Lab-on-glass system for DNA analysis using thin and thick film technologies
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1191-OO06-01
Lab-on-glass system for DNA analysis using thin and thick film technologies D. Caputo1, M. Ceccarelli1, G. de Cesare1, A. Nascetti2, R. Scipinotti1 1 Dept. of Electronic Engineering, “Sapienza” University of Rome, Rome (Italy) 2 Dept. of Aerospace and Astronautics Eng., “Sapienza” University of Rome, Rome (Italy) ABSTRACT In this paper, we present a compact lab-on-chip system suited for label-free DNA analysis. The system can be fabricated on a conventional microscope glass slide using thin-film and thick-film technologies. It integrates a heating chamber, an electrowetting-based droplet handling system and a hydrogenated amorphous silicon (a-Si:H) photosensor array for DNA detection. At this stage of research we have designed and tested the individual functional units. The heating chamber incorporates a thin metal film heater optimized for uniform temperature distribution on a 1cm2 area. A forward-biased a-Si:H p-i-n junction is used for temperature monitoring, achieving a linear temperature dependence with -3.3 mV/K sensitivity. The droplethandling unit, relying on the electrowetting method, is designed to move the sample from the heating chamber to the sensor array. The unit includes a set of metal pads beneath a layer of PDMS that provides both the electric insulation of the electrodes and the hydrophobic surface needed by the electrowetting technique. The UV sensor array allows measuring the DNA absorbance variation at 254nm related to the hybridization between probe-molecules contained in the sample and reference target molecules immobilized on the sensor surface. A preliminary test to detect the hybridization between a 25-mer single-stranded oligonucleotides and denaturated pBR 322 4162-mer single-stranded oligonucleotides has been carried out successfully. INTRODUCTION A variety of recent technological breakthroughs in molecular biology and microfabrication technology have made possible the development of lab-on-chip (LOC) systems. The high integration level of the LOCs allows to accomplish complex chemical or bio-chemical functions of large analytical devices on a single sensor-like system with a fast response time, low sample consumption and on-site operation [1][2]. The functional modules included in LOC systems are those capable of sample injection, reaction, separation and detection. In the framework of LOC systems the most promising are the DNA Chips (or DNA microarray) [3][4], which are already commercially available. Usually, DNA detection is performed using an offchip detection systems able to measure the fluorescence emitted by fluorescent dyes attached to the target DNA molecules (labeled DNA) [5]. In alternative, label-free methods relying on the measurement of changes in electrical charge [6], mass [7] or UV-absorbance [8, 9] have been proposed. In this paper we propose a LOC system able to perform pre-treatment, handling and detection of DNA molecules on a standard microscope slide fabricating by means of thin and thick film technologies. In particular, an on-chip detection is ach
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