Methods and apparatus for magnetic multi-bead assays

Abstract

The present application discloses methods and apparatus for detecting a complex including an analyte that include contacting a sample in a solution with a population of functionalized beads of a first type, which are magnetic functionalized beads and are functionalized to include a first moiety that associates with an analyte under suitable conditions, contacting the sample solution with a population of functionalized beads of a second type, which are functionalized to include a second moiety that associates with the analyte under suitable conditions, contact resulting in formation of a complex including one of the first type of functionalized bead, the analyte, and one of the second type of functionalized bead, and detecting the complex including the analyte by detecting magnetic fields produced by the magnetic functionalized bead and by detecting the functionalized bead of the second type associated with the analyte in the complex.

What is claimed is: 
     
         1 . A method of detecting a complex including an analyte, the method comprising:
 (a) contacting a sample in a solution with a population of functionalized beads of a first type, which are magnetic functionalized beads and are functionalized to include a first moiety that can specifically associate with an analyte under appropriate conditions;   (b) contacting the sample solution with a population of functionalized beads of a second type, which are functionalized to include a second moiety that associates with the analyte under suitable conditions, contact resulting in formation of a complex including one of the first type of functionalized bead, the analyte, and one of the second type of functionalized bead; and   (c) detecting the complex including the analyte by detecting magnetic fields produced by the magnetic functionalized bead and by detecting the functionalized bead of the second type associated with the analyte in the complex.   
     
     
         2 . The method of  claim 1 , further including disposing the sample solution including the complex over a substrate that includes at least one optically detected magnetic resonance (ODMR) center formed in the substrate; exciting electrons within the at least one ODMR center from a ground state to an excited state with incident light; applying a bias magnetic field on the complex; and generating a microwave field incident on the at least one ODMR center, the microwave field including frequencies that correspond to ground state transitions in the at least one ODMR center, wherein detecting the complex including the analyte further includes analyzing light emitted by the at least one ODMR center, characteristics of the emitted light being influenced by the microwave field and by the magnetic functionalized bead associated with the analyte in the complex. 
     
     
         3 . The method of  claim 2 , wherein the at least one ODMR center is a nitrogen-vacancy center in a diamond lattice. 
     
     
         4 . The method of  claim 3 , wherein the at least one ODMR center is formed in an upper surface of the substrate. 
     
     
         5 . The method of  claim 4 , wherein analyzing light emitted by the plurality of ODMR centers includes imaging the emitted light. 
     
     
         6 . The method of  claim 1 , further including applying a magnetic field gradient to the sample solution after contacting the sample with the population of functionalized beads of the first type. 
     
     
         7 . The method of  claim 1 , wherein the population of functionalized beads of the first type and the population of functionalized beads of the second type are added to the sample solution sequentially. 
     
     
         8 . The method of  claim 1 , wherein the functionalized beads of the second type are fluorescent functionalized beads, and the method further includes illuminating the complex with incident light that excites fluorescence within the functionalized beads of the second type and fluorescence imaging of the complex. 
     
     
         9 . The method of  claim 1 , wherein the functionalized beads of the second type are magnetic functionalized beads, including a magnetic property distinguishable from the functionalized beads of the first type. 
     
     
         10 . The method of  claim 1 , further including applying a magnetic field gradient to the sample solution after contacting the sample solution with the functionalized beads of the first and second types. 
     
     
         11 . The method of  claim 10 , further including varying the magnetic field gradient applied to the sample solution. 
     
     
         12 . The method of  claim 1 , further including concentrating the sample solution after contacting the sample solution with the population of functionalized beads of the second type. 
     
     
         13 . The method of  claim 1 , further including agglomerating a plurality of functionalized beads of the first and second types, after contacting the sample solution with the population of functionalized beads of the second type, before detecting the complex. 
     
     
         14 . The method of  claim 1 , further including dehydrating the sample solution after disposing the sample solution over the diamond substrate.