A universal and label-free sensor system based on aptamers and porous Silicon

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Rapid, sensitive and selective detection of various analytes is a critical step in quality assurance, environmental monitoring and production processes, as well as in diagnostics. Biosensors can fulfill these requirements. The aim of this research project is the development and testing of a novel label-free universal biosensor system based on aptamers as recognition elements combined with a porous silicon scaffold for simple real-time sensing. While the aptamers provide specificity along with the potential to design novel detection schemes based on their nucleic acid nature, the porous silicon allows for simple and label free detection.Within the first project phase the applicability of aptamer-modified porous silicon as a versatile, sensitive and rapid detection platform for larger analytes (even in complex samples), such as cells and proteins were shown as well as the possibility - in principle - to analyze small molecules. These systems were evaluated and tested in detail. In the second phase of the project we aim – as planned - to develop a multiplexed optical sensor system based on aptamer-modified porous silicon for simultaneous detection of different analytes. Additionally, in order to increase the sensitivity of the system – especially for the detection of small molecules - the development and implementation of more sophisticated signal enhancement strategies is planned. To achieve this, we will follow two strategies: (i) We will develop competitive assays in which oligonucleotides complementary to the aptamers target binding site are used and can therefore compete with the target. To further increase the signal, the oligonucleotides will be modified with nanoparticles. (ii) In the second signal enhancement strategy the porous silicon surface will be modified with fluorescent nanoparticles which are changing their emission upon binding of the target analyte, therefore allowing for bimodal and more sensitive detection. Moreover, to allow easy and accurate handling microfluidics will be introduced. Implementation of microarray technology will enable a high degree of multiplexing, facilitating the simultaneous detection of different analytes. These systems will be tested for the analytical procedures tested in the first phase but main focus will be placed on small molecules. As a highly relevant class of small molecules, antibiotics are chosen as model system to develop signal enhancement strategies and multiplexed biosensors within the second phase of the project. Nonetheless, the developed methods will be applicable to other small molecules, thereby providing a versatile platform technology for various applications ranging from environmental monitoring and food safety to diagnostics.