Effect of Molecular Parameters on the Architecture and Membrane Properties of 3D Assemblies of Amphiphilic Copolymers

Evaluation of polymersome permeability as a fundamental aspect towards the development of artificial cells and nanofactories

Polymersomes are synthetic vesicles with potential use in healthcare, chemical transformations in confined environment (nanofactories), and in the construction of artificial cells and organelles. In this framework, one of the most important features of such supramolecular structures is the permeability behavior allowing for selective control of mass exchange between the inner and outer compartments. The use of biological and synthetic nanopores in this regard is the most common strategy to impart permeability nevertheless, this typically requires fairly complex strategies to enable porosity. Yet, investigations concerning the permeability of polymer vesicles to different analytes still requires further exploration and, taking these considerations into account, we have detailed investigated the permeability behavior of a variety of polymersomes with regard to different analytes (water, protons, and rhodamine B) which were selected as models for solvents, ions, and small molecules. Polymersomes based on hydrophilic blocks of poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) or PEO (poly(ethylene oxide)) linked to the non-responsive blocks poly[N-(4-isopropylphenylacetamide)ethyl methacrylate] (PPPhA) or poly(methyl methacrylate) (PMMA), or to the stimuli pH-responsive block poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) have been investigated. Interestingly, the produced PEO-based vesicles are notably larger than the ones produced using PHPMA-containing block copolymers. The experimental results reveal that all the vesicles are inherently permeable to some extent with permeability behavior following exponential profiles. Nevertheless, polymersomes based on PMMA as the hydrophobic component were demonstrated to be the least permeable to the small molecule rhodamine B as well as to water. The synthetic vesicles based on the pH-responsive PDPA block exhibited restrictive and notably slow proton permeability as attributed to partial chain protonation upon acidification of the medium. The dye permeability was evidenced to be much slower than ion or solvent diffusion, and in the case of pH-responsive assemblies, it was demonstrated to also depend on the ionic strength of the environment. These findings are understood to be highly relevant towards polymer selection for the production of synthetic vesicles with selective and time-dependent permeability, and it may thus contribute in advancing biomimicry and nanomedicine.

Redefining drug therapy: innovative approaches using catalytic compartments

INTRODUCTION

Rapid excretion of drug derivatives often results in short drug half-lives, necessitating frequent administrations. Catalytic compartments, also known as nano- and microreactors, offer a solution by providing confined environments for in situ production of therapeutic agents. Inspired by natural compartments, polymer-based catalytic compartments have been developed to improve reaction efficiency and enable site-specific therapeutic applications.

AREAS COVERED

Polymer-based compartments provide stability, permeability control, and responsiveness to stimuli, making them ideal for generating localized compounds/signals. These sophisticated systems, engineered to carry active compounds and enable selective molecular release, represent a significant advancement in pharmaceutical research. They mimic cellular functions, creating controlled catalytic environments for bio-relevant processes. This review explores the latest advancements in synthetic catalytic compartments, focusing on design approaches, building blocks, active molecules, and key bio-applications.

EXPERT OPINION

Catalytic compartments hold transformative potential in precision medicine by improving therapeutic outcomes through precise, on-site production of therapeutic agents. While promising, challenges like scalable manufacturing, biodegradability, and regulatory hurdles must be addressed to realize their full potential. Addressing these will be crucial for their successful application in healthcare.

Formation of a planar biomimetic membrane with a novel zwitterionic polymer for nanopore sequencing

Biological membranes containing transmembrane channels play a crucial role in numerous cellular processes, and mimicking of cell membranes has garnered significant interest in various biomedical applications, particularly nanopore sequencing technology, where remarkable progress has been made with nanopore membranes. Considering the fragility of biomimetic membranes formed by artificial lipids and the limited mimicry of those formed by common block copolymers, this study developed a novel amphiphilic polymer by covalently linking hydrophilic heads of phospholipids to the ends of hydrophobic poly(dimethyl siloxane) (PDMS) chains. The absence of hydrophilic blocks allowed for good control over the polydispersity of this polymer within a narrow range. The high flexibility of PDMS chains, combined with relatively uniform molecular weights, would confer enhanced stability and robustness to polymeric membranes. Dynamic light scattering measurements and microdroplet formation tests demonstrated good amphipathic properties of these novel polymers when maintaining an appropriate hydrophilic-hydrophobic ratio. Moreover, the high similarity between the hydrophilic heads and natural phospholipids makes this polymer more compatible with biomolecules. A successful protein insertion experiment confirmed both the stability of this polymeric membrane and its compatibility with membrane proteins. As a result, this novel amphiphilic polymer exhibits great potential for biomembrane mimicking and paves a new path for material design in biomedical applications.

A polymeric 1H/19F dual-modal MRI contrast agent with a snowman-like Janus nanostructure

Magnetic resonance imaging (MRI) has emerged as a pivotal tool in contemporary medical diagnostics, offering non-invasive and high-resolution visualization of internal structures. Contrast agents are essential for enhancing MRI resolution, accurate lesion detection, and early pathology identification. While gadolinium-based contrast agents are widely used in clinics, safety concerns have prompted exploration of metal-free alternatives, including fluorine and nitroxide radical-based MRI contrast agents. Fluorine-containing compounds exhibit excellent MRI capabilities, with 19F MRI providing enhanced resolution and quantitative assessment. Nitroxide radicals, such as PROXYL and TEMPO, offer paramagnetic properties for MRI contrast. Despite their versatility, nitroxide radicals suffer from lower relaxivity values (r1) compared to gadolinium. Dual-modal imaging, combining 1H and 19F MRI, has gained prominence for its comprehensive insights into biological processes and disease states. However, existing dual-modal agents predominantly utilize gadolinium-organic ligands without incorporating nitroxide radicals. Here, we introduce a novel dual-modal MRI contrast agent (J-CA) featuring a Janus asymmetric nanostructure synthesized via seeded emulsion polymerization and post-modification. J-CA demonstrates excellent in vitro and in vivo performance in both 19F and 1H MRI, with a T2 relaxation time of 5 ms and an r1 value of 0.31 mM-1 s-1, ensuring dual-modal imaging capability. Moreover, J-CA exhibits superior biocompatibility and organ targeting, making it a promising candidate for precise lesion imaging and disease diagnosis. This work introduces a new avenue for metal-free dual-modal MRI, addressing safety concerns associated with traditional contrast agents.

Planar Polymer Membranes Accommodate Functional Self-Assembly of Inserted Resorcinarene Nanocapsules

Solid-supported polymer membranes (SSPMs) offer great potential in material and life sciences due to their increased mechanical stability and robustness compared to solid-supported lipid membranes. However, there is still a need for expanding the functionality of SSPMs by combining them with synthetic molecular assemblies. In this study, SSPMs served as a flexible matrix for the insertion of resorcinarene monomers and their self-assembly into functional hexameric resorcinarene capsules. Resorcinarene capsules provide a large cavity with affinity specifically for cationic and polyhydroxylated molecules. While the capsules are stable in apolar organic solvents, they disassemble when placed in polar solvents, which limits their application. Here, a solvent-assisted approach was used for copolymer membrane deposition on solid support and simultaneous insertion of the resorcinarene monomers. By investigation of the molecular factors and conditions supporting the codeposition of the copolymer and resorcinarene monomers, a stable hybrid membrane was formed. The hydrophobic domain of the membrane played a crucial role by providing a sufficiently thick and apolar layer, allowing for the self-assembly of the capsules. The capsules were functional inside the membranes by encapsulating cationic guests from the aqueous environment. The amount of resorcinarene capsules in the hybrid membranes was quantified by a combination of quartz-crystal microbalance with dissipation and liquid chromatography-mass spectrometry, while the membrane topography and layer composition were analyzed by atomic force microscopy and neutron reflectometry. Functional resorcinarene capsules inside SSPMs can serve as dynamic sensors and potentially as cross-membrane transporters, thus holding great promise for the development of smart surfaces.

Multicompartment Micro- and Nanoparticles Using Supramolecular Assembly of Core-Shell Bottlebrush Polymers

Multicompartment particles have been produced to date by the self-assembly of linear multiblock polymers. Besides the large diversity of structures that can be obtained with this approach, these are highly sensitive to dilution and environmental factors. Here we show that using core-shell bottlebrush polymers with a hydrophobic polyester core as starting materials it is possible to create compartmentalized particles from the micrometer size down to the molecular scale. These polymers can be used as building blocks to create multicompartment particles and networks via a self-assembly process. The polymers can encapsulate active compounds and slowly degrade in water into polymeric micelles, making them promising materials for drug delivery applications.

Tailoring a Solvent-Assisted Method for Solid-Supported Hybrid Lipid-Polymer Membranes

Combining amphiphilic block copolymers and phospholipids opens new opportunities for the preparation of artificial membranes. The chemical versatility and mechanical robustness of polymers together with the fluidity and biocompatibility of lipids afford hybrid membranes with unique properties that are of great interest in the field of bioengineering. Owing to its straightforwardness, the solvent-assisted method (SA) is particularly attractive for obtaining solid-supported membranes. While the SA method was first developed for lipids and very recently extended to amphiphilic block copolymers, its potential to develop hybrid membranes has not yet been explored. Here, we tailor the SA method to prepare solid-supported polymer-lipid hybrid membranes by combining a small library of amphiphilic diblock copolymers poly(dimethyl siloxane)-poly(2-methyl-2-oxazoline) and poly(butylene oxide)-block-poly(glycidol) with phospholipids commonly found in cell membranes including 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine, sphingomyelin, and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(glutaryl). The optimization of the conditions under which the SA method was applied allowed for the formation of hybrid polymer-lipid solid-supported membranes. The real-time formation and morphology of these hybrid membranes were evaluated using a combination of quartz crystal microbalance and atomic force microscopy. Depending on the type of polymer-lipid combination, significant differences in membrane coverage, formation of domains, and quality of membranes were obtained. The use of the SA method for a rapid and controlled formation of solid-supported hybrid membranes provides the basis for developing customized artificial hybrid membranes.

Artificial Melanogenesis by Confining Melanin/Polydopamine Production inside Polymersomes

Melanin and polydopamine are potent biopolymers for the development of biomedical nanosystems. However, applications of melanin or polydopamine-based nanoparticles are limited by drawbacks related to a compromised colloidal stability over long time periods and associated cytotoxicity. To overcome these hurdles, a novel strategy is proposed that mimics the confinement of natural melanin in melanosomes. Melanosome mimics are developed by co-encapsulating the melanin/polydopamine precursors L-DOPA/dopamine with melanogenic enzyme Tyrosinase within polymersomes. The conditions of polymersome formation are optimized to obtain melanin/polydopamine polymerization within the cavity of the polymersomes. Similar to native melanosomes, polymersomes containing melanin/polydopamine show long-term colloidal stability, cell-compatibility, and potential for cell photoprotection. This novel kind of artificial melanogenesis is expected to inspire new applications of the confined melanin/polydopamine biopolymers.

Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization

Increasingly precise control of polymer architectures generated by "Living" Anionic Ring-Opening Polymerization (Living AROP) is leading to a broad range of commercial advanced material applications, particularly in the area of siloxane macromers. While academic reports on such materials remain sparse, a significant portion of the global population interacts with them on a daily basis-in applications including medical devices, microelectronics, food packaging, synthetic leather, release coatings, and pigment dispersions. The primary driver of this increased utilization of siloxane macromers is their ability to incorporate the properties of silicones into organic structures in a balanced manner. Compared to organic polymers, the differentiating properties of silicones-low Tg, hydrophobicity, low surface energy, and high free molal space-logically lend themselves to applications in which low modulus, release, permeability to oxygen and moisture, and tactile interaction are desired. However, their mechanical, structural and processing properties have until recently precluded practical applications. This review presents applications of "Living" AROP derived polymers from the perspective of historical technology development. Applications in which products are produced on a commercial scale-defined as not only offered for sale, but sold on a recurrent basis-are emphasized. Hybrid polymers with intriguing nanoscale morphology and potential applications in photoresist, microcontact printing, biomimetic soft materials, and liquid crystals are also discussed. Previously unreported work by the authors is provided in the context of this review.

Effect of Detergents on Morphology, Size Distribution, and Concentration of Copolymer-Based Polymersomes

Polymersomes made of amphiphilic diblock copolymers are generally regarded as having higher physical and chemical stability than liposomes composed of phospholipids. This enhanced stability arises from the higher molecular weight of polymer constituents. Despite their increased stability, polymer bilayers are solubilized by detergents in a similar manner to lipid bilayers. In this work, we evaluated the stability of poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL)-based polymersomes exposed to three different detergents: N-octyl-β-d-glucopyranoside (OG), lauryldimethylamine N-oxide (LDAO), and Triton X-100 (TX-100). Changes in morphology, particle size distribution, and concentrations of the polymersomes were evaluated during the titration of the detergents into the polymersome solutions. Furthermore, we discussed the effect of detergent features on the solubilization of the polymeric bilayer and compared it to the results reported in the literature for liposomes and polymersomes. This information can be used for tuning the properties of PEG-PCL polymersomes for use in applications such as drug delivery or protein reconstitution studies.

Catalytic polymersomes to produce strong and long-lasting bioluminescence

Here, we introduce an artificial bioluminescent nanocompartment based on the encapsulation of light-producing enzymes, luciferases, inside polymersomes. We exploit nanocompartmentalization to enhance luciferase stability in a cellular environment but also to positively modulate enzyme kinetics to achieve a long-lasting glow type signal. These features pave the way for expanding bioluminescence to nanotechnology-based applications.

Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell-Sized Compartments

Cells rely upon producing enzymes at precise rates and stoichiometry for maximizing functionalities. The reasons for this optimal control are unknown, primarily because of the interconnectivity of the enzymatic cascade effects within multi-step pathways. Here, an elegant strategy for studying such behavior, by controlling segregation/combination of enzymes/metabolites in synthetic cell-sized compartments, while preserving vital cellular elements is presented. Therefore, compartments shaped into polymer GUVs are developed, producing via high-precision double-emulsion microfluidics that enable: i) tight control over the absolute and relative enzymatic contents inside the GUVs, reaching nearly 100% encapsulation and co-encapsulation efficiencies, and ii) functional reconstitution of biopores and membrane proteins in the GUVs polymeric membrane, thus supporting in situ reactions. GUVs equipped with biopores/membrane proteins and loaded with one or more enzymes are arranged in a variety of combinations that allow the study of a three-step cascade in multiple topologies. Due to the spatiotemporal control provided, optimum conditions for decreasing the accumulation of inhibitors are unveiled, and benefited from reactive intermediates to maximize the overall cascade efficiency in compartments. The non-system-specific feature of the novel strategy makes this system an ideal candidate for the development of new synthetic routes as well as for screening natural and more complex pathways.

Segregated Nanocompartments Containing Therapeutic Enzymes and Imaging Compounds within DNA-Zipped Polymersome Clusters for Advanced Nanotheranostic Platform

Nanotheranostics is an emerging field that brings together nanoscale-engineered materials with biological systems providing a combination of therapeutic and diagnostic strategies. However, current theranostic nanoplatforms have serious limitations, mainly due to a mismatch between the physical properties of the selected nanomaterials and their functionalization ease, loading ability, or overall compatibility with bioactive molecules. Herein, a nanotheranostic system is proposed based on nanocompartment clusters composed of two different polymersomes linked together by DNA. Careful design and procedure optimization result in clusters segregating the therapeutic enzyme human Dopa decarboxylase (DDC) and fluorescent probes for the detection unit in distinct but colocalized nanocompartments. The diagnostic compartment provides a twofold function: trackability via dye loading as the imaging component and the ability to attach the cluster construct to the surface of cells. The therapeutic compartment, loaded with active DDC, triggers the cellular expression of a secreted reporter enzyme via production of dopamine and activation of dopaminergic receptors implicated in atherosclerosis. This two-compartment nanotheranostic platform is expected to provide the basis of a new treatment strategy for atherosclerosis, to expand versatility and diversify the types of utilizable active molecules, and thus by extension expand the breadth of attainable applications.

Giant Polymer Compartments for Confined Reactions

In nature, various specific reactions only occur in spatially controlled environments. Cell compartment and subcompartments act as the support required to preserve the bio-specificity and functionality of the biological content, by affording absolute segregation. Inspired by this natural perfect behavior, bottom-up approaches are on focus to develop artificial cell-like structures, crucial for understanding relevant bioprocesses and interactions or to produce tailored solutions in the field of therapeutics and diagnostics. In this review, we discuss the benefits of constructing polymer-based single and multicompartments (capsules and giant unilamellar vesicles (GUVs)), equipped with biomolecules as to mimic cells. In this respect, we outline key examples of how such structures have been designed from scratch, namely, starting from the application-oriented selection and synthesis of the amphiphilic block copolymer. We then present the state-of-the-art techniques for assembling the supramolecular structure while permitting the encapsulation of active compounds and the incorporation of peptides/membrane proteins, essential to support in situ reactions, e.g., to replicate intracellular signaling cascades. Finally, we briefly discuss important features that these compartments offer and how they could be applied to engineer the next generation of microreactors, therapeutic solutions, and cell models.

DNA-directed arrangement of soft synthetic compartments and their behavior in vitro and in vivo

DNA has been widely used as a key tether to promote self-organization of super-assemblies with emergent properties. However, control of this process is still challenging for compartment assemblies and to date the resulting assemblies have unstable membranes precluding in vitro and in vivo testing. Here we present our approach to overcome these limitations, by manipulating molecular factors such as compartment membrane composition and DNA surface density, thereby controlling the size and stability of the resulting DNA-linked compartment clusters. The soft, flexible character of the polymer membrane and low number of ssDNA remaining exposed after cluster formation determine the interaction of these clusters with the cell surface. These clusters exhibit in vivo stability and lack of toxicity in a zebrafish model. To display the breadth of therapeutic applications attainable with our system, we encapsulated the medically established enzyme laccase within the inner compartment and demonstrated its activity within the clustered compartments. Most importantly, these clusters can interact selectively with different cell lines, opening a new strategy to modify and expand cellular functions by attaching such pre-organized soft DNA-mediated compartment clusters on cell surfaces for cell engineering or therapeutic applications.

Brushing the surface: cascade reactions between immobilized nanoreactors

Functionalization of hard or soft surfaces with, for example, ligands, enzymes or proteins, is an effective and practical methodology for the development of new applications. We report the assembly of two types of nanoreactors based upon poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) (PDMS-b-PMOXA) diblock copolymers as scaffold, uricase and lactoperoxidase as bio-catalysts located within the nanoreactors, and melittin as the biopores inserted into the hydrophobic shell. The nanoreactors were immobilized on poly(2-hydroxyethyl methacrylate)-co-poly(2-aminoethyl methacrylate hydrochloride) (PHEMA-co-P(2-AEMA·HCl) brushes-grafted wafer surfaces by utilizing the strong supramolecular interactions between biotin and streptavidin. The (PHEMA-co-P(2-AEMA·HCl) brushes on silicon surfaces were prepared by a surface initiating atom transfer radical polymerization (ATRP) "graft-from" technique. Cascade reactions between different surface-anchored nanoreactors were demonstrated by converting Amplex® Red to the fluorescent probe resorufin by using the H2O2 produced from uric acid and H2O. The detailed properties of the nanoreactors on the functionalized surface including the binding behaviours and cascade reactions were investigated using emission spectroscopy, transmission electron microscopy (TEM), light scattering (LS), atomic force microscopy (AFM) and a quartz crystal microbalance (QCM-D). The results are proof-of-principle for the preparation of catalytically functional engineered surface materials and lay the foundation for applying this advanced functional surface material in biosensing, implanting and antimicrobial materials preparation.

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.

Synthesis and complex self-assembly of amphiphilic block copolymers with a branched hydrophobic poly(2-oxazoline) into multicompartment micelles, pseudo-vesicles and yolk/shell nanoparticles

A new PEO-b-PEHOx amphiphilic diblock copolymer was achieved which unlocked new complex self-assembled structures. Thanks to its hydrophobic oxazoline block with a long branched side chain, EHOx, various potent structures were obtained.

Human adipose glycerol flux is regulated by a pH gate in AQP10

Obesity is a major threat to global health and metabolically associated with glycerol homeostasis. Here we demonstrate that in human adipocytes, the decreased pH observed during lipolysis (fat burning) correlates with increased glycerol release and stimulation of aquaglyceroporin AQP10. The crystal structure of human AQP10 determined at 2.3 Å resolution unveils the molecular basis for pH modulation-an exceptionally wide selectivity (ar/R) filter and a unique cytoplasmic gate. Structural and functional (in vitro and in vivo) analyses disclose a glycerol-specific pH-dependence and pinpoint pore-lining His80 as the pH-sensor. Molecular dynamics simulations indicate how gate opening is achieved. These findings unravel a unique type of aquaporin regulation important for controlling body fat mass. Thus, targeting the cytoplasmic gate to induce constitutive glycerol secretion may offer an attractive option for treating obesity and related complications.

Biomimetic artificial organelles with in vitro and in vivo activity triggered by reduction in microenvironment

Despite tremendous efforts to develop stimuli-responsive enzyme delivery systems, their efficacy has been mostly limited to in vitro applications. Here we introduce, by using an approach of combining biomolecules with artificial compartments, a biomimetic strategy to create artificial organelles (AOs) as cellular implants, with endogenous stimuli-triggered enzymatic activity. AOs are produced by inserting protein gates in the membrane of polymersomes containing horseradish peroxidase enzymes selected as a model for natures own enzymes involved in the redox homoeostasis. The inserted protein gates are engineered by attaching molecular caps to genetically modified channel porins in order to induce redox-responsive control of the molecular flow through the membrane. AOs preserve their structure and are activated by intracellular glutathione levels in vitro. Importantly, our biomimetic AOs are functional in vivo in zebrafish embryos, which demonstrates the feasibility of using AOs as cellular implants in living organisms. This opens new perspectives for patient-oriented protein therapy.

The efficacy of stimuli-responsive enzyme delivery systems is usually limited to in vitro applications. Here the authors form artificial organelles by inserting stimuli-responsive protein gates in membranes of polymersomes loaded with enzymes and obtain a triggered functionality both in vitro and in vivo.

Purification and functional comparison of nine human Aquaporins produced in Saccharomyces cerevisiae for the purpose of biophysical characterization

The sparse number of high-resolution human membrane protein structures severely restricts our comprehension of molecular physiology and ability to exploit rational drug design. In the search for a standardized, cheap and easily handled human membrane protein production platform, we thoroughly investigated the capacity of S. cerevisiae to deliver high yields of prime quality human AQPs, focusing on poorly characterized members including some previously shown to be difficult to isolate. Exploiting GFP labeled forms we comprehensively optimized production and purification procedures resulting in satisfactory yields of all nine AQP targets. We applied the obtained knowledge to successfully upscale purification of histidine tagged human AQP10 produced in large bioreactors. Glycosylation analysis revealed that AQP7 and 12 were O-glycosylated, AQP10 was N-glycosylated while the other AQPs were not glycosylated. We furthermore performed functional characterization and found that AQP 2, 6 and 8 allowed flux of water whereas AQP3, 7, 9, 10, 11 and 12 also facilitated a glycerol flux. In conclusion, our S. cerevisiae platform emerges as a powerful tool for isolation of functional, difficult-to-express human membrane proteins suitable for biophysical characterization.

Reproducible Preparation of Proteopolymersomes via Sequential Polymer Film Hydration and Membrane Protein Reconstitution

Film rehydration method is commonly used for membrane protein (MP) reconstitution into block copolymer (BCP), but the lack of control in the rehydration step formed a heterogeneous population of proteopolymersomes that interferes with the characterization and performance of devices incorporating them. To improve the self-assembly of polymersomes with simultaneous MP reconstitution, the study reported herein aimed to understand the effects of different variants of the rehydration procedure on the MP reconstitution into BCP membranes. The model MP used in this study was AquaporinZ (AqpZ), an α-helical MP that has been shown to have a high permeation rate exclusive to water molecules. Comparing four rehydration methods differing in the hydration time (i.e., brief wetting or full hydration) and medium (i.e., in buffer or AqpZ stock solution), prehydration with buffer prior to adding AqpZ was found to be most desirable and reproducible reconstitution method because it gave rise to the highest proportion of well-formed vesicles with intact AqpZ functionality as evidenced by the transmission electron microscopy images, dynamic light scattering, and stopped-flow analyses. The mechanisms by which effective AqpZ reconstitution takes place were also investigated and discussed. Small-angle X-ray scattering analysis shows that hydrating the initially dry multilamellar BCP films allows the separation of lamellae. This is anticipated to increase the membrane fluidity that facilitates a fast and spontaneous integration of AqpZ as the detergent concentration is considerably lowered below its critical micelle concentration. Dilution of detergent can result in precipitation of proteins in the absence of well-fluidized membranes for protein integration that underscores the importance of membrane fluidity in MP reconstitution.

Biomimetic Strategy To Reversibly Trigger Functionality of Catalytic Nanocompartments by the Insertion of pH-Responsive Biovalves

We describe an innovative strategy to generate catalytic compartments with triggered functionality at the nanoscale level by combining pH-reversible biovalves and enzyme-loaded synthetic compartments. The biovalve has been engineered by the attachment of stimuli-responsive peptides to a genetically modified channel porin, enabling a reversible change of the molecular flow through the pores of the porin in response to a pH change in the local environment. The biovalve functionality triggers the reaction inside the cavity of the enzyme-loaded compartments by switching the in situ activity of the enzymes on/off based on a reversible change of the permeability of the membrane, which blocks or allows the passage of substrates and products. The complex functionality of our catalytic compartments is based on the preservation of the integrity of the compartments to protect encapsulated enzymes. An increase of the in situ activity compared to that of the free enzyme and a reversible on/off switch of the activity upon the presence of a specific stimulus is achieved. This strategy provides straightforward solutions for the development of catalytic nanocompartments efficiently producing desired molecules in a controlled, stimuli-responsive manner with high potential in areas, such as medicine, analytical chemistry, and catalysis.

An amphiphilic graft copolymer-based nanoparticle platform for reduction-responsive anticancer and antimalarial drug delivery

Medical applications of anticancer and antimalarial drugs often suffer from low aqueous solubility, high systemic toxicity, and metabolic instability. Smart nanocarrier-based drug delivery systems provide means of solving these problems at once. Herein, we present such a smart nanoparticle platform based on self-assembled, reduction-responsive amphiphilic graft copolymers, which were successfully synthesized through thiol-disulfide exchange reaction between thiolated hydrophilic block and pyridyl disulfide functionalized hydrophobic block. These amphiphilic graft copolymers self-assembled into nanoparticles with mean diameters of about 30-50 nm and readily incorporated hydrophobic guest molecules. Fluorescence correlation spectroscopy (FCS) was used to study nanoparticle stability and triggered release of a model compound in detail. Long-term colloidal stability and model compound retention within the nanoparticles was found when analyzed in cell media at body temperature. In contrast, rapid, complete reduction-triggered disassembly and model compound release was achieved within a physiological reducing environment. The synthesized copolymers revealed no intrinsic cellular toxicity up to 1 mg mL(-1). Drug-loaded reduction-sensitive nanoparticles delivered a hydrophobic model anticancer drug (doxorubicin, DOX) to cancer cells (HeLa cells) and an experimental, metabolically unstable antimalarial drug (the serine hydroxymethyltransferase (SHMT) inhibitor (±)-1) to Plasmodium falciparum-infected red blood cells (iRBCs), with higher efficacy compared to similar, non-sensitive drug-loaded nanoparticles. These responsive copolymer-based nanoparticles represent a promising candidate as smart nanocarrier platform for various drugs to be applied to different diseases, due to the biocompatibility and biodegradability of the hydrophobic block, and the protein-repellent hydrophilic block.

Hybrid polymer-lipid films as platforms for directed membrane protein insertion

Hybrids composed of amphiphilic block copolymers and lipids constitute a new generation of biological membrane-inspired materials. Hybrid membranes resulting from self-assembly of lipids and polymers represent adjustable models for interactions between artificial and natural membranes, which are of key importance, e.g., when developing systems for drug delivery. By combining poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) amphiphilic copolymers (PDMS-b-PMOXA) with various phospholipids, we obtained hybrid films with modulated properties and topology, based on phase separation, and the formation of distinct domains. By understanding the factors driving the phase separation in these hybrid lipid-polymer films, we were able to use them as platforms for directed insertion of membrane proteins. Tuning the composition of the polymer-lipids mixtures favored successful insertion of membrane proteins with desired topological distributions (in polymer or/and lipid regions). Controlled insertion and location of membrane proteins in hybrid films make these hybrids ideal candidates for numerous applications where specific spatial functionality is required.

Selecting analytical tools for characterization of polymersomes in aqueous solution

We present 17 techniques to analyze polymersomes, in terms of their size, bilayer properties, elastic properties or surface charge.

Recent progress in designing shell cross-linked polymer capsules for drug delivery

This tutorial review highlights the progress made during recent years in the development of the shell cross-linked (SCL) polymer nanocapsules and the impact of the most important scientific ideas on this field of knowledge.