Multiplexed bead-based analytical assays

Abstract

Methods for performing bead-based analytical assays for detecting changes in abundance of target analytes in biological samples are disclosed. In an embodiment, a method involves eluting bead-captured analytes from a bead array under conditions that preserve spatial localization of the eluted analytes.

What is claimed is: 
     
         1 . A method for eluting an analyte from a bead array, the bead array comprising a bead positioned in a microwell, the bead being associated with an analyte, the microwell containing an aqueous medium, the method comprising the step of repeatedly depositing an elution medium into the microwell, the elution medium comprising a dissolved matrix for mass spectrometry (MS) and a solvent, wherein a rate, at which the elution medium is being deposited into the microwell, is approximately equivalent to a rate, at which the solvent is escaping from the microwell via evaporation, such that the bead is continuously exposed to the solvent and a solution that forms in the microwell has a higher concentration of the dissolved matrix relative to the elution medium. 
     
     
         2 . The method of  claim 1  wherein the bead is continuously exposed to the elution medium for at least 5 minutes. 
     
     
         3 . The method of  claim 1  wherein a concentration of the matrix in the elution medium is less than 10 mg/ml. 
     
     
         4 . The method of  claim 1  wherein the solvent contains more than 0.2% of a strong acid. 
     
     
         5 . The method of  claim 1  wherein the elution medium is being deposited into the microwell using conditions that substantially prevent splattering and spilling of the elution medium from the microwell. 
     
     
         6 . The method of  claim 1  wherein the elution medium is being deposited using a programmable device capable of producing an aerosol and the method further comprises the step of supplying at least one value to the programmable device, the at least one value being selected according to an ambient air humidity level. 
     
     
         7 . The method of  claim 6  wherein the at least one value is further selected according to at least one of a chemical composition of the analyte, a chemical composition of the elution medium, and a chemical composition of the aqueous medium. 
     
     
         8 . The method of  claim 6  wherein the programmable device is operably connected to a hygrometer. 
     
     
         9 . A method for eluting an analyte from a bead array, the method comprising the steps of receiving a bead array, the bead array comprising a bead that is positioned in a microwell, the bead being associated with an analyte, the microwell containing an aqueous medium,
 depositing a first amount of an elution medium into the microwell, the elution medium comprising a dissolved matrix for MS and a solvent, and allowing the aqueous medium and the elution medium to form a mixture, the mixture being sufficiently acidic to cause the analyte to dissociate from the bead,   depositing a second amount of the elution medium into the microwell such that a concentration of the matrix in the mixture exceeds a concentration of the matrix in the elution medium   and   allowing the solvent to evaporate from the microwell thereby causing the matrix to co-crystallize with the analyte.   
     
     
         10 . A method for eluting an analyte from a bead array, the method comprising the steps of
 receiving a bead array, the bead array comprising a bead that is positioned in a microwell, the bead being associated with an analyte, the microwell containing an aqueous medium,   depositing an elution medium into the microwell, the elution medium comprising a dissolved matrix for MS and a solvent, wherein the aqueous medium and the elution medium are allowed to form a mixture under conditions that substantially prevent the matrix from precipitating from the mixture and   providing a sufficient amount of time to allow the solvent to escape the microwell via evaporation thereby causing the dissolved matrix to precipitate.   
     
     
         11 . The method of  claim 10  wherein the amount of time is greater than 10 minutes.