Romain Melich Thesis Defense

Title: Preparation and characterization of microbubbles et microdroplets by membrane processes for biomedical applications of ultrasounds
Author: Romain MELICH
Summary: The development of various colloidal forms for therapy and diagnosis in medical ultrasound is of great interest since many years. In particular, microbubbles of perfluorocarbon (PFC) are interesting as contrast agents because their gas core is a strong ultrasound reflector. More recently, PFC droplets have been proposed for novel acoustic applications. Indeed, after an acoustic pulse, the ultrasound waves induce a phase change from the liquid state to the gaseous state. This phenomenon is called the acoustic vaporization of droplets. For all these new applications, the development of new techniques of preparation offering a precise control of the particle size is of great necessity. Novel methods of preparation based on membrane devices are particularly interesting for this purpose. The aim of the thesis is the development of new membrane process for the formulation of microbubbles and droplets with tight control of their size, to meet requirements for ultrasound applications in imaging and therapy. In this work, the direct membrane emulsification with a cross-flow membrane module was used for the preparation of microbubbles stabilized by soluble surfactants, while a microkit module was used to fabricate microbubbles stabilized by phospholipids. In a second step, the membrane emulsification by premix was used to formulate monodispersed droplets of PFC. For the various colloidal forms prepared, we documented the influence of the process parameters (pressure, flow rate and shear stress), the formulation parameters (surfactants, type of PFC of the dispersed phase) and the membrane parameters (pore size) on the formation of microbubbles and droplets. Finally, we demonstrated the functionality of microbubbles and droplets, by an acoustic characterization, and showed that they have properties that could be compatible for biomedical applications.
Time: Thursday, December 13th, 2018
Place: Amphithéâtre de physique nucléaire (Paul DIRAC), Campus La Doua