Polymersomes with splenic avidity target red pulp myeloid cells for cancer immunotherapy.

Regulating innate immunity is an emerging approach to improve cancer immunotherapy. Such regulation requires engaging myeloid cells by delivering immunomodulatory compounds to hematopoietic organs, including the spleen. Here we present a polymersome-based nanocarrier with splenic avidity and propensity for red pulp myeloid cell uptake.

Regulating Chemokine-Receptor Interactions through the Site-Specific Bioorthogonal Conjugation of Photoresponsive DNA Strands.

Oligonucleotide conjugation has emerged as a versatile molecular tool for regulating protein activity. A state-of-the-art labeling strategy includes the site-specific conjugation of DNA, by employing bioorthogonal groups genetically incorporated in proteins through unnatural amino acids (UAAs). The incorporation of UAAs in chemokines has to date, however, remained underexplored, probably due to their sometimes poor stability following recombinant expression.

Toward Artificial Cell-Mediated Tissue Engineering: A New Perspective.

The fast-growing pace of regenerative medicine research has allowed the development of a range of novel approaches to tissue engineering applications. Until recently, the main points of interest in the majority of studies have been to combine different materials to control cellular behavior and use different techniques to optimize tissue formation, from 3-D bioprinting to in situ regeneration. However, with the increase of the understanding of the fundamentals of cellular organization, tissue development, and regeneration, has also come the realization that for the next step in tissue engineering, a higher level of spatiotemporal control on cell-matrix interactions is required.

Enzymatic Regulation of Protein-Protein Interactions in Artificial Cells.

Membraneless organelles are important for spatial organization of proteins and regulation of intracellular processes. Proteins can be recruited to these condensates by specific protein-protein or protein-nucleic acid interactions, which are often regulated by post-translational modifications. However, the mechanisms behind these dynamic, affinity-based protein recruitment events are not well understood.

Confined Motion: Motility of Active Microparticles in Cell-Sized Lipid Vesicles.

Active materials can transduce external energy into kinetic energy at the nano and micron length scales. This unique feature has sparked much research, which ranges from achieving fundamental understanding of their motility to the assessment of potential applications. Traditionally, motility is studied as a function of internal features such as particle topology, while external parameters such as energy source are assessed mainly in bulk.

DNA-Mediated Protein Shuttling between Coacervate-Based Artificial Cells.

The regulation of protein uptake and secretion is crucial for (inter)cellular signaling. Mimicking these molecular events is essential when engineering synthetic cellular systems. A first step towards achieving this goal is obtaining control over the uptake and release of proteins from synthetic cells in response to an external trigger.

Engineering transient dynamics of artificial cells by stochastic distribution of enzymes.

Random fluctuations are inherent to all complex molecular systems. Although nature has evolved mechanisms to control stochastic events to achieve the desired biological output, reproducing this in synthetic systems represents a significant challenge. Here we present an artificial platform that enables us to exploit stochasticity to direct motile behavior.

Engineering of Biocompatible Coacervate-Based Synthetic Cells.

Polymer-stabilized complex coacervate microdroplets have emerged as a robust platform for synthetic cell research. Their unique core-shell properties enable the sequestration of high concentrations of biologically relevant macromolecules and their subsequent release through the semipermeable membrane. These unique properties render the synthetic cell platform highly suitable for a range of biomedical applications, as long as its biocompatibility upon interaction with biological cells is ensured.

Terpolymer-stabilized complex coacervates: A robust and versatile synthetic cell platform.

The utilization of liquid-liquid phase separated systems has seen increased attention as synthetic cell platforms due to their innate ability to sequester interesting, functional, and biologically relevant materials. However, their applications are limited by the temporal stability of such condensed phases. While there are a number of strategies toward droplet stabilization, in our group we have developed a polymer-based approach to stabilize complex coacervate microdroplets.

Programmed spatial organization of biomacromolecules into discrete, coacervate-based protocells.

The cell cytosol is crowded with high concentrations of many different biomacromolecules, which is difficult to mimic in bottom-up synthetic cell research and limits the functionality of existing protocellular platforms. There is thus a clear need for a general, biocompatible, and accessible tool to more accurately emulate this environment. Herein, we describe the development of a discrete, membrane-bound coacervate-based protocellular platform that utilizes the well-known binding motif between Ni-nitrilotriacetic acid and His-tagged proteins to exercise a high level of control over the loading of biologically relevant macromolecules.

Tuning Size and Morphology of mPEG--p(HPMA-Bz) Copolymer Self-Assemblies Using Microfluidics.

The careful design of nanoparticles, in terms of size and morphology, is of great importance to developing effective drug delivery systems. The ability to precisely tailor nanoparticles in size and morphology during polymer self-assembly was therefore investigated. Four poly(ethylene glycol)--poly(-2-benzoyloxypropyl methacrylamide) mPEG--p(HPMA-Bz) block copolymers with a fixed hydrophilic block of mPEG 5 kDa and a varying molecular weight of the hydrophobic p(HPMA-Bz) block (A: 17.

Supramolecular Nanoscaffolds within Cytomimetic Protocells as Signal Localization Hubs.

The programmed construction of functional synthetic cells requires spatial control over arrays of biomolecules within the cytomimetic environment. The mimicry of the natural hierarchical assembly of biomolecules remains challenging due to the lack of an appropriate molecular toolbox. Herein, we report the implementation of DNA-decorated supramolecular assemblies as dynamic and responsive nanoscaffolds for the localization of arrays of DNA signal cargo within hierarchically assembled complex coacervate protocells.

Pathway dependent shape-transformation of azide-decorated polymersomes.

Here we report the shape transformation of poly(ethylene glycol)-polystyrene (PEG-PS) polymersomes into ordered inverse morphologies, directed by the salt concentration of the medium and the presence of azide groups on the polymersome surface. The azide moieties introduced at the chain ends of the PEG blocks induce a difference in hydrodynamic volume of the hydrophilic domains at the inner and outer side of the vesicular membrane, allowing control over its spontaneous curvature and hence the pathway of shape deformation. This simple modification enables access to intricate morphologies which are traditionally only accessible via the application of complex polymer building blocks.

Multifaceted cell mimicry in coacervate-based synthetic cells.

Cells, the discrete living systems that comprise all life on Earth, are a boundless source of inspiration and motivation for many researchers in the natural sciences. In the field of bottom-up synthetic cells, researchers seek to create multifaceted, self-assembled, chemical systems that mimic the properties and behaviours of natural life. In this perspective, we will describe the relatively recent application of complex coacervates to synthetic cells, and how they have been used to model an expanding range of biologically relevant phenomena.

Tandem catalysis in multicomponent solvent-free biofluids.

Enzymes are widely employed to reduce the environmental impact of chemical industries as biocatalysts improve productivity and offer high selectively under mild reaction conditions in a diverse range of chemical transformations. The poor stability of biomacromolecules under reaction conditions is often a critical bottleneck to their application. Protein engineering or immobilization onto solid substrates may remedy this limitation but, unfortunately, this is often at the expense of catalytic potency or substrate specificity.

Mimicking Cellular Compartmentalization in a Hierarchical Protocell through Spontaneous Spatial Organization.

A systemic feature of eukaryotic cells is the spatial organization of functional components through compartmentalization. Developing protocells with compartmentalized synthetic organelles is, therefore, a critical milestone toward emulating one of the core characteristics of cellular life. Here we demonstrate the bottom-up, multistep, noncovalent, assembly of rudimentary subcompartmentalized protocells through the spontaneous encapsulation of semipermeable, polymersome proto-organelles inside cell-sized coacervates.

ATP-Mediated Transient Behavior of Stomatocyte Nanosystems.

In nature, dynamic processes are ubiquitous and often characterized by adaptive, transient behavior. Herein, we present the development of a transient bowl-shaped nanoreactor system, or stomatocyte, the properties of which are mediated by molecular interactions. In a stepwise fashion, we couple motility to a dynamic process, which is maintained by transient events; namely, binding and unbinding of adenosine triphosphate (ATP).

Physicochemical Characterization of Polymer-Stabilized Coacervate Protocells.

The bottom-up construction of cell mimics has produced a range of membrane-bound protocells that have been endowed with functionality and biochemical processes reminiscent of living systems. The contents of these compartments, however, experience semidilute conditions, whereas macromolecules in the cytosol exist in protein-rich, crowded environments that affect their physicochemical properties, such as diffusion and catalytic activity. Recently, complex coacervates have emerged as attractive protocellular models because their condensed interiors would be expected to mimic this crowding better.

The hallmarks of living systems: towards creating artificial cells.

Despite the astonishing diversity and complexity of living systems, they all share five common hallmarks: compartmentalization, growth and division, information processing, energy transduction and adaptability. In this review, we give not only examples of how cells satisfy these requirements for life and the ways in which it is possible to emulate these characteristics in engineered platforms, but also the gaps that remain to be bridged. The bottom-up synthesis of life-like systems continues to be driven forward by the advent of new technologies, by the discovery of biological phenomena through their transplantation to experimentally simpler constructs and by providing insights into one of the oldest questions posed by mankind, the origin of life on Earth.

Development of Morphologically Discrete PEG-PDLLA Nanotubes for Precision Nanomedicine.

Precise control over the morphological features of nanoparticles is an important requisite for their application in nanomedical research. Parameters such as size and shape have been identified as critical features for effective nanotherapeutic technologies due to their role in circulation, distribution, and internalization in vivo. Tubular PEG-PDLLA polymersomes (nanotubes) exhibit an interesting morphology with potential for immunotherapeutics, as the elongated shape can affect cell-particle interactions.

Hierarchical Self-Assembly of a Copolymer-Stabilized Coacervate Protocell.

Complex coacervate microdroplets are finding increased utility in synthetic cell applications due to their cytomimetic properties. However, their intrinsic membrane-free nature results in instability that limits their application in protocell research. Herein, we present the development of a new protocell model through the spontaneous interfacial self-assembly of copolymer molecules on biopolymer coacervate microdroplets.

Formation of non-spherical polymersomes driven by hydrophobic directional aromatic perylene interactions.

Polymersomes, made up of amphiphilic block copolymers, are emerging as a powerful tool in drug delivery and synthetic biology due to their high stability, chemical versatility, and surface modifiability. The full potential of polymersomes, however, has been hindered by a lack of versatile methods for shape control. Here we show that a range of non-spherical polymersome morphologies with anisotropic membranes can be obtained by exploiting hydrophobic directional aromatic interactions between perylene polymer units within the membrane structure.

Choice of Capping Group in Tripeptide Hydrogels Influences Viability in the Three-Dimensional Cell Culture of Tumor Spheroids.

Two peptide-derived low-molecular-weight gelators bearing different capping groups, 9-fluorenylmethyloxycarbonyl (Fmoc) and phenothiazine, were synthesized and their gel networks were characterized. The variation of the N-terminal capping group affects the viability of these hydrogels as a three-dimensional cell culture for multicellular tumor spheroids. These results indicate that the phenothiazine capping group is a more biocompatible alternative to the widely used Fmoc moiety.

Polymersomes with Asymmetric Membranes Based on Readily Accessible Di- and Triblock Copolymers Synthesized via SET-LRP.

One of the hallmarks of nature is compartmentalization, and natural cell membranes are often asymmetric in terms of the inner and outer side. This communication describes work toward synthesizing such an asymmetric membrane from the bottom-up. A family of amphiphilic di- and triblock copolymers were synthesized via Cu(0)-mediated single electron transfer-living radical polymerization with the aim to generate polymer vesicles, or polymersomes, with an asymmetric membrane.