Artificial Melanogenesis by Confining Melanin/Polydopamine Production inside Polymersomes

Melanin and polydopamine are potent biopolymers for the development of biomedical nanosystems. However, applications of melanin or polydopamine-based nanoparticles are limited by drawbacks related to a compromised colloidal stability over long time periods and associated cytotoxicity. To overcome these hurdles, a novel strategy is proposed that mimics the confinement of natural melanin in melanosomes. Melanosome mimics are developed by co-encapsulating the melanin/polydopamine precursors L-DOPA/dopamine with melanogenic enzyme Tyrosinase within polymersomes. The conditions of polymersome formation are optimized to obtain melanin/polydopamine polymerization within the cavity of the polymersomes. Similar to native melanosomes, polymersomes containing melanin/polydopamine show long-term colloidal stability, cell-compatibility, and potential for cell photoprotection. This novel kind of artificial melanogenesis is expected to inspire new applications of the confined melanin/polydopamine biopolymers

Tailoring a Solvent-Assisted Method for Solid-Supported Hybrid Lipid-Polymer Membranes

Combining amphiphilic block copolymers and phospholipids opens new opportunities for the preparation of artificial membranes. The chemical versatility and mechanical robustness of polymers together with the fluidity and biocompatibility of lipids afford hybrid membranes with unique properties that are of great interest in the field of bioengineering. Owing to its straightforwardness, the solvent-assisted method (SA) is particularly attractive for obtaining solid-supported membranes. While the SA method was first developed for lipids and very recently extended to amphiphilic block copolymers, its potential to develop hybrid membranes has not yet been explored. Here, we tailor the SA method to prepare solid-supported polymer-lipid hybrid membranes by combining a small library of amphiphilic diblock copolymers poly(dimethyl siloxane)-poly(2-methyl-2-oxazoline) and poly(butylene oxide)- block -poly(glycidol) with phospholipids commonly found in cell membranes including 1,2-dihexadecanoyl- sn -glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphoethanolamine, sphingomyelin, and 1,2-dioleoyl- sn -glycero-3-phosphoethanolamine- N -(glutaryl). The optimization of the conditions under which the SA method was applied allowed for the formation of hybrid polymer-lipid solid-supported membranes. The real-time formation and morphology of these hybrid membranes were evaluated using a combination of quartz crystal microbalance and atomic force microscopy. Depending on the type of polymer-lipid combination, significant differences in membrane coverage, formation of domains, and quality of membranes were obtained. The use of the SA method for a rapid and controlled formation of solid-supported hybrid membranes provides the basis for developing customized artificial hybrid membranes

Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell-Sized Compartments

Abstract Cells rely upon producing enzymes at precise rates and stoichiometry for maximizing functionalities. The reasons for this optimal control are unknown, primarily because of the interconnectivity of the enzymatic cascade effects within multi-step pathways. Here, an elegant strategy for studying such behavior, by controlling segregation/combination of enzymes/metabolites in synthetic cell-sized compartments, while preserving vital cellular elements is presented. Therefore, compartments shaped into polymer GUVs are developed, producing via high-precision double-emulsion microfluidics that enable: i) tight control over the absolute and relative enzymatic contents inside the GUVs, reaching nearly 100% encapsulation and co-encapsulation efficiencies, and ii) functional reconstitution of biopores and membrane proteins in the GUVs polymeric membrane, thus supporting in situ reactions. GUVs equipped with biopores/membrane proteins and loaded with one or more enzymes are arranged in a variety of combinations that allow the study of a three-step cascade in multiple topologies. Due to the spatiotemporal control provided, optimum conditions for decreasing the accumulation of inhibitors are unveiled, and benefited from reactive intermediates to maximize the overall cascade efficiency in compartments. The non-system-specific feature of the novel strategy makes this system an ideal candidate for the development of new synthetic routes as well as for screening natural and more complex pathways