Preparation of Electrochemical Sensor Based on Zinc Oxide Nanoparticles for Simultaneous Determination of AA, DA, and UA

Hydrothermal ZnO Nanomaterials: Tailored Properties and Infinite Possibilities

This review presents a comprehensive and precise summary of the hydrothermal synthesis and morphology control of zinc oxide (ZnO) nanomaterials, the advantages of hydrothermal synthesis, and the wide range of applications. ZnO nanomaterials have garnered significant attention in recent years for their diverse applications across various industries owing to their unique properties and versatility, with practical applications in healthcare, cosmetics, textiles, automotive, and other sectors. Specifically, the ability of ZnO-based nanomaterials to promote the production of reactive oxygen species, release of Zn2+ ions, and induce cell apoptosis makes them well-suited for bio-medicinal applications such as cancer treatment and microorganism control. Hydrothermal technique offers precise control over the synthesis of ZnO, metal/non-metal-doped ZnO, and related composites, enabling the tailoring of properties for specific applications. The significant feature of the hydrothermal technique is the use of water as a solvent, which is cheap, available, and environmentally benign. In the last section, we discussed the potential future direction of ZnO-based research.

Sea Urchin-like Magnetic Microbeads-Based Electrochemical Biosensor for Highly Sensitive Detection of Metabolites

Analyzing metabolite levels in bodily fluids is essential for disease diagnosis and surveillance. Electrochemical biosensors are ideal for monitoring metabolite levels due to their high sensitivity, rapid response, and low cost. The magnetic microbeads-based electrode functionalization method further promotes the automation development of electrochemical biosensors by eliminating the tedious electrode polishing process. In this study, we presented sea urchin-like magnetic microbeads (SMMBs) and constructed an SMMB-based electrochemical biosensor. The specific morphology of SMMBs provides a larger specific surface area and abundant enzyme binding sites, thereby expanding the active reaction interface on the electrode and improving the sensitivity of the biosensor. Experiment results demonstrated that the SMMB-based electrochemical biosensor achieves μM level detection sensitivity for glucose. Furthermore, by replacing the anchored oxidase on SMMBs, the biosensor can be extended to detect other metabolites, such as cholesterol. In summary, the SMMBs provide a new path to handily construct electrochemical biosensors and hold a great potential for metabolite detection and further development.

Application progress of nanomaterials in the treatment of prostate cancer

Prostate cancer is one of the most common malignant tumors in men, which seriously threatens the survival and quality of life of patients. At present, there are serious limitations in the treatment of prostate cancer, such as drug tolerance, drug resistance and easy recurrence. Sonodynamic therapy and chemodynamic therapy are two emerging tumor treatment methods, which activate specific drugs or sonosensitizers through sound waves or chemicals to produce reactive oxygen species and kill tumor cells. Nanomaterials are a kind of nanoscale materials with many excellent physical properties such as high targeting, drug release regulation and therapeutic monitoring. Sonodynamic therapy and chemodynamic therapy combined with the application of nanomaterials can improve the therapeutic effect of prostate cancer, reduce side effects and enhance tumor immune response. This article reviews the application progress of nanomaterials in the treatment of prostate cancer, especially the mechanism, advantages and challenges of nanomaterials in sonodynamic therapy and chemodynamic therapy, which provides new ideas and prospects for research in this field.

CeO2·ZnO@biomass-derived carbon nanocomposite-based electrochemical sensor for efficient detection of ascorbic acid

Ascorbic acid (AA), a prominent antioxidant commonly found in human blood serum, serves as a biomarker for assessing oxidative stress levels. Therefore, precise detection of AA is crucial for swiftly diagnosing conditions arising from abnormal AA levels. Consequently, the primary aim of this research is to develop a sensitive and selective electrochemical sensor for accurate AA determination. To accomplish this aim, we used a novel nanocomposite comprised of CeO2-doped ZnO adorned on biomass-derived carbon (CeO2·ZnO@BC) as the active nanomaterial, effectively fabricating a glassy carbon electrode (GCE). Various analytical techniques were employed to scrutinize the structure and morphology features of the CeO2·ZnO@BC nanocomposite, ensuring its suitability as the sensing nanomaterial. This innovative sensor is capable of quantifying a wide range of AA concentrations, spanning from 0.5 to 1925 μM in a neutral phosphate buffer solution. It exhibits a remarkable sensitivity of 0.2267 μA μM-1cm-2 and a practical detection limit of 0.022 μM. Thanks to its exceptional sensitivity and selectivity, this sensor enables highly accurate determination of AA concentrations in real samples. Moreover, its superior reproducibility, repeatability, and stability underscore its reliability and robustness for AA quantification.

Highly sensitive and simultaneous detection of ascorbic acid, dopamine, and uric acid using Pt@g-C3N4/N-CNTs nanocomposites

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is crucial for understanding and managing various illnesses. In this research, Pt@g-C3N4 nanoparticles were synthesized via hydrothermal method and combined with N-doped carbon nanotubes (N-CNTs). The Pt@g-C3N4/N-CNTs-modified glassy carbon (GC) electrode was fabricated as an electrochemical sensor for the determination of AA, DA, and UA. The linear response range of AA, DA, and UA in the optimal condition was 100-3,000 μM, 1-100 μM, and 2-215 μM boasting a low detection limit (S/N = 3) of 29.44 μM (AA), 0.21 μM (UA), and 2.99 μM (DA), respectively. Additionally, the recoveries of AA, DA, and UA in serum sample were 100.4%-106.7%. These results corroborate the feasibility of the proposed method for the simultaneous, sensitive, and reliable detection of AA, DA, and UA. Our Pt@g-C3N4/N-CNTs/GC electrode can provide a potential strategy for disease diagnosis and health monitoring in clinical settings.

A high-performance photoelectrochemical sensor based on CdS-Au composite nanomaterials and localized surface plasmon resonance for ultrasensitive detection of ascorbic acid

Ascorbic acid (AA), which plays a vital role in the metabolism of the human body, is closely correlated with various diseases, including rheumatoid arthritis, scurvy, Parkinson's disease, urinary stones, and diarrhea. The detection of AA is of great significance for early prevention and diagnosis of related diseases. In this paper, a high-performance photoelectrochemical (PEC) sensor was constructed based on cadmium sulfide-gold (CdS-Au) composite nanomaterials for ultrasensitive ascorbic acid (AA) detection. Due to the localized surface plasmon resonance (LSPR) effect of gold nanoparticles (AuNPs), the PEC performance of CdS-Au composite nanomaterials was significantly improved compared to CdS semiconductor nanomaterials. Under the optimal conditions, the AA concentration was linearly related to the photocurrent signal in the range of 0.01 μM-200 μM, with the detection limit being 0.2 nM (S/N = 3) and the sensitivity being 642.9 μA mM-1 cm-2. In addition, the mechanism of the PEC sensor based on CdS-Au composite nanomaterials for ultrasensitive AA detection was discussed. Lastly, the self-constructed PEC sensors have been successfully applied in detecting AA in vitamin C tablets and actual blood samples, meeting the detection criteria required by the Chinese Pharmacopoeia (CP, 2020 edition). The self-fabricated PEC sensors in this paper are expected to be used for quality assessment of AA-related drugs and diagnosis of relevant diseases.

Cd-MOF and Its Ln3+-Post Modification Products: Regulation of Luminescence Properties and Improved Detection of Uric Acid, Quinine, and Quinidine

One 3D Cd-MOF, namely, {[(HDMA)2][Cd3(L)2]·5H2O·2DMF}n (LCU-124, LCU indicates Liaocheng University), was synthesized from an ether-containing ligand 1,3-bis(3,5-dicarboxylphenoxy)benzene (H4L). Its Ln3+-postmodified samples, Eu3+@LCU-124 and Tb3+@LCU-124, were obtained through cation exchange of dimethylamine cation (HDMA) with Eu3+ and Tb3+. The successful entry of rare earth into LCU-124 by cation exchange modification was verified by IR, XRD, XPS, EDS mapping, and luminescence spectra. The proportion of Eu3+/Tb3+ was adjusted during the modification process, leading to fluorescent materials with different emissions. Luminescence measurements indicated that these complexes exhibited interesting multiresponsive sensing activities toward biomarkers urine acid (UA), quinine (QN), and quinidine (QND). First, LCU-124 has a pronounced quenching effect toward UA with the detection limit of 31.01 μM. After modification, the visualization of the detection was improved significantly and the detection limit of Eu3+@LCU-124 was reduced to 0.868 μM. Second, when QN and QND were present in the suspensions of Eu3+@LCU-124 and Tb3+@LCU-124, strong blue light emission peaks occurred, while the characteristic emission of Eu3+/Tb3+ decreased, forming ratiometric fluorescent sensors with the detection limit in the range of 0.199-9.49 μM. The fluorescent probes have high selectivity, excellent sensitivity recycling, and fast response time (less than 1 min). Besides, a simple logic gate circuit and a range of luminescent mixed matrix membranes were designed to provide simple and fast detection of above biomarkers. Our work indicated that modification of Eu3+/Tb3+ could improve the detection ability significantly.

Biosynthesis and Optimization of ZnO Nanoparticles Using Ocimum lamifolium Leaf Extract for Electrochemical Sensor and Antibacterial Activity

In this study, zinc oxide nanoparticles (ZnO NPs) were synthesized using an aqueous extract of the Ocimum lamifolium (O. lamifolium) plant. The I-optimal coordinate exchange randomized response surface methodology (RSM) was used to optimize the effect of the zinc acetate precursor, temperature, and time on ZnO NPs by designing nine runs. From ANOVA analysis, the significance and validity of the designed model showed that the optimal values of the zinc acetate precursor, temperature, and time during ZnO NPs synthesis were found to be ∼0.06 M, ∼30 °C, and ∼1.35 h, respectively. The obtained ZnO NPs under these optimized conditions were characterized and explored by UV-vis, TGA/DTA, FTIR, XRD, SEM-EDX, TEM, HRTEM, and SAED. Furthermore, the electrocatalytic performance of ZnO NPs was performed for sulfamethoxazole (SMZ) sensing activity with a 0.3528 μM (S/N = 3) limit of detection (LOD). In addition, an antibacterial study revealed that ZnO NPs confirmed an excellent zone of inhibition against E. coli, S. aureus, P. aeruginosa, and S. pyogen pathogenic drug resistance bacterial strains at concentrations of 50, 75, and 100 μg/mL. Thus, ZnO NPs synthesized using the O. lamifolium leaf have a potential electrocatalytic activity for diverse organic pollutant detection as well as a desirable material for such drug resistance antimicrobial strains.

Low Overpotential Amperometric Sensor Using Yb2O3.CuO@rGO Nanocomposite for Sensitive Detection of Ascorbic Acid in Real Samples

The ultimate objective of this research work is to design a sensitive and selective electrochemical sensor for the efficient detection of ascorbic acid (AA), a vital antioxidant found in blood serum that may serve as a biomarker for oxidative stress. To achieve this, we utilized a novel Yb₂O₃.CuO@rGO nanocomposite (NC) as the active material to modify the glassy carbon working electrode (GCE). The structural properties and morphological characteristics of the Yb₂O₃.CuO@rGO NC were investigated using various techniques to ensure their suitability for the sensor. The resulting sensor electrode was able to detect a broad range of AA concentrations (0.5-1571 µM) in neutral phosphate buffer solution, with a high sensitivity of 0.4341 µAµM^-1cm^-2 and a reasonable detection limit of 0.062 µM. The sensor's great sensitivity and selectivity allowed it to accurately determine the levels of AA in human blood serum and commercial vitamin C tablets. It demonstrated high levels of reproducibility, repeatability, and stability, making it a reliable and robust sensor for the measurement of AA at low overpotential. Overall, the Yb₂O₃.CuO@rGO/GCE sensor showed great potential in detecting AA from real samples.

GO/ZnO nanocomposite - as transducer platform for electrochemical sensing towards environmental applications

Graphene Oxide-Zinc Oxide (GO-ZnO) - a new nanomaterial that has queued the interest of researchers. Their intriguing promising physical and electrochemical features of electrode material have led to its widespread use in electrochemical sensor applications. GO-ZnO based nanomaterial were extensively exploited in the construction of electrochemical sensors due to their adaptability and distinct qualities. On understanding the structural role of these materials, their modification processes are critical for realizing their full potential. The advancement of technology on new concepts and strategies has revolutionized the field of sensor devices with high sensitivities and selectivity. These tools can test a range of contaminants quickly, accurately, and affordably while performing automated chemical analysis in complicated matrices. This paper highlights the electrochemical transducer surface for sensing various analytes and current research activity on GO-ZnO nanocomposite. Additionally, we talked about current developments in GO-ZnO nanostructured composites to identify relevant analytes (i.e., Nitrophenols, Antibiotic Drugs, Biomolecules). While being used in the laboratory, the majority of produced systems have proven to bring about excellent gains. Their monitoring application still has a long way to go before it is fixed due to problems like technological advancements and multifunctional strategies to get around the challenges for improving the sensing systems.

Carbon Inks-Based Screen-Printed Electrodes for Qualitative Analysis of Amino Acids

Due to the great significance of amino acids, a substantial number of research studies has been directed toward the development of effective and reliable platforms for their evaluation, detection, and identification. In order to support these studies, a new electrochemical platform based on PANI/ZnO nanowires' modified carbon inks screen-printed electrodes was developed for qualitative analysis of electroactive amino acids, with emphasis on tyrosine (Tyr) and tryptophan (Trp). A comparative investigation of the carbon ink before and after modification with the PANI/ZnO was performed by scanning electron microscopy and by Raman spectroscopy, confirming the presence of PANI and ZnO nanowires. Electrochemical investigations by cyclic voltammetry and electrochemical impedance spectroscopy have shown a higher charge-transfer rate constant, which is reflected into lower charge-transfer resistance and higher capacitance values for the PANI/ZnO modified ink when compared to the simple carbon screen-printed electrode. In order to demonstrate the electrochemical performances of the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes for amino acids analysis, differential pulse voltammograms were obtained in individual and mixed solutions of electroactive amino acids. It has been shown that the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes allowed for tyrosine and tryptophan a peak separation of more than 100 mV, enabling their screening and identification in mixed solutions, which is essential for the electrochemical analysis of proteins within the proteomics research field.

Motoc) S, Cretu C, Cseh L, Rastei M, Donnio B, Szerb EI, Manea F. Design of Nanostructured Hybrid Electrodes Based on a Liquid Crystalline Zn(II) Coordination Complex-Carbon Nanotubes Composition for the Specific Electrochemical Sensing of Uric Acid

A metallomesogen based on an Zn(II) coordination complex was employed as precursor to obtain a complex matrix nanoplatform for the fabrication of a high-performance electrochemical hybrid sensor. Three representative paste electrodes, which differ by the weight ratio between Zn(II) metallomesogen and carbon nanotubes (CNT), i.e., PE_01, PE_02 and PE_03, were obtained by mixing the materials in different amounts. The composition with the largest amount of CNT with respect to Zn complex, i.e., PE_03, gives the best electrochemical signal for uric acid detection by cyclic voltammetry in an alkaline medium. The amphiphilic structure of the Zn(II) coordination complex likely induces a regular separation between the metal centers favoring the redox system through their reduction, followed by stripping, and is characterized by enhanced electrocatalytic activity towards uric acid oxidation. The comparative detection of uric acid between the PE_03 paste electrode and the commercial zinc electrode demonstrated the superiority of the former, and its great potential for the development of advanced electrochemical detection of uric acid. Advanced electrochemical techniques, such as differential-pulsed voltammetry (DPV) and square-wave voltammetry (SWV), allowed for the highly sensitive detection of uric acid in aqueous alkaline solutions. In addition, a good and fast amperometric signal for uric acid detection was achieved by multiple-pulsed amperometry, which was validated by urine analysis.

Metal-organic framework-derived porous ternary ZnCo2O4 nanoplate arrays grown on carbon cloth for simultaneous electrochemical determination of ascorbic acid, dopamine, and uric acid

Metal-organic frameworks derived from ternary metal oxide directly grown on the conductive substrate have attracted great interest in electrochemical sensing. In this work, metal-organic framework-derived ternary ZnCo₂O₄ nanoplate arrays that were grown on carbon cloth (ZnCo₂O₄ NA/CC) are fabricated and applied for the electrochemical determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Field emission scanning electron microscope (FESEM) reveals that a network-like CC substrate is covered with considerable nanoplate arrays, presenting a large specific area. X-ray photoelectron spectroscopy (XPS) demonstrates the nanoplate arrays to be composed of ZnCo₂O₄. Benefiting from the unique array morphology and ternary element composition, the ZnCo₂O₄ NA/CC shows desirable performances for simultaneous detection of AA, DA, and UA. The individual detection limits are 7.14 μM for AA, 0.25 μM for DA, and 0.33 μM for UA. Additionally, the ZnCo₂O₄ NA/CC is successfully applied for the quantitative determination of AA, DA, and UA in spiked serum samples, showing its great application potential.

A carbon dots-enhanced laccase-based electrochemical sensor for highly sensitive detection of dopamine in human serum

Enzyme-based electrochemical sensor possesses a significant advantage in the highly efficient detection of small molecules, however, the poor electron transport efficiency limits their wide application. In this study, taking advantage of the distinct biocatalytic activity of laccase and the excellent electroconductibility of carbon dots, a carbon dots-enhanced laccase-based electrochemical sensor for the detection of dopamine (DA) is established. Thereinto, laccase can specifically recognize DA and promote its electrocatalytic oxidation on the electrode, while, the carbon dots can be used as the immobilization substrate of laccase and enhance its electron transfer efficiency, thus achieving the highly sensitive detection of dopamine. The electrochemical performance of the modified electrode interface is studied by electrochemical impedance spectroscopy and differential pulse voltammetry. As demonstrated, the electrocatalytic activity of the proposed electrochemical sensor for DA is significantly improved and exhibits a low detection limit (0.08 μM) and a wide linear range (0.25 μM-76.81 μM). The excellent selectivity allows the sensor has the capacity for specific discrimination the DA from other interferents. Furthermore, by analyzing the DA in human serum verifies the practicability of this assay in real sample analysis.

Nanomaterials-based electrochemical sensors for the detection of natural antioxidants in food and biological samples: research progress

Antioxidants are healthy substances that are beneficial to the human body and exist mainly in natural and synthetic forms. Among many kinds of antioxidants, the natural antioxidants have great applications in many fields such as food chemistry, medical care, and clinical application. In recent years, many efforts have been made for the determination of natural antioxidants. Nano-electrochemical sensors combining electrochemistry and nanotechnology have been widely used in the determination of natural antioxidants due to their unique advantages. Therefore, a large number of nanomaterials such as metal oxide, carbon materials, and conducting polymer have attracted much attention in the field of electrochemical sensors due to their good catalytic effect and stable performance. This review mainly introduces the construction of electrochemical sensors based on different nanomaterials, such as metallic nanomaterials, metal oxide nanomaterials, carbon nanomaterials, metal-organic frameworks, polymer nanomaterials, and other nanocomposites, and their application to the detection of natural antioxidants, including ascorbic acid, phenolic acids, flavonoid, tryptophan, citric acid, and other natural antioxidants. In the end, the limitations of the existing nano-sensing technology, the latest development trend, and the application prospect for various natural antioxidant substances are summarized and analyzed. We expect that this review will be helpful to researchers engaged in electrochemical sensors.

An Auto Adjustable Transimpedance Readout System for Wearable Healthcare Devices

The objective of this work was to design a versatile readout circuit for patch-type wearable devices consisting of a Transimpedance Amplifier (TIA). The TIA performs Current to Voltage (I–V) conversion, the most widely used technique for amperometry and impedance measurement for various types of electrochemical sensors. The proposed readout circuit employs a digitally controllable feedback resistor (Rf) technique in the TIA to improve accuracy, which can be utilized in a variety of electrochemical sensors within a current range of 0.1 µA–100 µA. It is designed to accommodate multiple sensors simultaneously to track multiple target analytes for high accuracy and versatile usage. The readout circuit consists of low power operational amplifier (op–amp) and digital circuit blocks, is designed and fabricated with Magna 0.18 µm Complementary Metal Oxide Semiconductor (CMOS) technology, which provides low power consumption and a high degree of integration. The design has a small size of 0.282 mm2 and low power consumption of 0.38 mW with a 3.3 V power supply, which are desirable factors in wearable device applications.

Solanum tuberosum Leaf Extract Templated Synthesis of Co3O4 Nanoparticles for Electrochemical Sensor and Antibacterial Applications

Green synthesis of metal oxide nanoparticles (NPs) is a viable alternative methodology because of cost-effective and availability of environmentally friendly templates for desired application, which has attracted the attention of researchers in recent years. In the present study, Co3O4 NPs were synthesized in various volume ratios in the presence of Solanum tuberosum leaf extract as a template. The synthesized Co3O4 NPs were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), surface area electron diffraction (SAED), UV-Vis diffuse reflectance spectroscopy (UV-DRS), and Fourier transform infrared (FTIR) spectroscopy. XRD analysis found that the average crystalline sizes for the 1 : 2, 1 : 1, and 2 : 1 volume ratios was 25.83, 21.05, and 27.98 nm, respectively. SEM-EDX and TEM analyses suggest that the green-synthesized Co3O4 NPs are spherical in shape without the presence of impurities. The band gap E g values of the 1 : 2, 1 : 1, and 2 : 1 volume ratios of Co3O4 NPs were found to be 1.83, 1.77, and 2.19 eV, respectively. FTIR analysis confirmed the presence of various bioactive ingredients within the leaf extract of Solanum tuberosum. Co3O4 NPs-modified electrodes showed better sensing capability towards ascorbic acid and citric acid due to enhanced electron transfer kinetics. Among three volume ratios (1 : 2, 1 : 1, and 2 : 1) of Co3O4 nanoelectrodes, 1 : 1 and 2 : 1 were identified as the best performing nanoelectrodes. This is possibly due to the high catalytic behavior and the more homogenized surface structure. Co3O4 (1 : 2) nanodrug showed the enhanced antibacterial activity (16 mm) towards S. aureus which is attributed to the formation of enhanced reactive oxygen species (ROS).

Highly Stable Buffer-Based Zinc Oxide/Reduced Graphene Oxide Nanosurface Chemistry for Rapid Immunosensing of SARS-CoV-2 Antigens

The widespread and long-lasting effect of the COVID-19 pandemic has called attention to the significance of technological advances in the rapid diagnosis of SARS-CoV-2 virus. This study reports the use of a highly stable buffer-based zinc oxide/reduced graphene oxide (bbZnO/rGO) nanocomposite coated on carbon screen-printed electrodes for electrochemical immuno-biosensing of SARS-CoV-2 nuelocapsid (N-) protein antigens in spiked and clinical samples. The incorporation of a salt-based (ionic) matrix for uniform dispersion of the nanomixture eliminates multistep nanomaterial synthesis on the surface of the electrode and enables a stable single-step sensor nanocoating. The immuno-biosensor provides a limit of detection of 21 fg/mL over a linear range of 1-10 000 pg/mL and exhibits a sensitivity of 32.07 ohms·mL/pg·mm² for detection of N-protein in spiked samples. The N-protein biosensor is successful in discriminating positive and negative clinical samples within 15 min, demonstrating its proof of concept used as a COVID-19 rapid antigen test.

Cerium(IV) and Iron(III) Oxides Nanoparticles Based Voltammetric Sensor for the Sensitive and Selective Determination of Lipoic Acid

A novel voltammetric sensor based on CeO2·Fe2O3 nanoparticles (NPs) has been developed for the determination of lipoic acid, playing an essential role in aerobic metabolism in the living organism. Sensor surface modification provides a 5.6-fold increase of the lipoic acid oxidation currents and a 20 mV anodic shift of the oxidation potential. The best voltammetric parameters have been obtained for the 0.5 mg mL-1 dispersion of CeO2·Fe2O3 NPs. Scanning electron microscopy (SEM) confirms the presence of spherical NPs of 25-60 nm, and their aggregates evenly distributed on the electrode surface and formed porous coverage. This leads to the 4.4-fold increase of the effective surface area vs. bare glassy carbon electrode (GCE). The sensor shows a significantly higher electron transfer rate. Electrooxidation of lipoic acid on CeO2·Fe2O3 NPs modified GCE is an irreversible diffusion-controlled pH-independent process occurring with the participation of two electrons. The sensor gives a linear response to lipoic acid in the ranges of 0.075-7.5 and 7.5-100 μM with the detection limit of 0.053 μM. The sensor is selective towards lipoic acid in the presence of inorganic ions, ascorbic acid, saccharides, and other S-containing compounds. The sensor developed has been tested on the pharmaceutical dosage forms of lipoic acid.

Disposable Voltammetric Sensor Modified with Block Copolymer-Dispersed Graphene for Simultaneous Determination of Dopamine and Ascorbic Acid in Ex Vivo Mouse Brain Tissue

Dopamine (DA) and ascorbic acid (AA) are two important biomarkers with similar oxidation potentials. To facilitate their simultaneous electrochemical detection, a new voltammetric sensor was developed by modifying a screen-printed carbon electrode (SPCE) with a newly synthesized block copolymer (poly(DMAEMA-b-styrene), PDbS) as a dispersant for reduced graphene oxide (rGO). The prepared PDbS–rGO and the modified SPCE were characterized using a range of physical and electrochemical techniques including Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. Compared to the bare SPCE, the PDbS–rGO-modified SPCE (PDbS–rGO/SPCE) showed better sensitivity and peak-to-peak separation for DA and AA in mixed solutions. Under the optimum conditions, the dynamic linear ranges for DA and AA were 0.1–300 and 10–1100 µM, and the detection limits were 0.134 and 0.88 µM (S/N = 3), respectively. Furthermore, PDbS–rGO/SPCE exhibited considerably enhanced anti-interference capability, high reproducibility, and storage stability for four weeks. The practical potential of the PDbS–rGO/SPCE sensor for measuring DA and AA was demonstrated using ex vivo brain tissues from a Parkinson’s disease mouse model and the control.

Synthesis of a clustered carbon aerogel interconnected by carbon balls from the biomass of taros for construction of a multi-functional electrochemical sensor

In this study, a clustered carbon aerogel interconnected by carbon balls (CCAI-CB) was prepared as an electrode material to construct a multi-functional electrochemical sensor. CCAI-CB derived from taros (Colocasia esculenta (L). Schott) possesses meso-macroporous structure and plenty of defective sites, and shows notable activity in electrocatalysis as an electrode material. We investigated the application of CCAI-CB modified glassy carbon electrode (CCAI-CB/GCE) for determination of ascorbic acid (AA) and hydrogen peroxide (H₂O₂). Compared with carbon nanotubes (CNTs) modified GCE (CNTs/GCE) and bare GCE, CCAI-CB/GCE shows lower detection limit (0.23 μM for AA and 1.31 μM, S/N = 3), higher sensitivities (220.53, 148.86 or 94.39 μA mM^-1 cm^-2 for AA and 83.06 or 49.07 μA mM^-1 cm^-2 for H₂O₂). Concentrations of AA and H₂O₂ in real samples were determined at CCAI-CB/GCE with satisfactory detection results obtained. In addition, when the CCAI-CB/GCE was used for electrocatalysis of other biomolecules, it also exhibits high electrochemical activity. Thus, CCAI-CB could be a promising electrode material for the construction of multi-functional electrochemical sensors.

An electrochemical sensor based on the modification of platinum nanoparticles and ZIF-8 membrane for the detection of ascorbic acid

In this manuscript, a layer of 2-methylimidazole zinc salt (ZIF-8) membrane is deposited on the surface of glassy carbon electrode (GCE) modified with platinum nanoparticles (Pt NPs) by reduction electrochemical method to obtain ZIF-8/Pt NPs/GCE, and then used for the detection of ascorbic acid (AA). The deposition of Pt NPs on the surface of GCE can not only guide the nucleation and growth of ZIF-8 membrane, but also exert a synergistic effect with it to enhance conductivity. For ZIF-8 membrane, it can increase the active area of electrode and thus improve the electrochemical response of the sensor for AA. Influence factors such as the deposition current density, deposition time on the surface morphology of the modified electrode, and the detection performance of the modified electrode during the electrochemical deposition of ZIF-8 membrane were explored to get the best performance. In addition, influence of conditions such as sweep speed and pH of the test solution on the electrochemical response signal of AA were also studied. Under the best conditions, the linear range of AA detection by this sensor is from 10 μmol L^-1 to 2500 μmol L^-1, and the detection limit is 5.2 μmol L^-1 based on S/N = 3. What's more, the modified electrode also has good anti-interference ability, reproducibility and stability, and has achieved satisfactory results in the detection for AA in real samples.

A highly sensitive uric acid biosensor based on vertically arranged ZnO nanorods on a ZnO nanoparticle-seeded electrode

Vertically-arranged ZnO nanorods grown on a ZnO nanoparticle-seeded FTO electrode using a hydrothermal method for highly sensitive uric acid biosensor fabrication.