Systems and methods for rapidly changing the solution environment around sensors

Abstract

The invention provides microfluidic systems for altering the solution environment around a nanoscopic or microscopic object, such as a sensor, and methods for using the same. The invention can be applied in any sensor technology in which the sensing element needs to be exposed rapidly, sequentially, and controllably, to a large number of different solution environments whose characteristics may be known or unknown.

1 .- 84 . (canceled) 
     
     
         85 . A method for generating an activated receptor, comprising a) providing a substrate, the substrate comprising: a chamber comprising a cell-based biosensor comprising a receptor which is activated by an agonist; and a plurality of delivery channels delivering agonist, antagonist, or both agonist and antagonist, each channel comprising an outlet for delivering a substantially separate aqueous stream into the chamber; and b) selectively exposing the biosensor to a fluid stream from one or more outlets. 
     
     
         86 . The method of  claim 85 , wherein the chamber comprises a buffer, at least one agonist, at least one antagonist, or a combination thereof. 
     
     
         87 . A method for detection of a modulator of a receptor, comprising a) providing a substrate, the substrate comprising: a chamber comprising a cell-based biosensor, the biosensor comprising the receptor; and a plurality of channels, each channel comprising an outlet for delivering a substantially separate fluid stream into the chamber; and a scanning mechanism for selectively exposing the biosensor to a fluid stream from one or more outlets, b) providing a sample suspected of containing a modulator to at least one of the channels; c) measuring the response of the biosensor as it is selectively exposed to a fluid stream comprising the sample, wherein a change in the response of the biosensor indicates the presence of a modulator in the sample. 
     
     
         88 . The method of  claim 85  or  87 , wherein the exposing step is performed by moving the substrate or the sensor or both the substrate and the sensor relative to at least one channel outlet. 
     
     
         89 . The method of  claim 88 , wherein both the substrate and sensor are moved independently of each other. 
     
     
         90 . The method of  claim 85  or  87 , wherein the exposing step further comprises producing pressure drops across one or more channels. 
     
     
         91 . The method of  claim 87 , wherein the same suspected modulator is provided to a plurality of channels. 
     
     
         92 . The method of  claim 87 , wherein different concentrations of the modulator are provided to the plurality of channels. 
     
     
         93 . The method of  claim 87 , wherein the modulator varies in concentration in at least one channel, forming a gradient of modulator in the at least one channel. 
     
     
         94 . The method of  claim 87 , further comprising generating a dose-response curve for the modulator. 
     
     
         95 . The method of  claim 87 , comprising exposing the biosensor to buffer delivered by at least one channel. 
     
     
         96 . The method of  claim 95 , comprising selectively exposing the biosensor to streams of buffer and sample. 
     
     
         97 . The method of  claim 96 , comprising selectively exposing the biosensor to alternating streams of buffer and sample. 
     
     
         98 . The method of  claim 85  or  87 , wherein the cell-based biosensor comprises a patch-clamped cell or patch-clamped cell membrane fraction. 
     
     
         99 . The method of  claim 98 , wherein the patch-clamped cell is positioned relative to the outlets using a patch clamp pipette coupled or connected to a positioner. 
     
     
         100 . The method of  claim 98 , wherein the patch-clamped cell or patch-clamped cell membrane fraction is positioned in a depression in the base of the chamber. 
     
     
         101 . The method of  claim 87 , wherein the receptor is activated by an agonist which produces a measurable response by the biosensor upon binding to the receptor, and wherein the modulator modulates the activity of the agonist. 
     
     
         102 . The method of  claim 87 , wherein the receptor is inactivated by an antagonist which eliminates or reduces a measurable response by the biosensor upon binding to the receptor, and wherein the modulator modulates the activity of the antagonist. 
     
     
         103 . The method of  claim 87 , wherein the modulator is an agonist. 
     
     
         104 . The method of  claim 87 , wherein the modulator is an antagonist. 
     
     
         105 . The method of  87 , wherein the channels deliver a buffer, at least one agonist; at least one antagonist; at least one agonist and a buffer; at least one antagonist and a buffer; or at least one antagonist, at least one agonist, and a buffer. 
     
     
         106 . The method of  claim 87  or  105 , wherein the chamber comprises a buffer, at least one agonist, or at least one antagonist. 
     
     
         107 . The method of  claim 85  or  87 , wherein the cell-based biosensor comprises an ion-channel. 
     
     
         108 . The method of  claim 85  or  87 , wherein the receptor comprises a G-protein coupled receptor. 
     
     
         109 . The method of  claim 85  or  87 , wherein the cell-based biosensor comprises a recombinantly expressed receptor. 
     
     
         110 . The method of  claim 109 , wherein the recombinantly expressed receptor is an orphan receptor. 
     
     
         111 . The method of  claim 87 , wherein the response is determined by measuring cell surface area. 
     
     
         112 . The method of  claim 87 , wherein the response is determined by measuring an electrical property of the cell-based biosensor. 
     
     
         113 . The method of  claim 87 , wherein the modulator is a modulator of neurotransmitter release. 
     
     
         114 . The method of  claim 87 , wherein the response is determined by measuring ion-channel permeability properties. 
     
     
         115 .- 170 . (canceled)