MicroAnalytical Systems (µAS) adapted to Point-of-Care Testing are expected to provide simple chemical, molecular or cellular analysis to be used directly on the field. Different formats of µAS are already classically used, from pregnancy tests to glycemia for diabetic people. Increasing µAS analytical performances involves for instance improving limits of detection, reduce time of analysis, or increase the amount of information provided per test. These improvements may be reached by using more refined technology, involving integrated technologies such as biosample processing, enzymatic reactions, fluidic circuitry and/or biosensors. However being able to fabricate and produce cheap µAS relying on miniaturized components is still a challenging goal, particularly when dealing with low concentrated species. For example, on the one hand it may be interesting to use miniaturize nanotransducers in biosensors (e.g. photonic transducer enabling both SPR and SERS thanks to nanostructuration) ; but on the other hand the transducers size reduction may prevent the targets to reach the biosensor’s active zone in a short time, because of mass transfer phenomena. Futhermore, when the sensing area is small by comparison with the other µAS zones, it targets are likely to get adsorbed on undesired surfaces. These targets are therefore lost and cannot contribute to the final, useful signal of the µAS. In these conditions the effectivity of the µAS can be questionned.
Different ways are being explored to overcome such challenges, and may enable µAS for detection of low concentration targets. For instance, it is possible to perform selective chemical modifications of surfaces bearing different materials, in order to bind molecular probes only on the transducing zone, while repelling molecular targets from other material surfaces. We will show how it is possible to perform such orthogonal surfaces modifications with a submicronic spatial resolution, relying on self-assembly phenomena.
The increasing demand for early detection of diseases drives the efforts to develop more and more sensitive techniques to detect biomarkers in extremely low concentrations. Electromagnetic modes at the surface of one dimensional photonic crystals, usually called Bloch surface waves, were demonstrated to enhance the resolution and constitute an attractive alternative to surface plasmon polariton optical biosensors. We report on the development of Bloch surface wave biochips operating in both label-free and fluorescence modes and demonstrate their use in ovalbumin recognition assays.
Surface plasmon resonance imaging is an optical method that allows the real time detection of small changes in the physical properties of a dielectric medium near a metallic surface. Using proper surface functionalization and structuration, this technique can be applied to the realization of optical biochips where multiple unlabeled interactions can be monitored. More precisely, thanks to the use of an adequate optical set-up built around a gold surface realized by self assembled monolayers or electrocopolymerization, we studied DNA:DNA interactions with potential application to genetic diagnostic and DNA:protein interactions to demonstrate the ability of the system to determine simultaneously different affinity constants.
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