A Stretchable Electrochemical Sensor for Inducing and Monitoring Cell Mechanotransduction in Real Time

Existing methods offer little direct and real‐time information about stretch‐triggered biochemical responses during cell mechanotransduction. A novel stretchable electrochemical sensor is reported that takes advantage of a hierarchical percolation network of carbon nanotubes and gold nanotubes (CNT‐AuNT). This hybrid nanostructure provides the sensor with excellent time‐reproducible mechanical and electrochemical performances while granting very good cellular compatibility, making it perfectly apt to induce and monitor simultaneously transient biochemical signals. This is validated by monitoring stretch‐induced transient release of small signaling molecules by both endothelial and epithelial cells cultured on this sensor and submitted to stretching strains of different intensities. This work demonstrates that the hybrid CNT‐AuNT platform offers a versatile and highly sensitive way to characterize and quantify short‐time mechanotransduction responses.     

Organic‐inorganic‐hybrid‐enhancement Electrochemical Sensor for Determination of Cu (II) in River Water

A dual strategy that the L‐cysteine self‐assembling on three‐dimensional network of organic‐hybrid‐materials realized by successive interaction of Au−S bond is employed to construct as the amplified electrochemical sensor for determination Cu (II). Specifically, the sensor combined a rigid three‐dimension inorganic net which provides a higher interfacial area as well as faster adsorption of ions. Accordingly, surface and interfacial‐dominated electro‐catalysis reactivity is used as an ideal test‐bed to verify the reliability of electrochemical sensor that reveal enhancement sensitiveness and selectivity, low detection limit, and stability over a long period of time. Time‐dependent density functional theory (TD‐DFT) were used to calculating the all complexes energies at the B3LYP/LANL2DZ level associated with the polarized continuum model (PCM). The result of calculation indicates that the binding strength of Cu (II), Cd (II), As (III), Hg (II) with L‐cysteine are decrease successively, and this is in well agreement with experimental results. This work not only achieves an unprecedented understanding to L‐cysteine/Au/TiO₂/GCE sensor but also provides a new perspective for application in detection of Cu (II) in real river waters.     

Fabrication of Au‐Nanoparticle/TiO2‐Nanotubes Electrodes Using Electrochemical Methods and Their Application for Electrocatalytic Oxidation of Hydroquinone

Gold nanoparticle (Au‐NPs)‐Titanium oxide nanotube (TiO₂‐NTs) electrodes are prepared by using galvanic deposition of gold nanoparticles on TiO₂‐NTs electrodes as support. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy results indicate that nanotubular TiO₂ layers consist of individual tubes of about 60–90 nm diameters and gold nanoparticles are well‐dispersed on the surface of TiO₂‐NTs support. The electrooxidation of hydroquinone of Au‐NPs/TiO₂‐NTs electrodes is investigated by different electrochemical methods. Au‐NPs/TiO₂‐NTs electrode can be used repeatedly and exhibits stable electrocatalytic activity for the hydroquinone oxidation. Also, determination of hydroquinone in skin cream using this electrode was evaluated. Results were found to be satisfactory and no matrix effects are observed during the determination of hydroquinone content of the “skin cream” samples.     

Prussian Blue Modified Submicron Structured Gold Electrodes for Amperometric Hydrogen Peroxide Sensing

In this work, we present a simple and effective approach for fabricating sub‐micron structured gold (SM−Au) electrodes by chemically etching the magnetron co‐sputtered gold film in KI solution for certain time. Such electrodes with a large surface area to volume ratio were used as the matrix for electrochemical deposition of Prussian blue (PB) to develop an electrochemical hydrogen peroxide sensor. Experimental characterization using scanning electron microscope and atomic force microscope shows that the thickness of PB layer on SM−Au electrode is around 140 nm, and is composited with cubic PB nanocrystals. The electrochemical performance of the designed sensor, studied using cyclic voltammograms and chronoamperometry methods, suggests that the sensor based on SM−Au/PB electrode presents the direct electron transfer of PB particle towards SM−Au film, and exhibits fast response, wide linearity, low detection limit and high stability. Under the optimized conditions, the sensitivity of the developed sensor for the detection of H₂O₂ reaches the value of 512 mA cm⁻² M⁻¹ with a linear range from 1 μM to 4.5 mM.     

Gold‐Iron Bimetallic Nanoparticles Impregnated Reduced Graphene Oxide Based Nanosensor for Label‐free Detection of Biomarker Related to Non‐alcoholic Fatty Liver Disease

We report for the first time a microwave assisted, one pot, direct, and facile synthesis of monodispersed iron‐gold bimetallic nanoparticles (BNP_Au‐Fe) using glucose as a reducing agent in merely 90 s. The as such synthesized BNP_Au‐Fe were thoroughly characterized using UV‐Vis, XRD, TEM, EDX, elemental mapping, and raman spectroscopy. These BNP_Au‐Fe were further impregnated with reduced graphene oxide (rGO) and coated onto glassy carbon electrode (GCE) to develop a sensor probe for label free electrochemical detection of acetaminophen, which is considered to be a most potent biomarker related to non‐alcoholic fatty liver disease. The sensor probe was systematically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BNP_Au‐Fe‐rGO nanocomposite matrix showed the sensing of acetaminophen with a wide dynamic range between 50 and 800 nM with detection limit (DL) of 0.14 nM (±0.05) nM (RSD<4.12 %) that was lower compared to previously reported acetaminophen sensors. To show the practical application of the sensor probe, acetaminophen was detected in human urine samples, which showed the percentage recovery between 86.65 % and 91.32 %. To the best of our knowledge, this is the first report where BNP_Au‐Fe impregnated rGO was used to detect acetaminophen. Interferences due to various molecules such as glucose, serum albumin, glycine, glutamic acid, alanine, citric acid, and ascorbic acid were tested individually and in mixed sample. Long‐term stability of sensor probe was examined which was found to be stable up to 12 weeks. The sensor fabricated using BNP_Au‐Fe‐rGO nanocomposite has many attractive features such as; simplicity, rapidity, and label free detection, hence it could be a method of choice for acetaminophen detection in clinical settings.     

Electrochemical Behavior and Amperometric Detection of 4‐Chlorophenol on Nano‐Au Thin Films Modified Glassy Carbon Electrode

An amperometric sensor based on nano‐Au thin films was fabricated, by means of which a fast response to 4‐chlorophenol (4‐CP) can be achieved in the range of mM concentrations. The nanostructured Au thin film was prepared on glassy carbon electrodes by a template‐free, double‐potential step electrodeposition technique. Its structural feature can be controlled well by adjusting the deposition time. The amperometric detection of 4‐CP was performed at +0.85 V with a linear detection range from 0.2 to 4.8 mM and a detection limit of 0.11 mM (S/N=3). Besides, the effect of concentrations on the electrochemical behavior of 4‐CP on the Au thin film was investigated by linear sweep voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy.     

An Electrochemical Sensor Based on Gold Nanoparticles Incorporated in Mesoporous MFI Zeolite for Determination of Purine Bases in DNA

An electrochemical sensor was developed based on gold nanoparticles incorporated in mesoporous MFI zeolite for the determination of purine bases. Au nanoparticles (AuNPs) were incorporated into the mesoporous MFI zeolite (AuNPs/m‐MFI) by post‐grafting reaction. The composite materials were characterized by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS) and electrochemical methods. Au nanoparticles with a size of 5‐20 nm are uniformly dispersed in the pores of mesoporous MFI zeolite. And the morphology of MFI zeolite can be perfectly kept after pore expansion and Au nanoparticles incorporation. The electrocatalytic oxidation of purine bases (guanine and adenine in DNA) is investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The surface‐confined Au nanoparticles provide the good catalytic activity for oxidation of purine bases. The simultaneous detection of guanine and adenine can be achieved at AuNPs/m‐MFI composites modified glassy carbon electrode (GCE). The electrochemical sensor based on AuNPs/m‐MFI exhibits wide linear range of 0.5–500 μM and 0.8–500 μM with detection limit of 0.25 and 0.29 μM for guanine and adenine, respectively. Moreover, the electrochemical sensor is applied to evaluation of guanine and adenine in herring sperm DNA samples with satisfactory results.     

Fabrication of Superoxide Dismutase (SOD) Imprinted Poly(ionic liquid)s via eATRP and its Application in Electrochemical Sensor

Superoxide dismutase (SOD) plays an important role in nearly all living cells. In this study, SOD imprinted poly(ionic liquid)s (SIPILs) were prepared on the surface of the bare Au electrode modified with nano‐palladium and nano‐gold (Au/nPd/nAu/SIPILs). SIPILs was synthesized with 1‐vinyl‐3‐propyl imidazole sulfonate ionic liquids as functional monomers via electrochemically mediated atom transfer radical polymerization (eATRP) catalyzed by SOD. The Au/nPd/nAu/SIPILs was examined by cyclic voltammetry (CV), scanning electron microscope (SEM), energy‐dispersive spectrometer (EDS) and X‐ray photoelectron spectroscopy (XPS). The Au/nPd/nAu/SIPILs was also used as an electrochemical sensor to determine SOD by differential pulse voltammetry (DPV). Under the optimal conditions, the detection range of SOD was from 1.0×10^?8 to 1.0×10² mg L^?1 with a limit of detection of 8.90×10^?9 mg L^?1 (S/N=3). Compared with other methods, the sensor based on SIPILs had the broader linear range and lower detection limit.     

Fe3O4@SiO2‐PANI‐Au Nanocomposite Prepared for Electrochemical Determination of Quercetin in Food Samples and Biological Fluids

A new electrochemical sensor based on Fe₃O₄@SiO₂‐PANI‐Au nanocomposite was fabricated for modification of glassy carbon electrode (Fe₃O₄@SiO₂‐PANI‐Au GCE). The Fe₃O₄@SiO₂‐PANI‐Au nanocomposite was characterized by TEM, FESEM‐EDS‐Mapping, XRD, and TGA methods. The Fe₃O₄@SiO₂‐PANI‐Au GC electrode exhibited an acceptable sensitivity, fast electrochemical response, and good selectivity for determination of quercetin. Under optimal conditions, the linear range for quercetin concentrations using this sensor was 1.0×10^?8 to 1.5×10^?5 mol L^?1, and the limit of detection was 3.8×10^?9 mol L^?1. The results illustrated that the offered sensor could be a possible alternative for the measurement of quercetin in food samples and biological fluids.     

Synergistic Modification of Electronic and Photocatalytic Properties of TiO2 Nanotubes by Implantation of Au and N Atoms

The structural and electronic properties of N‐doped, Au‐adsorbed, and Au/N co‐implanted TiO₂ nanotubes (NTs) were investigated by performing first‐principle density functional theory (DFT) calculations. For all the possible implanted configurations, the radius and bond length do not change significantly relative to the clean NTs. Our results indicate that the introduction of N into NTs is in favor of implantation of Au, and Au pre‐adsorption on the NTs can also enhance the N concentration in NTs. The synergistic stability can be mainly attributed to charge transfer between Au and N atoms. In co‐implanted configurations, the empty N 2p states in the band gap are occupied by one electron; denoted by Au 5s states. Thus, the associated electron transition among the valence band, the conduction band and the gap states results in redshift of the light absorption. In addition, the disappearance of N 2p empty states can effectively decrease the photogenerated carrier combination. Therefore, the Au/N implanted NTs should be regarded as a promising photocatalytic material under the visible light region.     

Mechanical Distension Induces Serotonin Release from Intestine as Revealed by Stretchable Electrochemical Sensing

The role of endogenous serotonin (5‐HT) in gastrointestinal motility is still highly controversial. Although electrochemical techniques allow for direct and real‐time recording of biomolecules, the dynamic monitoring of 5‐HT release from elastic and tubular intestine during motor reflexes remains a great challenge because of the specific peristalsis patterns and inevitable passivation of the sensing interface. A stretchable sensor with antifouling and decontamination properties was assembled from gold nanotubes, titanium dioxide nanoparticles, and carbon nanotubes. The sandwich‐like structure endowed the sensor with satisfying mechanical stability and electrochemical performance, high resistance against physical adsorption, and superior efficiency in the photodegradation of biofouling molecules. Insertion of the sensor into the lumen of rat ileum (the last section of the small intestine) successfully mimics intestinal peristalsis, and simultaneous real‐time monitoring of distension‐evoked 5‐HT release was possible for the first time. Our results unambiguously reveal that mechanical distension of the intestine induces endogenous 5‐HT overflow, and 5‐HT level is closely associated with the physiological or pathological states of the intestine.     

Highly selective electrochemical method for the detection of serotonin at carbon fiber microelectrode modified with gold nanoflowers and overoxidized polypyrrole

A gold nanoflowers and overoxidized polypyrrole modified carbon fiber microelectrode (OPPy/Au NFs/CFME) was fabricated using electroless deposition and electrochemical method for highly selective and sensitive detection of 5-HT.     

Plasticizer and catalyst co-functionalized PEDOT:PSS enables stretchable electrochemical sensing of living cells

Recently, stretchable electrochemical sensors have stood out as a powerful tool for the detection of soft cells and tissues, since they could perfectly comply with the deformation of living organisms and synchronously monitor mechanically evoked biomolecule release. However, existing strategies for the fabrication of stretchable electrochemical sensors still face with huge challenges due to scarce electrode materials, demanding processing techniques and great complexity in further functionalization. Herein, we report a novel and facile strategy for one-step preparation of stretchable electrochemical biosensors by doping ionic liquid and catalyst into a conductive polymer (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS). Bis(trifluoromethane) sulfonimide lithium salt as a small-molecule plasticizer can significantly improve the stretchability and conductivity of the PEDOT:PSS film, and cobalt phthalocyanine as an electrocatalyst endows the film with excellent electrochemical sensing performance. Moreover, the functionalized PEDOT:PSS retained good cell biocompatibility with two extra dopants. These satisfactory properties allowed the real-time monitoring of stretch-induced transient hydrogen peroxide release from cells. This work presents a versatile strategy to fabricate conductive polymer-based stretchable electrodes with easy processing and excellent performance, which benefits the in-depth exploration of sophisticated life activities by electrochemical sensing.

A facile strategy for constructing stretchable sensors with excellent mechanical, electrochemical and biocompatible performance is developed, and in situ inducing and monitoring of stretch-evoked H₂O₂ release from cells has been successfully achieved.     

生物样品中神经递质的定量测定及其应用研究进展

神经递质（NTs）是神经传递的内源性化学信使，在大脑功能中发挥重要作用。中枢神经系统中神经递质浓度的变化与许多精神和生理疾病有关。神经递质的测定已成为疾病诊断和监测以及治疗干预的重要手段，有效的神经递质体内监测对于疾病诊疗乃至新药研发都至关重要。该文就近年来神经递质的检测方法，包括仪器检测法、电化学检测法以及一些新型检测方法等进行综述，并总结了目前神经递质检测在一些疾病研究中的应用进展。     

Photocatalytically Renewable Micro‐electrochemical Sensor for Real‐Time Monitoring of Cells

Electrode fouling and passivation is a substantial and inevitable limitation in electrochemical biosensing, and it is a great challenge to efficiently remove the contaminant without changing the surface structure and electrochemical performance. Herein, we propose a versatile and efficient strategy based on photocatalytic cleaning to construct renewable electrochemical sensors for cell analysis. This kind of sensor was fabricated by controllable assembly of reduced graphene oxide (RGO) and TiO₂ to form a sandwiching RGO@TiO₂ structure, followed by deposition of Au nanoparticles (NPs) onto the RGO shell. The Au NPs‐RGO composite shell provides high electrochemical performance. Meanwhile, the encapsulated TiO₂ ensures an excellent photocatalytic cleaning property. Application of this renewable microsensor for detection of nitric oxide (NO) release from cells demonstrates the great potential of this strategy in electrode regeneration and biosensing.     

Highly selective electrochemical method for the detection of serotonin at carbon fiber microelectrode modified with gold nanoflowers and overoxidized polypyrrole

A highly selective and sensitive electrochemical method was developed for the detection of serotonin (5-hydroxytryptamine, 5-HT) at gold nanoflowers (Au NFs) and overoxidized polypyrrole (OPPy) modified carbon fiber microelectrode (CFME). Carbon fiber was firstly modified with gold nanoflowers using electroless deposition method, and then modified with overoxidized polypyrrole using electrochemical polymerization and overoxidization to obtain OPPy/Au NFs/CFME. The obtained OPPy/Au NFs/CFME was characterized by field emission scanning electron microscopy and electrochemical techniques. It was found that the OPPy/Au NFs/CFME showed good sensitivity for the detection of 5-HT in the range of 10 nmol/L − 7.0 μmol/L with detection limit of 2.3 nmol/L, and negligible interferences from ascorbic acid, 5-hydroxyindole acetic acid and uric acid. The OPPy/Au NFs/CFME was successfully applied to the detection of 5-HT in human serum samples with good recovery. The work demonstrates that the electrochemical method, incorporating signal amplification of Au NFs with higher cation selection of OPPy, provides a promising tool for the detection of 5-HT in biological systems     

Real‐Time Intracellular Measurements of ROS and RNS in Living Cells with Single Core–Shell Nanowire Electrodes

Nanoelectrodes allow precise and quantitative measurements of important biological processes at the single living‐cell level in real time. Cylindrical nanowire electrodes (NWEs) required for intracellular measurements create a great challenge for achieving excellent electrochemical and mechanical performances. Herein, we present a facile and robust solution to this problem based on a unique SiC‐core–shell design to produce cylindrical NWEs with superior mechanical toughness provided by the SiC nano‐core and an excellent electrochemical performance provided by the ultrathin carbon shell that can be used as such or platinized. The use of such NWEs for biological applications is illustrated by the first quantitative measurements of ROS/RNS in individual phagolysosomes of living macrophages. As the shell material can be varied to meet any specific detection purpose, this work opens up new opportunities to monitor quantitatively biological functions occurring inside cells and their organelles.     

“Green Electrodes” Modified with Au Nanoparticles Synthesized in Glycerol,as Electrochemical Nitrite Sensor

A new environmentally friendly Au nanoparticles (Au NPs) synthesis in glycerol by using ultraviolet irradiation and without extra‐added stabilizers is described. The synthesis proposed in this work may impact on the non‐polluting production of noble nanoparticles with simple chemicals normally found in standard laboratories. These Au NPs were used to modify a carbon paste electrode (CPE) without having to separate them from the reaction medium. This green electrode was used as an electrochemical sensor for the nitrite detection in water. At the optimum conditions the green sensor presented a linear response in the 2.0×10^?7–1.5×10^?5 M concentration range, a good detection sensitivity (0.268 A L mol^?1), and a low detection limit of 2.0×10^?7 M of nitrite. The proposed modified green CPE was used to determine nitrite in tap water samples.     

A Sensitive Electrochemical Sensor for Voltammetric Determination of Ganciclovir Based on Au‐ZnS Nanocomposite

An electrode modified with ZnS and gold nanoparticles (Au‐ZnS NPs) is introduced for highly sensitive voltammetric determination of ganciclovir (GCV). Surface structure and topography of the modified electrode was studied by SEM, EDX and XRD techniques. Electrochemical oxidation of GCV was investigated by cyclic (CV) and square wave voltammetry (SWV) in Briton‐Robinson buffer solution (pH 1.5). The results showed that electrochemical oxidation of GCV at the Au‐ZnS modified glassy carbon electrode (GCE) is irreversible and exhibited diffusion controlled electrode process over the pH range from 1.0 to 6.0. The oxidation potential peak and pH relationship showed that electrons and protons were transferred simultaneously over the electrochemical oxidation process. Using the proposed sensor, the linear calibration curves were obtained in the ranges of 0.04–1.50 μM and 1.5–70.0 μM with detection limit of 0.01 μM GCV by SWV technique. The modified electrode was successfully applied as a sensitive, reproducible and repeatable sensor for determination of the trace amount of GCV in human serum, urine and cymevene vials. Reasonable results were obtained from comparing the measurements of the real samples by the new sensor to high performance liquid chromatography (HPLC) as a standard method.     

Detection of Thiols by o‐Quinone Nanocomposite Modified Electrodes

A chemically modified glassy carbon (GC) electrode was developed as an amperometric sensor for detection of biological thiols. The electrode was modified by inclusion of co‐enzyme pyrroloquinoline quinone (PQQ) and a co‐catalyst of oxidized single wall carbon nanotubes (Ox‐SWNT) into a gold polypyrrole (Au‐PPy) nanocomposite matrix. The electrode (PQQ/Ox‐SWNT/Au‐PPy/GC) was characterized using scanning electron microscopy and cyclic voltammetry. Optimal conditions for the PQQ/Ox‐SWNT/Au‐PPy/GC electrode were determined and then utilized for the amperometric detection of L‐cysteine, N‐acetyl‐L‐cysteine, L‐penicillamine and D, L‐glutathione. The electrochemical response for each thiol in pH 3.2 citrate phosphate buffer at +450 mV (vs. Ag/AgCl) was found to be linear with limit of detections (LOD, S/N=3) ranging from 0.50 µM for L‐penicillamine to 1.55 µM for D, L‐glutathione with sensitivities of 30.2 nA/µM and 3.6 nA/µM respectively. The electrode design is simple and easy to construct using a minimum amount of co‐enzyme and co‐catalyst, resulting in detection methods with very good stability and improved sensitivity for thiol detection.