title: Nanoparticle probes and mid-infrared chemical imaging for DNA microarray detection.
abstract: To date most mid-infrared spectroscopic studies have been limited, due to lack of sensitivity, to the structural characterization of a single oligonucleotide probe immobilized over the entire surface of a gold-coated slide or other infrared substrate. By contrast, widely used and commercially available glass slides and a microarray spotter that prints approximately 120-μm-diameter DNA spots were employed in the present work. To our knowledge, mid-infrared chemical imaging (IRCI) in the external reflection mode has been applied in the present study for the first time to the detection of nanostructure-based DNA microarrays spotted on glass slides. Alkyl amine-modified oligonucleotide probes were immobilized on glass slides that had been prefunctionalized with succinimidyl ester groups. This molecular fluorophore-free method entailed the binding of gold-nanoparticle-streptavidin conjugates to biotinylated DNA targets. Hybridization was visualized by the silver enhancement of gold nanoparticles. The adlayer of silver, selectively bound only to hybridized spots in a microarray, formed the external reflective infrared substrate that was necessary for the detection of DNA hybridization by IRCI in the present proof-of-concept study. IRCI made it possible to discriminate between diffuse and specular external reflection modes. The promising qualitative results are presented herein, and the implications for quantitative determination of DNA microarrays are discussed.
authors.affiliation: Division of Analytical Chemistry, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, 5100 Paint Branch Parkway, College Park, Maryland 20740-3835, USA. magdi.mossoba@fda.hhs.gov
authors.forename: Magdi M
authors.initials: MM
authors.lastname: Mossoba
authors.forename: Sufian F
authors.initials: SF
authors.lastname: Al-Khaldi
authors.forename: Brianna
authors.initials: B
authors.lastname: Schoen
authors.forename: Betsy Jean
authors.initials: BJ
authors.lastname: Yakes
mesh_terms: D003016:Clostridium perfringens; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D005898:Glass; D006046:Gold / Q000737:chemistry; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D017640:Silicates; D012834:Silver / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods*; D019809:Streptavidin / Q000737:chemistry / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D015335:Molecular Probes; D017640:Silicates; D012834:Silver; D006046:Gold; D019809:Streptavidin