Method and apparatus for ordered nanoplasmonic sensor formation through microfluidic assembly

Abstract

A method of making a plasmon-resonance biosensor includes conjugating precious metal nanorods with form factor at least 1.5 with a biological probe material. Microfluidic chambers of volume under 0.025 microliter are formed over a substrate, and an aqueous suspension of the conjugated nanorods is injected into the chambers. The nanorods are organized in rows and aligned in long dimension along the rows. The biosensor is configured to be read by obtaining an optical absorption spectrum upon exposure to the analyte. The biosensor includes precious metal nanorods organized in rows with long dimension approximately parallel to the rows. The nanorods are conjugated with biological probes capable of binding to an analyte, the probes may be an aptamer, an antibody, a protein-nucleic acid (PNA), a complimentary DNA, or an enzyme having a binding site.

What is claimed is: 
     
         1 . A method of detecting an analyte in a sample comprising:
 providing a plasmon-resonance biosensor comprising:
 a plurality of noble or precious metal nanorods, the noble or precious metal nanorods having a long dimension greater than a narrow dimension by a factor of at least 1.5 and a maximum dimension less than one half micron, 
 the nanorods organized in rows with the long dimension oriented approximately parallel to the rows, and 
 the noble or precious metal nanorods are conjugated with a biological probe material capable of binding to the analyte; 
   exposing the plasmon-resonance biosensor to the sample; and   obtaining a post-exposure optical absorption spectrum of the plasmon-resonance biosensor.   
     
     
         2 . The method of  claim 1 , further comprising:
 obtaining a baseline absorbance spectrum prior to exposing the plasmon-resonance biosensor to the sample; and   comparing the post-exposure optical absorption spectrum with the baseline absorbance spectrum.   
     
     
         3 . The method of  claim 1 , obtaining a baseline absorbance spectrum comprises exposing the plasmon-resonance biosensor to a neutral solution not bearing the analyte and recording the baseline absorbance spectrum. 
     
     
         4 . The method of  claim 1 , wherein the noble or precious metal nanorods comprise gold. 
     
     
         5 . The method of  claim 1 , wherein the noble or precious metal nanorods are disposed in a plurality of patches on a substrate, with at least a first patch conjugated with a first biological probe material and a second patch on a same substrate conjugated with a second biological probe material. 
     
     
         6 . The method of  claim 1 , wherein the biological probe material is an aptamer, an antibody, a protein-nucleic acid (PNA), a complimentary DNA, or an enzyme having a binding site. 
     
     
         7 . The method of  claim 1 , wherein the biological probe material comprises a protein-nucleic acid (PNA) compound. 
     
     
         8 . The method of  claim 7 , wherein the PNA compound is configured to bind to deoxyribose nucleic acid (DNA) strands released by a particular tumor type. 
     
     
         9 . The method of  claim 8  wherein the particular tumor type is a cancerous tumor. 
     
     
         10 . The method of  claim 9 , wherein the cancer is a pancreatic cancer. 
     
     
         11 . The method of  claim 6 , wherein the analyte comprises DNA strands released by a particular tumor type. 
     
     
         12 . The method of  claim 11  wherein the analyte comprises a blood-based biomarker associated with cancer. 
     
     
         13 . The method of  claim 6  wherein the analyte is associated with an infectious disease. 
     
     
         14 . The method of  claim 6  wherein the biological probe material comprises an antibody. 
     
     
         15 . The method of  claim 6  wherein the analyte comprises a blood-based biomarker of interest during prenatal testing. 
     
     
         16 . A method of making a plasmon-resonance biosensor comprising:
 conjugating noble or precious metal nanorods, the noble or precious metal nanorods having a long dimension greater than a narrow dimension by a factor of at least 1.5 and the long dimension less than one half micron, with a biological probe material capable of binding to an analyte;   forming a plurality of microfluidic chambers, each chamber having volume less than 0.025 microliter, over a substrate;   injecting an aqueous suspension of the conjugated precious metal nanorods into the microfluidic chambers;   organizing the conjugated precious metal nanorods in rows of conjugated precious metal nanorods; and   aligning a long dimension of the conjugated precious metal nanorods along the rows of conjugated precious metal nanorods.   
     
     
         17 . The method of  claim 16  wherein:
 the step of forming a plurality of microfluidic chambers is performed by mating a stamp to a nanowrinkled substrate, the nanowrinkled substrate having nanowrinkles with depth less than 300 nanometers, and pitch less than 500 nanometers; and 
 the organizing the conjugated noble or precious metal nanorods in rows and aligning the long dimension of the conjugated noble or precious metal nanorods along the rows is performed by gravitational settling of the conjugated noble or precious metal nanorods into the nanowrinkles. 
 
     
     
         18 . The method of  claim 17  wherein the nanowrinkles align with a direction of flow in the microfluidic chambers of the aqueous suspension of the conjugated nanoparticles, and further comprising removing the stamp and transferring the rows of conjugated noble or precious metal nanorods from the nanowrinkled substrate onto a second substrate. 
     
     
         19 . The method of  claim 18  wherein the biological probe material comprises an aptamer, an antibody, a protein-nucleic acid (PNA), a complimentary DNA, or an enzyme having a binding site for the analyte. 
     
     
         20 . The method of  claim 18  wherein the noble or precious metal nanorods comprise gold.