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Integrated thin-film silicon photoluminescence sensors for DNA and protein detection
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´1012
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.
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Left: schematic diagram of the DNA chip surface with integrated photodetector for the quantification of tagged DNA molecules. Right: photodetector calibration. |
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