title: An on-chip thin film photodetector for the quantification of DNA probes and targets in microarrays.
abstract: A flat microdevice which incorporates a thin-film amorphous silicon (a-Si:H) photodetector with an upper layer of functionalized SiO2 is used to quantify the density of both immobilized and hybridized DNA oligonucleotides labeled with a fluorophore. The device is based on the photoconductivity of hydrogenated amorphous silicon in a coplanar electrode configuration. Excitation, with near UV/blue light, of a single-stranded DNA molecule tagged with the fluorophore 1-(3-(succinimidyloxycarbonyl)benzyl)-4-(5-(4-methoxyphenyl)oxazol-2-yl) pyridinium bromide (PyMPO), results in the emission of visible light. The emitted light is then converted into an electrical signal in the photodetector, thus allowing the optoelectronic detection of the DNA molecules. The detection limit of the present device is of the order of 1 x 10(12) molecules/cm2 and is limited by the efficiency of the filtering of the excitation light. A surface density of 33.5 +/- 4.0 pmol/cm2 was measured for DNA covalently immobilized to the functionalized SiO2 thin film and a surface density of 3.7 +/- 1.5 pmol/cm2 was measured for the complementary DNA hybridized to the bound DNA. The detection concept explored can enable on-chip electronic data acquisition, improving both the speed and the reliability of DNA microarrays.
authors.affiliation: INESC Microsistemas e Nanotecnologias (INESC-MN), Rua Alves Redol, 9, 1000-029 Lisboa, Portugal. ffixe@inesc-mn.pt
authors.forename: F
authors.initials: F
authors.lastname: Fixe
authors.forename: V
authors.initials: V
authors.lastname: Chu
authors.forename: D M F
authors.initials: DM
authors.lastname: Prazeres
authors.forename: J P
authors.initials: JP
authors.lastname: Conde
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D002138:Calibration; D015342:DNA Probes / Q000032:analysis* / Q000737:chemistry / Q000235:genetics; D004277:DNA, Single-Stranded / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D004581:Electronics; D005456:Fluorescent Dyes / Q000032:analysis; D008027:Light; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity; D012825:Silicon
chemical_list: D015342:DNA Probes; D004277:DNA, Single-Stranded; D005456:Fluorescent Dyes; D012825:Silicon