Polymeric nano‐ and microscale materials bear significant potential in manifold applications related to biomedicine. This is owed not only to the large chemical diversity of the constituent polymers, but also to the various morphologies these materials can achieve, ranging from simple particles to intricate self‐assembled structures. Modern synthetic polymer chemistry permits the tuning of many physicochemical parameters affecting the behavior of polymeric nano‐ and microscale materials in the biological context. In this Perspective, an overview of the synthetic principles underlying the modern preparation of these materials is provided, aiming to demonstrate how advances in and ingenious implementations of polymer chemistry fuel a range of applications, both present and prospective.

Giant unilamellar vesicles (GUVs) are microcompartments serving to confine reactions, allow signaling pathways, or design synthetic cells. Polymer GUVs are composed of copolymer membranes mimicking cell membranes, and present advantages over lipid‐based GUVs, such as higher mechanical stability and chemical versatility. Such microcompartments are essential for understanding reactions/signaling occurring in cells, which are difficult to study by in vivo approaches due to the cell's complexity. However, the lack of control over their production, stability, and membrane diffusion properties is still limiting their use for bio‐related applications. Here, polymer GUVs produced by microfluidics and permeabilized with DNA‐origami nanopores (DoNs) that present a high level of control over these essential properties are introduced. After systematic optimization of conditions, DoN‐GUVs reveal a narrow size distribution, allow for high encapsulation efficiencies, and are stable for weeks, protecting encapsulated biomolecules. The kinetics of diffusion of molecules through the GUV's membrane is tuned by insertion of DoNs with a controlled 3D‐ structure. DNA polymerase I, encapsulated as model for bioreactions, successfully produced DNA duplex strands with spatiotemporal control. DoN‐GUVs loaded with active molecules open new avenues in bioreactions, from the detection of biomolecules, over the tuning of molecular transport rates, to the investigation of cellular processes/signaling.

Protein body (PB) formation in wheat seeds is a critical process influencing seed content and nutritional quality. In this study, we investigate the potential mechanisms governing PB formation through an in vitro approach, focusing on γ-gliadin, a key wheat storage protein. We used a microfluidic technique to encapsulate γ-gliadin within giant unilamellar vesicles (GUVs) and tune the physicochemical conditions in a controlled and rapid way. We examined the influence of pH and protein concentration on LLPS and protein-membrane interactions using various microscopy and spectroscopy techniques. We showed that γ-gliadin encapsulated in GUVs can undergo a pH-triggered liquid-liquid phase separation (LLPS) by two distinct mechanisms depending on the γ-gliadin concentration. At low protein concentrations, γ-gliadins phase separate by a nucleation and growth-like process, while, at higher protein concentration and pH above 6.0, γ-gliadin formed a bi-continuous phase suggesting a spinodal decomposition-like mechanism. Fluorescence and microscopy data suggested that γ-gliadin dense phase exhibited affinity for the GUV membrane, forming a layer at the interface and affecting the reversibility of the phase separation.

Microfluidique à gouttes pour l'étude du comportement de phases de gliadines de blé au sein de vésicules lipidiques: Au cours du développement du grain de blé, les protéines de réserve s'assemblent sous la forme de phases denses appelés corpuscules protéiques (CPs). Ces assemblages servent de réserve de carbone, de soufre et d'azote essentielles au développement du grain et de la plante. Malgré de nombreuses études, les mécanismes à l'origine de leur formation restent indéterminés. Des études in vitro récentes tendent à montrer que la séparation de phase liquide-liquide (LLPS) des protéines ainsi que des interactions protéine-membrane pourraient être impliquées dans la formation des CPs au sein du grain de blé. Cependant, l'influence des interactions protéine-membrane sur la LLPS des protéines de blé n'a pas encore été étudiée. De plus, la LLPS des protéines de blé a peu été étudiée dans des conditions proches des conditions biologiques en raison de leur faible solubilité dans l'eau. Ce projet de thèse a donc consisté à étudier l'assemblage de protéines de blé en présence d'une membrane modèle, dans des conditions proches des conditions biologiques. La γ-gliadine, une protéine de réservé du blé, a été caractérisée dans des solutions aqueuses s'approchant des conditions biologiques. Aussi, une technique microfluidique à base de gouttelettes a été développée pour encapsuler des macromolécules au sein de vésicules lipidiques composées d’une membrane modèle. Ce dispositif a été utilisé pour étudier la LLPS de la γ-gliadine dans des conditions aqueuses se rapprochant des conditions biologiques en présence d'une membrane modèle.