Reagentless Ceria-Based Colorimetric Sensor

Abstract

A colorimetric reagent in the form of nanoparticles, composite nanoparticles, and nanoparticle coatings, including methods of use, methods of preparation, deposition, and assembly of related devices and specific applications. The colorimetric reagent comprises cerium oxide nanoparticles which are used in solution or immobilized on a solid support, either alone or in conjunction with oxidase enzymes, to form an active colorimetric component that reacts with an analyte to form a colored complex. The rate of color change and the intensity of the color are proportional to the amount of analyte present in the sample. Also described is the use of ceria and doped ceria nanoparticles as an oxygen storage/delivery vehicle for oxidase enzymes and applications in biocatalytic processes in anaerobic conditions of interest in biomedicine and bioanalysis. Further described are a variety of related applications of the disclosed technology including clinical diagnosis, in vivo implantable devices, food safety, and fermentation control.

What is claimed is: 
     
         1 . A system for the colorimetric determination of an analyte in a sample, the system comprising:
 a sample; and   a colorimetric reagent comprising a plurality of ceria nanoparticles and a plurality of analyte-specific oxidase enzyme molecules;   wherein a measureable change in an optical property of the colorimetric reagent is associated with the presence of the analyte in said sample.   
     
     
         2 . The system of  claim 1 , wherein at least a portion of the colorimetric reagent is immobilized on a support. 
     
     
         3 . The system of  claim 1 , wherein the colorimetric reagent further comprises a stabilizing agent. 
     
     
         4 . The system of  claim 1 , wherein the colorimetric reagent further comprises a linking agent. 
     
     
         5 . The system of  claim 1 , further comprising:
 an optical sensor adapted to measure said optical property.   
     
     
         6 . The system of  claim 1 , wherein the plurality of ceria nanoparticles comprise cerium oxides in at least two different valence states. 
     
     
         7 . The system of  claim 1 , wherein the plurality of ceria nanoparticles are doped with a metal. 
     
     
         8 . The system of  claim 7 , wherein the metal is gold. 
     
     
         9 . The system of  claim 1 , wherein the colorimetric reagent does not comprise a dye. 
     
     
         10 . The system of  claim 1 , wherein the analyte-specific oxidase enzyme molecule is glucose oxidase, and the analyte is glucose. 
     
     
         11 . The system of  claim 1 , wherein the analyte-specific oxidase enzyme molecule is alcohol oxidase, and the analyte is ethanol. 
     
     
         12 . The system of  claim 1 , wherein the analyte-specific oxidase enzyme molecule is cholesterol oxidase, and the analyte is cholesterol. 
     
     
         13 . The system of  claim 1 , wherein the analyte-specific oxidase enzyme molecule is lactate oxidase, and the analyte is lactate. 
     
     
         14 . The system of  claim 1 , wherein the plurality of ceria nanoparticles have a diameter ranging from about 2 nm to about 20 nm. 
     
     
         15 . The system of  claim 1 , wherein the colorimetric reagent is contacted by the sample under anaerobic conditions. 
     
     
         16 . A system for the colorimetric determination of an analyte in a sample, the system comprising:
 a sample;   a colorimetric reagent comprising a plurality of ceria nanoparticles doped with a metal, and a plurality of analyte-specific oxidase enzyme molecules; and   an optical sensor adapted to measure an optical property of the colorimetric reagent, wherein a change in said optical property is associated with the presence of the analyte in said sample.   
     
     
         17 . The system of  claim 16 , wherein at least a portion of the colorimetric reagent is immobilized on a support. 
     
     
         18 . A kit for the colorimetric determination of an analyte in a sample, the system comprising:
 a colorimetric reagent comprising a plurality of ceria nanoparticles and a plurality of analyte-specific oxidase enzyme molecules; and   an optical sensor adapted to measure an optical property of the colorimetric reagent, wherein a change in said optical property is associated with the presence of the analyte in said sample.   
     
     
         19 . The kit of  claim 18 , wherein at least a portion of the colorimetric reagent is immobilized on a support. 
     
     
         20 . The kit of  claim 18 , wherein the plurality of ceria nanoparticles comprise cerium oxides in at least two different valence states.