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Nanoparticle-Based Bio-Bar Codes for the Ultrasensitive Detection of Proteins
Jwa-Min Nam,*C. Shad Thaxton,*Chad A. Mirkin
An ultrasensitive method for detecting protein analytes hasbeen developed. The system relies on magnetic microparticleprobes with antibodies that specifically bind a target of interest[prostate-specific antigen (PSA) in this case] and nanoparticleprobes that are encoded with DNA that is unique to the proteintarget of interest and antibodies that can sandwich the targetcaptured by the microparticle probes. Magnetic separation ofthe complexed probes and target followed by dehybridizationof the oligonucleotides on the nanoparticle probe surface allowsthe determination of the presence of the target protein by identifyingthe oligonucleotide sequence released from the nanoparticleprobe. Because the nanoparticle probe carries with it a largenumber of oligonucleotides per protein binding event, thereis substantial amplification and PSA can be detected at 30 attomolarconcentration. Alternatively, a polymerase chain reaction onthe oligonucleotide bar codes can boost the sensitivity to 3attomolar. Comparable clinically accepted conventional assaysfor detecting the same target have sensitivity limits of 3 picomdar,six orders of magnitude less sensitive than what is observedwith this method.
Department of Chemistry and Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60201, USA
* These authors contributed equally to the work.
To whom correspondence should be addressed. E-mail: camirkin{at}chem.northwestern.edu
Low-Field Magnetic Separation of Monodisperse Fe3O4 Nanocrystals..
C. T. Yavuz, J. T. Mayo, W. W. Yu, A. Prakash, J. C. Falkner, S. Yean, L. Cong, H. J. Shipley, A. Kan, M. Tomson, et al. (2006)
Science
314, 964-967
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Acceleration of the recognition rate between grafted ligands and receptors with magnetic forces.
J. Baudry, C. Rouzeau, C. Goubault, C. Robic, L. Cohen-Tannoudji, A. Koenig, E. Bertrand, and J. Bibette (2006)
PNAS
103, 16076-16078
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Nanodiagnostics: A New Frontier for Clinical Laboratory Medicine.
H. M.E. Azzazy, M. M.H. Mansour, and S. C. Kazmierczak (2006)
Clin. Chem.
52, 1238-1246
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Oligonucleotide-modified gold nanoparticles for intracellular gene regulation..
N. L. Rosi, D. A. Giljohann, C. S. Thaxton, A. K. R. Lytton-Jean, M. S. Han, and C. A. Mirkin (2006)
Science
312, 1027-1030
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Gold nanoparticles-based protease assay..
C. Guarise, L. Pasquato, V. De Filippis, and P. Scrimin (2006)
PNAS
103, 3978-3982
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Homogeneous point mutation detection by quantum dot-mediated two-color fluorescence coincidence analysis.
H.-C. Yeh, Y.-P. Ho, I.-M. Shih, and T.-H. Wang (2006)
Nucleic Acids Res.
34, e35
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A real-time PCR-based method for determining the surface coverage of thiol-capped oligonucleotides bound onto gold nanoparticles..
E.-Y. Kim, J. Stanton, R. A. Vega, K. J. Kunstman, C. A. Mirkin, and S. M. Wolinsky (2006)
Nucleic Acids Res.
34, e54
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A modular microfluidic architecture for integrated biochemical analysis.
K. A. Shaikh, K. S. Ryu, E. D. Goluch, J.-M. Nam, J. Liu, C. S. Thaxton, T. N. Chiesl, A. E. Barron, Y. Lu, C. A. Mirkin, et al. (2005)
PNAS
102, 9745-9750
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Magnetically assisted DNA assays: high selectivity using conjugated polymers for amplified fluorescent transduction.
H. Xu, H. Wu, F. Huang, S. Song, W. Li, Y. Cao, and C. Fan (2005)
Nucleic Acids Res.
33, e83
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Nanoscience enables ultrasensitive detection of Alzheimer's biomarker.
From The Cover: Nanoparticle-based detection in cerebral spinal fluid of a soluble pathogenic biomarker for Alzheimer's disease.
D. G. Georganopoulou, L. Chang, J.-M. Nam, C. S. Thaxton, E. J. Mufson, W. L. Klein, and C. A. Mirkin (2005)
PNAS
102, 2273-2276
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Evaluating Sandwich Immunoassays in Microarray Format in Terms of the Ambient Analyte Regime.
P. Saviranta, R. Okon, A. Brinker, M. Warashina, J. Eppinger, and B. H. Geierstanger (2004)
Clin. Chem.
50, 1907-1920
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Sensitive Assay for Identification of Methicillin-Resistant Staphylococcus aureus, Based on Direct Detection of Genomic DNA by Use of Gold Nanoparticle Probes.
R. Ramakrishnan, W. Buckingham, M. Domanus, L. Gieser, K. Klein, G. Kunkel, A. Prokhorova, and P. V. Riccelli (2004)
Clin. Chem.
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Simultaneous Determination of {alpha}-Fetoprotein and Free {beta}-Human Chorionic Gonadotropin by Element-Tagged Immunoassay with Detection by Inductively Coupled Plasma Mass Spectrometry.
S. Zhang, C. Zhang, Z. Xing, and X. Zhang (2004)
Clin. Chem.
50, 1214-1221
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Methods for Transcriptional Profiling in Plants. Be Fruitful and Replicate.
B. C. Meyers, D. W. Galbraith, T. Nelson, and V. Agrawal (2004)
Plant Physiology
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3 picomdar, six orders of magnitude less sensitive than what is observed with this method. 
To whom correspondence should be addressed. E-mail: 
