PhD defense: Roch Sobczyk

Title

Microfluidic devices to detect bacteria / sepsis by nanoluminescence

Abstract

Bacterial antibioresistance is a phenomenon which conducts bacteria to restist to the action of antibiotics. It constitutes a mondial health issue, to the point that the WHO is on alert on that subject since several years. To limit the accentuation of this issue, several measures have been taken to reduce the use of antibiotics in agriculture and livestock. Moreover, several solutions exist, like developping new antibiotics, or a combined used of some of them. However, even these measures are necessary, it is also vital to be able to detect bacteria prematurely, and to assess their ability to resist or not to treatments. Many detection systems already exist, but those more often used present several drawbacks like a slow detection, not always selective, or require high quantities of expensive reactants, which make them onerous. The work conducted during this PhD aimed to the conception and developpment of a multidetector able to follow the microbial activity by following the pH, as it often induce a variation of the acidity of the medium, and also a selective detection of bacteria presence. The detector is then composed by a core made of CdSe QD, on which are bounded a pH sensible cyanine, and a BODIPY used as a selective Gram+ bacteria probe. In a first place, the synthesis of the cyanine has been conducted and improved, then its spectroscopic and biological properties have been studied. The observed toxicity leaded to the developpement of pH optodes using a matrix of HydroMed-D4 polymer. In a second place, QD have been synthesised, and their spectroscopic properties studied. Then successful ligand exchange have been realised. However, their degradation in saline aqueous media have not been solved, despite the exploration of several solutions, which make them non usable in biological media. Finally, the synthesis of the BODIPY have been initiated, but could not be completed by lack of time. Some prospects regarding the improvement of the work realised duting this PhD have been proposed, as well as prospects concerning long term developpement of the intial PhD project.

PhD supervision

• Director: Rachel Méallet, Professor, ISMO, University Paris-Saclay
• Co-director: Isabelle Leray, Research Director, PPSM, CNRS - ENS Paris-Saclay

Members of the jury

• Thanh Ha-Duong, Maitresse de conférences, ITODYS, Université Paris-Cité, Rapportrice

• Thibault Gallavardin, Chargé de Recherche, CARMeN, Université de Rouen Normandie, Rapporteur

• Hafsa Korri-Youssoufi, Directrice de Recherche, ICMMO, Université Paris-Saclay, Examinatrice

• Christophe Coudret, Directeur de Recherches, Softmat, Université de Toulouse, Examinateur

• Michel Sliwa, Directeur de Recherches, LASIRE, Université de Lille, Examinateur