Small – sized analytes biosensing on resonant nanostructures – NanoBioSensor

Our sensor is based on the combination of the QCM and of the enhanced spectroscopies principles. Whatever the complexity induces by our sensor implementation, our approach can be simplified, at first step, by dividing our system in two main components: the transducer (the multimodal biochip for QCM and SERS) and the bioreceptor (surface functionnalisation of the biochip).
As a consequence, our biosensor integrated in a QCM set-up and vibrational spectroscope (for the signal measurement) will allow the detection and the analysis of the piezoelectric and the enhanced vibrational signals from the targeted analytes.
Thus, we integrated several technologies (surface lithography, QCM, SERS, chemical surface engineering) in a single system to develop a new biosensor beyond the performance of each single technology. The project fits in with a transdisciplinary project. Since the scientific and technological knowledge used in our biosensor are yet established since several years, one of the main challenges was their adaptation and their optimisation to the specific application that we want to develop.

We designed and optimized the bimodal QCM/SERS transducer. Our detection method was validated on the streptomycin/aptamer system. QCM/SERS measurements enable the determination of the amount of bioreceptors deposited on the biochip and the observation of the aptamer/streptomycin interaction (calculation of the dissociation constant and observation of structural changes induced by the interaction). From these results, we have provided indisputable proof of the concept of QCM/SERS coupling and of its interest in the detection of molecules and the observation of molecular interactions.

As the coupling is validated, we want to use this new method to observe the biomolecular interactions.

3 publications were accepted in international journal with high impact factor (higher than 6). 3 more publications should also be submitted soon after the project end. Moreover, the results were presented in international and national congresses as oral presentation (12 in international congresses among which 6 were invited talks and 3 in national congresses) or as posters (8 in international congresses and 2 in national congresses).

Biosensors are analytical devices incorporating a biological material (a bioreceptor) intimately associated with a physicochemical transducer. These devices are elaborated with the objective of detecting a target, specifically and rapidly, even at trace amounts and even in a complex environment. One of the greatest challenges in the field of Biosensors is the sensitivity. This is particularly true in the case of small-sized target analyte (toxins, odorants) sensing, as the response of classical detection techniques is generally below the required detection limit. The detection sensitivity of biosensors can be increased either by improving the quality of the biological material or by amplifying the signal measured by the transduction techniques to be used. Many progresses have been made in increasing the avidity/affinity of bioreceptors, being either antibodies, aptamers, or specific “selectors” designed to recognize and bind small-sized targets from solution or from air. In addition, recent developments of nanostructuration processes opened the way to reproducible and reliable benefit from optical enhancement of spectroscopic transduction techniques.
Recent progress in the development of specifically designed nanostructures opened the way to reproducibly and reliably benefit from optical enhancement of spectroscopic transduction techniques.
In this context, we envision a combined piezoelectric-(vibrational) spectroscopic detection of small-sized analytes with two main objectives: (i) at the fundamental level, we aim at getting a detailed understanding of the molecular interactions occurring upon the molecular recognition and the binding event, while (ii) at the applied level we intend to design highly sensitive biosensors for small-sized analytes.
For small-sized analyte detection, we will use both antibodies and aptamers as biomolecular receptors, as well as synthetic chemical structures, referred to as “selectors”, and propose a combination of visco-elastic mass detection using a Quartz Crystal Microbalance with dissipation monitoring (QCM-D) with spectroscopic information from surface enhanced IR and Raman spectroscopies (SEIRAS and SERS, respectively) employing a nanopatterned QCM gold electrode. The objective of such combination is to enhance the performances of the biosensor. Firstly, the QCM will provide a fast detection of any interaction between the bioreceptor and the chosen target, paving the way for a detailed investigation of the interaction mechanism at the molecular level. Secondly, the SERS and the SEIRAS will provide the identification of the analytes as well as any structural modifications due to the interaction with the bioreceptor, through the spectral signature recorded by these vibrational spectroscopies. Moreover, such enhanced spectroscopies exploit the plasmonic properties of the metallic nanostructures that create a highly intense electromagnetic field at the vicinity of the nanostructures. This enhanced electromagnetic field will induce an enhancement of the Raman scattering and of the IR absorption. The enhancement factors in SERS and SEIRAS have been estimated to be close to 1010 and 106, respectively, and have allowed for the observation and the detection of a very small amount of molecules paving notably the way for the single molecule detection. Therefore, the designed biosensor based on these enhanced spectroscopies will be highly sensitive. By combining vibrational and piezoelectric techniques in a single set-up, we will be able to propose a fast, reliable, specific and highly sensitive biosensor.
The success of this project relies on the complementary expertise of the involved partners bringing together skills in vibrational spectroscopies, surface nanopatterning and controlled chemical functionalization of surfaces.