Molecular recognition at surfaces derivatized with self-assembled monolayers

Abstract

An article suitable for use as a biosensor includes a molecule of a formula X—R-Ch adhered to a surface of the article as part of a self-assembled monolayer. X is a functionality that adheres to the surface, R is a spacer moiety, and Ch is a chelating agent. A metal ion can be coordinated by the chelating agent, and a polyamino acid-tagged biological binding partner of a target biological molecule coordinated to the metal ion. A method of the invention involves bringing the article into contact with a medium containing or suspected of containing the target biological molecule and allowing the biological molecule to biologically bind to the binding partner. The article is useful particularly as a surface plasmon resonance chip.

1 . A molecule having a formula:  
         X—R-Ch  wherein X represents a functional group that adheres to a gold surface, R represents a spacer moiety that promotes formation of a self-assembled monolayer of a plurality of the molecules, and Ch represents a chelating agent that coordinates a metal ion, selected from the group consisting of bidentate, tridentate, and quadradentate chelating agents.    
     
     
         2 . The molecule as recited in  claim 1 , wherein the chelating agent is a quadradentate chelating agent.  
     
     
         3 . The molecule as recited in  claim 1 , wherein the chelating agent is nitrilotriacetic acid.  
     
     
         4 . The molecule as recited in  claim 1 , further comprising a metal ion coordinated to the chelating agent.  
     
     
         5 . The molecule as recited in  claim 4 , wherein the chelating agent and metal ion are selected such that the chelating agent coordinates all but at least two of the metal coordination sites.  
     
     
         6 . The molecule as recited in  claim 4 , wherein the chelating agent is a tetradentate chelating agent, and the metal ion has a coordination number of six.  
     
     
         7 . The molecule as recited in  claim 4 , wherein the metal ion is Ni 2+ .  
     
     
         8 . The molecule as recited in  claim 4 , further comprising a biological binding partner of a biological molecule coordinated to the metal ion.  
     
     
         9 . The molecule as recited in  claim 8 , wherein the biological binding partner includes a polyamino acid tag that coordinates the metal ion.  
     
     
         10 . The molecule as recited in  claim 9 , wherein the polyamino acid tag comprises at least two neighboring amino acids defining a chelating agent that coordinates the metal ion.  
     
     
         11 . The molecule as recited in  claim 10 , wherein the at least two neighboring amino acids are at least two neighboring histidines.  
     
     
         12 . The molecule as recited in  claim 8 , wherein the biological binding partner specifically binds a protein.  
     
     
         13 . An article comprising: 
 A solid phase having a surface;    a self-assembled mixed monolayer adhered to the surface, the mixed monolayer formed of at least a first species and a second species, the first species having a formula:      X—R-Ch    where X, R, and Ch are each selected such that X represents a functional group that adheres to the surface, R represents a spacer moiety that promotes self-assembly of the mixed monolayer, and Ch represents a chelating agent that coordinates a metal ion, and the second species being selected to form a mixed self-assembled monolayer with the first species,    wherein the mixed monolayer comprises the second and first species in a molar ratio at least 70:30.    
     
     
         14 . The article as recited in  claim 13 , wherein the mixed monolayer comprises the second and first species in a molar ratio at least 80:20.  
     
     
         15 . The article as recited in  claim 14 , wherein the mixed monolayer comprises the second and first species in a molar ratio at least 90:10.  
     
     
         16 . The article as recited in  claim 15 , wherein the mixed monolayer is comprised of about 95 mol % of the second species and about 5 mol % of the first species.  
     
     
         17 . The article as recited in  claim 13 , wherein the article comprises a chromatography solid phase.  
     
     
         18 . The article as recited in  claim 13 , wherein the article comprises a biosensor element.  
     
     
         19 . The article as recited in  claim 13 , wherein the article is a surface plasmon resonance chip.  
     
     
         20 . The article as recited in  claim 13 , wherein the second species has a formula:  
         X—R—O—(CH 2 CH 2 —O) n —H  wherein X represents a functional group that adheres to a surface, R represents a spacer moiety that promotes formation of a self-assembled monolayer of a plurality of the molecules, and n is from one to ten.    
     
     
         21 . The article as recited in  claim 13 , further comprising a metal ion coordinated to the chelating agent.  
     
     
         22 . The article as recited in  claim 21 , wherein the metal ion is Ni 2+ .  
     
     
         23 . The article as recited in  claim 21 , further Comprising a biological binding partner of a biological molecule coordinated to the metal ion.  
     
     
         24 . The article as recited in  claim 23  wherein the biological binding partner specifically binds a protein.  
     
     
         25 . The article as recited in  claim 13  wherein the solid phase is a film of gold.  
     
     
         26 . An article suitable for capturing a biological molecule, comprising: 
 A solid phase having a surface;    a self-assembled mixed monolayer adhered to the surface, the mixed monolayer formed of at least a first species and a second species,    wherein the first species has a formula:      X—R-Ch-M-BP    where X, R, Ch, M, and BP are each selected such that X represents a functional group that adheres to the surface, R represents a spacer moiety that promotes self-assembly of the mixed monolayer, Ch represents a chelating agent that coordinates a metal ion, M represents a metal ion, and BP represents a binding partner of the biological molecule, the binding partner being coordinated to the metal ion, and the second species is selected to form a mixed self-assembled monolayer with the first species.    
     
     
         27 . The article as recited in  claim 26 , wherein the mixed monolayer is comprised of the second and first species in a molar ratio of at least 70:30.  
     
     
         28 . The article as recited in  claim 26 , wherein the article comprises a biosensor element.  
     
     
         29 . The article as recited in  claim 26 , wherein the metal ion is Ni 2+ .  
     
     
         30 . The article as recited in  claim 26 , wherein the solid phase is a film of gold.  
     
     
         31 . The article as recited in  claim 26 , wherein the second species has a formula:  
         X—R—O—(CH 2 CH 2 ) n —H  wherein X represents a functional group that adheres to a surface, R represents a spacer moiety that promotes formation of a self-assembled monolayer of a plurality of the molecules, and n is from one to six.    
     
     
         32 . The article as recited in  claim 26 , wherein the binding partner includes a polyamino acid tag that coordinates the metal ion.  
     
     
         33 . A method of making an article having a surface for capturing a target molecule, comprising: 
 formulating a solution containing a mixture of at least a first and a second species, the first species having a formula:      X—R-Ch    where X, R, and Ch are each selected such that X represents a functional group that adheres to the surface, R represents a spacer moiety that promotes self-assembly of the mixed monolayer, and Ch represents a chelating agent that coordinates a metal ion,    wherein the second species is selected to form a mixed self-assembled monolayer with the first species, and the second species and first species are present in the solution at a molar ratio of at least 70:30; and    exposing to the surface the solution for a period of time sufficient to form a self-assembled mixed monolayer of the first and second species on the surface.    
     
     
         34 . The method as recited in  claim 33 , wherein the solution contains a molar ratio of the second species to the first species of at least about 70:30.  
     
     
         35 . The method as recited in  claim 33 , further comprising exposing to the surface a solution containing a metal ion and allowing the chelating agent to coordinate the metal ion.  
     
     
         36 . The method as recited in  claim 35 , further comprising exposing to the surface a solution containing a binding partner of a biological molecule, and allowing the binding partner to coordinate the metal ion.  
     
     
         37 . The method as recited in  claim 36 , further comprising exposing to the surface a solution containing a a biological molecule, and allowing the biological molecule to biologically bind to the binding partner.  
     
     
         38 . The method as recited in  claim 33 , wherein the article is a sensing element suitable for use in a biosensor, and the surface is a sensing surface.  
     
     
         39 . A method of capturing a biological molecule, comprising: 
 providing an article that has a surface having adhered thereto a species of a formula:      X—R-Ch-M-BP    wherein X represents a functional group that adheres to a surface, R represents a self-assembled monolayer-promoting spacer moiety, Ch represents a chelating agent that coordinates a metal ion, M represents a metal ion coordinated by the chelating agent, and BP represents a binding partner of the biological molecule, the binding partner being coordinated to the metal ion;    contacting the surface with a medium containing a biological molecule and allowing the molecule to biologically bind to the binding partner.    
     
     
         40 . The method as recited in  claim 39 , wherein the article is a biosensor element.  
     
     
         41 . The method as recited in  claim 39 , further comprising determining the biological molecule.  
     
     
         42 . The method as recited in  claim 41 , wherein the determining step comprises detecting a physical change associated with the surface.  
     
     
         43 . A method of capturing a biological molecule, comprising: 
 providing a solid phase having a surface, a chelating agent immobilized at the surface, a metal ion coordinated by the chelating agent, and a biological binding partner of the biological molecule coordinated to the metal ion; and    bringing into contact with the surface a medium containing the biological molecule for a period of time sufficient to allow the biological molecule to biologically bind to the binding partner.    
     
     
         44 . The method as recited in  claim 43 , wherein the biological binding partner includes a polyamino acid tag that coordinates the metal ion, and a recognition region for the biological molecule remote from the polyamino acid tag.  
     
     
         45 . The method as recited in  claim 43 , wherein the chelating agent, metal ion, and binding partner are members of a species of a formula:  
         X—R-Ch-M-BP  wherein X represents a functional group that adheres to the surface, R represents a self-assembled monolayer-promoting spacer moiety, Ch represents the chelating agent, M represents the metal ion coordinated by the chelating agent, and BP represents the binding partner coordinated to the metal ion.    
     
     
         46 . The method as recited in  claim 43 , further comprising determining the biological molecule.  
     
     
         47 . The method as recited in  claim 46 , wherein the determining step comprises detecting a physical change associated with the surface.  
     
     
         48 . The method as recited in  claim 47 , wherein the determining step comprises detecting a plasmon resonance change associated with the surface.  
     
     
         49 . A sensing element suitable for use in a biosensor, for determination of a biological molecule, comprising: 
 a substrate;    metal film on the substrate having a surface;    a self-assembled monolayer of a species X—R-NA-NAB adhered to the surface, wherein X represents a functional group that adheres to the surface, R represents a spacer moiety that promotes formation of a self-assembled monolayer of a plurality of the species, NA represents a nucleic acid strand, and NAB represents a nucleic acid strand that is a binding partner of NA and a binding partner of the biological molecule to be determined.