Methods and materials for the detection of melamine

Abstract

Methods and materials for the detection of melamine in test samples such as foodstuffs are described. Embodiments of the invention comprise combining a test sample suspected of containing melamine with a particle that produces a colorimetric and/or turbidimetric signal that is dependent upon the concentration of melamine in the test sample. In certain embodiments of the invention, the particles and test sample are combined together with a chemical compound selected to induce the aggregation melamine in a manner that amplifies the colorimetric and/or turbidimetric signal of the assay. In some embodiments of the invention, the aggregation inducing agent is not physically coupled to the particles used in the assays. In other embodiments of the invention, the aggregation inducing agent is physically coupled to the particles used in these assays.

1 . A method of observing the presence or absence of melamine in a test sample comprising:
 combining the test sample with a plurality of particles in an aqueous media, wherein the particles have an average diameter of between 1 and 2500 nm;   mixing the test sample and the particles so as to allow melamine, if present in the test sample, to interact with the particles;   monitoring the media to observe a change in color or turbidity; and   correlating changes in the color or turbidity of the media with the presence or absence of melamine in the test sample,   so that the presence or absence of melamine in a test sample is observed.   
     
     
         2 . The method of  claim 1 , further comprising combining the test sample with a melamine aggregation inducing agent. 
     
     
         3 . The method of  claim 2 , wherein the aggregation inducing agent is uric acid, cyanuric acid, uracil, acetic acid, oxalic acid, tannin, thymine, guanine, riboflavin, barbituric acid, maleimide, succinimide, diacetamide or glutarimide. 
     
     
         4 . The method of  claim 2 , wherein the aggregation inducing agent is coupled to the particles. 
     
     
         5 . The method of  claim 2 , wherein the aggregation inducing agent is not coupled to the particles. 
     
     
         6 . The method of  claim 1  wherein the media is monitored to observe changes in turbidity. 
     
     
         7 . The method of  claim 1  wherein the media is monitored to observe changes in both color and turbidity. 
     
     
         8 . The method of  claim 1 , wherein the media is monitored with the naked eye. 
     
     
         9 . The method of  claim 1 , wherein a change in the color of the media is observed with a spectrometer. 
     
     
         10 . The method of  claim 1 , wherein a change in the turbidity of the media is observed with a turbidimeter. 
     
     
         11 . The method of  claim 1 , wherein the change in color or turbidity is observed in less than 5, 4, 3, 2 or 1 minute(s). 
     
     
         12 . The method of  claim 1 , wherein the concentration of melamine in the test sample is less than 10, 5, 4, 3, 2 or 1 parts per million (PPM). 
     
     
         13 . The method of  claim 1 , wherein correlating changes in color or turbidity with the presence or absence of melamine in the test sample includes comparing changes in color or turbidity in the test sample with changes in color or turbidity in a control sample having a known amount of melamine. 
     
     
         14 . The method of  claim 1 , wherein the test sample is pretreated prior to its combination with the particles, wherein the pretreatment comprises:
 (a) altering pH;   (b) centrifugation;   (c) precipitation;   (d) extraction;   (e) filtration; or   (f) dilution.   
     
     
         15 . A kit for the detection of melamine in a test sample comprising:
 particles having an average diameter of between 1 and 2500 nm;   a melamine aggregation inducing agent; and   instructions for using the kit to detect melamine in a test sample.   
     
     
         16 . The kit of  claim 15 , wherein the particles are gold nanoparticles having an average diameter of between 1 and 100 nanometers. 
     
     
         17 . The kit of  claim 16 , wherein the aggregation inducing agent is uric acid, cyanuric acid, uracil, acetic acid, oxalic acid, tannin, thymine, guanine, riboflavin, barbituric acid, maleimide, succinimide, diacetamide or glutarimide. 
     
     
         18 . The kit of  claim 15 , wherein the aggregation forming agent is coupled to the gold nanoparticles. 
     
     
         19 . The kit of  claim 15 , further comprising a melamine control sample comprising a known amount of melamine. 
     
     
         20 . A composition of matter made by combining in an aqueous media:
 melamine; and   particles having an average diameter of between 1 and 2500 nm;   wherein the composition exhibits a color or a turbidity that is dependent upon the concentration of melamine in the composition.   
     
     
         21 . The composition of  claim 20 , wherein the particles are gold nanoparticles having an average diameter of between 1 and 25 nanometers. 
     
     
         22 . The composition of  claim 20 , further comprising an aggregation inducing agent selected from the group consisting of uric acid, cyanuric acid, uracil, acetic acid, oxalic acid, tannin, thymine, guanine, riboflavin, barbituric acid, maleimide, succinimide, diacetamide and glutarimide. 
     
     
         23 . The composition of  claim 22 , wherein the aggregation inducing agent is coupled to the particles. 
     
     
         24 . The composition of  claim 20 , further comprising a polypeptide compound. 
     
     
         25 . The composition of  claim 24 , wherein the polypeptide is casein or gluten.