Papers by Author: Xiao Fei Yan

Abstract: An interdigitated array microelectrodes (IDAMs) based impedance biosensor in combination with immunomagnetic separation was developed for rapid detection of avian influenza virus (AIV) subtype H5. Streptavidin-coated magnetic nanobeads were immobilized onto the biotin-labeled anti-H5 monoclonal antibodies to capture AIV H5 (e.g., H5N1) from sample solutions by the specific immunoreaction and form antibodies coated nanobeads-AIV complexes. Then these complexes were separated and concentrated by a magnetic field and the impedance magnitude was measured by IDAMs in a frequency range from 20 Hz to 1 MHz. The sensitivity and specificity of this biosensor were investigated. The biosensor could detect as few as 2-1 HA unit/50 μl of inactivated AIV H5N1. A linear relationship between the change of impedance magnitude and the logarithmic value of AIV H5N1 concentration was found in the range of 2-1 to 24 HA unit/50 μl. Non-target viruses, such as AIV subtype H1 and Newcastle disease virus, could not induce detectable signals. Equivalent circuit analysis showed that the medium resistance was responsible for the impedance change caused by the presence of AIV H5N1. The whole detection process from sampling to impedance measurement was able to be completed within 1.5 h.

Abstract: Magnetic separation is an emerging and promising technology in biological sample preparation. In this paper, a high-intensity and high-gradient magnetic separation system was developed to separate magnetic nanobeads from aqueous solution. This system mainly consisted of a magnetic separator, a micropump and an electronic timer. The magnetic separator was designed by placing two columns of permanent magnets in an aluminum holder. Two magnets in each column were laid out in repelling mode and a hole between the two columns was used to accommodate a 1.5 ml tube. Working with the electronic timer, the micropump was employed to remove waste solution at a certain rate after magnetic nanobeads captured onto the sides of the tube wall. The experiments for separation of magnetic nanobeads with diameters of 150 nm and 50 nm using the developed magnetic separation system were conducted to optimize the key parameters of the system including nanobeads concentration, separation time and flow rate. The separation efficiencies of magnetic nanobeads increased as the nanobeads concentration and the separation time increased, whereas decreased when the flow rate was increased. Experimental results proved that the proposed magnetic separation system was able to separate magnetic nanobeads (diameters of 150 nm and 50 nm) with separation efficiencies of 99% and 90% in 30 min and 150 min respectively.