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A sensitive and selective imprinted electrochemical sensor for the determination of aflatoxin B (AFB) was constructed on a glassy carbon electrode by stepwise modification of functional multiwalled carbon nanotubes (MCNTs), Au/Pt bimetallic nanoparticles (Au/PtNPs), and a thin imprinted film. The fabrication of a homogeneous porous poly o-phenylenediamine (POPD)-grafted Au/Pt bimetallic multiwalled carbon nanotubes nanocomposite film was conducted by controllable electrodepositing technology. The sensitivity of the sensor was improved greatly because of the nanocomposite functional layer; the proposed sensor exhibited excellent selectivity toward AFB owing to the porous molecular imprinted polymer (MIP) film. The surface morphologies of the modified electrodes were characterized using a scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. A linear relationship between the sensor response signal and the logarithm of AFB concentrations ranging from 1 × 10 to 1 × 10 mol L was obtained with a detection limit of 0.03 nmol L. It was applied to detect AFB in hogwash oil successfully. [ABSTRACT FROM AUTHOR]

Abstract: A novel nanocomposites film of conducting polymers including single-walled carbon nanotubes (SWCNTs), polypyrrole (PPy) and gold nanoparticles (AuNPs) modified electrode has been applied in voltammetric sensors to detect epinephrine (EP) sensitively when ascorbic acids (AA) and uric acids (UA) exist. The nanocomposites film of conducting polymers which show an excellent electrocatalystic activity for the oxidation of EP and UA was characterized by scanning electron microscopy (SEM) and electrochemical methods. The catalytic peak currents obtained from differential pulse voltammetry (DPV) increased linearly with increasing EP concentrations in the range of 4.0×10−9–1.0×10−7 M with a detection limit of 2.0×10−9 M (S/N=3), respectively. The results showed that the nanocomposites of conducting polymers can selectively determine EP in the coexistence of a large amount of UA and AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The PPy/AuNPs/SWCNTs nanocomposites film can also be satisfactorily used for detecting EP in epinephrine hydrochloride injection when contain AA and UA, which also shows good recovery for determination of EP in some biological fluids. [Copyright &y& Elsevier]

Tyrosine is the precursor of some neurotransmitters such as thyroxine and dopamine. It has the effect of regulating emotions and stimulating the nervous system. Changes in tyrosine levels in the human body are associated with certain diseases. Therefore, it is very necessary to prepare a new type of tyrosine sensor. In this work, an enzyme-free electrochemical sensor based on MXene/CNTs/CuMOF composite was developed for the detection of tyrosine. Embedding carbon nanotubes (CNTs) into MXene effectively prevented the aggregation of MXene sheets. Further modification of MXene/CNTs materials with CuMOF octahedral particles with porous structure can improve the porosity and catalytic capability of the composites. Under the optimal detection conditions, the prepared sensor has good linearity in the detection of tyrosine within range 0.53 μM–232.46 μM with a limit of detection (LOD) of 0.19 μM. The stability and selectivity of the sensor is high, and can be used to detect tyrosine in human serum. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering the crucial roles of superoxide anion (O 2 − ) in pathological conditions, it is of great urgency to establish a reliable approach for real-time determination of O 2 − . Herein, a sensitive non-enzymatic sensor was constructed based on silver nanoparticles (AgNPs) and sodium dodecyl sulfate functionalized carbon nanotubes (SDS-MWCNTs) composites to measure the release of O 2 − from living cells. As an analytical and sensing platform, the AgNPs/SDS-MWCNTs modified glassy carbon electrode exhibited excellent electrochemical performance toward O 2 − with a determination limit as low as 0.0897 nM and wide linear range of 6 orders of magnitude, which was superior to other O 2 − electrochemical sensors. The excellent performance was attributed to the SDS-MWCNTs composites being used as effective load matrix for the deposition of AgNPs. Importantly, this novel non-enzymatic sensor could be applied to determination of O 2 − released from living cells, and the amount of flux of O 2 − increased accordingly with the improving of the concentration of AA, which has the possibility of application in clinical diagnostics to assess oxidative stress of living cells. [ABSTRACT FROM AUTHOR]

In this paper, a novel and facile electrochemical sensor for the simultaneous detection of adenine and guanine was fabricated based on 3,4,9,10-perylene tetracarboxylic acid noncovalently modified multiwalled carbon nanotubes. It exhibited good electrochemical responses toward the oxidation of adenine and guanine with a linear ranges covering 1.74 × 10 − 7 –2.09 × 10 − 5 M and 7.59 × 10 − 8 –2.09 × 10 − 5 M, and the corresponding detection limit of 5.81 × 10 − 8 M and 2.53 × 10 − 8 M (S/N = 3), respectively. Moreover, the fabricated sensor was employed for the exploration the possible electrochemical reaction mechanism of guanine supported by cyclic voltammetry experiments (CV). Eventually, the proposed sensor was applied in the determination of adenine and guanine contents in calf thymus DNA with satisfactory results, which has the great potential application in the sensitive monitoring of electroactive bio-molecules. [ABSTRACT FROM AUTHOR]

8-Hydroxy-2′-deoxyguanosine (8-OHdG) is commonly identified as a biomarker of oxidative DNA damage. In this work, a novel and facile 8-OHdG sensor was developed based on the multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE). It exhibited good electrochemical responses toward the oxidation of 8-OHdG, and the linear ranges were 5.63×10 −8 −6.08×10 −6 M and 6.08×10 −6 −1.64×10 −5 M, with the detection limit of 1.88×10 −8 M (S/N=3). Moreover, the fabricated sensor was applied for the determination of 8-OHdG generated from damaged DNA and guanine, respectively, and the oxidation currents of 8-OHdG increased along with the damaged DNA and guanine within certain concentrations. These results could be used to evaluate the DNA damage, and provide useful information on diagnosing diseases caused by mutation and deficiency of the immunity system. [ABSTRACT FROM AUTHOR]

We report on a new approach for the electrochemical detection of hydrogen peroxide (H2O2) based on Cytochrome C (Cyt c) immobilized ionic liquid (IL)-functionalized multi-walled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE). Functionalization of multi-walled carbon nanotube with amine-terminated ionic liquid materials was characterized using fourier transform infrared spectroscopy (FTIR), UV–vis spectra, and electrochemical impedance spectroscopy (EIS), and the results showed that the covalent modification of MWCNTs with ILs exhibited a high surface area for enzyme immobilization and provided a good microenvironment for Cyt c to retain its bioelectrocatalytic activity toward H2O2. Amperometry was used to evaluate the catalytic activity of the cyt c towards H2O2. The proposed biosensor exhibited a wide linear response range nearly 4 orders of magnitude of H2O2 (4.0×10−8 M–1.0×10−4 M) with a good linearity (0.9980) and a low detection limit of 1.3×10−8 M (based on S/N=3). Furthermore, the biosensor also displays some other excellent characteristics such as high selectivity, good reproducibility and long-term stability. Thus, the biosensor constructed in this study has great potential for detecting H2O2 in the complex biosystems. [ABSTRACT FROM AUTHOR]

Abstract: Development of a highly sensitive nanostructured electrochemical biosensor based on the integrated assembly of horseradish peroxidase (HRP) and single-walled carbon nanotubes (SWNTs) is described. In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb the horseradish peroxidase (HRP) onto single-walled carbon nanotubes (SWNTs). We demonstrate that HRP–SWNTs conjugates can be assembled into amperometric biosensors which l-cysteine were assembled on a gold electrode through the covalent bond of S–Au and was used as a substrate for the immobilization of enzymes. Direct electron transfer of HRP is realized at SWNTs, and both anodic and cathodic currents of the redox reaction at the l-cysteine–HRP–SWNTs-modified gold film upon electrocatalysis are amplified. Meanwhile, experimental results reveal that HRP is stably immobilized onto the SWNTs and maintains inherent enzymatic activity toward H2O2. The modified electrode shows high sensitivity toward H2O2. A linear response to hydrogen peroxide measurement is obtained over the range from 1.0×10−12 to 1.0×10−11 M and an amperometric detection limit of 2.1×10−13 M due to its bioelectrocatalytic reduction based on direct electron transfer between gold electrode and the active site of the HRP. The biosensor displays excellent operational, storage stability and highly sensitive. The excellent performance validates the integrated assembly as an attractive sensing element for the development of a new hydrogen peroxide amperometric biosensor. [Copyright &y& Elsevier]