Self-assembled monolayers as a base for immunofunctionalisation: unequal performance for protein and bacteria detection |
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Authors: | Eva Baldrich Olivier Laczka F Javier del Campo Francesc Xavier Muñoz |
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Institution: | (1) Instituto de Microelectrónica de Barcelona (IMB-CNM), CSIC, Esfera UAB, Campus Universitat Autónoma de Barcelona, 08193 Barcelona, Spain |
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Abstract: | Biosensor development strongly depends on the optimisation of surface functionalisation strategies. When gold surfaces are
considered, immunofunctionalisation by modification of self-assembled monolayers (SAMs) is one of the preferred approaches.
In this respect, SAM-based antibody (Ab) incorporation has shown better performance than Ab physisorption for the detection
of proteins and small targets. Reports on bacteria detection are less frequent. In this work, we assess the performance of
various SAM-based gold immunofunctionalisation strategies, currently applied to protein detection, in the field of bacteria
determination. We present the results for Ab chemical conjugation on mercaptopropanoic acid and mercaptoundecanoic acid SAMs,
as well as on a dextranized cysteamine SAM. All the modified surfaces studied were shown to be appropriate for the direct
detection of an enzyme-labelled protein, but none succeeded in detecting a bacterial target in a sandwich assay format. Conversely,
gold functionalised by Ab physisorption allowed E. coli detection when a sandwich enzyme-linked assay was carried out. The implications of bacteria size and wall complexity are
discussed. These results indicate that immunofunctionalisation strategies appropriate for protein detection are not necessarily
transferable to work with more complex targets such as bacteria. In this respect, Ab physisorption appears to be a suitable
alternative to SAM-based gold functionalisation for bacteria detection. |
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Keywords: | Surface immunofunctionalisation Self-assembled monolayer Antibody conjugation Bacteria detection |
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