Jilin Yan

Study on a luminol-based electrochemiluminescent sensor for label-free DNA sensing.

Automatic, inexpensive, simple and sensitive methods for DNA sensing and quantification are highly desirable for biomedical research. The rapid development of both the fundamentals and applications of electrochemiluminescence (ECL) over the past years has demonstrated its potential for analytical and bio-analytical chemistry. This paper reports the quenching effect of DNA on the ECL of luminol and the further development of a DNA sensing device. With the pre-functionalization by a composite of carbon nano-tubes (CNTs) and Au nanoparticles (AuNPs), the sensor provides a novel and valuable label-free approach for DNA sensing. Here the ECL intensity was remarkably decreased when more than 1.0 × 10−12 molar of DNA were adsorbed on the sensor. Linearity of the DNA amount with the reciprocal of ECL intensity was observed. A saturated sensor caused a 92.8% quenching effect. The research also proposes the mechanism for the quenching effect which could be attributed to the interaction between luminol and DNA and the elimination of reactive oxygen species (ROSs) by DNA.

Gold nanocluster-based ratiometric fluorescent probes for hydrogen peroxide and enzymatic sensing of uric acid

AbstractA method is described for ratiometric fluorometric assays of H2O2xa0by using two probes that have distinct response profiles. Under the catalytic action of ferrous ion, the 615xa0nm emission of protein-stabilized gold nanoclusters (under 365xa0nm photoexcitation) is quenched by H2O2, while an increased signal is generated with a peak at 450xa0nm by oxidizing coumarin with the H2O2/Fe(II) system to form a blue emitting fluorophore. These decrease/increase responses give a ratiometric signal. The ratio of the fluorescences at the two peaks are linearly related to the concentration of H2O2 in the range from 0.05 to 10xa0μM, with a 7.7xa0nM limit of detection. The detection scheme was further coupled to the urate oxidase catalyzed oxidation of uric acid which proceeds under the formation of H2O2. This method provides an simple and effective means for the construction of ratiometric fluorometric (enzymatic) assays that involve the detection of H2O2.n Graphical abstractUnder catalysis byxa0ferrous ion, hydrogen peroxide quenches the luminescence of gold nanoclusters (AuNCs) and oxidizes coumarin into a fluorescent derivative, which rendered fluorescence ON and OFF at two distinct wavelengths for ratiometric measurements.

Copper ion detection with improved sensitivity through catalytic quenching of gold nanocluster fluorescence

In this report, a sensitive fluorescence detection of copper (Ⅱ) ion was developed. Although itself only a weak quencher toward gold nanocluster fluorescence, this ion functioned as a catalyst that accelerated the oxidation of iodide into iodine by a strong oxidant. The so-produced iodine quenched the nanocluster fluorescence through an efficient etching reaction, which rendered a much improved sensitivity for copper detection. Under the optimal conditions, the extent of quenching was found linear to the amount of copper in the range of 0.8-80u202fnM, and this strategy was capable of detecting copper ion as low as 0.33u202fnM. The method was selective and was successfully applied for related measurement in practical samples.

A label-free electrochemiluminescent immunosensor for glutamate decarboxylase antibody detection on AuNPs supporting interface

In this paper, we will describe a novel lable-free electrochemiluminescent (ECL) immunosensor for the detection of glutamate decarboxylase antibody (GADA) in which Au nanoparticles (AuNPs) had pre-functionalized the indium tin oxide (ITO) glass to support the sensing interface. The preparation of the basal electrode only need a simple two-step drop coating, a thin polymer of hydrolyzed 3-aminopropyl trimethoxysilane, and the AuNPs gel on the ITO substrate. The AuNPs not only enhanced the ECL signal of luminol, but also acted to immobilize the glutamate decarboxylase (GAD) to build the sensing host. This immunosensor exhibits excellent specificity, reproducibility and stability. On resultant sensor, after the direct immunoreaction, the decreased ECL intensity has a good linear regression toward the logarithm of GADA concentration in the range of 0.30u202fngu202fmL-1 to 50u202fngu202fmL-1 with a detection limit of 0.10u202fngu202fmL-1. The proposed senor has prospective capability for the clinical detection of GADA in human serums, which had important value for diagnosis and precaution of type-1 diabetes or latent autoimmune diabetes in adult (LADA).

Sensitization of luminol electrochemiluminescence by metallic oxide nano-particles

The sensitization of electrochemiluminescence of luminol by metallic oxide nano-particles of ZnO, MnO2, In2O3 and TiO2 under alkaline conditions were reported here and the related mechanism is studied. Furthermore a sol-gel method was taken for the immobilization of the metallic oxide nano-particles onto platinum electrode, the so-obtained modified electrodes also exhibited enhanced ECL intensity. Cyclic voltammetric and UV-Vis absorption studies proposed that the sensitization mainly comes from the electrochemical generation of reactive oxygen species and the adsorption of MONPs for luminol.