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Label-free microarrays for the parallel analysis of small (bio)molecules

Final Activity Report Summary - COMBIARRAY (Label-free microarrays for the parallel analysis of small (bio)molecules)

Combiarray aimed at designing and testing new fluorescent sensors for analysing specific biological interactions. The project has been concentrated mainly on the detection of DNA hybridisation, because of its potential applications in DNA microarrays. Nowadays, fluorescent DNA microarrays need a labelling step of the target molecule, which we would like to avoid by creating label-free fluorescent sensors. In addition, in the course to reduce the fabrication's costs of a sensor, we focused on the use of microcontact printing, a cheap soft lithography technique, for the deposition of DNA strands.

Synthetic oligonucleotides have been covalently attached to reactive self-assembled monolayers on glass surfaces, using microcontact printing deposition. The fabrication conditions have been studied and optimised in order to take into account i) the resistance of the surface to aqueous media, ii) the printing of polar molecules like DNA using a very apolar material.

Surfaces functionalised with oligonucleotides have been hybridised with complementary or non-complementary strands, and the process has been followed using labeled oligos and fluorescence microscopy.

The label-free sensing of hybridisation has been realised by using a fluorescent intercalator as the sensor molecule. For this purpose, non-labeled oligos have been deposited to glass surfaces, hybridised with complementary strands, and subsequently interacted with ethidium bromide to evidence the presence of single or double strands of DNA.