The development of biosensor with imaging ellipsometry

Analysis of interactions between SNARE proteins using imaging ellipsometer coupled with microfluidic array

The soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins are small and abundant membrane-bound proteins, whose specific interactions mediate membrane fusion during cell fusion or cellular trafficking. In this study, we report the use of a label-free method, called imaging ellipsometer to analyze the interactions among three SNAREs, namely Sec22p, Ykt6p and Sso2p. The SNAREs were immobilized on the silicon wafer and then analyzed in a pairwise mode with microfluidic array, leading us to discover the interactions between Ykt6p and Sso2p, Sec22p and Sso2p. Moreover, by using the real-time function of the imaging ellipsometer, we were able to obtain their association constants (K_A) of about 10⁴ M⁻¹. We argue that the use of imaging ellipsometer coupled with microfluidic device will deepen our understanding of the molecular mechanisms underlying membrane fusion process.

Label-free detection techniques for protein microarrays: prospects, merits and challenges

Protein microarrays, on which thousands of discrete proteins are printed, provide a valuable platform for functional analysis of the proteome. They have been widely used for biomarker discovery and to study protein–protein interactions. The accomplishments of DNA microarray technology, which had enabled massive parallel studies of gene expression, sparked great interest for the development of protein microarrays to achieve similar success at the protein level. Protein microarray detection techniques are often classified as being label‐based and label‐free. Most of the microarray applications have employed labelled detection such as fluorescent, chemiluminescent and radioactive labelling. These labelling strategies have synthetic challenges, multiple label issues and may exhibit interference with the binding site. Therefore, development of sensitive, reliable, high‐throughput, label‐free detection techniques are now attracting significant attention. Label‐free detection techniques monitor biomolecular interactions and simplify the bioassays by eliminating the need for secondary reactants. Moreover, they provide quantitative information for the binding kinetics. In this article, we will review several label‐free techniques, which offer promising applications for the protein microarrays, and discuss their prospects, merits and challenges.

Phage M13KO7 detection with biosensor based on imaging ellipsometry and AFM microscopic confirmation

A rapid detection and identification of pathogens is important for minimizing transfer and spread of disease. A label-free and multiplex biosensor based on imaging ellipsometry (BIE) had been developed for the detection of phage M13KO7. The surface of silicon wafer is modified with aldehyde, and proteins can be patterned homogeneously and simultaneously on the surface of silicon wafer in an array format by a microfluidic system. Avidin is immobilized on the surface for biotin-anti-M13 immobilization by means of interaction between avidin and biotin, which will serve as ligand against phage M13KO7. Phages M13KO7 are specifically captured by the ligand when phage M13KO7 solution passes over the surface, resulting in a significant increase of mass surface concentration of the anti-M13 binding phage M13KO7 layer, which could be detected by imaging ellipsometry with a sensitivity of 10⁹ pfu/ml. Moreover, atomic force microscopy is also used to confirm the fact that phage M13KO7 has been directly captured by ligands on the surface. It indicates that BIE is competent for direct detection of phage M13KO7 and has potential in the field of virus detection.