Nanocrystal based biomolecule detection

Abstract

A new signal amplification method exploiting the dense atom packing in metallic nanocrystals has been developed for detecting target substances. By dissolving nanocrystals to individual ions that are stoichiometrically converted to chromophores and quantified photometrically, extremely high signal amplification can be achieved. Signal amplification is fully determined by the total number of atoms in the nanocrystals bound to a single target molecule. The disclosed nanocrystal amplification method can be implemented with a rich selection of metal/metal oxide nanocrystals and metal-reactive chromogenic substrates. The chromogenic reactions can be either solution-based or surface-based and performed in aqueous or organic phase, supporting a variety of assay formats

We claim: 
     
         1 . A method for detecting or quantifying a target substance comprising contacting a sample containing or suspected of containing the target substance with a metal or metal oxide nanocrystal conjugated to a binding moiety that specifically binds to the target substance,
 inducing the release of the metal ions of the nanocrystals,   stoichiometrically converting the metal ions into chromophores; and   photometrically detecting or quantifying the chromophores.   
     
     
         2 . The method of  claim 1 , wherein the target substance is photometrically quantified by correlating to a predetermined standard curve. 
     
     
         3 . The method of  claim 1 , wherein the chromophores are detected by measuring absorbance of the sample. 
     
     
         4 . The method of  claim 3 , wherein the nanocrystal is wüstite and the absorbance is measured at 562 nm. 
     
     
         5 . The method of  claim 1 , wherein the chromophores are water-soluble chelates with ferrozine molecules or insoluble precipitates of Prussian blue. 
     
     
         6 . The method of  claim 1 , wherein the sample is adsorbed or bound to a solid substrate. 
     
     
         7 . A method for detecting or quantifying a target substance comprising applying a sample containing or suspected of containing a target substance to a solid support comprising a capture reagent immobilized on the solid support, wherein the capture reagent specifically binds the target substance;
 applying the detection agent of  claim 1  to the solid support, wherein the detection agent specifically binds the target substance;   inducing the release of the metal ions of the nanocrystals,   stoichiometrically converting the metal ions into chromophores; and   photometrically detecting or quantifying the chromophores   
     
     
         8 . The method of  claim 7 , wherein the nanocrystal comprises wüstite and the chromophores are water-soluble chelates with ferrozine molecules or insoluble precipitates of Prussian blue.