Polymer-based microfluidic device for measuring membrane protein activities

Functional assays of membrane proteins are becoming increasingly important, both in research and drug discovery applications. The majority of current assays use the patch-clamp technology to measure the activity of ion channels which are over-expressed in cells. In future, in vitro assay systems will be available, which use reconstituted membrane proteins in free-standing lipid bilayers suspended in nano- or micrometer-sized pores. Such functional assays require (1) expression, purification and reconstitution of the membrane protein of interest, (2) a reliable method for lipid bilayer formation and membrane protein integration, and (3) a sensitive detection system. For practical applications, especially for automation, the reliable and controllable transport of fluids is essential. In order to achieve a stable free-standing lipid bilayer, a pore diameter in the micro- to nanometer range is essential. Novel microfluidic devices were developed by bonding a thick (300μm) polyether ether ketone foil, bearing a channel structure, to a thin (12μm) foil with a micropore of about 10μm diameter and then utilized for the formation of stable, free-standing lipid bilayers within the pore. A bacterial voltage-gated potassium channel is integrated therein by fusion and the ion channel activity detected by voltage clam

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed

NOVEL COVALENT AVIDIN IMMOBILIZATION ON GLASSY CARBON ELECTRODES USING A BIFUNCTIONAL REAGENT

It is generally accepted that the stability and performance of a biosensor is determined by the way biocomponents are immobilized on the inorganic support. We present a covalent coupling method of the anchor protein avidin to a glassy carbon electrode surface using the heterobifunctional reagent m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS). Thus, a nearly complete, biologically active monolayer of avidin was obtained which is suitable for the immobilization of any biotinylated compound. These modified electrodes are potentially useful as amperometric biosensors

Adhesion proteins for a tight neuron-electrode contact.

The neural cell adhesion molecules axonin-1 and NgCAM have been genetically engineered and covalently immobilized on glass and silicon oxide surfaces in their correct orientation. Surfaces treated with these adhesion molecules were used as substrates for culturing dorsal root ganglion neurons. The cleft between the neuron cell membrane and the surface was determined using fluorescence interference contrast (FLIC) microscopy. For comparison, cell--material distances on laminin, RGDC, polylysine and amino-terminated surfaces were measured. When the neurons grow on axonin-1 the cell--surface distance is at a minimum (37 nm) probably because the glycocalyx hinders a closer contact. A selective treatment of extracellular electrodes with axonin-1 could be used to improve the cell-material contact and thus increase extracellularly recorded signals

Towards Amperometric Immunosensor Devices

In contrast to optical immunosensors, the electrochemical detection of an immunoanalytical reaction does require a labeling, but allows an easier discrimination of specific and non-specific binding. We present a concept and first results for a multivalent amperometric immunosensor system which is based on silicon technology. The capture molecule streptavidin, covalently immobilized on silica, allows the immobilization of biotinylated antigens at a defined density. A nanostructured gold electrode serving as a stable network of nanowires is expected to be beneficial for the electrochemical detection of bound ferrocene-labeled antibody molecules. The results presented focus on site-specific immobilization of streptavidin on silica and reduction of non-specific binding of proteins. | In contrast to optical immunosensors, the electrochemical detection of an immunoanalytical reaction does require a labeling, but allows an easier discrimination of specific and non-specific binding. We present a concept and first results for a multivalent amperometric immunosensor system which is based on silicon technology. The capture molecule streptavidin, covalently immobilized on silica, allows the immobilization of biotinylated antigens at a defined density. A nanostructured gold electrode serving as a stable network of nanowires is expected to be beneficial for the electrochemical detection of bound ferrocene-labeled antibody molecules. The results presented focus on site-specific immobilization of streptavidin on silica and reduction of non-specific binding of proteins