Imaging of enzymatic activity

Abstract

The invention features methods of detecting enzymatic activity (e.g., in a magnetic resonance image). In general, the methods include: (1) providing a monomeric substrate (e.g., a substrate that is polymerizable in the presence of an enzyme or as a result of an enzyme-catalyzed reaction), having the generic structure X-Y-Z, where X includes a chelator moiety having a chelated paramagnetic or superparamagnetic metal atom or ion, Y includes a linker moiety (e.g., to provide a covalent or non-covalent chemical bond or bonds between X and Z), and Z includes a polymerizing moiety; (2) contacting the substrate with a target tissue, wherein the substrate undergoes polymerization to form a paramagnetic or superparamagnetic polymer, the polymerization being catalyzed by an enzyme in an extracellular matrix or bound to the surfaces of cells of the target tissue; and (3) detecting an increase in relaxivity for the polymer relative to an equivalent amount of unpolymerized substrate. The invention also features substrate compositions.

1 - 27 . (canceled).  
     
     
         28 . A composition comprising a compound of formula X-Y-Z, wherein X comprises a chelator moiety, Y comprises a linker moiety, and Z comprises a polymerizing moiety.  
     
     
         29 . The composition of  claim 28 , wherein the compound further comprises a paramagnetic or superparamagnetic metal atom or ion.  
     
     
         30 . The composition of  claim 29 , wherein the paramagnetic or superparamagnetic metal atom or ion is a transition metal atom or ion.  
     
     
         31 . The composition of  claim 29 , wherein the paramagnetic or superparamagnetic metal atom or ion is a lanthanide atom or ion.  
     
     
         32 . The composition of  claim 29 , wherein the metal ion is selected from the group consisting of an iron ion, a dysprosium ion, a europium ion and a manganese ion.  
     
     
         33 . The composition of  claim 29 , wherein the metal ion is a gadolinium ion.  
     
     
         34 . The composition of  claim 28 , wherein the polymerizing moiety comprises any chemical group that can be chemically modified as a result of the catalytic activity of an enzyme to form a covalent chemical bond between either (1) Z and another compound of formula X-Y-Z or (2) Z and any polymer or macromolecule.  
     
     
         35 . The composition of  claim 28 , wherein Z is a moiety that can be accommodated by the catalytic center of an enzyme.  
     
     
         36 . The composition of  claim 28 , wherein X comprises a structure selected from the group consisting of: 
 1,4,7,10-tetraazacyclodo-decane-N,N′,N″,N′″-tetraacetic acid;    1,4,7,10-tetraaza-cyclododecane-N,N′,N″-triacetic acid;    1,4,7-tris(carboxymethyl)-10-(2′-hydroxypropyl)-1,4,7,10-tetraazocyclodecane;    1,4,7-triazacyclonane-N,N′,N″-triacetic acid;    1,4,8,11-tetraazacyclotetra-decane-N,N′,N″,N′″-tetraacetic acid;    diethylenetriamine-pentaacetic acid (DTPA);    ethylenedicysteine;    bis(aminoethanethiol)carboxylic acid;    triethylenetetraamine-hexaacetic acid;    ethylenediamine-tetraacetic acid (EDTA);    1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid;    N-(hydroxy-ethyl)ethylenediaminetriacetic acid;    nitrilotriacetic acid; and    ethylene-bis(oxyethylene-nitrilo)tetraacetic acid.    
     
     
         37 . The composition of  claim 28 , wherein Z comprises the following structure:  
       
         
           
           
               
               
           
         
         wherein:  
         R 1 , R 2 , R 3 , R 4  and R 5  are selected independently from the group consisting of H; R 6 , wherein R 6  is C 1 -C 6  unsubstituted alkyl; NHC(O)R 6 ; OH; or NR 7 R 8 , wherein R 7  and R 8  are H or R 6 ;  
         provided that at least one of R 1 , R 2 , R 3 , R 4  and R 5  is OH.  
       
     
     
         38 . The composition of  claim 37 , wherein R 1 , R 2 , R 3 , R 4  or R 5  is at an ortho position relative to the OH substituent, and is selected from the group consisting of OH and OCH 3 .  
     
     
         39 . The composition of  claim 37 , wherein R 1 , R 2 , R 3 , R 4  or R 5  is at a meta position relative to the OH substituent, and is selected from the group consisting of NHC(O)R 6  and NR 7 R 8 .  
     
     
         40 . The composition of  claim 28 , wherein Y comprises a structure selected from the group consisting of: an amino acid, an oligopeptide comprising 2-6 amino acid residues, a nucleotide, an oligonucleotide comprising 2-6 nucleotide residues, a C 3 -C 12  alkyl group, a polyethyleneimine, a saccharide, an oligosaccharide, a medium chain fatty acid, a polyamidoamine, a polyacrylic acid, and a polyalcohol.  
     
     
         41 . The composition of  claim 28 , wherein Y comprises an amino acid or oligopeptide containing 2-6 amino acid residues.  
     
     
         42 . The composition of  claim 41 , wherein the oligopeptide comprises a glycine residue.  
     
     
         43 . The composition of  claim 29 , wherein the compound comprises the formula:  
       
         
           
           
               
               
           
         
         where R1 is selected from the group consisting of H, OH, and OCH 3 .