Surface Of Glass Carbon Electrode Research Articles

Sensitive and selective detection of Hg2+ in tap and canal water via self-enhanced ECL aptasensor based on NH2–Ru@SiO2-NGQDs

In the present study, a novel self-enhanced electrochemiluminescence (ECL) aptasensor which combined self-enhanced ECL composite as signal response element and aptamer as the specific recognition element was firstly proposed for the sensitive and selective detection of Hg2+. Innovatively, the luminophore Ru(bpy)32+-doped silica nanoparticles functionalized with 3-aminopropyltriethoxysilane (NH2–Ru@SiO2) and the co-reactant nitrogen doped graphene quantum dots (NGQDs) were bound together to form the self-enhanced ECL composite, NH2–Ru@SiO2-NGQDs, by electrostatic adsorption. Satisfactorily, high and stable luminous efficiency of NH2–Ru@SiO2-NGQDs was obtained benefited from the short electron transfer distance and low energy loss of self-enhanced-typal ECL composite. For the fabrication of the self-enhanced ECL aptasensor for Hg2+ detection, the Hg2+ aptamer, of which one end was connected to NH2–Ru@SiO2-NGQDs, and the other end was fixed on glass carbon electrode (GCE) surface through Au–S bond, was served as a bridge. Upon the addition of Hg2+, the aptamer was bent due to the formation of thymine-Hg2+-thymine (T-Hg2+-T) specific structure, which caused the self-enhanced ECL composite was close to the GCE surface. On this basis, a linearly enhanced ECL signal was acquired with the concentration of Hg2+ in the range of 5.0 × 10−11 M − 1.0 × 10−6 M with excellent selectivity, repeatability and stability in 3 min for each assay. In addition, the proposed aptasensor showed satisfying accuracy and practicability for Hg2+ analysis in tap and canal water verified by the inductively coupled plasma-mass spectrometry (ICP-MS) method.

One-step preparation of carbon quantum dots-reduced graphene oxide nanocomposite–modified glass carbon electrode for the simultaneous detection of ascorbic acid, dopamine, and uric acid

In this manuscript, carbon quantum dots-reduced graphene oxide (CQDs-rGO) nanocomposite was modified on the surface of glass carbon electrode (GCE) via an one-step co-deposition method to fabricate an effective electrochemical senor for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Due to the strong synergetic effect between CQDs and rGO, the sensor exhibited good selectivity and high catalytic activity toward AA, DA, and UA. The peak potential differences of simultaneous detection for AA-DA, DA-UA, and AA-UA were calculated as 0.147 V, 0.135 V, and 0.282 V, respectively. And the linear responses of AA, DA, and UA were found in the ranges of 0.2–0.9 mM (R2 = 0.99) and 1.4–4.2 mM (R2 = 0.99), 5–9 μM (R2 = 0.98) and 11–81 μM (R2 = 0.99), and 20–90 μM (R2 = 0.99) and 140–300 μM (R2 = 0.99), respectively. The as-prepared sensor contributed a fresh idea to the simultaneous detection of AA, DA, and UA, and has a broad prospect in practical application.

A Novel Electrochemical Sensor Based on Electropolymerized Ion Imprinted PoPD/ERGO Composite for Trace Cd(II) Determination in Water.

A novel electrochemical sensor based on electropolymerized ion imprinted poly (o-phenylenediamine) PoPD/electrochemical reduced graphene (ERGO) composite on glass carbon electrode (GCE) was fabricated for selective and sensitive determination of trace Cd(II) in water. ERGO was first deposited on the surface of GCE by electrochemical cyclic voltammetry (CV) scanning to enhance the electron transport activity at electrode surface. The ion imprinted polymer (IIP) of imprinted PoPD was then in situ electropolymerized on ERGO via CV scanning with oPD as functional monomer and Cd(II) ions as template, following removal of the template using electrochemical peroxidation method. The obtained imprinted PoPD/RERGO composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray energy spectroscopy (EDS) for the observation of their morphologies and components. The electrochemical behavior of the imprinted PoPD/ERGO/GCE was performed by CV and SWASV. The fabricated sensor of the imprinted PoPD/ERGO/GCE showed a good selectivity toward target Cd(II) ions in the presence of other heavy metal ions. Under the optimized experimental conditions, the sensor exhibited a good linear relationship between SWASV stripping peak values and Cd(II) concentration in the range of 1 to 50 ng/mL, with the limit of detection as 0.13 ng/mL (S/N = 3). The proposed electrochemical sensor of imprinted PoPD/ERGO/GCE was successfully applied for trace Cd(II) determination in real water samples.

Binding of pDNA with cDNA using hybridization strategy towards monitoring of Haemophilus influenza genome in human plasma samples

Haemophilus Influenza leads to respiratory infections such as sinusitis, acute otitis media, pneumonia and bronchitis. In addition, it causes invasive infections such as cellulite, septic arthritis, and meningitis. Therefore, quick and sensitive detection of H. influenza is of great importance in medical microbiology. In this study, a novel DNA-based bioassay was developed to the monitoring of Haemophilus influenza genome in human plasma samples using binding of pDNA with cDNA. DNA hybridization strategy was used to investigation of DNAs binding. For this purpose, silver nanoparticle doped graphene quantum dots inks functionalized by D-penicillamine (Ag NPs-DPA-GQDs) were synthesized and deposited on the surface of glass carbon electrode (GCE). Also, gold nanoparticles functionalized with cysteamine (CysA-AuNPs) were deposited on the surface of the Ag-DPA-GQDs modified GCE. Afterward, thiolated DNA probe was immobilized on the surface of the modified electrode. DNA hybridization was monitored using square wave voltammetry (SWV) technique. Engineered genosensor indicated good performance with high specificity and sensitivity for detection of Haemophilus influenza genome. Under optimal conditions, linear range and low limit of quantitation (LLOQ) were obtained as target concentrations ranging from 1 pM–1 ZM and 1 ZM, respectively. The designed biosensor also showed high capability of discriminating one-base, two-base and three-base mismatched sequences. Also, the prepared genosensor could be easily regenerated and reused to evaluate hybridization process.

Facile strategy for synthesis of silver-graphene hybrid with controllable size and excellent dispersion for ultrasensitive electrochemical detection of acetamiprid

Electrochemical properties of metal-graphene hybrid depend on size and dispersion of metal nanoparticles on graphene sheets. The study reports a facile synthesis of silver-graphene hybrid with controllable size and excellent dispersion. Histidine-functionalized graphene quantum dots (His-GQDs) are firmly bound on graphene sheets of graphite oxide (GO) and then combined with Ag+ to form stable Ag/His-GQD/GO complex. Followed by heating in N2 to produce Ag/His-GQD/G. The resulting hybrid offers well-defined three-dimensional structure, in which all Ag nanoparticles are uniformly dispersed on the surface of graphene sheets. Interestingly, the size and density of Ag nanoparticles can be effectively adjusted by varying mass ratio of His-GQD/GO or Ag+/GO. To construct on the aptasensor, aptamer of acetamiprid was connected to Ag nanoparticles via Ag-S bond in the hybrid immobilized on surface of glass carbon electrode. The architecture creates an excellent catalytic activity. The aptasensor based on Ag/His-GQD/G exhibits ultrahigh sensitivity, specificity and stability for electrochemical detection of acetamiprid. A linear relationship between the peak current of differential pulse voltammetry and logarithm value of acetamiprid concentration was obtained in the range from 1.0 × 10−16 to 5.0 × 10−12 M with a detection limit of 4.0 × 10−17 M. The method has been successfully applied in detection of acetamiprid in tea.

Sensitive monitoring of riboflavin in commercial multivitamins using poly (chitosan)-based nanocomposite.

The rapid and sensitive determination of riboflavin (RF) is important for the treatment of seborrheic and glossitis dermatitis, sunlight sensitivity, mucosal, and skin disorders. In this work, an electrochemical sensor was developed by electrodes modification using poly (chitosan) to sensitive detection of RF in commercial multivitamin. Electrodeposition of chitosan on the surface of glass carbon electrode was performed using cyclic voltammetry technique in the range of -1 to +1 V. The modified electrode surface morphology was characterized using a high-resolution field emission scanning electron microscope. The modified electrode was used as an effective electrical interface for the detection of RF using cyclic, differential pulse, and square wave voltammetry techniques. Finally, the sensor was applied to determine RF in commercial multivitamins. In optimum conditions, the linear range for the standard sample of RF and commercial multivitamins 94 to 333μM and 24.6 to 176μM were obtained, respectively. Low limit of quantification (LLOQ) were obtained as 24.6μM.

One pot fabrication of graphene-bimetallic nanoparticles-based acetylcholinesterase electrochemical biosensor with ultralow detection limit toward methyl parathion

A one-step method was proposed to prepare graphene-bimetallic nanoparticles (NPs)-based acetylcholinesterase (AChE) biosensor for the detection of organophosphorus pesticides (OPs). Gold NPs (AuNPs) and silver NPs (AgNPs) were chosen as the bimetallic NPs, prepared by chemical reduction method and analyzed by transmission electron microscope. The graphene-polydopamine (RGO-PDA) was obtained by reducing graphene oxide (GO) with dopamine. The biosensor denoted as GCE/RGO-PDA-AuNPs-AgNPs-AChE-CS was fabricated by casting a mixture of RGO-PDA, AuNPs, AgNPs, AChE and chitason (CS) on the surface of glass carbon electrode (GCE). The response of the target electrode was significantly enhanced in the presence of nanostructured silver compared to that without AgNPs. The optimized amount of AChE in the electrode was 1.0 U. The optimized pH value of the buffer solution was 7.4. The proposed biosensor had a Michaelis–Menten constant () of 479.659 μM. The optimized incubation time was determined to be 10 min. Under optimal conditions, the linear detection range of methyl parathion for the biosensor was 0.076–3040 nM, and the limit of detection (LOD) was as low as 9.1pM. The biosensor had strong anti-interference performance, acceptable stability and good reproducibility. Considering the simplicity of preparation method, the electrochemical enzyme biosensor demonstrated in this study has good potential applications for the detection of real organophosphorus pesticides and even nerve agents.

Electrochemically Recognizing Tryptophan Enantiomers based on Carbon Black/Poly-l-Cysteine Modified Electrode

Construction of efficient and convenient sensors for recognition of chiral enantiomers is of much significance in the field of electrochemistry and life sciences. Herein, we designed an effective chiral interface for the successful identification of tryptophan (Trp) enantiomers by electrodepositing l-cysteine on the surface of glass carbon electrode modified with carbon black. The structure and morphology of the prepared sensor was characterized by scanning electron microscopy (SEM) and electrochemical methods. Compared with l-tryptophan (L-Trp), the sensor exhibits favorable chiral recognition towards D-tryptophan (D-Trp) with a separation coefficient of 2.50. Compared with existing studies on electrochemical chiral recognition of Trp enantiomers, our designed chiral platform boasts of a wider linear range (1.0–1400.0 μM) and lower limits of detection thus, 0.33 μM and 0.45 μM for L-Trp and D-Trp respectively. In addition, the proposed sensor has the capacity to recognize chiral molecules in Trp isomers mixture and the potential for the identification of other amino acids.

Fabrication of polyoxometalate/GO/PDDA hybrid nanocomposite modified electrode and electrocatalysis for nitrite ion, ascorbic acid and dopamine

Based on self-assembly and electrodepositing, a two-dimensional PMo10V2/GO/PDDA hybrid nanocomposite modified glass carbon electrode (GCE) was successfully fabricated for the first time. Graphene oxide (GO), PDDA, and PMo10V2 have been modified on GCE surface. Analysis by SEM and FTIR, GO has provided larger specific surface area for improving electrocatalysis activity of PMo10V2. The electrochemical behavior and electrocatalysis of the modified electrode were studied by detailed characterization of cyclic voltammetry (CV) and amperometric (i-t) methods. The experimental results demonstrated that PMo10V2/GO/PDDA/GCE has high stability, fast response, and good electrocatalytic activity towards the oxidation of nitrite ion (NO2−), ascorbic acid (AA), and dopamine (DA) compared to GCE, PDDA/GCE, and GO/PDDA/GCE respectively. Their concentrations are linearly proportional to the amperometric signals. The correlation coefficients of NO2−, AA, and DA are 0.999, 0.998, and 0.998 respectively. The detection limits were estimated to be 0.45 μM, 0.03 μM, and 0.18 μM for NO2−, AA, and DA with the signal to noise ratio of 3. Almost no interference effect was observed for sensing of NO2−, AA, and DA in the presence of each other. The proposed modified electrode was employed for the determination of the NO2−, AA, and DA level in human blood serum with recoveries between 97.35% and 104.2%.

Dual molecular recognition strategy for highly sensitive electrochemical detection of dopamine based on amplification of DNA–Au bio–bar codes

We had reported an electrochemical assay for dopamine with high sensitivity and selectivity based on dual molecular recognition strategy and amplification of DNA–Au bio–bar codes. In this assay, carbon nanotubes were first immobilized on the glass carbon electrode surface. Subsequently, a boronic acid-functionalized pyrene probe was self-assembled on the sidewalls of carbon nanotubes via π–π stacking interactions as a capture probe. 3,3′-Dithiodipropionic acid di(N-hydroxysuccinimide ester) (DSP) and double strands DNA functionalized AuNPs (DSP/AuNPs/dsDNA) were designed as signal probes and characterized by transmission electron microscopy and spectroscopic techniques. Upon the binding of dopamine with boronic acid followed by DSP/AuNPs/dsDNA, the AuNPs were captured on the electrode surface to enhance the signal. RuHex, an electroactive complex, which could bind to the anionic phosphate of DNA strands through electrostatic interaction, serves as signaling transducer. Signal amplification and dual recognition were used to quantify dopamine concentration from 30 pM to 30 nM, with a detection limit of 18 pM. Other small molecules could be measured by this assay after modification with differential recognition molecules.

Preparation of CuPc/RGO Nanocomposites and Their Electrocatalytic Behaviors for Oxygen Reduction Reaction

In this paper, copper phthalocyanine/reduced graphene oxide (CuPc/RGO) nanocomposites were synthesized by aromatic π-π stacking interaction and well characterized by scanning electron microscopy (SEM) and fluorescence spectrometry. The composites were modified on the surface of glass carbon electrode (GCE) and their electrochemical behaviors of CuPc/RGO for electrocatalytic oxygen reduction reaction (ORR) were studied by cyclic voltammetry (CV). The study showed when the mass ratio of RGO to CuPc in composite achieved 1:1, the composite film performed excellent electrocatalytic activity towards the ORR.

“Off-On”switching electrochemiluminescence biosensor for mercury(II) detection based on molecular recognition technology

A novel “off-On” electrogenerated chemiluminescence (ECL) biosensor has been developed for the detection of mercury(II) based on molecular recognition technology. The ECL mercury(II) biosensor comprises two main parts: an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Ruthenium(II) tris-(bipyridine)(Ru(bpy)32+)/Cyclodextrins-Au nanoparticles(CD-AuNps)/Nafion on the surface of glass carbon electrode (GCE), and the ECL intensity switch is the single hairpin DNA probe designed according to the “molecular recognition” strategy which was functionalized with ferrocene tag at one end and attached to Cyclodextrins (CD) on modified GCE through supramolecular noncovalent interaction. We demonstrated that, in the absence of Hg(II) ion, the probe keeps single hairpin structure and resulted in a quenching of ECL of Ru(bpy)32+. Whereas, in the presence of Hg(II) ion, the probe prefers to form the T-Hg(II)-T complex and lead to an obvious recovery of ECL of Ru(bpy)32+, which provided a sensing platform for the detection of Hg(II) ion. Using this sensing platform, a simple, rapid and selective “off-On” ECL biosensor for the detection of mercury(II) with a detection limit of 0.1 nM has been developed.

Simultaneous determination of trace Cd(II) and Pb(II) based on Bi/Nafion/reduced graphene oxide-gold nanoparticle nanocomposite film-modified glassy carbon electrode by one-step electrodeposition

In this paper, a simple and controllable one-step electrodeposition method was used to fabricate a novel reduced graphene oxide-gold nanoparticles (RGO-GNPs) nanocomposite film onto the surface of bare glass carbon electrode (GCE), and then, Nafion was modified onto the film to prepare an electrochemical sensor for simultaneous detection of trace Cd(II) and Pb(II) in square-wave anodic stripping voltammetry (SWASV) with situ plating bismuth film. The morphologies and electrochemistry properties of the modified electrode were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), cyclic voltammetry (CV), and SWASV. It was found that the formed RGO-GNPs nanocomposite film on the GCE surface could remarkably facilitate the electron transfer and enlarge the specific surface area of the electrode. While the Nafion film could effectively increase the adhesion and stability of RGO-GNPs nanocomposite layer, enhance cation-exchange capacity, and prevent the macromolecule in real samples absorbing on the surface of electrode. The Bi/Nafion/RGO-GNPs/GCE demonstrated a highly linear behavior in the simultaneous detection of Cd(II) and Pb(II) in the concentration range of 1.0 to 90 μg/L with detection limits of 0.08 and 0.12 μg/L (S/N = 3), respectively. Finally, The developed electrode was further applied to the determination of Cd(II) and Pb(II) in soil samples with satisfactory results.

Ultrasensitive electrochemical sensor for Hg2+ by using hybridization chain reaction coupled with Ag@Au core–shell nanoparticles

A novel electrochemical biosensor for Hg2+ detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg2+, the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg2+-T coordination chemistry. The carried DP then opened two ferrocene (Fc) modified hairpin DNA (H1 and H2) in sequence and propagated the happen of HCR to form a nicked double-helix. Numerous Fc molecules were formed on the neighboring probe and produced an obvious electrochemical signal. Moreover, (+)Ag@Au CSNPs were assembly onto such dsDNA polymers as electrochemical signal enhancer. Under optimal conditions, such sensor presents good electrochemical responses for Hg2+ detection with a detection limit of 3.6pM. Importantly, the methodology has high selectivity for Hg2+ detection.

Electrochemically Reduced Graphene Oxide-Nafion/Au Nanoparticle Modified Electrode for Hydrogen Peroxide Sensing

In this paper, a non-enzymatic hydrogen peroxide (H2O2) sensor, based on Au nanoparticles (AuNPs) electrodeposited on an electrochemically reduced graphene oxide(ERGO)-Nafion modified glass carbon electrode (GCE), was reported. The graphene oxide-(GO-)Nafion nanocomposites were first assembled on the GCE surface to produce a GO-Nafion electrode. GO was then electrochemically reduced to produce an ERGO-Nafion modified GCE (to be subsequently denoted as GCE/ERGO-Nafion). Afterwards, AuNPs were electrodeposited on the modified GCE to form a GCE/ERGO-Nafion/AuNPs electrode. The ERGO-Nafion nanocomposites and the electrodeposited AuNPs were characterized by infrared spectroscopy and scanning electron microscopy (SEM). The results showed that the GO was reduced successfully and the AuNPs were uniformly dispersed on the GCE/ERGO-Nafion electrode with a size of about 48nm. The cyclic voltammograms and the amperometric method were used to evaluate the electrocatalytic properties of the GCE/ERGO-Nafion/AuNPs electr...

Rapid, Simple and Selective Determination of 2,4,6-dinitrophenol Based on PtAg /Mesoporous SiO<sub>2</sub> Nanocomposite Sensor with Electrochemical Detection

5-10nmPt-Ag nanoparticles were synthesized by Water thermal reduction, pluronic F127 and tetraethyl Orthosilicate (TEOS) have been used to synthesized mesoporous SiO2template. Pt-Ag nanoparticles have been absorbed onto the surface of mesoporous SiO2. Finally, PtAg/mesoporous SiO2nanocomposites have been modified on the surface of glass carbon electrode to prepared electrochemcial sensor which used to detect 2,4,6-dinitrophenol. In order to optimize experimental conditions, the synergistic reaction, buffer solution has been studied. The result show, when the potential at-0.404V, 2,4,6-dinitrophenol could be determined with a detection limit of 0.163μmol/L and linearity between 0.49-1667μmol/L . This sensor has high sensitivity, good reproducibility and stability.

Electrochemical sensor based on electrodeposited graphene-Au modified electrode and nanoAu carrier amplified signal strategy for attomolar mercury detection.

An electrochemical sensor was developed for attomolar Hg(2+) detection. Three single-stranded DNA probes were rationally designed for selective and sensitive detection of the target, which combined T-Hg(2+)-T coordination chemistry and the characteristic of convenient modification of electrochemical signal indicator. Graphene and nanoAu were successively electrodeposited on a glass carbon electrode surface to improve the electrode conductivity and functionalize with the 10-mer thymine-rich DNA probe (P1). NanoAu carriers functionalized with 29-mer guanine-rich DNA probe (P3) labeled methyl blue (MB-nanoAu-P 3s) were used to further strengthen signal response. In the presence of Hg(2+), a T-T mismatched dsDNA would occur between P1 and a 22-mer thymine-rich DNA probe (P2) on the electrode surface due to T-Hg(2+)-T coordination chemistry. Followed by adding the MB-nanoAu-P 3s for hybridization with P2, square wave voltammetry was executed. Under optimal conditions, Hg(2+) could be detected in the range from 1.0 aM to 100 nM with a detection limit of 0.001 aM. Selectivity measurements reveal that the sensor is specific for Hg(2+) even with interference by high concentrations of other metal ions. Three different environmental samples were analyzed by the sensor and the results were compared with that from an atomic fluorescence spectrometry. The developed sensor was demonstrated to achieve excellent detectability. It may be applied to development of ultrasensitive detection strategies.

A novel solid-state Ru(bpy)32+ electrochemiluminescence immunosensor based on poly(ethylenimine) and polyamidoamine dendrimers as co-reactants

In this study, a novel solid-state Ru(bpy)32+ electrochemiluminescence (ECL) sandwiched immunosensor for sensitive detection of α-fetoprotein (AFP) was constructed based on poly(ethylenimine) (PEI) functionalized reduced graphene oxide (PEI-rGO) and Au nanoparticles (AuNPs) decorated polyamidoamine (PAMAM) dendrimers. Both PEI and PAMAM are polymers with a lot of amino groups, which are able to serve as good co-reactant to remarkably enhance the ECL signal of Ru(bpy)32+. For improving the poor conductivity of PAMAM, the AuNPs were decorated on the amino groups of PAMAM. Through Au-N bonds, the formed AuNPs-PAMAM was decorated on the PEI-rGO. The obtained AuNPs-PAMAM/PEI-rGO was introduced to immobilize the detection antibody (Ab2). Then, the Ab2 labeled AuNPs-PAMAM/PEI-rGO was modified onto the glass carbon electrode surface via sandwiched immunoreactions. The ECL substrate was prepared by mixing nafion and the complex (Ru-PtNPs) of Pt nanoparticles (PtNPs) and Ru(bpy)32+, which could reduce the consumption of Ru complex, simplify the operation and enhance the ECL efficiency. The experimental results demonstrated that the proposed immunosensor had good response to AFP. The linear range was from 0.01pgmL−1 to 10ngmL−1 with a low detection limit of 3.3fgmL−1. Meanwhile, with satisfying stability, selectivity and reproducibility, the proposed sandwiched immunosensor was presented to possess good potential in clinical detection.

Development of highly sensitive electrochemical genosensor based on multiwalled carbon nanotubes–chitosan–bismuth and lead sulfide nanoparticles for the detection of pathogenic Aeromonas

In this paper, we reported the construction of new high sensitive electrochemical genosensor based on multiwalled carbon nanotubes–chitosan–bismuth complex (MWCNT–Chi–Bi) and lead sulfide nanoparticles for the detection of pathogenic Aeromonas. Lead sulfide nanoparticles capped with 5′-(NH2) oligonucleotides thought amide bond was used as signalizing probe DNA (sz-DNA) and thiol-modified oligonucleotides sequence was used as fixing probe DNA (fDNA). The two probes hybridize with target Aeromonas DNA (tDNA) sequence (fDNA–tDNA–szDNA). The signal of hybridization is detected by differential pulse voltammetry (DPV) after electrodeposition of released lead nanoparticles (PbS) from sz-DNA on the surface of glass carbon electrode decorated with MWCNT–Chi–Bi, which improves the deposition and traducing electrical signal. The optimization of incubation time, hybridization temperature, deposition potential, deposition time and the specificity of the probes were investigated. Our results showed the highest sensibility to detect the target gene when compared with related biosensors and polymerase chain reaction (PCR). The detection limit for this biosensor was 1.0×10−14M. We could detect lower than 102CFUmL−1 of Aeromonas in spiked tap water. This method is rapid and sensitive for the detection of pathogenic bacteria and would become a potential application in biomedical diagnosis, food safety and environmental monitoring.

Development of spiropyran-based electrochemical sensor via simultaneous photochemical and target-activatable electron transfer

In traditional electrochemical sensors, the electrochemical signal transduction of the redox-active material is usually controlled by the analytical target. Due to non-specific interaction between the redox mediator and the target, false signal by single stimulus may not be avoided. To address this issue, we have developed a new electrochemical sensor that uses a functional spiropyran, an important class of photo and thermochromic compounds, as both recognition receptor and latent redox mediator, to realize simultaneous photochemical and target-modulated electron transfer. As a proof of principle, β-galactosidase was chosen as a model target. The new synthesized spiropyran probe, SP-β-gal, undergoes reversibly structural isomerization to form merocyanine under UV light irradiation. After the glycosidic bond being cleaved by β-galactosidase, the opened merocyanine of SP-β-gal forms redox-active 2-(2.5-dihydroxystyryl)-1.3.3-trimethyl-3H-indolium, and thus produces a pair of reversible redox current peaks under the electrochemical scanning. To amplify the detection signal, SP-β-gal was self-assembled with single-walled carbon nanotubes (SWCNTs) on the surface of glass carbon electrode. Kinetics experiments confirm that the probe is an ideal candidate for the determination of different concentrations of β-galactosidase digestion kinetics. Further, the SP-β-gal/SWCNTs-modified electrode is chemically stable in complex biological fluids. It was successfully applied to monitor β-galactosidase activity in the 10% calf thymus. This work represents not only a significant step forward in the further development of low-dimensional carbon nanomaterials/small organic molecular probes-based electrochemical biosensors, but also a new platform which may be extended to the assay of other enzyme such as β-d-glycosidase and so on by translating the biorecognition into electrochemical signal responses.