Artificial Channels Based on Bottlebrush Polymers: Enhanced Ion Transport Through Polymer Topology Control

Synthetic structures mimicking the transport function of natural ion channel proteins have a wide range of applications, including therapeutic treatments, separation membranes, sensing, and biotechnologies. However, the development of polymer-based artificial channels has been hampered due to the limitation on available models. In this study, we demonstrate the great potential of bottlebrush polymers as accessible and versatile molecular scaffolds for developing efficient artificial ion channels. Adopting the bottlebrush configuration enhanced ion transport activity of the channels compared to their linear analogs. Matching the structure of lipid bilayers, the bottlebrush channel with a hydrophilic-hydrophobic-hydrophilic triblock architecture exhibited the highest activity among the series. Functionalized with urea groups, these channels displayed high anion selectivity. Additionally, we illustrated that the transport properties could be fine-tuned by modifying the chemistry of ion binding sites. This work not only highlights the importance of polymer topology control in channel design, but also reveals the great potential for further developing bottlebrush channels with customized features and diverse functionalities.

Polymersomes in Drug Delivery─From Experiment to Computational Modeling

Polymersomes, composed of amphiphilic block copolymers, are self-assembled vesicles that have gained attention as potential drug delivery systems due to their good biocompatibility, stability, and versatility. Various experimental techniques have been employed to characterize the self-assembly behaviors and properties of polymersomes. However, they have limitations in revealing molecular details and underlying mechanisms. Computational modeling techniques have emerged as powerful tools to complement experimental studies and enabled researchers to examine drug delivery mechanisms at molecular resolution. This review aims to provide a comprehensive overview of the state of the art in the field of polymersome-based drug delivery systems, with an emphasis on insights gained from both experimental and computational studies. Specifically, we focus on polymersome morphologies, self-assembly kinetics, fusion and fission, behaviors in flow, as well as drug encapsulation and release mechanisms. Furthermore, we also identify existing challenges and limitations in this rapidly evolving field and suggest possible directions for future research.

Physically and Chemically Compartmentalized Polymersomes for Programmed Delivery and Biological Applications

Multicompartment polymersomes (MCPs) refer to polymersomes that not only contain one single compartment, either in the membrane or in the internal cavity, but also mimic the compartmentalized structure of living cells, attracting much attention in programmed delivery and biological applications. The investigation of MCPs may promote the application of soft nanomaterials in biomedicine. This Review seeks to highlight the recent advances of the design principles, synthetic strategies, and biomedical applications of MCPs. The compartmentalization types including chemical, physical, and hybrid compartmentalization are discussed. Subsequently, the design and controlled synthesis of MCPs by the self-assembly of amphiphilic polymers, double emulsification, coprecipitation, microfluidics and particle assembly, etc. are summarized. Furthermore, the diverse applications of MCPs in programmed delivery of various cargoes and biological applications including cancer therapy, antimicrobials, and regulation of blood glucose levels are highlighted. Finally, future perspectives of MCPs from the aspects of controlled synthesis and applications are proposed.

Membrane and Lumen-Compartmentalized Polymersomes for Biocatalysis and Cell Mimics

Compartmentalization is a crucial feature of a natural cell, manifested in cell membrane and inner lumen. Inspired by the cellular structure, multicompartment polymersomes (MCPs), including membrane-compartmentalized polymersomes and lumen-compartmentalized polymersomes (polymersomes-in-polymersomes), have aroused great expectations for biological applications such as biocatalysis and cell mimics in the past decades. Compared with traditional polymersomes, MCPs have advantages in encapsulating multiple enzymes separately for multistep enzymatic cascade reactions. In this review, first, the design principles and preparation methods of membrane-compartmentalized and lumen-compartmentalized polymersomes are summarized. Next, recent advances of MCPs as nanoreactors and cell mimics to mimic subcellular organelles or artificial cells are discussed. Finally, the future research directions of MCPs are prospected.

Multicompartment colloid systems with lipid and polymer membranes for biomedical applications

Multicompartment structures have the potential for biomedical applications because they can act as multifunctional systems and provide simultaneous delivery of drugs and diagnostics agents of different types. Moreover, some of them mimic biological cells to some extent with organelles as separate sub-compartments. This article analyses multicompartment colloidal structures with smaller sub-units covered with lipid or polymer membranes that provide additional protection for the encapsulated substances. Vesosomes with small vesicles encapsulated in the inner pools of larger liposomes are the most studied systems to date. Dendrimer molecules are enclosed by a lipid bilayer shell in dendrosomes. Capsosomes, polymersomes-in-polymer capsules, and cubosomes-in-polymer capsules are composed of sub-compartments encapsulated within closed multilayer polymer membranes. Janus or Cerberus emulsions contain droplets composed of two or three phases: immiscible oils in O/W emulsions and aqueous polymer or salt solutions that are separated into two or three phases and form connected droplets in W/O emulsions. In more cases, the external surface of engulfed droplets in Janus or Cerberus emulsions is covered with a lipid or polymer monolayer. eLiposomes with emulsion droplets encapsulated into a bilayer shell have been given little attention so far, but they have very great prospects. In addition to nanoemulsion droplets, solid lipid nanoparticles, nanostructured lipid carriers and inorganic nanoparticles can be loaded into eLiposomes. Molecular engineering of the external membrane allows the creation of ligand-targeted and stimuli-responsive multifunctional systems. As a result, the efficacy of drug delivery can be significantly enhanced.

Permeable polymersomes from temperature and pH dual stimuli-responsive PVCL-b-PLL block copolymers for enhanced cell internalization and lysosome targeting

A series of dual stimuli-responsive block copolymers comprising temperature-responsive poly(N-vinylcaprolactam) (PVCL) and biodegradable pH-responsive poly(l-lysine) (PLL) of varying chain length were synthesized by a combination of free radical polymerization and ring opening polymerization. The block copolymers formed micelles and vesicles (polymersomes) in response to temperature and pH, respectively, in aqueous solution. The nanoassemblies were characterized by transmission electron microscopy and dynamic light scattering techniques. Encapsulation of both hydrophobic and hydrophilic dyes in the polymersomes was shown. Doxorubicin (DOX) was loaded in the polymersomes and its controlled release in response to the two stimuli, independently and jointly, was studied. The drug was found to be released due to stimuli-induced increased permeability without disassembly of the polymersomes. A significant increase in the cellular uptake of the drug-loaded polymersomes at hyperthermia conditions was demonstrated at 41 °C and release of the drug upon localization in lysosomes was observed. Cellular internalization pathway of the polymersomes was investigated by competitive inhibition assay and a combination of endocytic pathways dominated by caveolae-mediated mechanism was found to be operative.

Overcoming the Dilemma of Permeability and Stability of Polymersomes through Traceless Cross-Linking

In nature, cells are highly compartmentalized into many organelles that are well separated from the rest of the cellular space by unique membrane structures, which are of crucial importance to allow cells to perform various physiological functions in such a small and crowded space. Learning from the ubiquitous membrane structures of cells and organelles has continuously inspired the development of artificial self-assembled nanostructures, with lipid vesicles (liposomes) and polymer vesicles (polymersomes) being the most representative examples. Similar to the membrane-bound structures of cells and organelles, both liposomes and polymersomes contain an aqueous interior enclosed by a bilayer membrane. Therefore, liposomes and polymersomes have been extensively investigated to mimic the fundamental structures and functions of living cells. For example, liposomes and polymersomes have been successfully engineered as nanocarriers, smart nanoreactors, artificial organelles, and so on. Notably, living cells can exchange both energy and materials with surrounding environments, benefiting from the selective permeability of lipid membranes. The permselectivity of cell membranes is thus an essential attribute of living organisms. Compared to liposomes, polymersomes have increased structural stability but low membrane permeability. Indeed, polymersomes are almost impermeable to small molecules, ions, and even water molecules. To improve the permeability of polymersomes, much effort has been devoted to the incorporation of channel proteins, the coassembly of oppositely charged block copolymers (BCPs), the development of stimuli-responsive BCPs, and so on. Despite great achievements, these approaches generally lead to decreased stability of polymersomes and, sometimes, polymersome disintegration. In this Account, we discuss our recent efforts to reconcile the stability and permeability of polymersomes via a traceless cross-linking approach. Although cross-linking reactions within bilayer membranes generally lead to decreased permeability, the traceless cross-linking approach can concurrently improve the stability and permeability of polymersomes. Specifically, stimuli-responsive polymersomes undergo either covalent cross-linking or noncovalent cross-linking reactions under specific stimuli to increase bilayer stability, while the cross-linking processes can concurrently permeabilize polymersome bilayers through cross-linking-driven hydrophobic-to-hydrophilic transitions. Notably, unlike conventional cross-linking processes requiring additional cross-linkers, the traceless cross-linking process does not involve extra cross-linking agents but takes full advantage of the in situ generated active moieties. By taking advantage of the simultaneous modulation of the stability and permeability of polymersomes via traceless cross-linking, these polymersomes can be further engineered as smart nanocarriers and nanoreactors. The robustness and generality of this approach have been validated by both extracellular and intracellular stimuli such as light irradiation, glutathione, and hydrogen peroxide. Moreover, many functional groups such as fluorescent dyes and contrast agents can be integrated into this versatile platform as well, enabling the construction of theranostic nanovectors capable of responding to pathological microenvironments. This Account provides a new approach to regulating the permeability of polymersomes while maintaining their structural stability.

Nanozyme-Based Artificial Organelles: An Emerging Direction for Artificial Organelles

Artificial organelles are compartmentalized nanoreactors, in which enzymes or enzyme-mimic catalysts exhibit cascade catalytic activities to mimic the functions of natural organelles. Importantly, research on artificial organelles paves the way for the bottom-up design of synthetic cells. Due to the separation effect of microcompartments, the catalytic reactions of enzymes are performed without the influence of the surrounding medium. The current techniques for synthesizing artificial organelles rely on the strategies of encapsulating enzymes into vesicle-structured materials or reconstituting enzymes onto the microcompartment materials. However, there are still some problems including limited functions, unregulated activities, and difficulty in targeting delivery that hamper the applications of artificial organelles. The emergence of nanozymes (nanomaterials with enzyme-like activities) provides novel ideas for the fabrication of artificial organelles. Compared with natural enzymes, nanozymes are featured with multiple enzymatic activities, higher stability, easier to synthesize, lower cost, and excellent recyclability. Herein, the most recent advances in nanozyme-based artificial organelles are summarized. Moreover, the benefits of compartmental structures for the applications of nanozymes, as well as the functional requirements of microcompartment materials are also introduced. Finally, the potential applications of nanozyme-based artificial organelles in biomedicine and the related challenges are discussed.

Manufacturing polymeric porous capsules

Polymeric porous capsules represent hugely promising systems that allow a size-selective through-shell material exchange with their surroundings. They have vast potential in applications ranging from drug delivery and chemical microreactors to artificial cell science and synthetic biology. Due to their porous core-shell structure, polymeric porous capsules possess an enhanced permeability that enables the exchange of small molecules while retaining larger compounds and macromolecules. The cross-capsule transfer of material is regulated by their pore size cut-off, which depends on the molecular composition and adopted fabrication method. This review outlines the main strategies for manufacturing polymeric porous capsules and provides some practical guidance for designing polymeric capsules with controlled pore size.

Construction of Supramolecular Systems That Achieve Lifelike Functions

The Nobel Prize in Chemistry was awarded in 1987 and 2016 for research in supramolecular chemistry on the "development and use of molecules with structure-specific interactions of high selectivity" and the "design and production of molecular machines", respectively. This confirmed the explosive development of supramolecular chemistry. In addition, attempts have been made in systems chemistry to embody the complex functions of living organisms as artificial non-equilibrium chemical systems, which have not received much attention in supramolecular chemistry. In this review, we explain recent developments in supramolecular chemistry through four categories: stimuli-responsiveness, time evolution, dissipative self-assembly, and hierarchical expression of functions. We discuss the development of non-equilibrium supramolecular systems, including the use of molecules with precisely designed properties, to achieve functions found in life as a hierarchical chemical system.

Membrane protein channels equipped with a cleavable linker for inducing catalysis inside nanocompartments

Precisely timed initiation of reactions and stability of the catalysts are fundamental in catalysis. We introduce here an efficient closing-opening method for nanocompartments that contain sensitive catalysts and so achieve a controlled and extended catalytic activity. We developed a chemistry-oriented approach for modifying a pore-forming membrane protein which allows for a stimuli-responsive pore opening within the membrane of polymeric nanocompartments. We synthesized a diol-containing linker that selectively binds to the pores, blocking them completely. In the presence of an external stimulus (periodate), the linker is cleaved allowing the diffusion of substrate through the pores to the nanocompartment interior where it sets off the in situ enzymatic reaction. Besides the precise initiation of catalytic activity by opening of the pores, oxidation by periodate guarantees the cleavage of the linker under mild conditions. Accordingly, this kind of responsive nanocompartment lends itself to harboring a large variety of sensitive catalysts such as proteins and enzymes.

Near-Infrared Photo-controlled Permeability of a Biomimetic Polymersome with Sustained Drug Release and Efficient Tumor Therapy

Synthetic polymersomes have structure similarity to bio-vesicles and could disassemble in response to stimuli for "on-demand" release of encapsulated cargos. Though widely applied as a drug delivery carrier, the burst release mode with structure complete destruction is usually taken for most responsive polymersomes, which would shorten the effective drug reaction time and impair the therapeutic effect. Inspired by the cell organelles' communication mode via regulating membrane permeability for transportation control, we highlight here a biomimetic polymersome with sustained drug release over a specific period of time via near-infrared (NIR) pre-activation. The polymersome is prepared by the self-assembling amphiphilic diblock copolymer P(OEGMA-co-EoS)-b-PNBOC and encapsulates the hypoxia-activated prodrug AQ4N and upconversion nanoparticle (PEG-UCNP) in its hydrophilic centric cavity. Thirty minutes of NIR pre-activation triggers cross-linking of NBOC and converts the permeability of the polymersome with sustained AQ4N release until 24 h after the NIR pre-activation. The photosensitizer EoS is activated and aggravates environmental hypoxic conditions during a sustained drug release period to boost the AQ4N therapeutic effect. The combination of sustained drug release with concurrent hypoxia intensification results in a highly efficient tumor therapeutic effect both intracellularly and in vivo. This biomimetic polymersome will provide an effective and universal tumor therapeutic approach.

Supramolecular tripeptide self-assembly initiated at the surface of coacervates by polyelectrolyte exchange

Spatial control of supramolecular self-assembly can yield compartmentalized structures, a key feature for the design of artificial cells. Inducing self-assembly from and on compartments is still a challenge. Polyelectrolyte complex coacervates are simple model droplet systems able to reproduce the basic features of membrane-less organelles, appearing in cells. Here, we demonstrate the supramolecular self-assembly of a phosphorylated tripeptide, Fmoc-FFpY (Fmoc: fluorenyl-methoxycarbonyl; F: phenyl alanine, pY: phosphorylated tyrosine), on the surface of poly(l-glutamic acid)/poly(allylamine hydrochloride) (PGA/PAH) complex coacervate microdroplets. The phosphorylated peptides self-assemble, without dephosphorylation, through ion pairing between the phosphate groups of Fmoc-FFpY and the amine groups of PAH. This process provides spontaneous capsules formed by an amorphous polyelectrolyte complex core surrounded by a structured peptide/PAH shell. Similar fibrillar Fmoc-FFpY self-assembled structures are obtained at the interface between the peptide solution and a PGA/PAH polyelectrolyte multilayer, a complex coacervate in the thin film or "multilayer" format. In contact with the peptide solution, PAH chains diffuse out of the coacervate or multilayer film and complex with Fmoc-FFpY at the solution interface, exchanging any PGA with which they were associated. Self-assembly of Fmoc-FFpY, now concentrated by complexation with PAH, follows quickly.

The rise of bio-inspired polymer compartments responding to pathology-related signals

Self-organized nano- and microscale polymer compartments such as polymersomes, giant unilamellar vesicles (GUVs), polyion complex vesicles (PICsomes) and layer-by-layer (LbL) capsules have increasing potential in many sensing applications. Besides modifying the physicochemical properties of the corresponding polymer building blocks, the versatility of these compartments can be markedly expanded by biomolecules that endow the nanomaterials with specific molecular and cellular functions. In this review, we focus on polymer-based compartments that preserve their structure, and highlight the key role they play in the field of medical diagnostics: first, the self-assembling abilities that result in preferred architectures are presented for a broad range of polymers. In the following, we describe different strategies for sensing disease-related signals (pH-change, reductive conditions, and presence of ions or biomolecules) by polymer compartments that exhibit stimuli-responsiveness. In particular, we distinguish between the stimulus-sensitivity contributed by the polymer itself or by additional compounds embedded in the compartments in different sensing systems. We then address necessary properties of sensing polymeric compartments, such as the enhancement of their stability and biocompatibility, or the targeting ability, that open up new perspectives for diagnostic applications.

Polymersome-Based Modular Nanoreactors with Size-Selective Transmembrane Permeability

Polymersome nanoreactors encapsulating the enzymes or particulate catalysts attract interest because of their potential use as modular reactors to synthesize complex compounds via a cascade of chemical reactions in a single batch. To achieve these goals, a key requirement is the tunable permeability of the polymersome membrane, which allows the size-selective transportation of reagents and products while protecting the encapsulated catalysts during the chemical reaction. We report here a stimuli-responsive route for controlling the permeability of the polymersomes of the binary blend of poly(ethylene glycol)-b-polystyrene (PEG-b-PS) and poly(ethylene glycol)-b-poly(acrylbenzylborate) (PEG-b-PABB). The presence of H₂O₂ (1 mM) in the medium (0.1 M PBS, pH 7.4) triggers the oxidation of benzyl borate pendants of PABB to form poly(acrylic acid) (PAA). This transformation results in the perforation of the compartmentalizing membrane of polymersomes by the dissolution of PEG-b-PAA domains embedded in the inert PEG-b-PS matrix. By controlling the composition of the stimuli-responsive block copolymer, the polymersomes of the binary blend exhibit size-selective permeability without losing the structural integrity. Release of fluorescent guests with different sizes (fluorescein, PEG2k-Cm, PEG5k-Rho) can be controlled by tuning the composition (PEG-b-PS/PEG-b-PABB = 100/0-80/20) of blended polymersomes. Selective permeability of the membrane provides protection of the encapsulated enzymes from external proteases present in the medium, resulting in the one-pot synthesis of small molecules via cascades of chemical reactions. The nanoparticular catalysts are also encapsulated within the permeable polymersomes, serving as modular reactors for the conversion of organic compounds via a cascade of reactions.

Intrinsically permeable polymer vesicles based on carbohydrate-conjugated poly(2-oxazoline)s synthesized using a carbohydrate-based initiator system

A thermo-responsive poly(n-propyl oxazoline) block was employed as the hydrophobic segment in an amphiphilic glyco polymer. This approach affords intrinsically permeable polymer vesicles for water-soluble compounds.

Biotransporting Biocatalytic Reactors toward Therapeutic Nanofactories

Drug-delivery systems (DDSs), in which drug encapsulation in nanoparticles enables targeted delivery of therapeutic agents and their release at specific disease sites, are important because they improve drug efficacy and help to decrease side effects. Although significant progress has been made in the development of DDSs for the treatment of a wide range of diseases, new approaches that increase the scope and effectiveness of such systems are still needed. Concepts such as nanoreactors and nanofactories are therefore attracting much attention. Nanoreactors, which basically consist of vesicle-encapsulated enzymes, provide prodrug conversion to therapeutic agents rather than simple drug delivery. Nanofactories are an extension of this concept and combine the features of nanoreactors and delivery carriers. Here, the required features of nanofactories are discussed and an overview of current strategies for the design and fabrication of different types of nanoreactors, i.e., systems based on lipid or polymer vesicles, capsules, mesoporous silica, viral capsids, and hydrogels, and their respective advantages and shortcomings, is provided. In vivo applications of biocatalytic reactors in the treatment of cancer, glaucoma, neuropathic pain, and alcohol intoxication are also discussed. Finally, the prospects for further progress in this important and promising field are outlined.

Antagonistic chemical coupling in self-reconfigurable host-guest protocells

Fabrication of compartmentalised chemical systems with nested architectures and biomimetic properties has important implications for controlling the positional assembly of functional components, spatiotemporal regulation of enzyme cascades and modelling of proto-organelle behaviour in synthetic protocells. Here, we describe the spontaneous capture of glucose oxidase-containing proteinosomes in pH-sensitive fatty acid micelle coacervate droplets as a facile route to multi-compartmentalised host–guest protocells capable of antagonistic chemical and structural coupling. The nested system functions co-operatively at low-substrate turnover, while high levels of glucose give rise to pH-induced disassembly of the droplets, release of the incarcerated proteinosomes and self-reconfiguration into spatially organised enzymatically active vesicle-in-proteinosome protocells. Co-encapsulation of antagonistic enzymes within the proteinosomes produces a sequence of self-induced capture and host–guest reconfiguration. Taken together, our results highlight opportunities for the fabrication of self-reconfigurable host–guest protocells and provide a step towards the development of protocell populations exhibiting both synergistic and antagonistic modes of interaction.

Multi-compartmentalised soft micro-systems are used as models of synthetic protocells. Here, the authors developed nested host–guest protocell constructs capable of self-reconfiguration in response to changes in pH generated by antagonistic modes of enzyme-mediated coupling.

Multifunctional GQDs-Concanavalin A@Fe3O4 nanocomposites for cancer cells detection and targeted drug delivery

Multifunctional nanocomposites containing intrinsic property for serving as the sensing elements as well as targeted nanoconjugates are highly preferred in various therapeutic applications. In this work, nanocomposites of graphene quantum dots (GQDs) and Fe₃O₄ with conjugation of lectin protein, concanavalin A, to form GQD-ConA@Fe₃O₄ nanocomposites are developed for both detection of cancer cell and release of drugs to HeLa cells. The GQD-ConA@Fe₃O₄ nanocomposites deposited on Pt electrode can detect cancerous HeLa cells over normal endothelial cells with a dynamic linear range of 5 × 10² to 1 × 10⁵ cells mL^-1 with a detection limit of 273 cell mL^-1. The GQD-ConA@Fe₃O₄ also can serve as nanocarriers for loading and delivering doxorubicin (Dox). The in vitro cell images show that the Dox concentration in HeLa cells is enhanced more than double in the presence of external magnetic field due to the incorporation of Fe₃O₄ in the nanocarrier. The cytotoxicity assay indicates that the susceptibility of cancerous HeLa cells to Dox is 13% higher than that of normal cells, confirming the selective role of ConA in nanocarriers. Results clearly indicate the GQD-ConA@Fe₃O₄ nanocomposites as a promising material for cancer cell detection and targeted Dox release toward HeLa cells which can serve as the multifunctional platform for novel cancer cell diagnostic and therapeutic applications.

Preparation and Properties of Asymmetric Synthetic Membranes Based on Lipid and Polymer Self-Assembly

Cell membrane asymmetry is a common structural feature of all biological cells. Researchers have tried for decades to better study its formation and its function in membrane-regulated phenomena. In particular, there has been increasing interest in developing synthetic asymmetric membrane models in the laboratory, with the aim of studying basic physical chemistry properties that may be correlated to a relevant biological function. The present article aims to summarize the main presented approaches to prepare asymmetric membranes, which are most often made from lipids, polymers, or a combination of both.

Recent Progress in Micro/Nanoreactors toward the Creation of Artificial Organelles

Artificial organelles created from a bottom up approach are a new type of engineered materials, which are not designed to be living but, instead, to mimic some specific functions inside cells. By doing so, artificial organelles are expected to become a powerful tool in biomedicine. They can act as nanoreactors to convert a prodrug into a drug inside the cells or as carriers encapsulating therapeutic enzymes to replace malfunctioning organelles in pathological conditions. For the design of artificial organelles, several requirements need to be fulfilled: a compartmentalized structure that can encapsulate the synthetic machinery to perform an enzymatic function, as well as a means to allow for communication between the interior of the artificial organelle and the external environment, so that substrates and products can diffuse in and out the carrier allowing for continuous enzymatic reactions. The most recent and exciting advances in architectures that fulfill the aforementioned requirements are featured in this review. Artificial organelles are classified depending on their constituting materials, being lipid and polymer-based systems the most prominent ones. Finally, special emphasis will be put on the intracellular response of these newly emerging systems.

Enhanced Antitumor Effects of Epidermal Growth Factor Receptor Targetable Cetuximab-Conjugated Polymeric Micelles for Photodynamic Therapy

Nanocarrier-based delivery systems are promising strategies for enhanced therapeutic efficacy and safety of toxic drugs. Photodynamic therapy (PDT)—a light-triggered chemical reaction that generates localized tissue damage for disease treatments—usually has side effects, and thus patients receiving photosensitizers should be kept away from direct light to avoid skin phototoxicity. In this study, a clinically therapeutic antibody cetuximab (C225) was conjugated to the surface of methoxy poly(ethylene glycol)-b-poly(lactide) (mPEG-b-PLA) micelles via thiol-maleimide coupling to allow tumor-targetable chlorin e6 (Ce6) delivery. Our results demonstrate that more C225-conjugated Ce6-loaded polymeric micelles (C225-Ce6/PM) were selectively taken up than Ce6/PM or IgG conjugated Ce6/PM by epidermal growth factor receptor (EGFR)-overexpressing A431 cells observed by confocal laser scanning microscopy (CLSM), thereby decreasing the IC₅₀ value of Ce6-mediated PDT from 0.42 to 0.173 μM. No significant differences were observed in cellular uptake study or IC₅₀ value between C225-Ce6/PM and Ce6/PM groups in lower EGFR expression HT-29 cells. For antitumor study, the tumor volumes in the C225-Ce6/PM-PDT group (percentage of tumor growth inhibition, TGI% = 84.8) were significantly smaller than those in the Ce6-PDT (TGI% = 38.4) and Ce6/PM-PDT groups (TGI% = 53.3) (p < 0.05) at day 21 through reduced cell proliferation in A431 xenografted mice. These results indicated that active EGFR targeting of photosensitizer-loaded micelles provides a possible way to resolve the dose-limiting toxicity of conventional photosensitizers and represents a potential delivery system for PDT in a clinical setting.

Synthetic beta cells for fusion-mediated dynamic insulin secretion

Generating artificial pancreatic beta cells by using synthetic materials to mimic glucose-responsive insulin secretion in a robust manner holds promise for improving clinical outcomes in people with diabetes. Here, we describe the construction of artificial beta cells (AβCs) with a multicompartmental 'vesicles-in-vesicle' superstructure equipped with a glucose-metabolism system and membrane-fusion machinery. Through a sequential cascade of glucose uptake, enzymatic oxidation and proton efflux, the AβCs can effectively distinguish between high and normal glucose levels. Under hyperglycemic conditions, high glucose uptake and oxidation generate a low pH (<5.6), which then induces steric deshielding of peptides tethered to the insulin-loaded inner small liposomal vesicles. The peptides on the small vesicles then form coiled coils with the complementary peptides anchored on the inner surfaces of large vesicles, thus bringing the membranes of the inner and outer vesicles together and triggering their fusion and insulin 'exocytosis'.

Asymmetric Hybrid Polymer-Lipid Giant Vesicles as Cell Membrane Mimics

Lipid membrane asymmetry plays an important role in cell function and activity, being for instance a relevant signal of its integrity. The development of artificial asymmetric membranes thus represents a key challenge. In this context, an emulsion-centrifugation method is developed to prepare giant vesicles with an asymmetric membrane composed of an inner monolayer of poly(butadiene)-b-poly(ethylene oxide) (PBut-b-PEO) and outer monolayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). The formation of a complete membrane asymmetry is demonstrated and its stability with time is followed by measuring lipid transverse diffusion. From fluorescence spectroscopy measurements, the lipid half-life is estimated to be 7.5 h. Using fluorescence recovery after photobleaching technique, the diffusion coefficient of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (DOPE-rhod, inserted into the POPC leaflet) is determined to be about D = 1.8 ± 0.50 μm2 s-1 at 25 °C and D = 2.3 ± 0.7 μm2 s-1 at 37 °C, between the characteristic values of pure POPC and pure polymer giant vesicles and in good agreement with the diffusion of lipids in a variety of biological membranes. These results demonstrate the ability to prepare a cell-like model system that displays an asymmetric membrane with transverse and translational diffusion properties similar to that of biological cells.

Planar and Cell Aggregate-Like Assemblies Consisting of Microreactors and HepG2 Cells

The assembly of microreactors has made considerable progress toward the fabrication of artificial cells. However, their characterization remains largely limited to buffer solution-based assays in the absence of their natural role model-the biological cells. Herein, the combination of microreactors with HepG2 cells either in planar cell cultures or in the form of cell aggregates is reported. Alginate (Alg)-based microreactors loaded with catalase are assembled by droplet microfluidics, and their activity is confirmed. The acceptance of polymer-coated ∼40 μm Alg particles by proliferating HepG2 cells is depending on the terminating polymer layer. When these functional microreactors are cocultured with HepG2 cells, they can be employed for detoxification, that is, hydrogen peroxide removal, and by doing so, they assist the cells to survive. This report is among the first successful combination of microreactors with biological cells, that is, HepG2 cells, contributing to the fundamental understanding of integrating synthetic and biological partners toward the maturation of this semisynthetic concept for biomedical applications.

Biotransporting Self-Assembled Nanofactories Using Polymer Vesicles with Molecular Permeability for Enzyme Prodrug Cancer Therapy

As "biotransporting nanofactories", in vivo therapeutic biocatalyst nanoreactors would enable encapsulated enzymes to transform inert prodrugs or neutralize toxic compounds at target disease sites. This would offer outstanding potential for next-generation therapeutic platforms, such as enzyme prodrug therapy. Designing such advanced materials has, however, proven challenging. Here, it is shown that self-assembled nanofactories formulate with polymeric vesicles with an intrinsically permeable membrane. The vesicles, CAPsomes, are composed of carbohydrate-b-poly(propylene glycol) and show molecular-weight-depended permeability. This property enables CAPsomes to act as biocatalyst nanoreactors, protecting encapsulated enzymes from degradation while acting on low-molecular-weight substrates. In tumor bearing mice, combined treatment with enzyme-loaded CAPsomes and doxorubicin prodrug inhibit tumor growth in these mice without any observable toxicity. The results demonstrate, for the first time, in vivo therapeutic efficacy of CAPsomes as nanofactories for enzyme prodrug cancer therapy.

Fabrication of Multicomponent Multivesicular Peptidoliposomes and Their Directed Cytoplasmic Delivery

A novel self-assembly strategy for the formation of multicomponent and multicompartment vesicles via the hierarchical assembly of the cyclic peptide and lipid building blocks is reported. The primary driving force underlying the formation of dual-component (i.e., peptide and lipid) heteromultivesicular vesicles (hMVVs) is the differential thermostability between the supramolecular building blocks. Furthermore, the combination of the differential thermostability and charge-based separation further enables the fabrication of the hMVVs that incorporate up to four different components (i.e., two different building blocks and two different encapsulated molecules). The quadruple-component hMVVs consist of cyclic peptides, lipids, negatively charged green fluorescent probes (GFPr), and positively charged red fluorescent probes (RFPr). Intracellular delivery study shows that cellular localization of hMVVs is directed by the function of hMVV envelopes, and the nuclear localization signal (NLS) of peptide vesicles appears to use different cellular pathways depending on the site of action (i.e., extracellular space or cytoplasm). This study provides the hierarchical peptide-based hMVVs with sophisticated architectures and cell delivery characteristics, thus making a step toward artificial cells or viruses.

Photo-Cross-Linked Dual-Responsive Hollow Capsules Mimicking Cell Membrane for Controllable Cargo Post-Encapsulation and Release

Multifunctional and responsive hollow capsules are ideal candidates to establish highly sophisticated compartments mimicking cell membranes for controllable bio-inspired functions. For this purpose pH and temperature dual-responsive and photo-cross-linked hollow capsules, based on silica-templated layer-by-layer approach by using poly(N-isopropyl acrylamide)-block-polymethacrylate) and polyallylamine, have been prepared to use them for the subsequent and easily available post-encapsulation process of protein-like macromolecules at room temperature and pH 7.4 and their controllable release triggered by stimuli. The uptake and release properties of the hollow capsules for cargos are highly affected by changes in the external stimuli temperature (25, 37, or 45 °C) and internal stimuli pH of the phosphate-containing buffer solution (5.5 or 7.4), by the degree of photo-cross-linking, and the size of cargo. The photo-cross-linked and dual stimuli-responsive hollow capsules with different membrane permeability can be considered as attractive material for mimicking cell functions triggered by controllable uptake and release of different up to 11 nm sized biomolecules.

Ancient, highly conserved proteins from a LUCA with complex cell biology provide evidence in support of the nuclear compartment commonality (NuCom) hypothesis

The nuclear compartment commonality (NuCom) hypothesis posits a complex last common ancestor (LUCA) with membranous compartments including a nuclear membrane. Such a LUCA then evolved to produce two nucleated lineages of the tree of life: the Planctomycetes-Verrucomicrobia-Chlamydia superphylum (PVC) within the Bacteria, and the Eukarya. We propose that a group of ancient essential protokaryotic signature proteins (PSPs) originating in LUCA were incorporated into ancestors of PVC Bacteria and Eukarya. Tubulins, ubiquitin system enzymes and sterol-synthesizing enzymes are consistent with early origins of these features shared between the PVC superphylum and Eukarya.

Single-step fabrication of multi-compartmentalized biphasic proteinosomes

Multi-compartmentalized biphasic proteinosomes were self-assembled using a single-step double Pickering emulsion procedure, and exploited for enzyme-mediated interfacial catalysis, polysaccharide shell templating, and hydrogel functionalization.

Stimuli-Responsive Polymeric Systems for Controlled Protein and Peptide Delivery: Future Implications for Ocular Delivery

Therapeutic proteins and peptides have become notable in the drug delivery arena for their compatibility with the human body as well as their high potency. However, their biocompatibility and high potency does not negate the existence of challenges resulting from physicochemical properties of proteins and peptides, including large size, short half-life, capability to provoke immune responses and susceptibility to degradation. Various delivery routes and delivery systems have been utilized to improve bioavailability, patient acceptability and reduce biodegradation. The ocular route remains of great interest, particularly for responsive delivery of macromolecules due to the anatomy and physiology of the eye that makes it a sensitive and complex environment. Research in this field is slowly gaining attention as this could be the breakthrough in ocular drug delivery of macromolecules. This work reviews stimuli-responsive polymeric delivery systems, their use in the delivery of therapeutic proteins and peptides as well as examples of proteins and peptides used in the treatment of ocular disorders. Stimuli reviewed include pH, temperature, enzymes, light, ultrasound and magnetic field. In addition, it discusses the current progress in responsive ocular drug delivery. Furthermore, it explores future prospects in the use of stimuli-responsive polymers for ocular delivery of proteins and peptides. Stimuli-responsive polymers offer great potential in improving the delivery of ocular therapeutics, therefore there is a need to consider them in order to guarantee a local, sustained and ideal delivery of ocular proteins and peptides, evading tissue invasion and systemic side-effects.