Free solution measurement of molecular interactions by backscattering interferometry

Abstract

Disclosed are methods, systems, and apparatuses for the free solution measurement of molecular interactions by backscattering interferometry. In one aspect, the invention relates to method and systems for detecting molecular interaction between analytes in free-solution wherein the analytes are label-free and detection is performed by back-scattering interferometry. Also disclosed are label-free, free-solution, and/or real-time measurements of characteristic properties and/or chemical events using the disclosed techniques. The disclosed methods can have very low detection limits and/or very low sample volume requirements. Also disclosed are various biosensor applications of the disclosed techniques. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.

What is claimed is: 
     
         1 . A method comprising detecting molecular interaction between analytes in free-solution wherein at least one of the analytes is label-free and detection is performed by back-scattering interferometry. 
     
     
         2 . The method of  claim 1 , wherein at least two analytes are label-free. 
     
     
         3 . The method of  claim 1 , wherein the interaction is a biomolecular interaction. 
     
     
         4 . The method of  claim 1 , wherein the analytes are present in a sample in a microfluidic channel in a substrate and back-scattering interferometry comprises directing a coherent light beam onto the substrate such that the light beam is incident on the channel to generate backscattered light through reflective and refractive interaction of the light beam with a substrate channel interface and the sample, the backscattered light comprising interference fringe patterns including a plurality of spaced light bands whose positions shift in response to changes in the refractive index of the fluid sample. 
     
     
         5 . The method of  claim 1 , wherein the interaction is a binding event between one or more of antibody-antigen, protein-protein, small molecule-small molecule; small molecule-protein, drug-receptor; antibody-cell; protein-cell; oligonucleotide-cell; carbohydrate-cell; cell-cell; enzyme-substrate; protein-DNA; protein-aptamer; DNA-DNA; RNA-RNA; DNA-RNA; protein-RNA; small molecule-nucleic acid; biomolecule-molecular imprint; biomolecule-protein mimetic; biomolecule-antibody derivatives; lectin-carbohydrate; biomolecule-carbohydrate; small molecule-micelle; small molecule-cell membrane; and enzyme-substrate. 
     
     
         6 . The method of  claim 1 , wherein the substrate and channel together comprise a capillary tube. 
     
     
         7 . The method of  claim 1 , wherein the substrate and channel together comprise a microfluidic device. 
     
     
         8 . A method for real-time, free-solution determination of molecular interactions comprising the step of detecting the formation of one or more interaction products of two unlabeled, non-immobilized analytes, wherein at least one of the analytes is present during the determination at a concentration of less than about 5.0×10 −5 M and/or wherein at least one of the analytes is present during the determination in a solution with a volume in the detection zone of less than about 500 nL. 
     
     
         9 . The method of  claim 8 , wherein at least two analytes are label-free. 
     
     
         10 . The method of  claim 8 , wherein one of the analytes is present in a concentration of less than about 5.0×10 −7 M. 
     
     
         11 . The method of  claim 8 , wherein one of the analytes is present in a concentration of less than about 5.0×10 −9 M. 
     
     
         12 . The method of  claim 8 , wherein the interaction is a biomolecular interaction. 
     
     
         13 . The method of  claim 8 , wherein the volume in the detection zone of less than about 300 nL. 
     
     
         14 . The method of  claim 8 , wherein the volume in the detection zone of less than about 100 nL. 
     
     
         15 . A detection system comprising:
 (a) a microfluidic channel formed in a substrate;   (b) a solution comprising label-free analytes in free solution in the channel; and   (c) an interferometer that detects molecular interactions between the analytes in the channel.   
     
     
         16 . The system of  claim 15 , wherein the detector is an interferometer. 
     
     
         17 . The system of  claim 15 , wherein the interaction is a biomolecular interaction. 
     
     
         18 . The system of  claim 15 , wherein one of the analytes is present in a concentration of less than about 5.0×10 −5 M. 
     
     
         19 . The system of  claim 15 , wherein the volume in the detection zone of less than about 500 nL. 
     
     
         20 . The system of  claim 15 , wherein one of the analytes is present in a concentration of less than about 5.0×10 −5 M and wherein the volume in the detection zone of less than about 500 nL.