Disclosed is an immunoassay method for detecting an analyte such as an antigen or an antibody in an isolated sample suspected to contain the analyte by incubating the sample with a plurality of binding partners, one of which carries a detectable label, wherein a label-specific binding partner is added that does not carry a label but binds to the detectable label. The method is applicable for a large variety of analytes and has proven particularly useful for analyte antibodies of the IgG and IgM class present in samples due to infections by pathogens. Also disclosed is a reagent kit useful for the method comprising at least two analyte-specific binding partners one of which carries a detectable label and a label-specific binding partner that binds to said detectable label but itself does not carry a detectable label.

An electrochemiluminescence method of detecting an analyte in a liquid sample and a corresponding analysis system. An analyte in a liquid sample is detected by first providing a receptacle containing a fluid comprising protein coated magnetic microparticles to a stirring unit. Stirring of the fluid is necessary since the density of the microparticles is usually higher than the density of the buffer fluid. Thus the microparticles tend to deposit on the bottom of the receptacle leading to an aggregation of the microparticles because of weak interactions. To obtain representative measurements a homogeneous distribution of the microparticles in the buffer fluid is necessary to ensure a constant concentration of microparticles for each analysis cycle. It is further necessary to provide disaggregation of the microparticles, which is also realized by stirring the fluid. Stirring is conducted with a rotational frequency that is adapted to the amount of fluid to be stirred.

A magnetic bead is respectively modified by two functional molecular layers from the inside out, termed as the polyethylene glycol (PEG) passivation layer and the photo-affinity peptide probe layer, respectively; PEG passivation layer is introduced at the surface of a magnetic bead, forming a PEG-modified magnetic bead, and the photo-affinity peptide probe layer is a molecular layer of peptide whose N-terminal end is modified with the thiol group and the diazirine group; the PEG passivation layer on the capture magnetic bead is used to reduce non-specific interaction of protein molecules, while the photo-affinity peptide probe layer can specifically recognize and capture target proteins; the weak interaction between the photo-affinity peptide probe and target proteins is converted to covalent linkage under the UV irradiation, thus achieving specific and efficient capture and magnetic separation of interacted proteins.

The present invention relates to a nanoplasmonic sensor based on gold nanoparticle to which an antibody or an aptamer binds, the antibody or the aptamer recognizing Aβ 1-40, Aβ 1-42, and τ protein, which are Alzheimer's disease onset markers that are present in blood, and a multi-detection method of Alzheimer's disease using Rayleigh scattering phenomenon and colorimetric assay of the sensor. The present invention has advantages in that it is possible to perform simultaneous multiple detect with respect to various onset markers by using a simple diagnosis method using blood, and sensitivity of diagnosis is improved by using a chaotropic solvent.

A substrate in accordance with an embodiment of the present invention is a substrate that has a surface to which a substance is to be immobilized and on which a layer of a substance immobilizing agent is formed. The substance immobilizing agent has photoreactive groups and contains a water-soluble polymer or a water-soluble monomer which turns into the water-soluble polymer by polymerization, and a thickness of the layer of the substance immobilizing agent is not less than 3 nm and less than 500 nm.

A piezoelectric plate sensor comprising a piezoelectric layer; two electrodes; and an insulation layer. The insulation layer is produced by soaking the piezoelectric layer and two electrodes in a mercaptopropyltrimethoxysilane solution with an amount of water from 0.1 v/v. % to about 1 v/v % and at pH from about 8 to about 150 for a period from about 8 to about 15 hours, and the mercaptopropyltrimethoxysilane solution has a concentration of mercaptopropyltrimethoxysilane from about 0.01 v/v % to about 0.5 v/v %. A method of detecting a biomolecule in a sample using the piezoelectric plate sensor in particular, that of detecting a genetic marker with PCR sensitivity and specificity without the need of DNA isolation or amplification is also provided. The piezoelectric plate sensor may be used to diagnose various diseases including breast cancer, myocardial infarction, diarrhea, Clostridium difficile infection, and hepatitis B infection.

The purpose of the present invention is to: provide an agent that effectively suppresses inhibition of antigen-antibody reaction in an immunoassay using a sample containing a body fluid, in particular, a component derived from a biological mucosal membrane, such as saliva; and to suppress false positive and false negative results in the immunoassay. The present invention provides an agent for suppressing inhibition of immune reaction, characterized in that the agent comprises a compound of the following (1) or (2): (1) Sulfonic acid compound of the formula R.sup.1—SO.sub.3H or a salt thereof. (In the formula, R.sup.1 is selected from the group consisting of: a straight-chain C.sub.5-C.sub.30 alkyl group; a straight-chain C.sub.1-C.sub.30 alkyl group substituted with an aryl group having at least one straight-chain C.sub.5-C.sub.30 alkyl group; and an aryl group having at least one straight-chain C.sub.5-C.sub.30 alkyl group. These groups may include a substituent group); and (2) Quaternary ammonium ion of the formula N.sup.+—R.sup.2R.sup.3R.sup.4R.sup.5 or a salt thereof. (In the formula, R.sup.2—R.sup.5 are each independently a straight-chain C.sub.1-C.sub.30 alkyl group, or an aryl group substituted with at least one straight-chain C.sub.5-C.sub.30 alkyl group. These groups may include a substituent group); wherein the agent is capable of suppressing immune reaction inhibitory action caused by a body fluid in an immunoassay sample.

An interdigitated electrode biosensor includes an insulating layer configured to fully cover a sensor forming region of a substrate, a first interdigitated microelectrode configured such that a plurality of first protruding electrodes is arranged in a shape of a comb on the substrate, a second interdigitated microelectrode configured such that a plurality of second protruding electrodes is arranged in a shape of a comb and each interdigitates with the plurality of first protruding electrodes, and a plurality of receptors that is immobilized in a space between the first interdigitated microelectrode and the second interdigitated microelectrode and reacts specifically to target biomaterials. Different voltages are uniformly or nonuniformly applied to the first interdigitated microelectrode and the second interdigitated microelectrode to generate a dielectrophoretic force by a nonuniform electric field, improving the sensor by increasing the probability of specific reaction with the target biomaterials using the concentration effect through dielectrophoresis.

This invention provides, and in certain specific but non-limiting aspects relates to: assays that can be used to predict whether a given ISV will be subject to protein interference as described herein and/or give rise to an (aspecific) signal in such an assay (such as for example in an ADA immunoassay). Such predictive assays could for example be used to test whether a given ISV could have a tendency to give rise to such protein interference and/or such a signal; to select ISV's that are not or less prone to such protein interference or to giving such a signal; as an assay or test that can be used to test whether certain modification(s) to an ISV will (fully or partially) reduce its tendency to give rise to such interference or such a signal; and/or as an assay or test that can be used to guide modification or improvement of an ISV so as to reduce its tendency to give rise to such protein interference or signal; —methods for modifying and/or improving ISV's to as to remove or reduce their tendency to give rise to such protein interference or such a signal; —modifications that can be introduced into an ISV that remove or reduce its tendency to give rise to such protein interference or such a signal; ISV's that have been specifically selected (for example, using the assay(s) described herein) to have no or low(er)/reduced tendency to give rise to such protein interference or such a signal; modified and/or improved ISV's that have no or a low(er)/reduced tendency to give rise to such protein interference or such a signal.

A method of applying a blocking composition (116) on a substrate for an assay (20) comprises: providing a substrate for an assay (20), wherein the substrate for an assay comprises a solid substrate provided with a plurality of discrete spots of a biological material on a surface thereof; and spraying the blocking composition (116) onto the substrate (20) as particles or droplets having a diameter being less than the diameter of the printed spots of biological material.