Biobarcode assay

Hill HD, Mirkin CA. The biobarcode assay for the detection of protein and nucleic acid targets using DTT-induced hgand exchange. Nat. Rotoc. 2006 1 324-336. 

Figure 12.12 Biobarcode assay for DNA detection. Magnetic microparticles (Mag) hybridize to specific targets. AuNPs functionalized with target-specific barcode strands are then added. After magnetic separation, the barcodes are released from the surface of the AuNPs by DTT. Subsequently the barcodes are detected using the scanometric method. (Reproduced with permission fi om C. S. Thaxton et al., Anal. Chem. 2005, 77, 8174-8178. Copyright 2005 American Chemical Society.) (See color insert.)...

While this prototype assay was relatively simple, the LOD was only 20 nM, still far above that of a conventional ELISA method. To overcome the hmitations of the prototype protein assay, a new generation of the biobarcode assay for protein detection was developed (66). The fundamental scheme of this assay is similar to the biobarcode assay for DNA detection discussed previously. This assay relies on MMPs functionalized with antibodies specific to the target protein. To enable protein detection and take... 

In addition to the solution-phase protein detection assays such as biobarcode assays, a surface-based protein detection method was developed by Niemeyer and Ceyhan (70). In this work, a biotin-labeled antibody was conjugated to DNA using streptavidin as a tinker molecule. This conjugate was hybridized to complementary DNA-AuNPs and antibody-functionalized AuNPs. These particles are allowed to form a sandwich structure with a target protein and a second antibody immobilized on a flat surface. This was followed by a silver enhancement step catalyzed by the AuNPs which resulted in a LOD of 50 fmol (200 pM). This method is conceptually similar to the corresponding surface-based scanometric detection of DNA. Further work demonstrated a similar protein detection scheme without the silver enhancement (71). Instead, multiple layers of secondary DNA-AuNPs were used to increase signal enhancement [LOD = 0.1 finol (2 pM)]. 

C) Biobarcode assay and scanometric detection of Itie barcodes... 

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