MOFs-Based Magnetic Nanozyme to Boost Cascade ROS Accumulation for Augmented Tumor Ferroptosis.

The emerging cell death modality of ferroptosis has garnered increasing attention for antitumor treatment but still suffers from low therapeutic efficacy. A metal-organic frameworks (MOFs)-based magnetic nanozyme (PZFH) comprising porphyrin-based Zr-MOF (PCN) on zinc ferrite (ZF) nanoparticles modified with hyaluronic acid, delivering excellent magnetophotonic response for efficient ferroptosis, is reported here. PZFH shows multienzyme-like cascade activity encompassing a photon-triggered oxidase-like catalysis to generate O2 -, which is converted to H2O2 by superoxide dismutase-like activity and subsequent ·OH by magneto-promoted peroxidase (POD) behavior. Newly formed Fe─N coordination and increased Fe2+/Fe3+ levels in the PZFH contribute to the enhanced POD activity, which is further enhanced by accelerated surface electron transfer when exposure to alternated magnetic field. Accumulation of lipid peroxides is eventually accomplished through the conversion of ·OH radicals and singlet oxygen (1O2) produced through laser irradiation. When combined with the depletion of inhibition of glutathione and glutathione peroxidase 4, PZFH exhibits significantly enhanced ferroptosis in tumor-bearing mice, offering insights into nanomedicine for ferroptosis and holding great promise in clinical antitumor therapies.

Boosting the Proton-coupled Electron Transfer via Fe-P Atomic Pair for Enhanced Electrochemical CO2 Reduction.

Single-atom catalysts exhibit superior CO2 -to-CO catalytic activity, but poor kinetics of proton-coupled electron transfer (PCET) steps still limit the overall performance toward the industrial scale. Here, we constructed a Fe-P atom paired catalyst onto nitrogen doped graphitic layer (Fe1 /PNG) to accelerate PCET step. Fe1 /PNG delivers an industrial CO current of 1 A with FECO over 90 % at 2.5 V in a membrane-electrode assembly, overperforming the CO current of Fe1 /NG by more than 300 %. We also decrypted the synergistic effects of the P atom in the Fe-P atom pair using operando techniques and density functional theory, revealing that the P atom provides additional adsorption sites for accelerating water dissociation, boosting the hydrogenation of CO2 , and enhancing the activity of CO2 reduction. This atom-pair catalytic strategy can modulate multiple reactants and intermediates to break through the inherent limitations of single-atom catalysts.

A novel micron europium cluster coordination polymer as a strong electrochemiluminescent emitter for accurate and sensitive detection of tetracycline.

In this work, a self-luminescent micron europium cluster coordination polymer (Eu-CCP) cathode electrochemiluminescence (ECL) emitter is first reported. The mass percentage of Eu in Eu-CCP is 50.1%, indicating that Eu-CCP has a high-nucleation luminescence center. In addition, our Eu-CCP possesses a stable and efficient ECL red emission performance, and the intensity is approximately 6.5-fold higher than that of the traditional tris(2,2'-bipyridyl)ruthenium(II) dichloride. The enhancement of Eu-CCP luminescence in our system is due to the following reasons: (1) the mixed ligand and high nuclear europium luminescent center can cooperate to improve the quenching effect induced by water or hydroxyl groups; and (2) external coreaction accelerator and coreactant enhancement. We also investigate the application of Eu-CCP in ECL sensors by sensitive detection of tetracycline (TC). The low detection limit (73.5 fmol·L-1), high selectivity, good stability and satisfactory recoveries indicate that our ECL strategy can be used to detect TC accurately and sensitively.

Boosting Photo-Electro-Fenton Process Via Atomically Dispersed Iron Sites on Graphdiyne for InVitro Hydrogen Peroxide Detection.

Hydrogen peroxide (H2 O2 ) is essential in oxidative stress and signal regulation of organs of animal body. Realizing in vitro quantification of H2 O2 released from organs is significant, but faces challenges due to short lifetime of H2 O2 and complex bio-environment. Herein, rationally designed and constructed a photoelectrochemical (PEC) sensor for in vitro sensing of H2 O2 , in which atomically dispersed iron active sites (Hemin) modified graphdiyne (Fe-GDY) serves as photoelectrode and catalyzes photo-electro-Fenton process. Sensitivity of Fe-GDY electrode is enhanced 8 times under illumination compared with dark condition. The PEC H2 O2 sensor under illumination delivers a wide linear range from 0.1 to 48 160 µm and a low detection limit of 33 nm, while demonstrating excellent selectivity and stability. The high performance of Fe-GDY is attributed to, first, energy levels matching of GDY and Hemin that effectively promotes the injection of photo-generated electrons from GDY to Fe3+ for reduced Fe2+ , which facilitates the Fe3+ /Fe2+ cycle. Second, the Fe2+ actively catalyzes H2 O2 to OH- through the Fenton process, thereby improving the sensitivity. The PEC sensor demonstrates in vitro quantification of H2 O2 released from different organs, providing a promising approach for molecular sensing and disease diagnosis in organ levels.

Modulating Hydrogen Adsorption via Charge Transfer at the Semiconductor-Metal Heterointerface for Highly Efficient Hydrogen Evolution Catalysis.

Designing and synthesizing highly efficient and stable electrocatalysts for hydrogen evolution reaction (HER) is important for realizing the hydrogen economy. Tuning the electronic structure of the electrocatalysts is essential to achieve optimal HER activity, and interfacial engineering is an effective strategy to induce electron transfer in a heterostructure interface to optimize HER kinetics. In this study, ultrafine RhP2 /Rh nanoparticles are synthesized with a well-defined semiconductor-metal heterointerface embedded in N,P co-doped graphene (RhP2 /Rh@NPG) via a one-step pyrolysis. RhP2 /Rh@NPG exhibits outstanding HER performances under all pH conditions. Electrochemical characterization and first principles density functional theory calculations reveal that the RhP2 /Rh heterointerface induces electron transfer from metallic Rh to semiconductive RhP2 , which increases the electron density on the Rh atoms in RhP2 and weakens the hydrogen adsorption on RhP2 , thereby accelerating the HER kinetics. Moreover, the interfacial electron transfer activates the dual-site synergistic effect of Rh and P of RhP2 in neutral and alkaline environments, thereby promoting reorganization of interfacial water molecules for faster HER kinetics.

miR-146a-5p promotes epithelium regeneration against LPS-induced inflammatory injury via targeting TAB1/TAK1/NF-κB signaling pathway.

Intestinal inflammation often restricts the health and production of animals. MiR-146a has been proved to be an anti-inflammatory molecule in inflammatory disorders, but its role in the intestinal injury and regeneration remains unclear. The study aimed to explore the inflammatory response of intestinal epithelial cells (IECs) in intestinal tissue-specific miR-146a-5p knockout mouse models. We identified the role of miR-146a-5p in inhibiting inflammatory response and promoting proliferation under lipopolysaccharide (LPS) stimulation in vitro and vivo. LPS stimulation significantly increased the expression of TNF-α, IL6 and inhibited IPEC-J2 cell proliferation. Overexpression of miR-146a-5p can reverse the effect of LPS stimulation, and promote the proliferation of intestinal epithelial cells. In the LPS challenge experiment in intestine-specific miR-146a knock-out mice (CKO) and Floxp+/+ mice (CON), CKO mice were more sensitive to LPS stimulation, with more weight loss and more severe intestinal morphological damage than CON mice. Also, miR-146a-5p regulated LPS-induced intestinal injury, inflammation by targeting TAB1. Taken together, miR-146a may function as an anti-inflammatory factor in IECs by targeting TAB1/TAK1-IKK-NF-κB signaling pathway. miR-146a-5p may represent a promising biomarker for inflammatory disorders, and may provide an effective therapeutic method to alleviate weaning stress in piglets and some experimental basis to improve the intestinal health of livestock.

Lanthanide Ce(III)/Tb(III) bimetallic coordination polymer as an advanced electrochemiluminescence emitter for epinephrine sensing application.

By rationally introducing Ce(III) and Tb(III) into a coordination polymer (CP), a series of lanthanide bimetallic coordination polymers (Tb:Ce-BCPs) has been prepared in this work. Compared with pure Tb-CP and Ce-CP, bimetallic Tb:Ce-BCPs show stronger and more stable ECL intensity, which is mainly attributed to the "dual sensitization effect" combined with the energy transfer from Ce(III) to Tb(III) and the antenna effect from the ligand to the center atoms of Ce(III) and Tb(III). In the meantime, after explore the ECL intensity and morphologies of all these Tb:Ce-BCPs, the results show that the morphologies and ECL intensities of Tb:Ce-BCPs can be adjusted by doping different molar ratios of Ce(III) in Tb:Ce-BCP. Excitingly, Ce(III) can also act as a co-reaction accelerator, effectively promoting S2O82- to generate more SO4•-, thereby enhancing the ECL intensity of Tb:Ce-BCP. That is to say, Ce(III) plays a triple role in Tb:Ce-BCP. Furthermore, the ECL strength of Tb:Ce-BCP decreased by only 1.8% and 3.5%, respectively after the modified electrode was scanned for 800 s and stored for one month. Enlightened by the excellent ECL properties of Tb:Ce-BCP, we modified Tb:Ce-BCP directly on the surface of electrode, and explored its application in electroanalytical chemistry through the detection of epinephrine (EP) and the detection limit is 33 fmol L-1. Significantly, our ECL sensing strategy promotes the application of lanthanides in ECL sensor and opens vast possibilities for the synthesis of a new generation of ECL emitter in electroanalytical fields.

Finite-Element Analysis of High-Strength Steel Extended End-Plate Connections under Cyclic Loading.

In order to examine the seismic behavior of high-strength steel extended end-plate connections, a three-dimensional efficient finite-element model in Abaqus was established subjected to cyclic loading at the beam end. Geometrical dimensions, boundary conditions, element types, contact properties between the bolts, end-plate and column flange, and material cyclic constitutive models were described in detail. Geometry and material nonlinearity were adequately considered. In particular, a cyclic plasticity model for high-strength steels was employed that was easily calibrated based on the tension coupon test, so as to describe the complicated cyclic hardening and softening response. The simulated results of the finite-element model were compared to the test ones in terms of both deformation modes and hysteresis loops. The results showed that the bending deformation of the end-plate and column flange was accurately captured, and the gap phenomena among the bolt nuts, the end-plate, and column flange was described in a satisfactory manner as well. The hysteresis loops from the simulation agreed well with the test results, reproducing the pinched shape due to the end-plate gap evolution under cyclic loading as well as the quite plump shape with stable energy dissipation when the panel zone dominated the cyclic response. Therefore, the accuracy of the finite-element model was verified and it provided a strong benchmark tool for investigating the cyclic or seismic performance of this kind of connection. The connection failure including the bolt fracture and cracking in the end-plate needs further numerical study by calibrating accurate material failure models for high-strength steels and bolts.

Sandwiching Phosphorene with Iron Porphyrin Monolayer for High Stability and Its Biomimetic Sensor to Sensitively Detect Living Cell Released NO.

Instability of 2D phosphorene material is the major obstacle for its broad applications. Herein phosphorene is sandwiched with self-assembled iron porphyrin monolayers on both sides (I-Phene) to significantly enhance stability. Iron porphyrin has strong interaction with phosphorene through formation of PFe bonds. The sandwich structure offers excellent stability of phosphorene by both-sided monolayer protections for an intact phosphorene structure more than 40 days under ambient conditions. Meanwhile, the electron transfer between iron porphyrin and phosphorene result in a high oxidation state of Fe, making I-Phene biomimetic sensitivity toward oxidation of nitric oxide (NO) for 2.5 and 4.0 times higher than phosphorene and iron-porphyrin alone, respectively. Moreover, I-Phene exhibits excellent selectivity, a wide detection range, and a low detection limit at a low oxidation potential of 0.82 V, which is comparable with the reported noble metal based biomimetic sensors while ranking the best among all non-noble biomimetic ones. I-Phene is further used for real-time monitoring NO released from cells. This work provides effective approach against phosphorene degrading for outstanding stability, which has universal significance for its various important applications, and holds a great promise for a highly sensitive biomimetic sensor in live-cell assays.

Molecularly assembled graphdiyne with atomic sites for ultrafast and real-time detection of nitric oxide in cell assays.

Nitric oxide as a signal molecule participates in a variety of physiological and pathological processes but its real-time detection in cell assays still faces challenging because of the trace amount, short half-life and easy conversion to other substances. We report here a rational design by assembling highly π-conjugated and small capacitive gaphdiyne (GDY) with a coordination complex of hemin (HEM) into a molecularly assembled material of GDY/HEM to achieve ultrafast and real-time monitoring of nitric oxide in cell assays. GDY comprising alkynyl C atoms can hybridize with the HEM to enable strong π-π interaction and atomic dispersion of iron sites while avoiding the formation of catalytically inactive dimer for the HEM. These characteristics make the GDY/HEM an excellent sensing material towards nitric oxide, which has an ultrafast response time of 0.95 s, a low detection limit of 7 nM and long linear range up to 151.38 µΜ. The GDY/HEM realizes real-time monitoring nitric oxide released from cancer and normal cells, demonstrating its capability for cell analysis.

Recent Advances in Colorimetric Sensors Based on Gold Nanoparticles for Pathogen Detection.

Infectious pathogens cause severe threats to public health due to their frightening infectivity and lethal capacity. Rapid and accurate detection of pathogens is of great significance for preventing their infection. Gold nanoparticles have drawn considerable attention in colorimetric biosensing during the past decades due to their unique physicochemical properties. Colorimetric diagnosis platforms based on functionalized AuNPs are emerging as a promising pathogen-analysis technique with the merits of high sensitivity, low-cost, and easy operation. This review summarizes the recent development in this field. We first introduce the significance of detecting pathogens and the characteristics of gold nanoparticles. Four types of colorimetric strategies, including the application of indirect target-mediated aggregation, chromogenic substrate-mediated catalytic activity, point-of-care testing (POCT) devices, and machine learning-assisted colorimetric sensor arrays, are systematically introduced. In particular, three biomolecule-functionalized AuNP-based colorimetric sensors are described in detail. Finally, we conclude by presenting our subjective views on the present challenges and some appropriate suggestions for future research directions of colorimetric sensors.

Bifunctional Moderator-Powered Ratiometric Electrochemiluminescence Enzymatic Biosensors for Detecting Organophosphorus Pesticides Based on Dual-Signal Combined Nanoprobes.

The bifunctional moderator is urgently needed in the field of ratiometric electrochemiluminescence (ECL) sensing since it can mediate simultaneously two ECL signals to conveniently realize their opposite change trend. This work designed a novel dual-signal combined nanoprobe with carboxyl-functionalized poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadazole)] nanoparticles (c-PFBT NPs) as the anodic ECL probe and L-cysteine capped CdS quantum dots (L-CdS QDs) as the cathodic ECL probe, which performed a dual-signal output capability without any additional coreactants. More importantly, hydrogen peroxide (H2O2) produced in situ by enzyme-catalyzed reaction was developed as a bifunctional moderator for simultaneously regulating two signals. The dual-signal combined nanoprobe (c-PFBT NPs@CdS QDs) served as the matrix to immobilize acetylcholinesterase (AChE) and choline oxidase for organophosphorus (OPs) analysis. In the absence of OPs, H2O2 was produced by catalyzing the substrate acetylthiocholine (ATCl) with enzymes and it quenched the anodic ECL signal from c-PFBT NPs and simultaneously promoted the cathodic ECL signal from L-CdS QDs. When OPs was present, the activity of AChE was inhibited, the anodic signal would increase, and the cathodic signal would accordingly decrease. The integration of the bifunctional moderator H2O2 and dual-signal combined nanoprobe c-PFBT NPs@CdS QDs not only provides an attractive ECL platform for enzymatic sensing involving the generation or consumption of H2O2 but also paves a new pathway for other ratiometric ECL systems involving enzyme catalytic amplification for detecting antigens, antibodies, DNA, RNA, etc.

Screen-printed analytical strip constructed with bacteria-templated porous N-doped carbon nanorods/Au nanoparticles for sensitive electrochemical detection of dopamine molecules.

Dopamine (DA) as an important neurotransmitter plays an important role in physiological activities, and its abnormal level can cause diseases such as Parkinson's disease. However, the clinical analysis of DA mainly relies on time-consuming and expensive liquid chromatography and molecular spectrometer. We present here a design and fabrication of inexpensive strip sensor constructed from screen printed electrodes for sensitive and selective detection of DA. The ink used for printing the strips contains Shewanella putrefaciens-templated porous N-doped carbon nanorods (N-doped CN) and Au nanoparticles (Au NPs), in which the N-doping enhances CN's negative charge to electrostatically attract the positively charged DA with strong adsorption for achieving fast electron transfer. Moreover, results indicate that the Au NPs impregnation in N-doped CN renders much more catalytic reaction sites toward DA oxidation current. The strip sensor exhibits high sensitivity for DA detection with a broad linear range of 0.02-700 µM and a low detection limit of 0.007 µM as well as good selectivity and superior flexibility for great potential in wearable applications. The strip sensor further performs an accurate detection of DA in human serum, providing a powerful analytical tool for diagnosis of DA related diseases in clinical analysis.

DNA branched junctions induced the enhanced fluorescence recovery of FAM-labeled probes on rGO for detecting Pb2.

The reduced graphene oxide (rGO) could strongly adsorb and quench the fluorescence of dye-labeled single-stranded DNA (ssDNA); thus, it is widely applied in fluorescent sensors. However, these sensors may suffer from a limited sensitivity due to the low fluorescence recovery when adding the complementary DNA (cDNA) sequence. In this work, the powerful DNA branched junctions were constructed to improve the fluorescence recovery of FAM-labeled probe on rGO. In the presence of target Pb2+, the ribonucleotide (rA) in the substrate was cleaved specifically and the catalytic hairpin assembly of three metastable hairpins was further initiated, accompanied by the formation of DNA branched junctions. Then, the liberated Pb2+ could be recyclable. Impressively, the DNA branched junctions not only hybridize with the FAM-labeled probes with a high efficiency, but also are significantly undesirable for the rGO. Thus, a high fluorescence recovery of FAM-labeled probe on rGO was expected. The integration of the high fluorescence recovery and dual-cycle signal amplification endows the sensing strategy with a good performance for Pb2+ detection, including low detection limit (0.17 nM), good selectivity, and satisfactory practical applicability. The proposed DNA branched junctions offer a novel avenue to improve the fluorescence recovery of the dye-labeled probes on rGO for biological analysis.

An electrochemiluminescence biosensor for the detection of soybean agglutinin based on carboxylated graphitic carbon nitride as luminophore.

As an important glycoprotein of the lectin family, soybean agglutinin (SBA) is an anti-nutritional factor with considerable toxic and side effects and plays a significant role in tumor analysis. In order to achieve the sensitive detection of SBA, a sandwich-structured electrochemiluminescence (ECL) biosensor was constructed using carboxylated carbon nitride (C-g-C3N4) as luminophore and D-galactosamine (galM) as a recognition element. A glassy carbon electrode (GCE) was modified with Au nanoparticles (Au NPs) for capturing the galM via Au-N bond, and further capturing the target SBA by specific recognition between galM and SBA. In the presence of SBA, the composite C-g-C3N4-galM was immobilized onto the electrode. With the increase in the concentration of SBA, the ECL signal from C-g-C3N4 increased, thus achieving a signal-on detection of SBA. The linear range of the biosensor was 1.0 ng/mL~10 µg/mL and detection limit for SBA was as low as 0.33 ng/mL. In this construction strategy, C-g-C3N4 not only acted as an excellent signal probe, but also as an immobilization matrix to easily achieve a high loading of the small molecule recognition element galM. This strategy provides a simple alternative SBA detection platform. Graphical abstract.

Simultaneous determination of ascorbic acid, dopamine, uric acid and tryptophan on gold nanoparticles/overoxidized-polyimidazole composite modified glassy carbon electrode.

A novel electrode was developed through electrodepositing gold nanoparticles (GNPs) on overoxidized-polyimidazole (PImox) film modified glassy carbon electrode (GCE). The combination of GNPs and the PImox film endowed the GNPs/PImox/GCE with good biological compatibility, high selectivity and sensitivity and excellent electrochemical catalytic activities towards ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp). In the fourfold co-existence system, the peak separations between AA-DA, DA-UA and UA-Trp were large up to 186, 165 and 285 mV, respectively. The calibration curves for AA, DA and UA were obtained in the range of 210.0-1010.0 µM, 5.0-268.0 µM and 6.0-486.0 µM with detection limits (S/N=3) of 2.0 µM, 0.08 µM and 0.5 µM, respectively. Two linear calibrations for Trp were obtained over ranges of 3.0-34.0 µM and 84.0-464.0 µM with detection limit (S/N=3) of 0.7 µM. In addition, the modified electrode was applied to detect AA, DA, UA and Trp in samples using standard addition method with satisfactory results.

Highly-sensitive cholesterol biosensor based on platinum-gold hybrid functionalized ZnO nanorods.

A novel scheme for the fabrication of gold/platinum hybrid functionalized ZnO nanorods (Pt-Au@ZnONRs) and multiwalled carbon nanotubes (MWCNTs) modified electrode is presented and its application for cholesterol biosensor is investigated. Firstly, Pt-Au@ZnONRs was prepared by the method of chemical synthesis. Then, the Pt-Au@ZnONRs suspension was dropped on the MWCNTs modified glass carbon electrode, and followed with cholesterol oxidase (ChOx) immobilization by the adsorbing interaction between the nano-material and ChOx as well as the electrostatic interaction between ZnONRs and ChOx molecules. The combination of MWCNTs and Pt-Au@ZnONRs provided a favorable environment for ChOx and resulted in the enhanced analytical response of the biosensor. The resulted biosensor exhibited a linear response to cholesterol in the wide range of 0.1-759.3 µM with a low detection limit of 0.03 µM and a high sensitivity of 26.8 µA mM(-1). The calculated apparent Michaelis constant K(M)(app) was 1.84 mM, indicating a high affinity between ChOx and cholesterol.

Study on the application of reduced graphene oxide and multiwall carbon nanotubes hybrid materials for simultaneous determination of catechol, hydroquinone, p-cresol and nitrite.

In this paper, the reduced graphene oxide and multiwall carbon nanotubes hybrid materials (RGO-MWNTs) were prepared and a strategy for detecting environmental contaminations was proposed on the basis of RGO-MWNTs modified electrode. The hybrid materials were characterized by the scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and N(2) sorption-desorption isotherms. Due to the excellent catalytic activity, enhanced electrical conductivity and high surface area of the RGO-MWNTs, the simultaneous measurement of hydroquinone (HQ), catechol (CC), p-cresol (PC) and nitrite (NO(2)(-)) with four well-separate peaks was achieved at the RGO-MWNTs modified electrode. The linear response ranges for HQ, CC, PC and NO(2)(-) were 8.0-391.0 µM, 5.5-540.0 µM, 5.0-430.0 µM and 75.0-6060.0 µM, correspondingly, and the detection limits (S/N=3) were 2.6 µM, 1.8 µM, 1.6 µM and 25.0 µM, respectively. The outstanding film forming ability of RGO-MWNTs hybrid materials endowed the modified electrode enhanced stability. Furthermore, the fabricated sensor was applied for the simultaneous determination of HQ, CC, PC and NO(2)(-) in the river water sample.

Multi-wall carbon nanotube-polyaniline biosensor based on lectin-carbohydrate affinity for ultrasensitive detection of Con A.

In this paper, a novel method for detecting concanavalin A (Con A) was developed based on lectin-carbohydrate biospecific interactions. Multi-wall carbon nanotube-polyaniline (MWNT-PANI) nanocomposites, synthesized by in situ polymerization, were chosen to immobilize d-glucose through the Schiff-base reaction. The immobilized D-glucose showed high binding sensitivity and excellent selectivity to its target lectin, Con A. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM) and atomic force microscopy (AFM) were applied to characterize the assembly process of the modified electrode. Due to the high affinity of Con A for D-glucose and high stability of the propounded sensing platform, the fabricated biosensor achieved ultrasensitive detection of Con A with good sensitivity, acceptable reproducibility and stability. The changes of response current were proportional to the Con A concentrations from 3.3 pM to 9.3 nM, with a detection limit of 1.0 pM. Therefore, the combination of MWNT-PANI nanocomposites and the special binding force between lectin and carbohydrate provides an efficient and promising platform for the fabrication of bioelectrochemical devices.

Au-nanoclusters incorporated 3-amino-5-mercapto-1,2,4-triazole film modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid and nitrite.

A novel biosensor has been constructed by the electrodeposition of Au-nanoclusters (nano-Au) on poly(3-amino-5-mercapto-1,2,4-triazole) (p-TA) film modified glassy carbon electrode (GCE) and employed for the simultaneous determination of dopamine (DA), ascorbic acid (AA), uric acid (UA) and nitrite (NO(2)(-)). NH(2) and SH groups exposed to the p-TA layer are helpful for the electrodeposition of nano-Au. The combination of nano-Au and p-TA endow the biosensor with large surface area, good biological compatibility, electricity and stability, high selectivity and sensitivity and flexible and controllable electrodeposition process. In the fourfold co-existence system, the linear calibration plots for AA, DA, UA and NO(2)(-) were obtained over the range of 2.1-50.1 µM, 0.6-340.0 µM, 1.6-110.0 µM and 15.9-277.0 µM with detection limits of 1.1×10(-6) M, 5.0×10(-8) M, 8.0×10(-8) M and 8.9×10(-7) M, respectively. In addition, the modified biosensor was applied to the determination of AA, DA, UA and NO(2)(-) in urine and serum samples by using standard adding method with satisfactory results.