Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Objective• DNA amplification (eg. PCR) advances in forensic, clinical applications• Comparable protein amplification tools (?) aid medical diagnostics, etc.• Current approach: Immuno-PCR (tag proteins with DNA, then detect with PCR)• Drawbacks: 1. Complex conjugation chemistries to link DNA and protein, 2. PCR requirements, 3. Low sensitivity • Need for simple, sensitive assay for protein amplification and detectionNanoparticle-Based Bio-Bar Codes for the Ultrasensitive Detection of ProteinsJwa-Min Nam, C. Shad Thaxton , Chad A. Mirkin , Science September 2003Some background info:1. Model protein detection assay using Prostate Specific Antigen (PSA)• PSA – widely used tumor marker in prostate and breast cancer detection • Disease relapse after surgery marked by very low levels of PSA• Need for ultrasensitive assay to detect PSA levels at early stage of relapse2. Antibodies (Ab) are a class of proteins that recognize and specifically bind to their target protein 3. DNA hybridization: Based on binding of complementary DNA sequencesA-TC-GT-AG-CProbe design and preparationGold nanoparticles (NP) heavily functionalized with hybridized DNA (biobarcodes + capture DNA) and PSA Ab Magnetic microparticles (MMP, 1 µm polyamine beads with magnetic iron oxide cores) functionalized with PSA AbPSA detection and bar-code DNA amplification and identificationScanometric detection of PSA-specific bar-code DNAMol. BioSyst., 2006, 2, 470–476Bio barcode assay vs. ELISA (gold standard)SummaryBiobarcode assay offers several advantages over current methods1. Signal amplification due to high ratio of biobarcodes per protein molecule2. Also, assay is homogenous (i.e. MMPs are added in solution) – hence the volume of MMPs can be increased to improve binding kinetics Faster, more sensitive assay3. No need for complex conjugation chemistries 4. Direct detection of DNA – hence elimination of background signal from protein or other biomolecules5. Potential for multiplexing and simultaneous detection of several
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