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Microchips and single-photon avalanche diodes for DNA separation with high sensitivity
Ivan Rech1, Sergio Cova, Alessandro Restelli
1Dipartimento di Elettronica e Informazione, Politecnico di Milano, Milano, Italy. rech@elet.polimi.it
Electrophoresis
|October 13, 2006
Summary
Silicon single-photon avalanche diodes (SPADs) offer a compact, cost-effective alternative to bulky detectors for laser-induced fluorescence (LIF) analysis. These ultrasensitive photodetectors enable advanced DNA and protein analysis with smaller sample volumes.
Area of Science:
- Analytical Chemistry
- Biotechnology
- Microfluidics
Background:
- Modern DNA and protein analysis increasingly use laser-induced fluorescence (LIF) with smaller sample sizes.
- Existing ultra-high sensitivity detectors, like photomultiplier tubes (PMTs), are often bulky, costly, and delicate.
- Miniaturized, inexpensive, and ultrasensitive photodetectors are crucial for developing compact analytical instruments.
Purpose of the Study:
- To evaluate the suitability of planar epitaxial silicon single-photon avalanche diodes (SPADs) for microchip capillary electrophoresis (CE) with dual-wavelength LIF detection.
- To develop a new apparatus for ultrasensitive LIF detection using SPADs in microchip CE.
- To demonstrate the performance of SPADs in analyzing small sample volumes for DNA and protein analysis.
Main Methods:
- Development of a novel dual-wavelength LIF detection apparatus utilizing silicon SPADs.
- Integration of SPADs into a microchip CE system for high-sensitivity analysis.
- Experimental validation through studies on electroosmotic flow (EOF) suppression, coating stability, and rapid DNA fragment sizing.
- Separation and detection of Cy5-labeled oligonucleotides.
Main Results:
- Demonstrated the high sensitivity of SPADs, achieving better than 3 pM for Cy5-labeled oligonucleotides.
- Quantified detection of fewer than 100 fluorescent molecules within a 50 pL illuminated volume.
- Confirmed the suitability of SPADs for microchip CE, offering advantages over traditional PMTs.
- Successfully applied the apparatus to study EOF suppression and coating stability.
Conclusions:
- Planar epitaxial silicon SPADs provide an ultrasensitive, miniaturized, and cost-effective photodetector solution for LIF-based microchip CE.
- SPADs offer comparable or superior sensitivity to PMTs with the added benefits of microelectronic integration.
- The developed apparatus enables advanced, high-throughput analysis of DNA and proteins using minimal sample volumes.
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