Triggered cargo release by encapsulated enzymatic catalysis in capsosomes

Self-Organization of Iron Sulfide Nanoparticles into Complex Multicompartment Supraparticles

Self-assembled compartments from nanoscale components are found in all life forms. Their characteristic dimensions are in 50-1000 nm scale, typically assembled from a variety of bioorganic "building blocks". Among the various functions that these mesoscale compartments carry out, protection of the content from the environment is central. Finding synthetic pathways to similarly complex and functional particles from technologically friendly inorganic nanoparticles (NPs) is needed for a multitude of biomedical, biochemical, and biotechnological processes. Here, it is shown that FeS2 NPs stabilized by l-cysteine self-assemble into multicompartment supraparticles (mSPs). The NPs initially produce ≈55 nm concave assemblies that reconfigure into ≈75 nm closed mSPs with ≈340 interconnected compartments with an average size of ≈5 nm. The intercompartmental partitions and mSP surface are formed primarily from FeS2 and Fe2 O3 NPs, respectively. The intermediate formation of cup-like particles enables encapsulation of biological cargo. This capability is demonstrated by loading mSPs with DNA and subsequent transfection of mammalian cells. Also it is found that the temperature stability of the DNA cargo is enhanced compared to the traditional delivery vehicles. These findings demonstrate that biomimetic compartmentalized particles can be used to successfully encapsulate and enhance temperature stability of the nucleic acid cargo for a variety of bioapplications.

Artificial Antigen Presenting Cells for Detection and Desensitization of Autoreactive T cells Associated with Type 1 Diabetes

Autoimmune diseases and in particular type 1 diabetes rely heavily on treatments that target the symptoms rather than prevent the underlying disease. One of the barriers to better therapeutic strategies is the inability to detect and efficiently target rare autoreactive T-cell populations that are major drivers of these conditions. Here, we develop a unique artificial antigen-presenting cell (aAPC) system from biocompatible polymer particles that allows specific encapsulation of bioactive ingredients. Using our aAPC, we demonstrate that we are able to detect rare autoreactive CD4 populations in human patients, and using mouse models, we demonstrate that our particles are able to induce desensitization in the autoreactive population. This system provides a promising tool that can be used in the prevention of autoimmunity before disease onset.

Recent Advancements of Stimuli-Responsive Targeted Liposomal Formulations for Cancer Drug Delivery

Liposomes have gained attention as a well-accepted nanocarrier for several chemotherapeutic drugs and are considered a drug delivery system of choice for a wide range of products. These amphipathic spherical vesicles primarily consist of one or more phospholipid bilayers, showing promise for drug delivery of both hydrophilic and hydrophobic components in addition to unique properties such as biocompatibility, biodegradability, low toxicity, and non-immunogenicity. Recent advances in liposomes are mainly centered on chemical and structural modification with the multifunctional approach to target the cancer cells activating the offensive mechanisms within the proximity of the tumors. Stimuli-responsive liposomes are a precisive approach to deliver and release chemotherapeutic drugs in the tumor site in a controlled fashion, thus reducing damage to normal tissues and preventing the side effects of the conventional chemotherapy regimen. The unique characteristics in the tumor microenvironment facilitate applying an endogenous stimulus (pH, redox potential, or enzymatic activity) to trigger the release of the drug, or external stimulus (heat or light) could be applied to tailor the drug release from liposomes. This review focuses on newer developments in stimuli-sensitive liposomal drug delivery systems designed to apply either exogenous (temperature, light, and magnetic field) or endogenous (pH changes, enzymatic triggers, or redox potential) approaches.

Concentrically Encapsulated Dual-Enzyme Capsules for Synergistic Metabolic Disorder Redressing and Cytotoxic Intermediates Scavenging

Enzyme therapy has important implications for the treatment of metabolic disorders and biological detoxification. It remains challenging to prepare enzymatic nanoreactors with high therapeutic efficiency and low emission of cytotoxic reaction intermediates. Here, we propose a novel strategy for the preparation of enzymes-loaded polypeptide microcapsules (EPM) with concentrically encapsulated enzymes to achieve higher cascade reaction rates and minimal emission of cytotoxic intermediates. Mesoporous silica spheres (MSS) are used as a highly porous matrix to efficiently load a therapeutic enzyme (glucose oxidase, GOx), and a layer-by-layer (LbL) assembly strategy is employed to assemble the scavenging enzyme (catalase) and polyelectrolyte multilayers on the MSS surface. After removal of the MSS, a concentrically encapsulated EPM is obtained with the therapeutic enzyme encapsulated inside the capsule, and the scavenging enzyme immobilized in the polypeptide multilayer shell. Performance of the concentrically encapsulated GOx-catalase capsules is investigated for synergistic glucose metabolism disturbance correction and cytotoxic intermediate H₂O₂ clearance. The results show that the EPM can simultaneously achieve 99% H₂O₂ clearance and doubled glucose consumption rate. This strategy can be extended to the preparation of other dual- or multi-enzyme therapeutic nanoreactors, showing great promise in the treatment of metabolic disorders.

Biocatalytic self-assembled synthetic vesicles and coacervates: From single compartment to artificial cells

Compartmentalization is an intrinsic feature of living cells that allows spatiotemporal control over the biochemical pathways expressed in them. Over the years, a library of compartmentalized systems has been generated, which includes nano to micrometer sized biomimetic vesicles derived from lipids, amphiphilic block copolymers, peptides, and nanoparticles. Biocatalytic vesicles have been developed using a simple bag containing enzyme design of liposomes to multienzymes immobilized multi-vesicular compartments for artificial cell generation. Additionally, enzymes were also entrapped in membrane-less coacervate droplets to mimic the cytoplasmic macromolecular crowding mechanisms. Here, we have discussed different types of single and multicompartment systems, emphasizing their recent developments as biocatalytic self-assembled structures using recent examples. Importantly, we have summarized the strategies in the development of the self-assembled structure to improvise their adaptivity and flexibility for enzyme immobilization. Finally, we have presented the use of biocatalytic assemblies in mimicking different aspects of living cells, which further carves the path for the engineering of a minimal cell.

Macromolecular Engineering of Thermoresponsive Metal-Phenolic Networks

Dynamic nanostructured materials that can react to physical and chemical stimuli have attracted interest in the biomedical and materials science fields. Metal-phenolic networks (MPNs) represent a modular class of such materials: these networks form via coordination of phenolic molecules with metal ions and can be used for surface and particle engineering. To broaden the range of accessible MPN properties, we report the fabrication of thermoresponsive MPN capsules using Fe^III ions and the thermoresponsive phenolic building block biscatechol-functionalized poly(N-isopropylacrylamide) (biscatechol-PNIPAM). The MPN capsules exhibited reversible changes in capsule size and shell thickness in response to temperature changes. The temperature-induced capsule size changes were influenced by the chain length of biscatechol-PNIPAM and catechol-to-Fe^III ion molar ratio. The metal ion type also influenced the capsule size changes, allowing tuning of the MPN capsule mechanical properties. Al^III-based capsules, having a lower stiffness value (10.7 mN m^-1), showed a larger temperature-induced size contraction (∼63%) than Tb^III-based capsules, which exhibit a higher stiffness value (52.6 mN m^-1) and minimal size reduction (<1%). The permeability of the MPN capsules was controlled by changing the temperature (25-50 °C)─a reduced permeability was obtained as the temperature was increased above the lower critical solution temperature of biscatechol-PNIPAM. This temperature-dependent permeability behavior was exploited to encapsulate and release model cargo (500 kDa fluorescein isothiocyanate-tagged dextran) from the capsules; approximately 70% was released over 90 min at 25 °C. This approach provides a synthetic strategy for developing dynamic and thermoresponsive-tunable MPN systems for potential applications in biological science and biotechnology.

Multicompartment Polymeric Nanocarriers for Biomedical Applications

Multicompartment polymeric nanocarriers which mimic the compartmentalized architecture of living cells have received considerable research attention in the biomedical field. The advancement of synthetic polymeric chemistry has allowed multicompartment polymeric nanocarriers to be tailored for biomedical applications such as drug delivery, encapsulated catalysis, and artificial cellular mimics. In this review, polymer-based multicompartment nanocarriers (multicompartment micelles, multicompartment polymersomes, and capsosomes) have been discussed. This review focuses on multicompartment systems applied to biomedical applications over the last ten years. The synthetic procedures and structural properties that impact the specific application are also highlighted.

Bioinspired Protein-Based Assembling: Toward Advanced Life-Like Behaviors

The ability of living organisms to perform structure, energy, and information-related processes for molecular self-assembly through compartmentalization and chemical transformation can possibly be mimicked via artificial cell models. Recent progress in the development of various types of functional microcompartmentalized ensembles that can imitate rudimentary aspects of living cells has refocused attention on the important question of how inanimate systems can transition into living matter. Hence, herein, the most recent advances in the construction of protein-bounded microcompartments (proteinosomes), which have been exploited as a versatile synthetic chassis for integrating a wide range of functional components and biochemical machineries, are critically summarized. The techniques developed for fabricating various types of proteinosomes are discussed, focusing on the significance of how chemical information, substance transportation, enzymatic-reaction-based metabolism, and self-organization can be integrated and recursively exploited in constructed ensembles. Therefore, proteinosomes capable of exhibiting gene-directed protein synthesis, modulated membrane permeability, spatially confined membrane-gated catalytic reaction, internalized cytoskeletal-like matrix assembly, on-demand compartmentalization, and predatory-like chemical communication in artificial cell communities are specially highlighted. These developments are expected to bridge the gap between materials science and life science, and offer a theoretical foundation for developing life-inspired assembled materials toward various applications.

Biomolecule–polymer hybrid compartments: combining the best of both worlds

Recent advances in bio/polymer hybrid compartments in the quest to obtain artificial cells, biosensors and catalytic compartments.

The Future of Layer-by-Layer Assembly: A Tribute to ACS Nano Associate Editor Helmuth Möhwald

Layer-by-layer (LbL) assembly is a widely used tool for engineering materials and coatings. In this Perspective, dedicated to the memory of ACS Nano associate editor Prof. Dr. Helmuth Möhwald, we discuss the developments and applications that are to come in LbL assembly, focusing on coatings, bulk materials, membranes, nanocomposites, and delivery vehicles.

Efficient chiral synthesis by Saccharomyces cerevisiae spore encapsulation of Candida parapsilosis Glu228Ser/(S)-carbonyl reductase II and Bacillus sp. YX-1 glucose dehydrogenase in organic solvents

BACKGROUND

Saccharomyces cerevisiae AN120 osw2∆ spores were used as a host with good resistance to unfavorable environment. This work was undertaken to develop a new yeast spore-encapsulation of Candida parapsilosis Glu228Ser/(S)-carbonyl reductase II and Bacillus sp. YX-1 glucose dehydrogenase for efficient chiral synthesis in organic solvents.

RESULTS

The spore microencapsulation of E228S/SCR II and GDH in S. cerevisiae AN120 osw2∆ catalyzed (R)-phenylethanol in a good yield with an excellent enantioselectivity (up to 99%) within 4 h. It presented good resistance and catalytic functions under extreme temperature and pH conditions. The encapsulation produced several chiral products with over 70% yield and over 99% enantioselectivity in ethyl acetate after being recycled for 4-6 times. It increased substrate concentration over threefold and reduced the reaction time two to threefolds compared to the recombinant Escherichia coli containing E228S and glucose dehydrogenase.

CONCLUSIONS

This work first described sustainable enantioselective synthesis without exogenous cofactors in organic solvents using yeast spore-microencapsulation of coupled alcohol dehydrogenases.

Tuning crystallization and morphology of zinc oxide with polyvinylpyrrolidone: Formation mechanisms and antimicrobial activity

Zinc oxide (ZnO) particles with different shapes and sizes have been previously reported to possess unique optical, electrical, photocatalytic, and antimicrobial properties. Capping agents are routinely used to control particle morphologies; however, few studies have evaluated the influence of capping agents on the growth kinetics of ZnO particles of different shapes. Herein, we report a simple water-based chemical precipitation method to produce unique bowtie-, flower-, and nest-shaped ZnO particles using zinc nitrate and urea in the presence of polyvinylpyrrolidone (PVP). Three distinct particle morphologies are obtained by adjusting polymer concentration during synthesis. This approach is simple and could enable large-scale production of ZnO particles with diverse shapes. We monitor the morphological evolution of ZnO particles and, at different polymer concentrations, uncover the preferable PVP adsorption onto different ZnO facets that controls the growth directions of ZnO. Previous reports have demonstrated the influence of particle shape on ZnO antibacterial activity. In this study, we show that ZnO particles with these three morphologies exhibit similar bacterial killing efficacy towards Escherichia coli and Staphylococcus aureus. Our detailed mechanistic studies suggest that the antibacterial mechanism of ZnO particles can be attributed to both Zn²⁺ release and oxidative stress, whereas shape plays only a minor role in the antibacterial activity of ZnO particles.

Polymer Capsules for Enzymatic Catalysis in Confined Environments

Catalysis is at the base of a series of biological and technological application processes. In recent years, the tendency has developed to carry out catalyzed reactions within confined structures, thus forming systems called micro or nanoreactors. Compartmentalized structures are cavities delimited by a wall where specific functions are introduced with a defined concentration and in the desired sites. These containers are generally referred to as nano or microcapsules, assuming the function of reactors in the presence of chemical reactions. Among the various types of existing structures, one of the most interesting is represented by systems made with polymers. This review aims to highlight some of the current advances in the use of functionalized structures that are useful for catalysis reactions, paying particular attention to polymer capsules and enzymes. The built-up methods used for the production of polymer capsules, as well as the aspects that influence membrane permeability and reactivity to environmental conditions, are discussed. Recent advances on biocatalysis confined in polymeric capsules are illustrated, and the strengths and weaknesses of the principal nanoreactors are considered.

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.

Progress of Multicompartmental Particles for Medical Applications

Particulate materials are becoming increasingly used in the literature for medical applications, but translation to the clinical setting has remained challenging as many particle systems face challenges from in vivo barriers. Multicompartmental particles that can incorporate several materials in an individual particle may allow for more intricate control and addressing of issues that otherwise standard particles are unable to. Here, some of the advances made in the use of multicompartmental particles for medical applications are briefly described.

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.

Layer-by-Layer Engineered Polymer Capsules for Therapeutic Delivery

Polymer capsules fabricated via layer-by-layer (LbL) assembly have emerged as promising carriers for therapeutic delivery. The versatile assembly technique allows an extensive choice of materials to be incorporated as constituents of the multilayers, which therefore endow capsules with specific properties and functionalities. This chapter describes protocols for fabrication of LbL-engineered poly(methacrylic acid) (PMA) capsules for applications in gene delivery, including (1) synthesis of building blocks, (2) cargo encapsulation, (3) multilayer film formation, (4) surface modification, and (5) cross-linking of multilayer films and dissolution of particle templates. DNA is adsorbed onto positively charged silica particle templates, followed by formation of polymer films via hydrogen-bonded multilayers of thiol-functionalized PMA and poly(N-vinylpyrrolidone) (PVP). The outer polymer membranes can be surface modified with copolymers of PMA and poly(ethylene glycol) (PEG). Upon film stabilization and dissolution of particle templates, disulfide-cross-linked DNA-loaded PMA capsules are obtained, which serve as therapeutic carriers that can degrade and facilitate cargo release in intracellular reducing environment.

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.

Stimuli-responsive liposomes for drug delivery

The ultimate goal of drug delivery is to increase the bioavailability and reduce the toxic side effects of the active pharmaceutical ingredient (API) by releasing them at a specific site of action. In the case of antitumor therapy, association of the therapeutic agent with a carrier system can minimize damage to healthy, nontarget tissues, while limit systemic release and promoting long circulation to enhance uptake at the cancerous site due to the enhanced permeation and retention effect (EPR). Stimuli-responsive systems have become a promising way to deliver and release payloads in a site-selective manner. Potential carrier systems have been derived from a wide variety of materials, including inorganic nanoparticles, lipids, and polymers that have been imbued with stimuli-sensitive properties to accomplish triggered release based on an environmental cue. The unique features in the tumor microenvironment can serve as an endogenous stimulus (pH, redox potential, or unique enzymatic activity) or the locus of an applied external stimulus (heat or light) to trigger the controlled release of API. In liposomal carrier systems triggered release is generally based on the principle of membrane destabilization from local defects within bilayer membranes to effect release of liposome-entrapped drugs. This review focuses on the literature appearing between November 2008-February 2016 that reports new developments in stimuli-sensitive liposomal drug delivery strategies using pH change, enzyme transformation, redox reactions, and photochemical mechanisms of activation. WIREs Nanomed Nanobiotechnol 2017, 9:e1450. doi: 10.1002/wnan.1450 For further resources related to this article, please visit the WIREs website.

Small Subcompartmentalized Microreactors as Support for Hepatocytes

Mimicking specific structural or functional aspects of cells is considered a promising approach to substitute for missing or lost cellular functions. However, the interaction of such artificial assemblies with their biological counterparts including the exploitation of the activity of the synthetic partner remains thus-far a rather unexplored avenue. Herein, the assembly of active microreactors with similar size to hepatocytes is reported. These microreactors are successfully cocultured with hepatocytes into bionic tissue for up to 10 d. Further, microreactors loaded with the liver enzyme catalase are effective in alleviating external pressure, induced by the addition of hydrogen peroxide, from such bionic tissue in an attempt to mimic the detoxification ability of hepatocytes. Taken together, the findings open up a different route in combining synthetic and biological entities for tissue engineering by using the former partner not only as structural support, but also to induce beneficial activity.

Multicompartment Artificial Organelles Conducting Enzymatic Cascade Reactions inside Cells

Cell organelles are subcellular structures entrapping a set of enzymes to achieve a specific functionality. The incorporation of artificial organelles into cells is a novel medical paradigm which might contribute to the treatment of various cell disorders by replacing malfunctioning organelles. In particular, artificial organelles are expected to be a powerful solution in the context of enzyme replacement therapy since enzymatic malfunction is the primary cause of organelle dysfunction. Although several attempts have been made to encapsulate enzymes within a carrier vehicle, only few intracellularly active artificial organelles have been reported to date and they all consist of single-compartment carriers. However, it is noted that biological organelles consist of multicompartment architectures where enzymatic reactions are executed within distinct subcompartments. Compartmentalization allows for multiple processes to take place in close vicinity and in a parallel manner without the risk of interference or degradation. Here, we report on a subcompartmentalized and intracellularly active carrier, a crucial step for advancing artificial organelles. In particular, we develop and characterize a novel capsosome system, which consists of multiple liposomes and fluorescent gold nanoclusters embedded within a polymer carrier capsule. We subsequently demonstrate that encapsulated enzymes preserve their activity intracellularly, allowing for controlled enzymatic cascade reaction within a host cell.

Localized and Controlled Delivery of Nitric Oxide to the Conventional Outflow Pathway via Enzyme Biocatalysis: Toward Therapy for Glaucoma

Nitric oxide (NO) is able to lower intraocular pressure (IOP); however, its therapeutic effects on outflow physiology are location- and dose-dependent. A NO delivery platform that directly targets the resistance-generating region of the conventional outflow pathway and locally liberates a controlled dose of NO is reported. An increase in outflow facility (decrease in IOP) is demonstrated in a mouse model.

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.

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.

Hierarchical Proteinosomes for Programmed Release of Multiple Components

A facile route to hierarchically organized multicompartmentalized proteinosomes based on a recursive Pickering emulsion procedure using amphiphilic protein-polymer nanoconjugate building blocks is described. The number of incarcerated guest proteinosomes within a single host proteinosome is controlled, and enzymes and genetic polymers encapsulated within targeted subcompartments to produce chemically organized multi-tiered structures. Three types of spatiotemporal response-retarded concomitant release, synchronous release or hierarchical release of dextran and DNA-are demonstrated based on the sequential response of the host and guest membranes to attack by protease, or through variations in the positioning of disulfide-containing cross-links in either the host or guest proteinosomes integrated into the nested architectures. Overall, our studies provide a step towards the construction of hierarchically structured synthetic protocells with chemically and spatially integrated proto-organelles.

Dynamic biomaterials: toward engineering autonomous feedback

Dynamic biomaterials are biocompatible engineered systems capable of sensing and actively responding to their surrounding environment. They are of growing interest, both as models in basic research to understand complex cellular systems and in medical applications. Here, we review recent advances in nano-scale and micro-scale biomaterials, specifically artificial cells consisting of compartmentalized biochemical reactions and biologically compatible hydrogels. These dynamic biomaterials respond to stimuli through triggered reactions, reaction cascades, logic gates, and autonomous feedback loops. We outline the advances and remaining challenges in implementing such 'smart' biomaterials capable of autonomously responding to environmental stimuli.

Compartmentalization Approaches in Soft Matter Science: From Nanoreactor Development to Organelle Mimics

Compartmentalization is an essential feature found in living cells to ensure that biological processes occur without being affected by undesired external influences. Over the years many scientists have designed self-assembled soft matter structures that mimic these natural catalytic compartments. The rationale behind this research is threefold. First of all, compartmentalization leads to the creation of a secluded environment for the catalytic species, which solves compatibility issues and which can improve catalyst efficiency and selectivity. Secondly, nano- and micro-compartments are constructed with the aim to obtain microenvironments that more closely mimic the cellular architecture. These biomimetic platforms are used to attain a better understanding of how cellular processes are executed. Thirdly, natural design rules are applied to create biomolecular assemblies with unusual functionality, which for example are used as artificial organelles. Here, recent developments will be discussed regarding these compartmentalized catalytic systems, with a selected number of illustrative examples to demonstrate which strategies have been followed, and to show to what extent the ambitious goals of this field of science have been reached. The focus here is on the field of soft matter science, covering the wide spectrum from polymeric assemblies to protein nanocages.

Recent developments in poly(dopamine)-based coatings for biomedical applications

The success of polymer coatings for biomedical applications is undeniable. Among the very successful examples are poly(dopamine) (PDA) films due to their simplicity in deposition and beneficial interaction with biomolecules and cells. The aim of this review is to highlight the findings and achievement of PDA in nanomedicine since 2011. We discuss the progress that has been made to elucidate the structure of PDA and novel aspects considering the assembly of PDA-based films on diverse substrates. We highlight the newest results considering the biological evaluation PDA-based coatings to control cell behavior and the use of PDA in biosensing. The popularity of PDA remains unchanged, but the research efforts start to be consolidated toward more specific aims and clinical applications.

Janus subcompartmentalized microreactors

We report on Janus subcompartmentalized assemblies with enzyme loaded liposomes entrapped within a polymer carrier capsule - Janus subcompartmentalized microreactors. The concept is based on the use of Pickering emulsions and the subsequent deposition of interacting liposomes and polymer layers. We demonstrate the adjustment of the size of the Janus domains and the control over the amount of trapped liposomes using multiple liposome deposition steps. The obtained Janus capsosomes feature a distinct liposome domain within a closed polymeric hydrogel shell. The assembly of functional Janus microreactors using trypsin as cargo within the liposomal subcompartments is shown by performing locally confined enzymatic encapsulated catalysis. The presented assemblies with spatial control over the position of their liposomal subunits are a fascinating first step towards artificial cells with polarity.

Aggregation of poly(acrylic acid)-containing elastin-mimetic copolymers

Polymer-peptide conjugates were produced via the copper-catalyzed azide-alkyne cycloaddition of poly(tert-butyl acrylate) (PtBA) and elastin-like peptides. An azide-functionalized polymer was produced via atom transfer radical polymerization (ATRP) followed by conversion of bromine end groups to azide groups. Subsequent reaction of the polymer with a bis-alkyne-functionalized, elastin-like peptide proceeded with high efficiency, yielding di- and tri-block conjugates, which after deprotection, yielded poly(acrylic acid) (PAA)-based diblock and triblock copolymers. These conjugates were solubilized in dimethyl formamide, and addition of phosphate buffered saline (PBS) induced aggregation. The presence of polydisperse spherical aggregates was confirmed by dynamic light scattering and transmission electron microscopy. Additionally, a coarse-grained molecular model was designed to reasonably capture inter- and intramolecular interactions for the conjugates and its precursors. This model was used to assess the effect of the different interacting molecular forces on the conformational thermodynamic stability of the copolymers. Our results indicated that the PAA's ability to hydrogen-bond with both itself and the peptide is the main interaction for stabilizing the diblocks and triblocks and driving their self-assembly, while interactions between peptides are suggested to play only a minor role on the conformational and thermodynamic stability of the conjugates.

Versatile Loading of Diverse Cargo into Functional Polymer Capsules

Polymer microcapsules are of particular interest for applications including self-healing coatings, catalysis, bioreactions, sensing, and drug delivery. The primary way that polymer capsules can exhibit functionality relevant to these diverse fields is through the incorporation of functional cargo in the capsule cavity or wall. Diverse functional and therapeutic cargo can be loaded into polymer capsules with ease using polymer-stabilized calcium carbonate (CaCO3) particles. A variety of examples are demonstrated, including 15 types of cargo, yielding a toolbox with effectively 500+ variations. This process uses no harsh reagents and can take less than 30 min to prepare, load, coat, and form the hollow capsules. For these reasons, it is expected that the technique will play a crucial role across scientific studies in numerous fields.

Encapsulation of photoactive porphyrinoids in polyelectrolyte hollow microcapsules viewed by fluorescence lifetime imaging microscopy (FLIM)

Fluorescence Lifetime Imaging Microscopy (FLIM) was used to investigate the encapsulation of porphyrinoids in multilayer hollow microcapsules assembled layer by layer with poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH).

Convective polymer assembly for the deposition of nanostructures and polymer thin films on immobilized particles

We report the preparation of polymer particles via convective polymer assembly (CPA). Convection is used to move polymer solutions and cargo through an agarose gel that contains immobilized template particles. This method both coats and washes the particles in a process that is amenable to automation, and does not depend on passive diffusion or electrical currents, thus facilitating incorporation of fragile and nanoscale objects, such as liposomes and gold nanoparticles, into the thin polymer films. Template dissolution leads to the formation of stable polymer particles and capsules.

Enhanced synergism of thermo-chemotherapy by combining highly efficient magnetic hyperthermia with magnetothermally-facilitated drug release

A magnetothermally-responsive nanocarrier was developed for efficient thermo-chemotherapy by combining efficient magnetic hyperthermia (MH) and magnetothermally-facilitated drug release. The effective magnetothermal-response contributed to high enhancement of tumor cell killing by an operating mechanism involving MH-facilitated cellular uptake and Heat Shock Protein over-expression.

Pharmacological aspects of release from microcapsules - from polymeric multilayers to lipid membranes

This review is devoted to pharmacological applications of principles of release from capsules to overcome the membrane barrier. Many of these principles were developed in the context of polymeric multilayer capsule membrane modulation, but they are also pertinent to liposomes, polymersomes, capsosomes, particles, emulsion-based carriers and other carriers. We look at these methods from the physical, chemical or biological driving mechanisms point of view. In addition to applicability for carriers in drug delivery, these release methods are significant for another area directly related to pharmacology - modulation of the permeability of the membranes and thus promoting the action of drugs. Emerging technologies, including ionic current monitoring through a lipid membrane on a nanopore, are also highlighted.

Fluidized bed layer-by-layer microcapsule formation

Polymer microcapsules can be used as bioreactors and artificial cells; however, preparation methods for cell-like microcapsules are typically time-consuming, low yielding, and/or involve custom microfluidics. Here, we introduce a rapid (∼30 min per batch, eight layers), scalable (up to 500 mg of templates), and efficient (98% yield) microcapsule preparation technique utilizing a fluidized bed for the layer-by-layer (LbL) assembly of polymers, and we investigate the parameters that govern the formation of robust capsules. Fluidization in water was possible for particles of comparable diameter to mammalian cells (>5 μm), with the experimental flow rates necessary for fluidization matching well with the theoretical values. Important variables for polymer film deposition and capsule formation were the concentration of polymer solution and the molecular weight of the polymer, while the volume of the polymer solution had a negligible impact. In combination, increasing the polymer molecular weight and polymer solution concentration resulted in improved film deposition and the formation of robust microcapsules. The resultant polymer microcapsules had a thickness of ∼5.5 nm per bilayer, which is in close agreement with conventionally prepared (quiescent (nonflow) adsorption/centrifugation/wash) LbL capsules. The technique reported herein provides a new way to rapidly generate microcapsules (approximately 8 times quicker than the conventional means), while being also amenable to scale-up and mass production.

Confined multiple enzymatic (cascade) reactions within poly(dopamine)-based capsosomes

The design of compartmentalized carriers as artificial cells is envisioned to be an efficient tool with potential applications in the biomedical field. The advent of this area has witnessed the assembly of functional, bioinspired systems attempting to tackle challenges in cell mimicry by encapsulating multiple compartments and performing controlled encapsulated enzymatic catalysis. Although capsosomes, which consist of liposomes embedded within a polymeric carrier capsule, are among the most advanced systems, they are still amazingly simple in their functionality and cumbersome in their assembly. We report on capsosomes by embedding liposomes within a poly(dopamine) (PDA) carrier shell created in a solution-based single-step procedure. We demonstrate for the first time the potential of PDA-based capsosomes to act as artificial cell mimics by performing a two-enzyme coupled reaction in parallel with a single-enzyme conversion by encapsulating three different enzymes into separated liposomal compartments. In the former case, the enzyme uricase converts uric acid into hydrogen peroxide, CO2 and allantoin, followed by the reaction of hydrogen peroxide with the reagent Amplex Ultra Red in the presence of the enzyme horseradish peroxidase to generate the fluorescent product resorufin. The parallel enzymatic catalysis employs the enzyme ascorbate oxidase to convert ascorbic acid into 2-L-dehydroascorbic acid.

Liposome-containing polymer films and colloidal assemblies towards biomedical applications

Liposomes are important components for biomedical applications. Their unique architecture and versatile nature have made them useful carriers for the delivery of therapeutic cargo. The scope of this minireview is to highlight recent developments of biomimetic liposome-based multicompartmentalized assemblies of polymer thin films and colloidal carriers, and to outline a selection of recent applications of these materials in bionanotechnology.

Emerging methods for the fabrication of polymer capsules

Hollow polymer capsules are attracting increasing research interest due to their potential application as drug delivery vectors, sensors, biomimetic nano- or multi-compartment reactors and catalysts. Thus, significant effort has been directed toward tuning their size, composition, morphology, and functionality to further their application. In this review, we provide an overview of emerging techniques for the fabrication of polymer capsules, encompassing: self-assembly, layer-by-layer assembly, single-step polymer adsorption, bio-inspired assembly, surface polymerization, and ultrasound assembly. These techniques can be applied to prepare polymer capsules with diverse functionality and physicochemical properties, which may fulfill specific requirements in various areas. In addition, we critically evaluate the challenges associated with the application of polymer capsules in drug delivery systems.