thermometers and thermography images. Six structures were evaluated, one of the conventional housing materials and five of alternative or vernacular materials. The predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD) were determined using the average temperature and relative humidity values, and they were considered to be dynamic because they can change depending on many factors. The six dwelling insulating properties were associated with their construction materials, design, location, and other factors. The six houses have many differences, but considering their behavior in their location, the two floor porous stone house got the best results. On the contrary, the flagstone house with a gabled roof of galvanized sheets had a cold perception despite many advantageous elements, failing to provide comfort in such a cold location. Contrasting these with other adobe constructions, the analyzed one had low thermal insulation, which was explained by its characteristics. PET and adobe uninhabited prototypes had medium to cold perceptions. The PET prototype has excellent and adjustable insulations, both on temperature and RH, considering the passive illumination and ventilation of its glass bottle skylights.

A Comprehensive Review on the Electrochemical Sensing of Flavonoids

Flavonoids are bioactive polyphenolic compounds, widespread in the plant kingdom. Flavonoids possess broad-spectrum pharmacological effects due to their antioxidant, anti-tumor, anti-neoplastic, anti-mutagenic, anti-microbial, anti-inflammatory, anti-allergic, immunomodulatory, and vasodilatory properties. Care must be taken, since excessive consumption of flavonoids may have adverse effects. Therefore, proper identification, quantification and quality evaluations of flavonoids in edible samples are necessary. Electroanalytical approaches have gained much interest for the analysis of redox behavior and quantification of different flavonoids. Compared to various conventional methods, electrochemical techniques for the analysis of flavonoids offer advantages of high sensitivity, selectivity, low cost, simplicity, biocompatibility, easy on-site evaluation, high accuracy, reproducibility, wide linearity of detection, and low detection limits. This review article focuses on the developments in electrochemical sensing of different flavonoids with emphasis on electrode modification strategies to boost the electrocatalytic activity and analytical efficiency.

Metal-Organic Framework-Based Composites for the Detection and Monitoring of Pharmaceutical Compounds in Biological and Environmental Matrices

The production of synthetic drugs is considered a huge milestone in the healthcare sector, transforming the overall health, aging, and lifestyle of the general population. Due to the surge in production and consumption, pharmaceutical drugs have emerged as potential environmental pollutants that are toxic with low biodegradability. Traditional chromatographic techniques in practice are time-consuming and expensive, despite good precision. Alternatively, electroanalytical techniques are recently identified to be selective, rapid, sensitive, and easier for drug detection. Metal-organic frameworks (MOFs) are known for their intrinsic porous nature, high surface area, and diversity in structural design that provides credible drug-sensing capacities. Long-term reusability and maintaining chemo-structural integrity are major challenges that are countered by ligand-metal combinations, optimization of synthetic conditions, functionalization, and direct MOFs growth over the electrode surface. Moreover, chemical instability and lower conductivities limited the mass commercialization of MOF-based materials in the fields of biosensing, imaging, drug release, therapeutics, and clinical diagnostics. This review is dedicated to analyzing the various combinations of MOFs used for electrochemical detection of pharmaceutical drugs, comprising antibiotics, analgesics, anticancer, antituberculosis, and veterinary drugs. Furthermore, the relationship between the composition, morphology and structural properties of MOFs with their detection capabilities for each drug species is elucidated.

A facile fabrication of a hierarchical ZIF-8/MWCNT nanocomposite for the sensitive determination of rutin

In this paper, a novel type of zeolitic imidazolate framework-8 (ZIF-8) polyhedron/multi-walled carbon nanotube (MWCNT) modified electrode was successfully prepared for effective on-site detection of rutin. The morphology and microstructure of the ZIF-8/MWCNT nanocomposite were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The electrochemical performance of the ZIF-8/MWCNT based electrode for the determination of rutin was studied by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPV). The as-prepared sensor illustrates better electrocatalytic activity and lower background current than the MWCNT modified electrode for the oxidation of rutin. Besides, the ZIF-8/MWCNTs sensor offers a remarkable linear response for rutin concentrations from 0.1 to 15 μM. The detection limit (LOD) was calculated to be 0.26 nM (S/N = 3). Also, the ZIF-8/MWCNT electrode showed high anti-interference ability towards common interfering species. More importantly, the fabricated electrode was quickly evaluated for determination of rutin in medicine tablets with satisfactory recoveries and the obtained results successfully achieved good consistency with the data from high performance liquid chromatography (HPLC). Finally, the method shows an enhanced electrocatalytic property and sensitivity for the analysis of rutin, which may provide an economical and promising electrochemical sensor for practical on-site detection of rutin.

A magnetic copper organic framework material as an efficient and recyclable catalyst for the synthesis of 1,2,3-triazole derivatives

In this study, a core-shell magnetic metal organic framework (MOF) catalyst was introduced based on Fe3O4 magnetic nanoparticles (MNPs) and copper organic frameworks. In this catalyst, Fe3O4 MNPs have been coated with MOFs in which copper was the inorganic nodes and 1,3,5-benzenetricarboxylic acid was the organic linkers. Then, the core-shell structures and catalytic efficiency have been confirmed properly and completely with various analyses such as FT-IR, TEM, SEM, TEM mapping, SEM mapping, EDX, PXRD, TGA, ICP and VSM. The Cu moieties in MOF and shell structures can catalyze the synthesis of 1,2,3-triazole derivatives with good to excellent yields in the presence of water as a green solvent. Moreover, this catalyst showed the high reusability due to the super paramagnetic properties.

Novel luteolin sensor of tannic acid-stabilized copper nanoclusters with blue-emitting fluorescence

In this work, the fluorescent copper nanoclusters (Cu NCs) were firstly adopted to detect luteolin with excellent performance. The blue-emitting Cu NCs was successfully prepared through a facile one-pot approach by protection of tannic acid (TA) and chemical reduction of ascorbic acid (AA). The water-soluble nanoclusters possessed uniform size and displayed good stability. The TA-Cu NCs showed maximum luminescence at 434 nm when excited at 366 nm. Based on the static quenching and inner filter effect (IFE) mechanism, the TA-Cu NCs was efficiently and selectively quenched by luteolin. The detection limit was 0.12 μM and linear relationship existed in the range of 0.2-100 μM. Moreover, the TA-Cu NCs probe was successfully employed to detect luteolin in bovine serum samples with satisfactory recoveries. This novel platform was expected to expand the possible detection method based on fluorescence properties.

Recent Developments in Flexible Transparent Electrode

With the rapid development of flexible electronic devices (especially flexible LCD/OLED), flexible transparent electrodes (FTEs) with high light transmittance, high electrical conductivity, and excellent stretchability have attracted extensive attention from researchers and businesses. FTEs serve as an important part of display devices (touch screen and display), energy storage devices (solar cells and super capacitors), and wearable medical devices (electronic skin). In this paper, we review the recent progress in the field of FTEs, with special emphasis on metal materials, carbon-based materials, conductive polymers (CPs), and composite materials, which are good alternatives to the traditional commercial transparent electrode (i.e., indium tin oxide, ITO). With respect to production methods, this article provides a detailed discussion on the performance differences and practical applications of different materials. Furthermore, major challenges and future developments of FTEs are also discussed.

A Multifunctional N-Doped Cu-MOFs (N-Cu-MOF) Nanomaterial-Driven Electrochemical Aptasensor for Sensitive Detection of Deoxynivalenol

Deoxynivalenol (DON) is one of the most common mycotoxins in grains, causing gastrointestinal inflammation, neurotoxicity, hepatotoxicity and embryotoxicity, even at a low quantity. In this study, a facile electrochemical aptasensor was established for the rapid and sensitive determination of DON based on a multifunctional N-doped Cu-metallic organic framework (N–Cu–MOF) nanomaterial. The N–Cu–MOF, with a large specific surface area and good electrical conductivity, served not only as an optimal electrical signal probe but also as an effective supporting substrate for stabilizing aptamers through the interactions of amino (-NH₂) and copper. Under the optimal conditions, the proposed sensor provided a wide linear concentration range of 0.02–20 ng mL⁻¹ (R² = 0.994), showing high sensitivity, with a lower detection limit of 0.008 ng mL⁻¹, and good selectivity. The sensor’s effectiveness was also verified in real spiked wheat samples with satisfactory recoveries of 95.6–105.9%. The current work provides a flexible approach for the rapid and sensitive analysis of highly toxic DON in food samples and may also be easily extended to detect other hazardous substances with alternative target-recognition aptamers.

Analytical determinations of luteolin

Plants, through the photosynthesis process, produce the substances necessary for all the life cycles of nature, which are called "primary metabolites." Moreover, there are some plants that synthesize, in addition to these, other substances with more specific functions, which are known as "secondary metabolites." It is inside this group that flavonoids are located, whose main function is to protect organisms from damage caused by different oxidizing agents. Luteolin (3,4,5,7-tetrahydroxy-flavone) belongs to the sub-class of flavonoids known as flavones and is one of 10,000 flavonoids currently known, being one of the most bio-active flavonoids. Its various beneficial properties for health, together with the increasing reduction in the use of synthetic antioxidants, make the study of luteolin a very active field. Within this, the quantification of this molecule has become a subject of very special interest given that it is transversal to all fields. In this review article, we aim to give the reader a broad and deep vision of this topic, focusing on the events reported in the last 5 years and covering all possible techniques related to analytical determinations. We will discuss in terms of advantages and disadvantages between techniques, selectivity, sensitivity, costs, time consumption, and reagents as well as in the complexity of operations.

Construction of an electrochemical sensor with graphene aerogel doped with ZrO2 nanoparticles and chitosan for the selective detection of luteolin

A simple, fast and sensitive method for the detection of luteolin is proposed based on the chitosan/reduced graphene oxide aerogel with dispersed ZrO₂ nanoparticles modified glassy carbon electrode (ZrO₂/CS/rGOA-GCE) as an electrochemical sensor. The ZrO₂/CS/rGOA composite was prepared by one pot synthesis from a mixture of GO, CS and zirconyl chloride octahydrate, and subsequently be freeze-dried. Scanning electron microscope images showed a typical thin, wrinkled and fluctuant morphology of graphene nanosheets and the polymerized CS and ZrO₂ nanoparticles deposited on the surface of rGOA. Cyclic voltammetry and differential pulse voltammetry were used to measure the electrochemical response of ZrO₂/CS/rGOA composite-based biosensor towards luteolin at the working potential window (-0.8-0.8 V). The improved performance of this biosensor was attributed to efficient electron transfer and large surface area of 3D rGOA, and high specific activity of Zr towards adjacent hydroxyl groups. Under optimized conditions, the analytical performance of this method towards luteolin was investigated with a detection limit of 1 nM and a linear range from 5 nM to 1000 nM.. Finally, the ZrO₂/CS/rGOA-GCE electrochemical method coupled with solid phase extraction was used for the detection of luteolin in real samples. Recoveries of  spiked samples with different concentrations were in the range 78.6-103.3% with a relative RSD lower than 12.0%. Graphical abstract Schematic representation of the preparation of the ZrO₂ nanoparticles and chitosan doped graphene aerogel modified electrode. The electrode was employed for the detection of luteolin coupled with the solid-phase extraction technique.

Design and synthesis of a new magnetic metal organic framework as a versatile platform for immobilization of acidic catalysts and CO2 fixation reaction

The first report of the use of an acidic magnetic metal organic framework for the chemical fixation of CO2 as an environmentally friendly reaction.

A core–shell superparamagnetic metal–organic framework: a recyclable and green catalyst for the synthesis of propargylamines

This is the first report on the use of a magnetic metal–organic framework for the green synthesis of propargylamine derivatives.

Gallic acid-affinity molecularly imprinted polymer adsorbent for capture of cis-diol containing Luteolin prior to determination by high performance liquid chromatography

A gallic acid-affinity molecularly imprinted polymer (G-MIP) was first used as an adsorbent for selective identification and capture of luteolin (LTL) in herbal medicine samples. The G-MIP was prepared by using LTL as the template, gallic acid (GA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent, and 2,2'-azobis(2-methylpropionitrie) (AIBN) as the initiator. The properties of G-MIP were characterized by FT-IR, transmission electron microscope, scanning electron microscope, dynamic light scattering, specific surface area, and X-ray photoelectron spectrum. The adsorption conditions were optimized, and the adsorption equilibrium model and adsorption kinetics model of the adsorbent were investigated under the best experimental conditions. The saturated adsorption capacity is 1.24 mg g^-1, which is not only higher than the adsorption capacity of 4-carboxyphenylboronic acid-affinity MIP adsorbent but also superior to those of many reported adsorbents for enriching of LTL. The LTL was quantified by HPLC. The linear range is 0.05-100 mg L^-1, the detection limit is 0.020 mg L^-1. This method was successfully applied in the selective recognition of LTL in herbal medicines with recoveries of 93.9-114.2%, and the relative standards deviations (RSDs) are 0.4-5.6%. Thus, this work provides a potential possibility and practical platform for the determination of LTL in complex matrices.

Ultrasensitive Electrochemical Sensor for Luteolin Based on Zirconium Metal-Organic Framework UiO-66/Reduced Graphene Oxide Composite Modified Glass Carbon Electrode

Luteolin is a kind of natural flavonoid with many bioactivities purified from a variety of natural herbs, fruits and vegetables. Electrochemical sensing has become an outstanding technology for the detection of luteolin in low concentration due to its fast response, easy operation and low cost. In this study, electroreduced graphene oxide (ErGO) and UiO-66 were successively modified onto a glassy carbon electrode (UiO-66/ErGO/GCE) and applied to the detection of luteolin. A combination of UiO-66 and ErGO showed the highest promotion in the oxidation peak current for luteolin compared with those of a single component. The factors affecting the electrochemical behavior of UiO-66/ErGO/GCE were evaluated and optimized including pH, accumulation potential, accumulation time and scan rate. Under optimum conditions, UiO-66/ErGO/GCE showed satisfactory linearity (from 0.001 μM to 20 μM), reproducibility and storage stability. The detection limit of UiO-66/ErGO/GCE reached 0.75 nM of luteolin and was suitable for testing real samples. Stable detection could be provided at least eight times by one modified electrode, which guaranteed the practicability of the proposed sensor. The fabricated UiO-66/ErGO/GCE showed a rapid electrochemical response and low consumption of materials in the detection of luteolin. It also showed satisfactory accuracy for real samples with good recovery. In conclusion, the modification using MOFs and graphene materials made the electrode advanced property in electrochemical sensing of natural active compounds.

A novel selective ternary platform fabricated with MgAl-layered double hydroxide/NiMn2O4 functionalized polyaniline nanocomposite deposited on a glassy carbon electrode for electrochemical sensing of levodopa

In this study, a novel selective electrochemical sensor was fabricated for determination of levodopa (LD) using a glassy carbon electrode modified with MgAl-layered double hydroxide/NiMn₂O₄ functionalized polyaniline nanocomposite (LDH/NMO/PANI) and its successful formation was confirmed by various techniques. Owing to the high surface area and outstanding conductivity features provided by the combination of MgAl-LDH, NiMn₂O₄ and PANI nanoparticles, this ternary nanocomposite exhibited excellent electrochemical activity towards the detection of LD compared with the electrode modified by the pristine MgAl-LDH and MgAl-LDH/NiMn₂O₄ binary nanocomposite. In addition, enormous quantities of amine and imine functional groups on the surface of PANI lead to a strong affinity for attachment to organic molecules such as LD. The ternary nanocomposite modified electrode exhibited excellent analytical parameters such as wide linear response from 0.1 to 100 μM with very low detection limit of 0.005 μM, good reproducibility and long-term stability which are superior among the LD electrochemical sensors. Besides, the constructive sensor possessed acceptable selectivity for recognition of LD in the presence of a variety of potentially interfering species and can also effectively avoid the interference of dopamine (DA) and ascorbic acid (AA). Consequently, the LDH/NMO/PANI/GC electrode was effectively applied to detect LD in human plasma and urine samples with good recoveries, ranging from 98.0-100.1% and it shows potential usage in clinical researches.

Metal–organic frameworks: a future toolbox for biomedicine?

The present review focuses on the use of Metal–Organic Frameworks, (MOFs) highlighting the most recent developments in the biological field and as bio-sensors.