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An electrochemical sensor capable of detecting glutathione (GSH) with high sensitivity and selectivity was developed based on the unique novel electroactive silver-based metal organic framework (Ag-MOF). The Ag-MOF obtained by silver nitrate and 1,3,5-benzoic acid (H 3 BTC) was thoroughly characterized and was modified onto the electrode via facile drop-casting method. The electrochemical response of GSH on the Ag-MOF modified electrode showed a significant reduction in the current signal because the Ag-GSH complex had stronger specific affinity than Ag-H 3 BTC and resulted in the collapse of the Ag-MOF. This sensor demonstrated an extensive linear dynamic range of 0.1 nM-1 µM, along with the low detection limit of 0.018 nM. Additionally, it exhibited good reproducibility, stability, and resistance to interfering compounds. The Ag-MOF modified electrode demonstrated superior performance attributed to its rapid electron transfer rate, outstanding electrochemical redox activity, and specific recognition/competitive reaction. These factors improved both sensitivity and selectivity. The high anti-interference ability allowed for the selective detection of GSH in intricate surroundings. In the real sample testing, the RSD was lower than 3.1% and the recovery was between 98.1 and 103%. This research highlights the potential of Ag-MOFs in developing electrochemical sensors and their promising applications in determining GSH for food screening and early disease diagnosis., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Aeromonas salmonicida (A. salmonicida) is an important opportunistic pathogen to aquatic animals that causes severe economic losses to aquaculture, which makes its rapid detection and prevention are critical. In this work, a single-stranded DNA (ssDNA) aptamer (A.s-2) with high specificity to the bacteria was selected by Systematic Evolution of Ligands by Exponential Enrichment (SELEX). The selected aptamer was confirmed with high binding ability and specificity (K d  = 32 ± 8 nM). Furthermore, a novel dual-model colorimetric and ratiometric fluorescent aptasensor was constructed based on the G-quadruplex-modified aptamer and g-C 3 N 4 for sensitive, reliable, and visual detection of the diseased bacteria in fishes. The quantitative detection was achieved in the linear range of 10 3 -10 7  CFU mL -1 with a detection limit of 1.9 × 10 2  CFU mL -1 . Meanwhile, the semi-quantitative detection can also be performed visually through fluorescence or color changes of the solution, which is suitable for the early diagnosis of pathogen infection in grassroots farms. Moreover, the developed aptasensor was successfully applied to detect A. salmonicida infection in zebrafish samples with satisfactory results. This work provides a framework for the rapid detection of pathogens in aquaculture, indicating its great prospects in food safety., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Chemical biosensing techniques are essential for food analysis and disease diagnosis. Nanomaterials with redox activity show great potential in electrochemical analysis, acting as signal labels or signal amplification unit, which can reflect the targets concentration in foods and biological samples. Here, an ultra-sensitive dual-signal intrinsic self-calibration electrochemical platform for GSH was firstly fabricated based on the novel electroactive nanomaterial of ferrocene-functionalized copper metal-organic framework (Fc-Cu-MOF). Due to the solid-state electrochemical property of cuprous chloride (CuCl), a sharp characteristic peak with an increased signal appears with the coexistence of chloride ions in solution. The stronger specific affinity between Cu + and GSH than that of Cu + and Cl - triggers a "crowding effect" that causes the current signal of CuCl decrease greatly. Meanwhile, the peak current of ferrocene keeps unchanged as an internal reference. Based on the ratio of the peak current variation (ΔI Cu /ΔI Fc ) as the signal output, Fc-Cu-MOF modified electrode showed wider linear range in 0.1 nM -1 μM for GSH with the detection limit as low as 0.025 nM. And the sensor was successfully applied in the determination of GSH with excellent recoveries in various real samples such as food and serum samples, providing good prospect in application of bioanalysis and food screening., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

An electrochemiluminescence (ECL) sensor provides a sensitive and convenient method for early diagnosis of diseases; however, it is still a challenge to develop simple and sensitive sensing platforms based on efficient ECL signals and luminophore groups. Porphyrin-based metal-organic frameworks (MOFs) show great potential in ECL sensing; however, the mechanism and structure-activity relationship, as well as application, are rarely reported. Herein, hydrothermal reactions obtained porphyrin Zr-MOFs (PCN-222) with different specific surface areas, pore sizes, structures, and surface charge states by tuning the reaction time were developed, which served both as the ECL luminophore, coreaction promoter for S 2 O 8 2- , and a connection in the ECL immunoassay. By progressively controlling the condition of the hydrothermal reaction, PCN-222 with large surface area-abundant micropores can be obtained, which has good conductivity and positively charged surfaces, obtaining excellent ECL performance. The ECL performance and the enhancement mechanism were investigated in detail. Using PCN-222-6h with the best ECL intensity as the immobilization matrix for the aptamer, a highly sensitive and selective assay for thrombin was developed. The decrease of the ECL signal was logarithmically linear with the concentration of thrombin in the range from 50 fg mL -1 to 100 pg mL -1 with a low detection limit of 2.48 fg/mL. This proposed strategy provides a brand new approach for tuning of the structures of MOFs as effective ECL signal probes, thus providing wider possibilities for effective ECL immunoassays in the detection of other biomarkers in diagnosis of diseases.

A sensitive electrogenerated chemiluminescence (ECL) biosensor for glucose was developed based on in situ growth of TiO 2 nanowires on Ti 3 C 2 MXenes (TiO 2 -Ti 3 C 2 ) as the nanoplatform. Via tuning the alkaline oxidation time, different amount of TiO 2 nanowires can be found on MXenes. An ECL biosensor for glucose was constructed by covalent immobilization of glucose oxidase (GODx) on the glycine functional TiO 2 -Ti 3 C 2 surface, with the ECL signal depending on the in-situ formation of H 2 O 2 via the specifically catalysis of glucose by GODx, resulting in the apparent increase of ECL signal. The TiO 2 -Ti 3 C 2 can also act as the catalyst for the oxidation of H 2 O 2 into O 2 to enhance the ECL of luminol. Based on this strategy, a highly sensitive ECL biosensor for glucose was obtained in wide concentration range of 20 nM-12 mM with a low detection limit of 1.2 nM (S/N = 3). The synergistic effects of large surface area, excellent conductivity, and high catalytic activity of the TiO 2 -Ti 3 C 2 make the sensor highly sensitive toward glucose; the specific enzyme catalysis reaction promises excellent selectivity of the ECL sensor. The proposed biosensor has been employed to detect glucose in human serum, fruits, and sweat samples with excellent performance, providing a universal approach for glucose in various samples, which shows great prospect in clinical diagnostics and wearable sensors., (Copyright © 2021 Elsevier B.V. All rights reserved.)

It remains an unanswered question whether the flux of K + and H + in lysosomes are correlated due to difficulties in simultaneously imaging these two ions. This question is of great value for understanding lysosomal acidification. Herein, we designed DNA quadruplex and triplex based luminescent nanosensors that can, respectively monitor K + and pH in lysosomal lumen. Each sensor contained an upconversion nanoparticle luminophore and a gold nanoparticle quencher, producing green and blue luminescence signals for K + and H + , respectively. The sensors were tested in buffers showing dynamic ranges of 5 to 200 mM K + and pH 5.0 to 8.2. Co-imaging using these two sensors in cells indicated that the influx of H + was accompanied with the efflux of K + , solving this long-standing question of the lysosomal biochemistry., (© 2020 Wiley-VCH GmbH.)

Transition metal carbides/carbonitrides (MXenes), as one of the emerging two-dimensional (2D) materials, have attracted tremendous attention in recent years. Developing MXenes based biosensing platforms is fantastic for the applications of diagnostic and biological research. In this regard, it is pressing need for the synthesis, exfoliation, intercalation, and tuning the surface of MXenes. Compared with the electrochemical implements of MXenes, the optical biosensing applications are in the earlier stage. In this review, the research significance and types of MXenes are introduced followed by the recent progress of synthesis and functionalization of two kinds of titanium carbide (Ti 3 C 2 ) MXenes including nanosheets (NSs) and quantum dots (QDs). In addition, the special properties and applications in optical biosensing platforms including photoluminescence, electrogenerated chemiluminescence (ECL), surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS), photoelectrochemical (PEC), colorimetric and photothermal sensors are highlighted. Finally, the possible remaining challenges and future trends of Ti 3 C 2 MXenes in optical biosensing platforms are outlined., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Herein, a novel electrogenerated chemiluminescence (ECL) method for highly sensitive kinase activity and inhibitors screening was developed based on graphitic carbon nitride nanosheet (g-C 3 N 4 ) nanoparticle embellished titanium carbide (Ti 3 C 2 ) MXene nanosheets, integrating the highly efficient recognition and signal amplification activity. In this strategy, kemptide was first immobilized onto a gold electrode, and it was phosphorylated by the protein kinase A which was used as a model. The g-C 3 N 4 -MXene probe can adsorb explicitly onto the electrode based on chelation between the phosphate group and Ti defect sites enriched in MXenes. Besides the abundant active sites on MXene for the highly efficient binding with phosphate groups, the Ti 3 C 2 MXene not only provides a unique conductive platform to accommodate more g-C 3 N 4 nanoparticles but also facilitates the electron transfer on the electrode interface and suppresses the passivation of g-C 3 N 4 that explores their highly efficient ECL emission with high stability. The obtained ECL signals were closely related to the kinase activity and can be applied for protein kinase A (PKA) activity detection. Under the optimal conditions, the proposed ECL biosensor provided a quantitative readout to PKA concentration in the range 0.015-40 U mL -1 with the detection limit of 1.0 mU mL -1 . The ECL biosensor was also successfully applied to monitor drug-triggered kinase activation and quantitative analysis of the kinase inhibitors in MCF-7 cell lysates. This work shows that the proposed ECL biosensor has the potential to be a powerful tool for PKA study and clinical diagnostics as well as the discovery of new targeted drugs.

In recent years, germanium nanoparticles (Ge NPs) have attracted considerable research attention because of its excellent electrical and optical properties. However, it is mainly applied in the field of solar cells, photodetectors and photothermal therapy. Actually, Ge NPs have the advantages of low toxicity and excellent biocompatibility, which means that they have great potential in biosensing applications. However, there are few related reports. In this paper, we discovered that Ge NPs have the intrinsic peroxidase-like catalytic activity and can significantly accelerate the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H 2 O 2 for the first time. Compared with natural enzyme (horseradish peroxidase, HRP), Ge NPs maintain higher catalytic stability after treatment at different pH, temperature and ionic strength. Furthermore, a Ge NPs-based colorimetric platform was established for the first time to detect biomolecules with favourable sensitivity and selectivity, such as uric acid, glucose and choline. This work finds the new property of Ge NPs and extends its application in biosensing., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Exosomes, as novel noninvasive biomarkers for disease prediction and diagnosis, have shown fascinating prospects in monitoring cancer-linked public health issues. Herein, a unique Cy3 labeled CD63 aptamer (Cy3-CD63 aptamer)/Ti 3 C 2 MXenes nanocomplex was constructed as a self-standard ratiometric fluorescence resonance energy transfer (FRET) nanoprobe for quantitative detection of exosomes. The Cy3-CD63 aptamer can be selectively adsorbed onto the Ti 3 C 2 MXene nanosheets by hydrogen bond and metal chelate interaction between the aptamer and MXenes, and the fluorescence signal from Cy3-CD63 aptamer was quenched quickly owing to the FRET between the Cy3 and MXenes. The fluorescence of Cy3 greatly recovered after the addition of the exosomes which can specifically combine with the aptamer and release from the surface of Ti 3 C 2 MXenes due to the high affinity between the aptamer and CD63 protein on exosome surface. Meanwhile, the self-fluorescence signal of MXenes in the whole process showed little change, which can be used as a standard reference. Based on the self-standard turn-on FRET biosensing platform the detection limit of exosome was determined as 1.4 × 10 3 particles mL -1 , which was over 1000× lower than that of conventional ELISA method. This fluorescence sensor can also be used for the identification of multiple biomarkers on the exosome surface and different kinds of exosomes, combining with the fluorescent confocal scanning microscope image. The proposed strategy not only provides a universal nanoplatform for exosomes, but also can be extensively expanded to multiple biomarkers detection, which may promise the prospect of MXenes as robust candidates in biological fields.

The selective and sensitive detection of dopamine (DA) is of great significance for the identification of schizophrenia, Huntington's disease, and Parkinson's disease from the perspective of molecular diagnostics. So far, most of DA fluorescence sensors are based on the electron transfer from the fluorescence nanomaterials to DA-quinone. However, the limited electron transfer ability of the DA-quinone affects the level of detection sensitivity of these sensors. In this work, based on the DA can reduce Ag + into AgNPs followed by oxidized to DA-quinone, we developed a novel silicon nanoparticles-based electron transfer fluorescent sensor for the detection of DA. As electron transfer acceptor, the AgNPs and DA-quinone can quench the fluorescence of silicon nanoparticles effectively through the synergistic electron transfer effect. Compared with traditional fluorescence DA sensors, the proposed synergistic electron transfer-based sensor improves the detection sensitivity to a great extent (at least 10-fold improvement). The proposed sensor shows a low detection limit of DA, which is as low as 0.1 nM under the optimal conditions. This sensor has potential applicability for the detection of DA in practical sample. This work has been demonstrated to contribute to a substantial improvement in the sensitivity of the sensors. It also gives new insight into design electron transfer-based sensors., (Copyright © 2018. Published by Elsevier B.V.)

In this paper, the colorimetric sensing of H 2 O 2 related molecules and biothiols based on etching and anti-etching strategy was firstly proposed. Ag/carbon nanocomposite (Ag/C NC) was served as the sensing nanoprobe, which was synthesized via carbon dots (C-dots) as the reductant and stabilizer. The characteristic surface plasmon resonance (SPR) absorbance of Ag nanoparticles (AgNPs) was sensitive to the amount of hydrogen peroxide (H 2 O 2 ). It exhibited strong optical responses to H 2 O 2 with the solution colour changing from yellow to nearly colourless, which is resulted from the etching of Ag by H 2 O 2 . The sensing platform was further extended to detect H 2 O 2 related molecules such as lactate in coupling with the specific catalysis oxidation of L-lactate by lactate oxidase (LOx) and formation of H 2 O 2 . It provides wide linear range for detecting H 2 O 2 in 0.1-80μM and 80-220μM with the detection limit as low as 0.03μM (S/N=3). In the presence of biothiols, the etching from the H 2 O 2 can be hampered. Other biothiols exhibit anti-etching effects well. The strategy works well in detecting of typical biothiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH). Thus, a simple colorimetric strategy for sensitive detection of H 2 O 2 and biothiols is proposed. It is believed that the colorimetric sensor based on etching and anti-etching strategy can be applied in other systems in chemical and biosensing areas., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Construction of a new multifunctional chemo/biosensing platform for small biomolecules and tumor markers is of great importance in analytical chemistry. Herein, a novel universal multifunctional nanoplatform for biomolecules and enzyme activity detection was proposed based on fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) and target-inducing enlarged gold nanoparticles (AuNPs). The reductive molecule such as H 2 O 2 can act as the reductant to reduce HAuCl 4 , which will make the Au seeds grow. The enlarged AuNPs can effectively quench the fluorescence of UCNPs owing to the good spectral overlap between the absorption band of the AuNPs and the emission band of the UCNPs. Utilizing the FRET between the UCNPs and enlarged AuNPs, good linear relationship between the fluorescence of UCNPs and the concentration of H 2 O 2 can be found. Based on this strategy, H 2 O 2 related molecules such as l-lactate, glucose, and uric acid can also be quantified. On the basis of UCNPs and PVP/HAuCl 4 , a general strategy for other reductants such as ascorbic acid (AA), dopamine (DA), or enzyme activity can be established. Therefore, the universal multifunctional nanoplatform based on UCNPs and the target-inducing in situ enlarged Au NPs will show its potential as a simple method for the detection of some life related reductive molecules, enzyme substrates, as well as enzyme activity.

A new upconversion colorimetric and ratiometric fluorescence detection method for uric acid (UA) has been designed. Yb(3+), Er(3+) and Tm(3+) co-doped NaYF4 nanoparticles (UCNPs) was synthesized. The co-doped NaYF4 nanoparticles, emit upconversion fluorescence with four typical emission peaks centered at 490nm, 557nm, 670nm and 705nm under the 980nm near-infrared (NIR) irradiation. The ZnFe2O4 magnetic nanoparticles (MNPs) possessing excellent peroxidase-like activity was prepared and used to catalyze oxidation the coupling of N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt (TOPS) and 4-amino-antipyrine (4-AAP) in the presence of H2O2 to form purple products (compound 1) which has a characteristic absorption peak located at 550nm. The upconversion fluorescence at 557nm was quenched by the compound 1 while the upconversion emission at 705nm was essentially unchanged, the fluorescence ratio ((I557/I705)0/(I557/I705)) is positively proportional to UA concentration in existence of uricase. More importantly, colorimetric signal can be easily observed and applied to directly distinguish the concentration of UA by the naked eye. Under the optimized conditions, the linear range of colorimetric and ratiometric fluorescence sensing towards UA was 0.01-1mM, the detection limits were as low as 5.79μM and 2.86μM (S/N=3), respectively. The proposed method has been successfully applied to the analysis of UA in human serum. These results indicate that the colorimetric and ratiometric fluorescence dual-readout assay method has great potential for applications in physiological and pathological diagnosis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A multivalent recognition and alkaline phosphatase (ALP)-responsive electrogenerated chemiluminescence (ECL) biosensor for cancer cell detection and in situ evaluation of cell surface glycan expression was developed on a poly(amidoamine) (PAMAM) dendrimer-conjugated, chemically reduced graphene oxide (rGO) electrode interface. In this strategy, the multivalency and high affinity of the cell-targeted aptamers on rGO provided a highly efficient cell recognition platform on the electrode. The ALP and concanavalin A (Con A) coated gold nanoparticles (Au NPs) nanoprobes allowed the ALP enzyme-catalyzed production of phenols that inhibited the ECL reaction of Ru(bpy)3(2+) on the rGO electrode interface, affording fast and highly sensitive ECL cytosensing and cell surface glycan evaluation. Combining the multivalent aptamer interface and ALP nanoprobes, the ECL cytosensor showed a detection limit of 38 CCRF-CEM cells per mL in human serum samples, broad dynamic range and excellent selectivity. In addition, the proposed biosensor provided a valuable insight into dynamic profiling of the expression of different glycans on cell surfaces, based on the carbohydrates recognized by lectins applied to the nanoprobes. This biosensor exhibits great promise in clinical diagnosis and drug screening.

A new ferrocene benzyne derivative (Fc-SAc) that contained oligo-(phenylene-ethynylene) skeleton, ferrocene and thiolate terminal groups was firstly synthesized. The hydrolysis product of Fc-SAc (Fc-SH) was immobilized onto gold nanoparticles (AuNPs) modified glass carbon electrode (GCE) as sensing element for rutin detection with high sensitivity. The new sensing strategy was proposed by using two Fc-SH modified electrodes: Fc-S/AuNPs/GCE (Electrode1) and Fc-S/AuNPs/graphene-chitosan/GCE (Electrode2). The electrochemical oxidation of rutin on Electrode2 was a diffusion-controlled process, which was different from a mass-controlled process on Electrode1. Under the optimal conditions, the peak currents of the sensors were linearly related to the concentrations of rutin. The linear responses ranges were 0.05-30 μM and 0.04-100 μM with the regression coefficients of 0.998 and 0.997 on Electrode1 and Electrode2, respectively. Electrode2 presented wider linear range, superior high sensitivity, lower detection limit and better stability on determination of rutin., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A novel and ultrasensitive sandwich-type electrochemical aptasensor has been developed for the detection of thrombin, based on dual signal-amplification using HRP and apoferritin. Core/shell Fe(3)O(4)/Au magnetic nanoparticles (AuMNPs) loading aptamer1 (Apt1) was used as recognition elements, and apoferritin dually labeled with Aptamer2 (Apt2) and HRP was used as a detection probe. Sandwich-type complex, Apt1/thrombin/Apt2-apoferritin NPs-HRP was formed by the affinity reactions between AuMNPs-Apt1, thrombin, and Apt2-apoferritin-HRP. The complex was anchored on a screen-printed carbon electrode (SPCE). Differential pulse voltammetry (DPV) was used to monitor the electrode response. The proposed aptasensor yielded a linear current response to thrombin concentrations over a broad range of 0.5-100 pM with a detection limit of 0.07 pM (S/N=3). The detection signal was amplified by using apoferritin and HRP. This nanoparticle-based aptasensor offers a new method for rapid, sensitive, selective, and inexpensive quantification of thrombin, and offers a promising potential in protein detection and disease diagnosis., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Four new conjugated oligo-phenylene-ethynylenes derivatives, N-methyl-4-(4-acetylthiophenylethynyl)-1,8-naphthalimide (1), thioacetic acid S-[4-(4-aminophenyl-ethynyl)phenyl]ester (2), 4-methylthiophenylethynylbenzenamine (3), N-methyl-4-(4-methyl-thiophenyl-ethynyl)-1,8-naphthalimide (4), were synthesized by Sonogashira and Eglinton cross-coupling reactions. The structures of the four compounds were confirmed by (1)HNMR, (13)CNMR, MS and IR and their spectral characteristics were studied by ultraviolet and visible (UV) spectroscopy as well as fluorescence spectroscopy in different medium. It was found that the fluorescence properties of compounds 2 and 3 were notably improved in aqueous solutions in the presence of β-cyclodextrin (β-CD). Spectral analysis supported the suppositions that the fluorescence intensity enhancement was due to the formation of inclusion complex with β-CD. The supramolecular interaction was investigated in detail and the reaction mechanism was provided. A salicylaldehyde determination method in aqueous medium was established based on the supramolecular complex of compound 3. Under the optimum conditions, the supramolecular complex exhibited a dynamic fluorescence response range for salicylaldehyde from 0.6 to 240×10(-6) molL(-1), with a detection limit of 1×10(-8) molL(-1)., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A new ferrocene derivative (1-[(4-amino) phenylethynyl]ferrocene, Fc-NH(2)) was synthesized for the first time. The ferrocene derivative molecule contained the phenylethynyl skeleton, ferrocene and amino groups with excellent electrochemical properties. The graphene/Fc-NH(2) nanocomposite was prepared by mixing graphene solution and Fc-NH(2) solution in one pot and the nanocomposite was utilized to construct a Nafion/graphene/Fc-NH(2) modified glassy carbon electrode (GCE). The ferrocene derivative immobilized on the graphene can enhance the charge-transport ability of the nanocomposite, stabilize the graphene and prevent the leakage of ferrocene. The detection signal of dopamine (DA) was significantly amplified on the Nafion/graphene/Fc-NH(2)/GCE. It was experimentally demonstrated that the signal enhancement results from the synergy amplification effect of graphene and the Fc-NH(2). The oxidation peak currents of DA were linearly related to the concentrations in the range of 5 × 10(-8) to 2 × 10(-4) M with the detection limit of 20 nM in the absence of uric acid (UA) and ascorbic acid (AA). In the presence of 10(-3) M AA and 10(-4) M UA, the linear response range was 1 × 10(-7) to 4 × 10(-4) M, and the detection limit was 50 nM at S/N = 3. Using the proposed Nafion/Fc-NH(2)/graphene/GCE, DA was successfully determined in real samples with the standard addition method.

A three-dimensional network PAMAM-Au nanocomposite (3D-PAMAM-Au NC) was prepared by using the first generation polyamidoamine dendrimer (G1 PAMAM) as the dispersant agent. The resultant 3D-PAMAM-Au NC was successfully used as an immobilization matrix for the construction of a reagentless mediator-free horseradish peroxidase (HRP)-based H(2)O(2) biosensor on a multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode. With the advantages of the three-dimensional network, the organic-inorganic hybrid materials dramatically facilitate the direct electron transfer of HRP, and good bioelectrocatalytic activity towards H(2)O(2) was demonstrated. Under optimum conditions, the current response of the enzyme modified electrode at -0.30 V was detected. The current response is linearly correlated to H(2)O(2) concentration within the range of 18.00 μM to 20.80 mM with a correlation coefficient of 0.9992 and a sensitivity of 377.78 μA mM(-1) cm(-2). The detection limit was down to 6.72 μM (S/N = 3). Furthermore, the biosensor exhibits some other excellent characteristics, such as high selectivity, short response time, and long-term stability. The 3D-PAMAM-Au NC has proved to be a promising biosensing platform for the construction of mediator-free biosensors, and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biofuel cells.