Synthesis of palladium@gold nanoalloys/nitrogen and sulphur-functionalized multiple graphene aerogel for electrochemical detection of dopamine

Aerogel-Based Biomaterials for Biomedical Applications: From Fabrication Methods to Disease-Targeting Applications

Aerogel-based biomaterials are increasingly being considered for biomedical applications due to their unique properties such as high porosity, hierarchical porous network, and large specific pore surface area. Depending on the pore size of the aerogel, biological effects such as cell adhesion, fluid absorption, oxygen permeability, and metabolite exchange can be altered. Based on the diverse potential of aerogels in biomedical applications, this paper provides a comprehensive review of fabrication processes including sol-gel, aging, drying, and self-assembly along with the materials that can be used to form aerogels. In addition to the technology utilizing aerogel itself, it also provides insight into the applicability of aerogel based on additive manufacturing technology. To this end, how microfluidic-based technologies and 3D printing can be combined with aerogel-based materials for biomedical applications is discussed. Furthermore, previously reported examples of aerogels for regenerative medicine and biomedical applications are thoroughly reviewed. A wide range of applications with aerogels including wound healing, drug delivery, tissue engineering, and diagnostics are demonstrated. Finally, the prospects for aerogel-based biomedical applications are presented. The understanding of the fabrication, modification, and applicability of aerogels through this study is expected to shed light on the biomedical utilization of aerogels.

Controllable assembly of three-dimensional porous graphene-Au dual aerogels and its application for high-efficient bioelectrocatalytic O2 reduction

Aerogels derived from the colloidal nanoparticles featured with hierarchical interconnected pore-rich networks guarantee their great potentials in various applications. Herein, the controllable assembly of three-dimensional aerogels based on Au nanoparticles (Au NPs) and reduced graphene oxide (rGO) nanosheets as building blocks via a bottom-up approach have been systematically clarified. The difference of building blocks and their assembly sequence were crucially to the final aerogel morphologies and electrochemical properties. Specifically, the highly porous graphene-gold dual aerogels (rGO-Au DAGs) with interconnected rGO nanosheets and Au nanowires showed high conductivity, large surface area and good biocompatibility. Thus, it was employed as an excellent matrix to immobilize enzyme for high-efficient bioelectrocatalysis. Taking bilirubin oxidase as an example, a more positive on-set potential (0.60 V) and a larger catalytic current density (0.77 mA cm^-2@0.40 V) than those of other rGO-Au assemblies were achieved for direct bioelectrocatalytic O₂ reduction. This study will provide an efficient strategy for unique dual-structural aerogels design and shed light to develop new functional materials for bioelectrocatalytic applications such as biosensors and biofuel cells.

Electrochemical Biosensors in the Diagnosis of Acute and Chronic Leukemias

Until now, morphological assessment with an optical or electronic microscope, fluorescence in situ hybridization, DNA sequencing, flow cytometry, polymerase chain reactions, and immunohistochemistry have been employed for leukemia identification. Nevertheless, despite their numerous different vantages, it is difficult to recognize leukemic cells correctly. Recently, the electrochemical evaluation with a nano-sensing interface seems an attractive alternative. Electrochemical biosensors measure the modification in the electrical characteristics of the nano-sensing interface, which is modified by the contact between a biological recognition element and the analyte objective. The implementation of nanosensors is founded not on single nanomaterials but rather on compilating these components efficiently. Biosensors able to identify the molecules of deoxyribonucleic acid are defined as DNA biosensors. Our review aimed to evaluate the literature on the possible use of electrochemical biosensors for identifying hematological neoplasms such as acute promyelocytic leukemia, acute lymphoblastic leukemia, and chronic myeloid leukemia. In particular, we focus our attention on using DNA electrochemical biosensors to evaluate leukemias.

Carbon-based aerogels for biomedical sensing: Advances toward designing the ideal sensor

Carbon based aerogels are special solid-state materials comprised of interconnected networks of 3D nanostructures with high amount of air-filled nanoporous. They expand the structural properties along with physicochemical characteristics of nanoscale construction blocks to macroscale, and incorporate distinctive attributes of aerogels, like large surface area, high porosity, and low density, with particular features of the different constituents. These features impart aerogels with rapid response signal, high selectivity, and ultra-sensitivity for sensing diverse targets in biomedical media. This has prompted researchers to develop a variety of aerogel-based sensors with encouraging achievements. Hence, this work outlines sensing applications of aerogel-based sensors with a comprehensive overview on the carbon aerogel hybrid materials and their analytical performances. Authors tried to list advantages and limitations of the developed approach and introduced more potent research for possible devices designing. We also point out some challenges and future perspectives related to the improvement of high-efficiency aerogel-based sensors.

Graphene and Carbon Nanotube-based Electrochemical Sensing Platforms for Dopamine

Dopamine (DA) is an important neurotransmitter, which is created and released from the central nervous system. It plays a crucial role in human activities, like cognition, emotions, and response to anything. Maladjustment of DA in human blood serum results in different neural diseases, like Parkinson's and Schizophrenia. Consequently, researchers have started working on DA detection in blood serum, which is undoubtedly a hot research area. Electrochemical sensing techniques are more promising to detect DA in real samples. However, utilizing conventional electrodes for selective determination of DA encounters numerous problems due to the coexistence of other materials, such as uric acid and ascorbic acid, which have an oxidation potential close to DA. To overcome such problems, researchers have put their focus on the modification of bare electrodes. The aim of this review is to present recent advances in modifications of most used bare electrodes with carbonaceous materials, especially graphene, its derivatives, and carbon nanotubes, for electrochemical detection of DA. A brief discussion about the mechanistic phenomena at the electrode interface has also been included in this review.

β-Cyclodextrin functionalized 3D reduced graphene oxide composite-based electrochemical sensor for the sensitive detection of dopamine

A three-dimensional reduced graphene oxide nanomaterial with β-cyclodextrin modified glassy carbon electrode (3D-rGO/β-CD/GCE) was constructed and used to detect the electrochemical behavior of dopamine (DA). The nanocomposite materials were characterized by scanning electron microscopy (SEM), infrared spectrometry (FT-IR), Raman spectrogram and thermogravimetric analysis (TGA), which showed that β-CD was well modified on 3D graphene with a porous structure. The electrochemical properties of different modified electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), proving the highest electron transfer rate of the 3D-rGO/β-CD modified electrode. The experimental conditions such as scan rate, pH, enrichment time and layer thickness were optimized. Under the best experimental conditions, DA was detected by differential pulse voltammetry (DPV) by 3D-rGO/β-CD/GCE with excellent electrocatalytic ability and satisfactory recognition ability, resulting in a wide linear range of 0.5-100 μM and a low detection limit (LOD) of 0.013 μM. The modified electrode based on 3D-rGO/β-CD nanocomposites is promising in the field of electrochemical sensors due to its high sensitivity and other excellent properties.

Electrochemical detection of carbendazim with mulberry fruit-like gold nanocrystal/multiple graphene aerogel and DNA cycle amplification

An aptasensor for electrochemical detection of carbendazim is reported with mulberry fruit-like gold nanocrystal (MF-Au)/multiple graphene aerogel (MGA) and DNA cycle amplification. HAuCl₄ was reduced by ascorbic acid in a CTAC solution containing KBr and KI and formed trioctahedron gold nanocrystal. The gold nanocrystal underwent structural evolution under enantioselective direction of l-cysteine. The resulting MF-Au shows a mulberry fruit-like nanostructure composed of gold nanocrystals of about 200 nm as the core and many irregular gold nanoparticles of about 30 nm as the shell. The exposure of high-index facets improves the catalytic activity of MF-Au. MF-Au/MGA was used for the construction of an aptasensor for electrochemical detection of carbendazim. The aptamer hybridizes with assistant strand DNA to form duplex DNA. Carbendazim binds with the formed duplex DNA to release assistant strand DNA, triggering one three-cascade DNA cycle. The utilization of a DNA cycle allows one carbendazim molecule to bring many methylene blue–labeled DNA fragments to the electrode surface. This promotes significant signal amplification due to the redox reaction of methylene blue. The detection signal is further enhanced by the catalysis of MF-Au and MGA towards the redox of methylene blue. A differential pulse voltammetric signal, best measured at − 0.32 V vs. Ag/AgCl, increases linearly with the carbendazim concentration ranging from 1.0 × 10⁻¹⁶ to 1.0 × 10⁻¹¹ M with a detection limit of 4.4 × 10⁻¹⁷ M. The method provides ultrahigh sensitivity and selectivity and was successfully applied to the electrochemical detection of carbendazim in cucumber.

Ultrafine Bi-Sn nanoparticles decorated on carbon aerogels for electrochemical simultaneous determination of dopamine (neurotransmitter) and clozapine (antipsychotic drug)

This present study describes the synthesis of ultrafine Bi-Sn nanoparticles decorated on carbon aerogels (Bi-Sn NP/CAG) as a nanocomposite for the electrochemical simultaneous determination of dopamine (DA) and clozapine (CLZ). The typical characterization techniques, such as XRD, Raman, BET, FT-IR, TGA, XPS, and FE-SEM/TEM, showed useful insights into the crystal phase and morphology of Bi-Sn NP/CAG. Integrated Bi-Sn NP/CAG built into a cost-effective screen printed carbon electrode (SPCE) offers a high electrochemical surface area (ECSA) compared to unmodified, Bi-Sn, and CAG/SPCEs, such that it favourably allowed the binding of DA and CLZ molecules onto the surface at the Bi-Sn/CAG, which was demonstrated by cyclic and differential pulse voltammetry techniques. As a result, the DA and CLZ sensing exhibited low detection limits (DL, 4.6 and 97.6 nM (S/N = 3)), and sensitivity (3.402 and 0.4 μA μM-1 cm-2) over a wide linear range (0.02-97.59 and 0.5-2092 μM), respectively. To go a step further, the Bi-Sn NP/CAG/SPCE was applied for the simultaneous determination of DA and CLZ which featured lower DL (23.1 and 31.3 nM (S/N = 3)), and sensitivity (0.4979 and 0.04 μA μM-1 cm-2) over a wide linear range (2-182 and 10-910 μM), respectively. The selectivity for DA and CLZ in the presence of a 10-fold concentration of their potentially interfering active species was demonstrated. Finally, this sensing methodology enables the rapid electrochemical determination of the amount of DA and CLZ in a rat brain region serum sample with successful recovery outcomes.

Electrochemical biosensor for detection of MON89788 gene fragments with spiny trisoctahedron gold nanocrystal and target DNA recycling amplification

The shape-controlled synthesis of gold nanocrystals via shape induction of hexadecyltrimethylammonium chloride, potassium bromide, and potassium iodide and enantioselective direction of L-cysteine is reported. The resulting gold nanocrystals (STO-Au) offer spiny trisoctahedron nanostructures with good monodispersity and enhanced exposed high-index facets and high catalytic activity. Construction of the electrochemical sensing platform for MON89788 gene involves the modification of STO-Au, thionine (Thi), and labeled bipedal DNA probe 1 or 2 (P1 or P2) for target DNA-induced recycling amplification. In the detection, two surface DNA probes were immobilized on gold electrode via the Au-S bond. Then, hairpin DNA 1 (H1), Thi-STO-Au-P1, and Thi-STO-Au-P2 self-assemble into two-dimensional DNA nanopores (DNPs) on the electrode surface. Target DNA hybridizes with hairpin DNA 2 (H2) to open hairpin structure of H2. The opened H2 binds with H1 in the DNPs to release Thi-STO-Au-P1, Thi-STO-Au-P2, and target DNA by toehold-mediated strand-displacement. The utilization of target DNA-induced recycling allows one target DNA to release 2N STO-Au-labeled DNA strands, promoting significant signal amplification. The detection signal is further enhanced by the catalyzed redox reaction of Thi with STO-Au. The differential pulse voltammetric signal, best measured at - 0.18 V vs. Ag/AgCl, decreases linearly with increasing concentration of MON89788 in the range 0.02-8 × 104 fM, and the detection limit is 0.0048 fM (S/N = 3). The proposed method was successfully applied for electrochemical detection of MON89788 gene fragments in the PCR products from genetically modified soybean. Graphical Abstract We develop l-cysteine controlled synthesis of spiny trisoctahedron gold nanocrystals with good monodispersity and highly exposed high-index facets. The architecture achieves to ultrahigh catalytic activity. The electrochemical biosensor based on gold nanocrystals and target DNA recycling amplification provides advantage of sensitivity, repeatability, and regeneration-free.

N-doped Cu-MOFs for efficient electrochemical determination of dopamine and sulfanilamide

Fast and efficient tracking of micropollutants in aquatic environment by developing novel electrode materials is of great significance. Herein, a polyvinylpyrrolidone (PVP) assisted strategy is applied for synthesis of nitrogen doped Cu MOFs (N-Cu-MOF) for micropollutants electrochemical detection. The designed N-Cu-MOFs possess uniform octahedral shape with large surface area (1184 m² g^-1) and an average size of roughly 450 nm, exhibiting the excellent electroanalytical capability for the detection of multipollutants. In the case of dopamine (DA) and sulfonamides (SA) as typical microcontaminants, the designed N-Cu-MOFs exhibited wide linear ranges of 0.50 nM-1.78 mM and low detection limit (LOD, 0.15 nM, S/N = 3) for the determination of DA, as well as a linear range of 0.01-58.3 μM and LOD (0.003 μM, S/N = 3) for monitoring SA. The improved performance is attributed to the heteroatom introduction and good dispersion stability of N-Cu-MOF with PVP-decorated. The good electroanalytical ability of N-Cu-MOF for detection of DA and SA can provide a guide to efficient and rapid monitor other micropollutants and construct novel electrochemical sensors.

Lateral flow assay using aptamer-based sensing for on-site detection of dopamine in urine

A lateral flow assay using DNA aptamer-based sensing for the detection of dopamine in urine is reported. Dopamine duplex aptamers (hybridized sensor with capture probe) are conjugated to 40-nm Au nanoparticles (AuNPs) with 20T linkers. The detection method is based on the dissociation of the duplex aptamer in the presence of dopamine, with the sensor part undergoing conformational changes and being released from the capture part. Hybridization between the complementary DNA in the test line and the conjugated AuNP-capture DNA produces a red band, whose intensity is related to the dopamine concentration. The minimum detectable concentration obtained by ImageJ analysis was <10 ng/mL (65.2 nM), while the visual limit of detection is estimated to be ~50 ng/mL (normal range of dopamine in urine of 52-480 ng/mL or 0.3-3.13 μM). No cross reactivity to other stress biomarkers in urine was confirmed. These results indicate that this robust and user-friendly point-of-care biosensor has significant potential for providing a cost-effective alternative for dopamine detection in urine.

Versatile Aerogels for Sensors

Aerogels are unique solid-state materials composed of interconnected 3D solid networks and a large number of air-filled pores. They extend the structural characteristics as well as physicochemical properties of nanoscale building blocks to macroscale, and integrate typical characteristics of aerogels, such as high porosity, large surface area, and low density, with specific properties of the various constituents. These features endow aerogels with high sensitivity, high selectivity, and fast response and recovery for sensing materials in sensors such as gas sensors, biosensors and strain and pressure sensors, among others. Considerable research efforts in recent years have been devoted to the development of aerogel-based sensors and encouraging accomplishments have been achieved. Herein, groundbreaking advances in the preparation, classification, and physicochemical properties of aerogels and their sensing applications are presented. Moreover, the current challenges and some perspectives for the development of high-performance aerogel-based sensors are summarized.

A core-shell molybdenum nanoparticles entrapped f-MWCNTs hybrid nanostructured material based non-enzymatic biosensor for electrochemical detection of dopamine neurotransmitter in biological samples

Dopamine (DA) is a critical neurotransmitter and has been known to be liable for several neurological diseases. Hence, its sensitive and selective detection is essential for the early diagnosis of diseases related to abnormal levels of DA. In this study, we reported novel molybdenum nanoparticles self-supported functionalized multiwalled carbon nanotubes (Mo NPs@f-MWCNTs) based core-shell hybrid nanomaterial with an average diameter of 40–45 nm was found to be the best for electrochemical DA detection. The Mo NPs@f-MWCNTs hybrid material possesses tremendous superiority in the DA sensing is mainly due to the large surface area and numerous electroactive sites. The morphological and structural characteristics of the as-synthesized hybrid nanomaterial were examined by XRD, Raman, FE-SEM, HR-TEM, EDX. The electrochemical characteristics and catalytic behavior of the as-prepared Mo NPs@f-MWCNTs modified screen-printed carbon electrode for the determination of DA were systematically investigated via electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The results demonstrate that the developed DA biosensor exhibit a low detection limit of 1.26 nM, excellent linear response of 0.01 µM to 1609 µM with good sensitivity of 4.925 µA µM⁻¹ cm⁻². We proposed outstanding appreciable stability sensor was expressed to the real-time detection of DA in the real sample analysis of rat brain, human blood serum, and DA hydrochloride injection.

Electroanalysis of Catecholamine Drugs using Graphene Modified Electrodes

Background:

Catecholamine drugs are a family of electroactive pharmaceutics, which are widely analyzed through electrochemical methods. However, for low level online determination and monitoring of these compounds, which is very important for clinical and biological studies, modified electrodes having high signal to noise ratios are needed. Numerous materials including nanomaterials have been widely used as electrode modifies for these families during the years. Among them, graphene and its family, due to their remarkable properties in electrochemistry, were extensively used in modification of electrochemical sensors.

Objective:

In this review, working electrodes which have been modified with graphene and its derivatives and applied for electroanalyses of some important catecholamine drugs are considered.

Fabrication of hexahedral Au-Pd/graphene nanocomposites biosensor and its application in cancer cell H2O2 detection

Currently, real time monitoring of chemical substances in vivo and in vitro has gained enormous attraction, and many researches reports have been focused on the design and construction of high-performance biosensor devices. In this work, a high-performance sensor was constructed by taking advantage of the excellent electrochemical activity and high-index facets of Au-Pd nanocubes and the large surface of rGO. Glassy carbon electrodes (GCEs) were modified by both Au-Pd nanocubes and rGO nanocomposites via physical adsorption. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were utilized to characterize and identify this unique nanostructure. These three-dimensional nanocomposites possess a high electroactive surface area and an excellent electrical conductivity, which resulted in favorable electroreduction activity toward H₂O₂ with a lower detection limit of 4 nM, a wide linear range from 0.005 μM to 3.5 mM and a rapid response time. Furthermore, the proposed sensor exhibited desirable performance in the detection of endogenous H₂O₂ in human serum samples and real-time monitoring of H₂O₂ released from living breast cancer cell lines. In summary, this work not only provides a potential method to construct a physiological and pathological H₂O₂ biosensor but also makes a valuable contribution to the early diagnosis of different cancers.

A sensitive electrochemical sensor for bisphenol A on the basis of the AuPd incorporated carboxylic multi-walled carbon nanotubes

A sensitive electrochemical sensor for BPA based on the AuPd incorporated carboxylic multi-walled carbon nanotubes (MWCNT) with synergetic amplified current signal was developed, where MWCNT was used as supporter to improve electron transport and poly (diallyldimethylammonium chloride) (PDDA) was used as dispersant for MWCNT and overcome the intrinsic van der Waals interactions between MWCNT and further increase metal NPs loading. The prepared MWCNT-PDDA-AuPd showed enhanced electrocatalytic performance toward BPA, which is better than those of homologous monometallic counterparts and MWCNT-PDDA though the content of AuPd is really low. The peak currents of BPA increased with BPA concentration in linear range of 0.18-18 μM and the detection limit of 60 nM. The sensor showed high sensitivity, good stability, repeatability and can be used to detect BPA in milk and water samples with good performance, which demonstrate that MWCNTs-PDDA-AuPd nanocomposite may be an attractive material in applications of environmental and food analysis.

Facile synthesis of highly ordered mesoporous Fe3O4 with ultrasensitive detection of dopamine

Dopamine (DA) detection is significant for the prevention of unfavorable neuronal illness. However, the detection of DA with low concentration still face tremendous challenges. In this study, highly ordered mesoporous Fe₃O₄ materials were synthesized as a biosensor by using mesoporous silica KIT-6 with different aging temperature as hard template. The ordered mesoporous Fe₃O₄ with high surface area modified glassy carbon electrode shows the high sensitivity for detecting DA. Fe₃O₄-40 mesoporous material modified electrode has the highest catalytic activity to DA with a sensitivity of 0.053 nA nM^-1 and a detection limit of 0.8 nM (S/N = 3). The results indicating that the mesoporous Fe₃O₄ material modified electrode exhibits high sensitivity to determine DA at low levels, which can be used for DA real-time monitoring in neutral biological media.

Selective Determination of Levodopa in the Presence of Vitamin B6, Theophylline and Guaifenesin Using a Glassy Carbon Electrode Modified with a Composite of Hematoxylin and Graphene/ZnO

An electrode has been developed based on using a composite of hematoxylin/graphene/ZnO nanocomposite to modify a glassy carbon electrode (GCE). The electrode (HGGCE) was tested and found to be applicable for the voltammetric analysis of levodopa in the presence of vitamin B₆, theophylline and guaifenesin using a 0.1 M phosphate buffer solution (PBS) pH 7 as the solvent. The HGGCE was used as the working electrode in cyclic voltammetry (CV) and square wave voltammetry (SWV) studies on the electrochemical behavior of levodopa at its surface. The results showed a dramatic enhancement in the oxidation current of levodopa and a shift in its oxidation potential towards more negative potentials as opposed to identical tests using bare GCE as the working electrode. The studies showed that the increase in the oxidation current has two linear profiles in two concentration ranges of 0.05 - 90.0 and 90.0 - 1000.0 μM. The detection limit of SWV analysis using the modified electrode was determined to be 0.03 μM (S/N = 3). Further advantages of the methods based on HGGCE include the simple modification procedure of the electrode, as well as its excellent sensitivity and reproducibility. The modified electrode was eventually found to be applicable to the determination of mixtures of levodopa, vitamin B₆, theophylline and guaifenesin in real samples.

Electrochemical sensor for detection of cancer cell based on folic acid and octadecylamine-functionalized graphene aerogel microspheres

Early diagnosis of cancers is critical for prevention of metastasis and early treatment. The study reports an electrochemical sensor for detection of cancer cell based on folic acid (FA) and octadecylamine (OA)-functionalized graphene aerogel microspheres (FA-GAM-OA). Citric acid was mixed with FA and OA and heated at 180 °C for 4 h to form FA and OA-functionalized graphene oxide. The graphene oxide was employed as solid particle surfactant for stabilizing toluene-in-water emulsion. The graphene oxide sheets in the emulsion were self-assembled into graphene oxide gel microspheres on the water/toluene interfaces. Followed by free drying and reduction in H₂ at 400 °C for 5 h. The resulted FA-GAM-OA shows a sphere-like structure with an average diameter of 1.2 µm, the rich of open-pores and folic acid groups. Small particle size and good hydrophilicity make FA-GAM-OA can be dispersed in water for sensor preparation. The small size of graphene sheets and their self-assembly avoid a serious agglomeration of graphene sheets. The FA-GAM-OA offers a large surface area (1723.6 m² g^-1) and high electronic conductivity (2978.2 S m^-1). The covalent linkage and ordered alignment of folic acid groups at FA-GAM-OA surface achieve to specific cancer cell capture with high capture efficiency. The electrochemical sensor based on FA-GAM-OA exhibits extremely good analytical performances in detection of liver cancer cells with a linear range of 5-10⁵ cell mL^-1 giving a low detection limit of 5 cells mL^-1 (S/N = 3). The method was successfully applied to electrochemical detection of liver cancer cells in whole blood.

Trimetallic AuPtPd nanocomposites platform on graphene: Applied to electrochemical detection and breast cancer diagnosis

Recently, great efforts have been made to use biosensors for the early diagnosis of cancer. Specifically, using a biomarker to detect H₂O₂ in physiological conditions is of great significance for understanding the signal transduction pathways and achieving early cancer diagnosis. In this work, we report an innovative H₂O₂ sensor that was fabricated by trimetallic AuPtPd nanocomposites platform on reduced graphene oxide (rGO) nanosheets with the modification of the rGO and trimetallic AuPtPd nanoparticles on a glassy carbon electrode (GCE) by physical adsorption. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were utilized to characterize and identify these unique nanocomposites. In addition, the electrochemical properties of the proposed sensor were evaluated by cyclic voltammetry and chronoamperometry. Electrochemical research has demonstrated that the AuPtPd/rGO-modified GCE showed excellent electrocatalytic activity towards the reduction of H₂O₂, including a wider linear range from 0.005 μM to 6.5 mM, a low detection limit of 2 nM, good selectivity and acceptable repeatability. Moreover, the sensor can monitor the release of H₂O₂ release from living cancer cells. Therefore, this study not only improves simplicity, sensitivity and quantitatively for detection H₂O₂ in cells at nM level but also provides a foundation for the biological and biomedical applications such as the early diagnosis of cancer.

Study of the interactions of influencing parameters on electrocatalytic determination of dopamine by a carbon paste electrode based on Fe(ii)–clinoptilolite nanoparticles

In this study, after ion exchange of clinoptilolite nanoparticles (CLN) in Fe(ii) solution, the prepared Fe(ii)–CLN was used for the modification of a carbon paste electrode (CPE).

Au-Pt bimetallic nanoparticles decorated on sulfonated nitrogen sulfur co-doped graphene for simultaneous determination of dopamine and uric acid

In this work, a novel nanohybrid (AuPtNPs/S-NS-GR) of well-defined Au-Pt bimetallic nanoparticles (Au-PtNPs) decorated on sulfonated nitrogen sulfur co-doped graphene (S-NS-GR) was developed. Firstly, nitrogen sulfur co-doped graphene (NS-GR) was synthesized by one-step thermal annealing method. Secondly, phenyl SO₃H- group was introduced onto the surface of NS-GR via diazotization reaction, which could provide more binding sites for the formation of metal nanoparticles. Finally, Au-Pt bimetallic nanoparticles were anchored on the surface of S-NS-GR by using electrochemical deposition. The prepared material was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and electrochemical impedance spectra (EIS). In addition, the electrocatalytic activity towards dopamine (DA) and uric acid (UA) was systematically studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Under optimum conditions, the linear ranges for the detection of DA and UA were 1.0×10^-8 - 4.0×10^-4 M and 1.0×10^-6 - 1.0×10^-3 M with the limits of detection (LOD, S/N = 3) of 0.006μM and 0.038μM, respectively. Furthermore, the modified electrode was applied to real sample analysis.