Patent ID: 8076163
Filing Date: 2011-12-13
Classification: C12Q,G01N

Abstract:
1. A method of detecting the presence, absence or amount of an analyte in a sample comprising the steps of: bringing a plurality of particles into contact with a sample suspected to contain the analyte under conditions adapted to form said particles and said analyte into binding pairs, wherein the particles are of a size of about 5 nm to 50 μm and have a predetermined isoelectric point in a pH range of about 2.5 to 11 and contain at least about 100 positively and negatively charged groups derived from at least one organic acid monomer and at least one organic base monomer linked by non-peptide bonds, wherein the charged groups define the isoelectric point of the particles, wherein the ratio of said monomers is selected such that after free radical copolymerization their charged groups determine the isoelectric point of the particles, wherein, under the influence of an electric field, the particles are adapted to migrate in a medium containing a pH gradient formed by carrier ampholytes and to focus at a position in the pH gradient that is not broader than about 0.2 pH units and corresponds to their isoelectric point, and wherein the particles contain a label and a binding member adapted to participate in the formation of a binding pair with the analyte, separating the particles that participated in the formation of the binding pairs from the particles that did not participate in the formation of the binding pairs, subjecting the particles that participated in the formation of the binding pairs to isoelectric focusing, and detecting the particles.