Developpement d'un biocapteur combinant la plasmonique et l'electrochimie
Abstract
Biosensors are powerful tools that are used for a wide range of applications in fields like biomedical research, healthcare, pharmaceuticals and many more. Plasmonic and electrochemical techniques have each their advantages and their weaknesses for biodetection applications. A biosensor combining both these measurement techniques was fabricated for this project. Gold interdigitated electrodes (IDEs) were used as a surface plasmon resonance (SPR) propagation surface and as electrodes for impedance measurements. Different types of measurements are enabled in real time within a closed measuring cell with a two-electrode impedance system. The limit of detection of the SPR system compares well with commercial systems. For this project, an ultrafast laser (120 femtosecond pulses) was used for fast prototyping of the interdigitated electrodes on a glass slide on which a 50 nm thin film was previously deposited. The fabrication process was optimized in order to obtain the optimal electrode width and a good surface quality for the propagation of surface plasmons. The period of the sample that was used is 30 mum and the distance between the electrodes is of 6 mum. These dimensions are compatible with standard microfabrication techniques, which would enable fabrication at a low price for a market entry. Two optical setups based on the Kretschmann configuration were realised in order to take spectral SPR measurements once the sample was fabricated. The first of these systems used the specular reflection on the sample and the second used the first order of diffraction from the interdigitated electrodes which acts as a grating. The limit of detection of those systems, measured with a change between water and ethanol solution are 7.9x10-7 RIU (refractive index units) and 7.2x10-6 RIU respectively. An equivalent circuit model is presented for the electrical impedance system. Based on changes between solutions with different salt concentrations, the model was verified. The limit of detection for a NaCl solution is 1.3x10 -3 mg/100ml. The combination of these two types of measurements showed that the SPR system as a better sensitivity to variations in ethanol concentration and the impedance system to variations in salt concentrations. Oligonucleotides sequences from the normal and mutated genes of mycobacterium tuberculosis were detected with this system. The experiments showed specific attachment of the complementary oligonucleotides compared to the non-complementary ones.
- Publication:
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Masters Thesis
- Pub Date:
- 2013
- Bibcode:
- 2013MsT..........5L
- Keywords:
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- Engineering, Biomedical;Physics, Optics;Engineering, System Science