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    Biomaterials Friday Sessions
       Session BI-FrM

Paper BI-FrM7
DNA Assay Sensitivity in the BARC Magnetoresistive Biosensor

Friday, November 2, 2001, 10:20 am, Room 102

Session: Biosensors
Presenter: M.A. Piani, NOVA Research, Inc.
Authors: M.A. Piani, NOVA Research, Inc.
R.J. Colton, Naval Research Laboratory
M. Miller, Naval Research Laboratory
J.C. Rife, Naval Research Laboratory
P.E. Sheehan, Naval Research Laboratory
C.R. Tamanaha, Geo-Centers, Inc.
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
The Bead ARray Counter (BARC) biosensor uses DNA microarrays, magnetic microbeads, and giant magnetoresistive (GMR) magnetic field sensors to detect and identify biological molecules.@footnote 1@ The core of the sensor is a small, microfabricated chip containing an array of 64 GMR sensors. Distinct single stranded DNA capture probes are immobilized on each sensor. Complementary DNA in a sample is allowed to hybridize on the chip, and is then labeled with magnetic microbeads that are detected by the GMR sensors. The overall system sensitivity is a convolution of the chemical and GMR sensor sensitivities. The chemical sensitivity is determined by the effectiveness of the hybridization and labeling assay. Our current chemical sensitivity is 10 fM for a 60 minute hybridization of 30 bp oligonucleotides. Our efforts to improve this sensitivity involves two tracks. First, we are working with chemiluminescent assays in order to optimize the immobilization and hybridization steps. Second, we are experimenting with peptide nucleic acid (PNA) capture probes instead of DNA. PNA is a synthetic oligonucleotide analog with a neutral backbone that hybridizes with complementary DNA with a higher affinity then the DNA complement. Furthermore, PNA molecules are resistant to nucleases ("DNAses"), enabling the BARC chip to be reconstituted and reused following treatment with the enzyme. Our initial results with PNA indicate an increase in chemical sensitivity of one to two orders of magnitude. @FootnoteText@ @footnote 1@Edelstein et al., Biosensors & Bioelectronics 14, 805 (2000).