Project: Biomimetic Microparticles
Following our expertise in microfluidics and crystallization, we are conducting projects aiming at the generation and characterization of biomimetic microparticles. The method consists in generating drops in a microfluidic channel (diameter from 100 to 500µm) and contracting them along the flow. This confines the solute (polymer and/or molecules to be crystallized) that the drops contain, initiating gelation and/or crystallization reactions. In these studies, we start from the scaling law relating microdrop size to tangential shear that we established in Shuheng Zhang's thesis (Chemical Engineering Science 138:128-139 (2015)). Thus, we control the generation of drops, in terms of size and frequency, and we explore the experimental conditions of confinement in several projects:- The production of alginate microparticles mimicking red blood cells:Red blood cells aggregate and disintegrate in the blood, notably according to the value of the shear to which they are subjected. Pathologies (thrombosis, diabetes, atherosclerosis, ...) are associated with the hyper-aggregation of red blood cells. In order to validate an ultrasound tool for quantitative measurement of aggregation in situ and in vivo for diagnostic purposes, it is necessary to have calibrated and reproducible red blood cell mimetics. In microfluidics, our objective is to fabricate reproducible microparticles controlled in size and mechanical properties. To do so, we proceeded by ionic gelation of a natural polymer, sodium alginate (Na-alginate), with calcium chloride to form a calcium alginate (Ca-alginate) gel.We first generated 150µm diameter Na-alginate drops in a microfluidic flow, without addition of surfactant. As the contraction of these drops is necessary to reach the size of red blood cells (10µm), we proceeded by water diffusion of the drops in the continuous phase of the microfluidic flow. Then we used different methods of gelation of Na-alginate microparticles: in situ in the microfluidic system or ex situ after the collection of Na-alginate microparticles. The size, shape, structure and alginate content of the formed Na- and Ca-alginate microparticles were studied as a function of the operating parameters of the microfluidic setup. The obtained deformable microparticles are characterized in terms of mechanical properties by Atomic Force Microscopy (AFM) and by manipulation with micro clamps, and in terms of structures by Scanning Electron Microscopy (SEM). (Zhang, C.et al., Chem. Eng. Sci. 211, 115322 (2020)).
This work led to a microfluidic method to control the size and mechanical properties of Ca-alginate microparticles while avoiding their coalescence, despite the absence of surfactants. Thus, we obtained monodisperse Ca-alginate microparticles with a Young's modulus close to that of red blood cells and the feasibility of their use for ultrasound measurements was also shown. In addition, we explored alternative methods in parallel, which we compared with the literature. (Zhang, C. et al. Biomater Res 25, 41 (2021)).
This project is the subject of a collaboration with the Institute for Research on Non-Equilibrium Phenomena (IRPHE) and the Mechanics and Acoustics Laboratory (LMA) in the framework of the ANR "Cellular Ultrasonic imaging Modality to assess red Blood cell Aggregation in vivo" (ANR CUMBA).
Non-permanents involved in the project:
2016-2020 Cheng Zhang, PhD thesis "Development of a microfluidic method for the preparation of red blood cell mimicking Microparticles with controllable size and mechanical properties "
2018 Romain Buisson, M2 Bio-engineering of Tissues and Implants- Aix-Marseille University
2018 Hajar Blladi, Mobility of studies in 5th year Biomedical Engineering - Polytech Marseille
2016 Paulin Ngounstop, Ecole des Mines d'Albi2015 Guillem Peybernes, M2 Bio-engineering of Tissues and Implants-Aix-Marseille University
- The encapsulation of microcrystals:
Currently, we combine the know-how acquired on droplet contraction in a microfluidic flow and our expertise in solution crystallization to put them to use in the encapsulation of crystals of molecules of interest. The objective is to generate microcapsules of crystals in order to facilitate their manipulation and/or targeting, for localized therapy or imaging diagnosis.The first step is to control the contraction of solution drops of molecules of interest and to estimate their supersaturation in the drops after contraction. Simulations on COMSOL will be able to confirm our approach. The knowledge of the supersaturation allows us to locate in the phase diagram of the molecule of interest to cause the nucleation of crystals. In a second step, we will proceed to the gelation of the drop containing the crystal before, during or after the nucleation of the crystals.
Non-permanents involved in the project:
2021-2022 Guillem Peybernes, Attaché Temporaire d'Enseignement et de Recherche - Polytech
2020-2021 Karen Silva Vargas , Attaché Temporaire d'Enseignement et de Recherche - Polytech