High throughput and sensitive biosensing based on whispering gallery mode and plasmonic resonances in monodisperse TiO2 microcapsules

• Auteur / Autrice : Naheed Hossain
• Direction : Abdel Illah El Abed, Jérôme Claverie
• Type : Projet de thèse
• Discipline(s) : Physique
• Date : Inscription en doctorat le 30/09/2021
• Etablissement(s) : université Paris-Saclay en cotutelle avec Université de Sherbrooke
• Ecole(s) doctorale(s) : École doctorale Electrical, optical, bio : physics and engineering (Orsay, Essonne ; 2015-....)
• Partenaire(s) de recherche : Laboratoire : Laboratoire Lumière, Matière et Interfaces
• Partenaire(s) de recherche : Référent : Ecole Normale Supérieure Paris-Saclay

Mots clés

Mots clés libres

Whispering Gallery Modes

Biosensing

Droplets-based microfluidics

TiO2

Résumé

The ability to detect and identify biological molecules and microorganisms in aqueous solutions is of primary importance in a wide range of fields. A rapid, efficient, and low-cost detection is critical for clinical diagnostics, food industries, environmental monitoring, and for military agencies in countering biological warfare and bioterrorism. Such a biosensing method can be developed thanks to the resonances (modes) of confined light, as the later may propagate in the form of whispering gallery modes (WGMs) when it is confined in appropriate spherical cavities. This behaviour results from the total internal refection of the light along the curved surface of such cavities. A change of the refractive index N, due for instance to the capture of target molecules or micro-organisms on the surface of the resonator, leads to a shift Δλ in the WGM spectral position, which allows in turn for monitoring quantitatively and accurately any change in the target analytes concentration. WGMs biosensing techniques show sensitivities exceeding that of the extensively documented plasmon surface resonance technology [1]. Also, we have shown recently that WGMs can be detected and analyzed versus time at different wavelengths and at kHz rates, by analyzing the fluorescence intensity emitted by hundreds monodisperse droplets [2]. The aim of the present proposal is to kick-start the development an innovative label-free biosensor platform based on analysis of WGM temporal and spectral shifts in highly monodisperse microdroplets and ZnO microcapsules using droplet-based microfluidics technology [3,4]. This technology allows for the production and manipulation at micrometer and microsecond scales of thousands to millions of highly monodisperse nanolitre (nL) to picolitre (pL) microdroplets, generally dispersed in low refractive index inert perfluorinated oil [4]. In our project, the use of droplet-based microfluidic technique will allow for an extra flexibility and detection using liquid microdroplets and mesoporous hollow microspheres (microcapsules), where sensing schemes can now include selectivity on the analytes going in and out of such microdroplets and microcapsules. In this PhD project, we will focus mainly on ZnO microdroplets and microcapsules, as Zinc oxide (ZnO) micro/nanostructures have many potential applications in optoelectronics, energy harvesting, photocatalyst, sensors, and biotechnology applications. They show also low toxicity, high refractive index, chemical stability, electrochemical activity, etc. ZnO possesses also a high isoelectric point, which makes it suitable for absorption of proteins, as the protein immobilization is primarily driven by electrostatic interaction. Nevertheless, one major problem that needs to be overcome is the synthesis of highly monodisperse ZnO microspheres with smooth and functionalized surface. We have developed a droplet-based approach, which enables for the producing of highly monodisperse microcapsules of ZnO with a controllable size and shape, which opens up the way for the study of optical properties of ZnO micro-resonators with functionalized surfaces and to develop biosensing applications. [1] F. Vollmer, S. Arnold, Nature Methods 5, 591, 2008 [2] A. El Abed, V. Taly, Optical Materials 36, 64–68 (2014). [3] Z. Hayat and A. El Abed, “High-Throughput Optofluidic Acquisition of Microdroplets in Microfluidic Systems” Micromachines 9 (2018). [4] N. Bchellaoui, Z. Hayat, M. Mami, R. Dorbez-Sridi, and A. I. El Abed, “Microfluidic assisted Formation of Highly Monodisperse and Mesoporous Silica Soft Microcapsules,” Sci. Rep. 7(1), 16326, Nature Publishing Group (2017) [doi:10.1038/s41598-017-16554-4].