Integrated fluorescence sensing in a lab-on-a-chip for DNA analysis
C. Dongre1, J. van Weerd2, R. van Weeghel2, R. Martinez Vazquez3, R. Osellame3, R. Ramponi3, G. Cerullo3, R. Dekker4, G.A.J. Besselink4, H.H. van den Vlekkert4, H.J.W.M. Hoekstra1 and M. Pollnau1
1Integrated Optical MicroSystems (IOMS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
Tel. +31 (0) 53 489 4449 Fax +31 (0) 53 489 3343 E-mail: C.Dongre@ewi.utwente.nl
2 Zebra Bioscience BV, W. Beversstraat 185, 7543 BK Enschede, The Netherlands 3Istituto di Fotonica e Nanotecnologie del CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
4LioniX BV, P.O. Box 456, 7500 AL Enschede, The Netherlands
We report on monolithic optical sensor integration in a lab-a-chip toward on-chip diagnosis of all kinds of genetic diseases, e.g. breast cancer. Such an analysis of genetic diseases is based on the capillary electrophoresis separation of DNA fragments amplified from diagnostically relevant regions of the concerned gene.
This paper presents a proof of principle, demonstrating real time integrated fluorescence monitoring during the capillary electrophoresis separation of fluorescent dyes as well as fluorescently labeled DNA molecules in an on-chip microfluidic channel [1]. To this end, sensing waveguides were integrated monolithically by means of femtosecond laser irradiation, in a commercial fused silica lab-on-a-chip, to perpendicularly intersect the microfluidic separation channel [2]. Laser excitation through these waveguides induces fluorescence in the flowing microfluidic plugs. Depending on the number of species present, and the difference between their mobility, a corresponding number of electropherogram peaks are detected. Detection has been performed by a CCD camera in order to visualize the on-chip events and to provide access to spatial information, as well as by a photomultiplier tube in order to detect low values of fluorescence signal. The present limit of detection is estimated to be approximately 6 nM. The presented setup achieves high spatial resolution due to the small cross section of the waveguides, ~12 μm. This is an improvement over the conventional approach to place a pinhole in the path of the fluorescence output signal generated by a broadband background illumination, e.g. with an Hg or a Xe lamp. Future work will focus on extension of this principle to real world diagnostic samples for development of a fast and compact point of care optical biosensing device.
During the conference we will present the latest results in wavelength- multiplexed fluorescence monitoring of DNA separation at low limits of detection.
Keywords: femtosecond laser, optical waveguide, microfluidics, capillary electrophoresis, point-of-care diagnostics
References
[1] C. Dongre, R. Dekker, H.J.W.M. Hoekstra, M. Pollnau, R. Martinez Vazquez, R. Osellame, G.Cerullo, R. Ramponi, R. van Weeghel, G.A.J. Besselink and H.H. van den Vlekkert, “Fluorescence monitoring of microchip capillary electrophoresis separation with monolithically integrated waveguides”, Opt. Lett. 33, 2503 (2008).
[2] R. Martinez Vazquez, R. Osellame, D. Nolli, C. Dongre, H.H. van den Vlekkert, R. Ramponi, M. Pollnau and G. Cerullo, “Integration of femtosecond laser written optical waveguides in a lab-on-chip”, Lab. Chip 9, 91 (2009).
