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Biochips based on silicon for detecting the interaction between aptamers and pathogens

Abstract : Rapid and sensitive detection of pathogenic targets play a crucial role in biosecurity. Biochips are ideal for this, as they allow easy and multiplex detection of targets. A crucial limitation in biochips is that they often suffer from low reliability and sensitivity. The goal of this thesis is to develop a stable and reproducible architecture for biochips based on an amorphous silicon carbon alloy (a-SiC:H) deposited on an aluminium back-reflector for reliable and sensitive detection of pathogens. On these biochips we introduced the interaction of the food and feed toxin ochratoxin A (OTA) with its 36mer aptamer AntiOTA as a model system. Aptamers (single strands of DNA) are ideal as probes for biochips as they display high specificity and affinity towards a wide range of targets (i.e. proteins, bacteria…). The well-controlled multi-step fabrication process consists of the reliable photochemical grafting of acid-terminated organic monolayers on silicon surfaces by robust Si C bonds, which in turn were functionalized with aptamers by stable peptide coupling. Carrying out this process on crystalline silicon allowed monitoring and quantification of every step by infrared spectroscopy (IR-ATR). The interaction OTA – AntiOTA was shown for the first time on surfaces by IR, and an IR in situ calibration allowed the quantification of OTA which was bound by the aptamers on the surface. The specificity of AntiOTA towards OTA was demonstrated by using a chemically similar molecule (warfarin), for which AntiOTA shows no affinity. The well-controlled protocols were transferred to the a-SiC:H biochip. The immobilized aptamers were hybridized with complementary and fluorescent-labeled DNA-strands. In presence of OTA, dehybridization of the complementary strands is expected, resulting in a decrease of fluorescent signal. Different lengths of complementary strands were compared, exhibiting up to 13% signal decrease due to OTA.
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Submitted on : Tuesday, April 11, 2017 - 4:15:07 PM
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  • HAL Id : tel-01505677, version 1

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Timothy Aschl. Biochips based on silicon for detecting the interaction between aptamers and pathogens. Materials and structures in mechanics [physics.class-ph]. Université Paris Saclay (COmUE), 2016. English. ⟨NNT : 2016SACLX103⟩. ⟨tel-01505677⟩

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