The POCT technology involving low cost Lab-On-Chip label-free biosensing opens up an opportunity to drastically reduce the total cost of plant health and disease monitoring tools. The main requirement for a POCT tool is that it should involve relatively inexpensive equipment ensuring a sufficiently high accuracy of the plant disease early diagnostic. The principal objective of the presented work was to develop of a cost effective tool for biosensing assay, easy to use even for unskilled user. The label-free biosensing involving an optical near-field resonance phenomenon, such as Surface Plasmon Resonance (SPR) or localized surface plasmon resonance (LSPR), appears to be an appropriate approach for the above requirements. In this paper, we present a concept of multichannel biosensing platform dedicated to POCT, as well as the first proof-of-concept experimental investigations, demonstrating its practical feasibility. The instrumental platform investigated by our research group includes both disposable multichannel biochip and spectroscopic optical readout device. The proposed approach gives access to two plasmonic detection formats on the same lab-on-chip device: SPR and LSPR biosensing. In order to implement the LSPR sensing approach, our team has developed an original microfabrication method involving gold nanoparticles (Au_NPs) synthesis by pulsed laser writing. The biochip includes both microfluidic and biosensor structures formed into a single plastic slab.
We present three optical multi-channels spectrometers for the interrogation of label-free biosensors based on different kinds of transducers : resonant nanopillars (RNP), microring resonators (MRR), localized and propagative surface plasmon resonance (LSPR and SPR). Light is collected from the multi-channel biosensors (up to 12-channels) with optical fibers and is remapped to a packed straight line forming the input slit of the spectrometers. The combination of high resolution CMOS sensors and embedded signal processing makes it possible to extract the resonant wavelengths of the transducers with a precision in the range of 1-20 pm depending on the type of transducer. The performance of the three transducer / spectrometer systems has been evaluated in the framework of EU and regional projects for the monitoring of chemical pollutants found in oceanic waters (FP7 - EnviGuard), crop health monitoring (Interreg France-Wallonie-Vlaanderen - SmartBioControl/BioSens) and bioreactor monitoring (EutoTransBio - APTACHIP).