Thin film biosensor for rapid visual detection of nucleic acid targets

Background: We have developed a silicon-based biosensor that generates a vi sual signal in response to nucleic acid targets. Methods: In this system, capture oligonucleotide probes are immobilized on the surface of the biosensor. Interaction of the capture probes with a comp lementary target and a biotinylated detector oligonucleotide allows initiat ion of formation of an organic thin film on the biosensor. Thin film format ion is completed by enzymatic activity of peroxidase conjugated to an antib iotin antibody. Peroxidase catalyzes deposition of an insoluble product ont o the silicon surface, generating a uniform thin film. The increased thickn ess on the surface alters the perceived color of the biosensor through chan ges in the interference patterns of reflected light from the surface, causi ng a color change from gold to purple. Results: The biosensor results may be evaluated by direct visual inspection or quantified by ellipsometry. Results are obtained in 25 min with a detec tion limit of 5 pmol/L (150 amol/sample). Selectivity of the biosensor is d emonstrated by discrimination of single nucleotide mismatches. Multitarget arrays are also analyzed with the thin film biosensor, and the system is ca pable of detecting targets from human serum and urine. Conclusions: The biosensor surface is inexpensive to produce, and the assay format is simple and rapid. The thin film biosensor is adaptable to a wide variety of nucleic acid detection applications, including rapid diagnostic testing for infectious disease panels, antibiotic resistance panels, or al lelic discrimination of specific genetic markers. (C) 1999 American Associa tion for Clinical Chemistry.