Biomedical subjects

Danke Xu

Publications and source records attributed to Danke Xu.

7 recordsLinked to original sources

PubMed2006

Matrix with high salt tolerance for the analysis of peptide and protein samples by desorption/ionization time-of-flight mass spectrometry.

High concentrations of urea and guanidine hydrochloride are commonly used for the denaturation of protein, which was digested by enzymatic proteolysis for the identification by MS analysis. The presence of these contaminants seriously suppresses the ion signal of analytes in MALDI-TOF MS analysis. Herein, a novel MALDI matrix, 3, 4-diaminobenzophenone (DABP), has been found with high tolerance for these contaminants in MALDI MS analysis. The ion signal of analyte insulin can be detected in the presence of 2 M guanidine hydrochloride and 1.5 M urea using DABP as matrix. The tryptic digest of BSA (400 fmol) in 1 M guanidine hydrochloride or 1 M urea was successfully analyzed without any pretreatment prior to MS analysis. Furthermore, it has been found that this matrix can also effectively suppress the cation ion adduction of the peptides in the presence of high concentrations of metal ions in sample solution.

Benzophenones↗

PubMed2006

An impedance array biosensor for detection of multiple antibody-antigen interactions.

Electrochemical impedance spectroscopy (EIS) combined with a gold electrode array was developed to detect multiple antibody-antigen interactions. Hepatitis B surface antigen (HBsAg), as a model sample, was employed to evaluate the characteristics of the biosensor. The array was fabricated by immobilizing antibodies on the self-assembled molecules surface of the electrodes. The surface characteristics of the array during the binding process including the antibody-antigen conjugation and the sandwich complex with HRP-labeled antibody, as well as the precipitation layer, were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy, respectively. A linear relationship between electron-transfer resistance and the concentrations of HBsAg ranged from 10 pg ml(-1) to 1 ng ml(-1) and the detection limit of 10 pg ml(-1) was obtained. 100 pg ml(-1) antigen samples, such as rat IgG, HBsAg and HBeAg, as well as the antigen mixture, were incubated with the relative antibody-modified electrodes on the array. No obvious cross-talk reaction was observed. All these results confirm the feasibility of applying electrochemical impedance spectroscopy to the electrode array.

Animals↗

PubMed2006

An impedance biosensor array for label-free detection of multiple antigen-antibody reactions.

An electrochemical impedance biosensor array with protein-modified electrodes was designed and fabricated in this report. To demonstrate its feasibility of the detection of multiple antigen-antibody binding reactions based on a label-free approach, human IgG (hIgG), rat IgG (rIgG), human globin and bovine serum albumin were immobilized, respectively, on the gold electrodes and then the resultant array was incubated with goat anti-hIgG, goat anti-rIgG, anti-human globin antibody and the mixture of three antibodies, respectively. The results indicated that the electron transfer resistance of the electrodes was significantly changed due to formation of the antigen-antibody conjugated layer. In addition, experimental conditions such as the protein concentration for the immobilization and screen were studied and optimized. Furthermore, the surface of various protein-modified electrodes was imaged with atomic force microscopy and the height distribution of protein particles was obtained with the Particle Analysis Software. The relative results were fully in accordance with the ones from the electrochemical impedance spectroscopy.

Animals↗

PubMed2006

Label-free detection methods for protein microarrays.

With the growth of the "-omics" such as functional genomics and proteomics, one of the foremost challenges in biotechnologies has become the development of novel methods to monitor biological process and acquire the information of biomolecular interactions in a systematic manner. To fully understand the roles of newly discovered genes or proteins, it is necessary to elucidate the functions of these molecules in their interaction network. Microarray technology is becoming the method of choice for such a task. Although protein microarray can provide a high throughput analytical platform for protein profiling and protein-protein interaction, most of the current reports are limited to labeled detection using fluorescence or radioisotope techniques. These limitations deflate the potential of the method and prevent the technology from being adapted in a broader range of proteomics applications. In recent years, label-free analytical approaches have gone through intensified development and have been coupled successfully with protein microarray. In many examples of label-free study, the microarray has not only offered the high throughput detection in real time, but also provided kinetics information as well as in situ identification. This article reviews the most significant label-free detection methods for microarray technology, including surface plasmon resonance imaging, atomic force microscope, electrochemical impedance spectroscopy and MS and their applications in proteomics research.

Animals↗

PubMed2005

Label-free electrochemical detection for aptamer-based array electrodes.

An electrochemical impedance spectroscopy method of detection for aptamer-based array electrodes is reported in which the binding of aptamers immobilized on gold electrodes leads to impedance changes associated with target protein binding events. Human IgE was used as a model target protein and incubated with the aptamer-based array consisting of single-stranded DNA containing a hairpin loop. To increase the binding efficiency for proteins, a hybrid modified layer containing aptamers and cysteamine was fabricated on the photolithographic gold surface through molecular self-assembly. Atomic force microscopy analysis demonstrated that human IgE could be specifically captured by the aptamer and stand well above the self-assembled monolayer (SAM) surface. Compared to immunosensing methods using anti-human IgE antibody as the recognition element, impedance spectroscopy detection could provide higher sensitivity and better selectivity for aptamer-modified electrodes. The results of this method show good correlation for human IgE in the range of 2.5-100 nM. A detection limit of 0.1 nM (5 fmol in a 50-microL sample) was obtained, and an average of the relative standard deviation was <10%. The method herein describes the first label-free detection for arrayed electrodes utilizing electrochemical impedance spectroscopy.

Aptamers, Nucleotide↗

PubMed2002

Surface-bound lipid vesicles encapsulating redox species for amperometric biosensing of pore-forming bacterial toxins.

A new method is described to signal the presence of a staphylococcal toxin (streptolysin, SLO) by a membrane-based biosensor fabricated with bilayer vesicles of phosphatidylcholine lipids and cholesterol on a gold electrode. The controlled release of encapsulated redox species from the surface-bound vesicles is mediated by the pore-formation functionality of SLO, allowing amperometric detection of the targeted toxin. Effects of BSA and Triton-100 on membrane permeability and redox release have been assessed, and a thin layer electrolysis mechanism has been proposed to account for the observed voltammetric behavior. The method is applicable to the detection of functionally similar protein toxins.

Bacterial Proteins↗

PubMed2002

Magnetically-induced solid-state electrochemical detection of DNA hybridization.

A magnetic triggering of a solid-state electrical transduction of DNA hybridization is described. Positioning of an external magnet below the thick-film electrode attracts the DNA/particle network and enables the solid-state electrochemical stripping detection of the silver tracer. TEM imaging indicates that the hybridization event results in a three-dimensional aggregate structure in which duplex segments link the metal nanoparticles and magnetic spheres, and that most of this assembly is covered with the silver precipitate. This leads to a direct contact of the metal tag with the surface (in connection to the magnetic collection) and enables the solid-state electrochemical transduction (without prior dissolution and subsequent electrodeposition of the metal), using oxidative dissolution of the silver tracer. No such aggregates (and hence magnetic "collection") are observed in the presence of noncomplementary DNA, that is, without the linking hybrid. The new method couples high sensitivity of silver-amplified assays with effective discrimination against excess of closely related nucleotide sequences (including single-base imperfections). Such direct electrical detection of DNA/metal-particle assemblies can bring new capabilities to the detection of DNA hybridization, and could be applied to other bioaffinity assays.

DNA↗