Dominik Söder

Cell membranes play a key role in bottom‐up synthetic biology, as they enable interaction control, transport, and other essential functions. These ultra‐thin, flexible, yet stable structures form through the self‐assembly of lipids and proteins. While liposomes are common mimics, their synthetic membranes often fail to replicate natural properties due to poor structural control. To address this, pepticombs are introduced, a new family of supramolecular building blocks. They are synthesized by regularly appending anionic surfactants with lipid‐long alkyl tails to cationic amino acid residues of recombinant elastin‐like supercharged unfolded polypeptides (SUPs). Using microscopy techniques and molecular dynamics simulations, the formation of giant unilamellar vesicles, termed pepticombisomes, is demonstrated and their membrane properties are characterized. The molecular topology of pepticombs allows for precise mimicry of membrane thickness and flexibility, beyond classic polymersomes. Unlike the previously introduced ionically‐linked comb polymers, all pepticombs exhibit a uniform degree of polymerization, composition, sequence, and spontaneous curvature. This uniformity ensures consistent hydrophobic tail distribution, facilitating intermolecular hydrogen bonding within the backbone. This generates elastic heterogeneities and the concomitant formation of non‐icosahedral faceted vesicles, as previously predicted. Additionally, pepticombisomes can incorporate functional lipids, enhancing design flexibility.

The immobilization of vesicles has been conceptualized as a method to functionalize biointerfaces. However, the preservation of their integrity post immobilization remains a considerable challenge. Interfacial interactions can cause vesicle rupture upon close surface contact and non‐specific protein adsorption impairing surface functions. To date, immobilization of vesicles has relied solely on either entrapment or prior modification of vesicles, both of which require laborious preparation and limit their applications. This work develops a bioinspired strategy to pin vesicles without prior modification while preserving their intact shape. This work introduces antifouling diblock copolymers and ultrathin surface‐attached hydrogels containing a brush‐like interface consisting of a bottle brush copolymer of N ‐(2‐hydroxypropyl) methacrylamide (HPMA) and N ‐(3‐methacrylamidopropyl)‐ N , N ‐dimethyldodecan‐1‐aminiumiodide (C12+). The presence of positive charges generates an attractive force that pulls vesicles toward the surface. At the surface, the amphiphilic properties of the combs facilitate their insertion into the membrane, mimicking the harpooning mechanism observed in antimicrobial peptides. Importantly, the antifouling poly(HPMA) backdrop serves to safeguard the vesicles by preventing deformation and breakage. Using a combination of thermodynamic analysis, surface plasmon resonance, and confocal laser scanning microscopy, this work demonstrates the efficiency of this biomimetic system to capture vesicles while maintaining an antifouling interface necessary for bioapplications.

Building functional mimics of cell membranes is an important task toward the development of synthetic cells. So far, lipid and amphiphilic block copolymers are the most widely used amphiphiles with the bilayers by the former lacking stability while membranes by the latter are typically characterized by very slow dynamics. Herein, a new type of Janus dendrimer containing a zwitterionic phosphocholine hydrophilic headgroup (JD^PC) and a 3,5‐substituted dihydrobenzoate‐based hydrophobic dendron is introduced. JD^PC self‐assembles in water into zwitterionic dendrimersomes (z‐DSs) that faithfully recapitulate the cell membrane in thickness, flexibility, and fluidity, while being resilient to harsh conditions and displaying faster pore closing dynamics in the event of membrane rupture. This enables the fabrication of hybrid DSs with components of natural membranes, including pore‐forming peptides, structure‐directing lipids, and glycans to create raft‐like domains or onion vesicles. Moreover, z‐DSs can be used to create active synthetic cells with life‐like features that mimic vesicle fusion and motility as well as environmental sensing. Despite their fully synthetic nature, z‐DSs are minimal cell mimics that can integrate and interact with living matter with the programmability to imitate life‐like features and beyond.

The construction of biomembranes that faithfully capture the properties and dynamic functions of cell membranes remains a challenge in the development of synthetic cells and their application. Here a new concept for synthetic cell membranes based on the self‐assembly of amphiphilic comb polymers into vesicles, termed ionic combisomes (i‐combisomes) is introduced. These combs consist of a polyzwitterionic backbone to which hydrophobic tails are linked by electrostatic interactions. Using a range of microscopies and molecular simulations, the self‐assembly of a library of combs in water is screened. It is discovered that the hydrophobic tails form the membrane's core and force the backbone into a rod conformation with nematic‐like ordering confined to the interface with water. This particular organization resulted in membranes that combine the stability of classic polymersomes with the biomimetic thickness, flexibility, and lateral mobility of liposomes. Such unparalleled matching of biophysical properties and the ability to locally reconfigure the molecular topology of its constituents enable the harboring of functional components of natural membranes and fusion with living bacteria to “hijack” their periphery. This provides an almost inexhaustible palette to design the chemical and biological makeup of the i‐combisomes membrane resulting in a powerful platform for fundamental studies and technological applications.

The ability of proteins to adsorb irreversibly onto surfaces opens new possibilities to functionalize biological interfaces. Herein, the mechanism and kinetics of adsorption of protein‐polymer macromolecules with the ability to equip surfaces with antifouling properties are investigated. These macromolecules consist of the liquid chromatography peak I peptide from which antifouling polymer brushes are grafted using single electron transfer‐living radical polymerization. Surface plasmon resonance spectroscopy reveals an adsorption mechanism that follows a Langmuir‐type of binding with a strong binding affinity to gold. X‐ray reflectivity supports this by proving that the binding occurs exclusively by the peptide. However, the lateral organization at the surface is directed by the cylindrical eGFP. The antifouling functionality of the unimolecular coatings is confirmed by contact with blood plasma. All coatings reduce the fouling from blood plasma by 8894% with only minor effect of the degree of polymerization for the studied range (DP between 101 and 932). The excellent antifouling properties, combined with the ease of polymerization and the straightforward coating procedure make this a very promising antifouling concept for a multiplicity of applications.

The effect of the two‐dimensional glycan display on glycan‐lectin recognition remains poorly understood despite the importance of these interactions in a plethora of cellular processes, in (patho)physiology, as well as its potential for advanced therapeutics. Faced with this challenge we utilized glycodendrimersomes, a type of synthetic vesicles whose membrane mimics the surface of a cell and offers a means to probe the carbohydrate biological activity. These single‐component vesicles were formed by the self‐assembly of sequence‐defined mannose‐Janus dendrimers, which serve as surrogates for glycolipids. Using atomic force microscopy and molecular modeling we demonstrated that even mannose, a monosaccharide, was capable of organizing the sugar moieties into periodic nanoarrays without the need of the formation of liquid‐ordered phases as assumed necessary for rafts. Kinetics studies of Concanavalin A binding revealed that those nanoarrays resulted in a new effective ligand yielding a ten‐fold increase in the kinetic and thermodynamic constant of association.

The effect of the two‐dimensional glycan display on glycan‐lectin recognition remains poorly understood despite the importance of these interactions in a plethora of cellular processes, in (patho)physiology, as well as its potential for advanced therapeutics. Faced with this challenge we utilized glycodendrimersomes, a type of synthetic vesicles whose membrane mimics the surface of a cell and offers a means to probe the carbohydrate biological activity. These single‐component vesicles were formed by the self‐assembly of sequence‐defined mannose‐Janus dendrimers, which serve as surrogates for glycolipids. Using atomic force microscopy and molecular modeling we demonstrated that even mannose, a monosaccharide, was capable of organizing the sugar moieties into periodic nanoarrays without the need of the formation of liquid‐ordered phases as assumed necessary for rafts. Kinetics studies of Concanavalin A binding revealed that those nanoarrays resulted in a new effective ligand yielding a ten‐fold increase in the kinetic and thermodynamic constant of association.