Engineering artificial cells is currently an emerging area of research that involves constructing mimics of biological cells. These biomimetic cellular systems hold tremendous promise for the different biomedical applications (diagnostics, therapy, tissue engineering, gene transfection, bioactive coatings) as well as aspects of synthetic biology. A key architectural principle of the cell is a multicompartmentalized assembly, which is one of the features of biological cells that enable the performance of multiple complex biochemical reactions within confined environments. For this purpose, this study demonstrates novel artificial cells, not only presenting organelle mimics but also incorporating various stimuli for regulating enzymatic cascade reactions within the artificial cell and for controlled simultaneous and/or subsequent release of the encapsulated (therapeutic) molecules.
To successfully fabricate the multifunctional polymeric multicompartmentalized systems as artificial cells aimed for, in the first step a hollow capsule as biomimetic cellular membrane was developed to simulate a key characteristic of functional artificial cells for the selective uptake and release of (bio)molecules and particles for intra- and intercellular signaling processes. Herein using LbL technique which involved alternate deposition of oppositely charged polyelectrolytes on silica template via electrostatic interaction, the pH and temperature dual-responsive and photo-crosslinked hollow capsule was fabricated and they can be used for the subsequent post-encapsulation process of protein-like macromolecules (≤ 11 nm) and their controllable release triggered by external stimuli for mimicking the controllable bio-inspired functions of cell membranes. The reversible temperature and pH dual-response ability of the hollow capsules has been analyzed. The uptake and release properties of the resulting hollow capsules with different degree of photo-crosslinking for cargos have been further investigated at various temperatures (25, 37 or 45°C) and pH (5.5 or 7.4) of the solution.
Next, the design of the polymersomal subcompartmens as organelle mimics, which divide the interior of the multicompartmentalized systems into subcompartments and can stably encapsulate fragile hydrophobic and hydrophilic cargo, e.g., enzymes in order to conduct encapsulated catalysis-resembling cell organelles, was also an important subject. The fabrication of these subcompartments was starting with the synthesis of suitably end-group block copolymers to realize the enzyme-loaded, multifunctional, pH-responsive, photo-crosslinked and post-labelled polymersomes decorated with adamantane groups. The pH sensitivity and various enzymatic reactions of the established multifunctional Ada-polymersomes have been investigated.
Based on the above concepts, a bottom-up approach was developed to assemble a structural and functional eukaryotic cell mimics, including “membrane-associated” multicompartmentalized system (MS1) and “free-floating” multicompartmentalized system (MS2), by loading pH-sensitive Ada-polymersomes inside the multifunctional cell membrane. The creation of these multicompartmentalized systems was based on the assembly of enzyme-loaded Ada-polymersomes as organelle mimics onto sacrificial particle templates by host-guest interaction, followed by the LbL deposition of temperature-responsive and photo-crosslinkable PMA(β-CD)/[PAH/PNMD]3 multilayers and outer protective capping PAH/PMA(PEG) bilayer as biomimetic cellular membrane. Upon photo-crosslinking the polymer biomimetic membrane and dissolution of the particle templates, multicompartmentalized systems were obtained. Spatial position of the subcompartments can be controlled using non-covalent host-guest concept, which yielded multicompartmentalized systems containing “membrane-associated” and “free-floating” subunits. Moreover, the metabolism mimicry of multicompartmentalized systems by performing multiple successive two-enzyme cascade reactions in the cells and the multiple parallel reactions by using a third enzyme for deactivating the reaction product and interfering the cascade reaction have been investigated.
In conclusion, these multicompartmentalized systems, combining the advantages of both pH-responsive Ada-polymersomes as organelle mimics and multifunctional hollow capsule as biomimetic cellular membrane, present new opportunities for the development of functional cell mimics. The presented studies highlight crucial aspects for the successful applications of such cell mimics for diagnostics, tissue engineering, as nanoreactors, as carriers for multiple drug delivery with controlled release profiles, or as therapeutic artificial cells.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:30634 |
| Date | 07 November 2017 |
| Creators | Liu, Xiaoling |
| Contributors | Voit, Brigitte, Feng, Xinliang, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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