Substrate-Sorting Nanoreactors Based on Permeable Peptide Polymer Vesicles and Hybrid Liposomes with Synthetic Macromolecular Channels

Advances in block copolymer-phospholipid hybrid vesicles: from physical-chemical properties to applications

Hybrid vesicles, made of lipids and amphiphilic block copolymers, have become increasingly popular thanks to their versatile properties that enable the construction of intricate membranes mimicking cellular structures. This tutorial review gives an overview over the different hybrid vesicle designs, and provides a detailed analysis of their properties, including their composition, membrane fluidity, membrane homogeneity, permeability, stability. The review puts emphasis on the application of these hybrid vesicles in bottom-up synthetic biology and aims to offer an overview of design guidelines, particularly focusing on composition, to eventually realize the intended applications of these hybrid vesicles.

Poly(Sitosterol)-Based Hydrophobic Blocks in Amphiphilic Block Copolymers for the Assembly of Hybrid Vesicles

Amphiphilic block copolymer and lipids can be assembled into hybrid vesicles (HVs), which are an alternative to liposomes and polymersomes. Block copolymers that have either poly(sitostryl methacrylate) or statistical copolymers of sitosteryl methacrylate and butyl methacrylate as the hydrophobic part and a poly(carboxyethyl acrylate) hydrophilic segment are synthesized and characterized. These block copolymers assemble into small HVs with soybean L-α-phosphatidylcholine (soyPC), confirmed by electron microscopy and small-angle X-ray scattering. The membrane's hybrid nature is illustrated by fluorescence resonance energy transfer between labeled building blocks. The membrane packing, derived from spectra when using Laurdan as an environmentally sensitive fluorescent probe, is comparable between small HVs and the corresponding liposomes with molecular sitosterol, although the former show indications of transmembrane asymmetry. Giant HVs with homogenous distribution of the block copolymers and soyPC in their membranes are assembled using the electroformation method. The lateral diffusion of both building blocks is slowed down in giant HVs with higher block copolymer content, but their permeability toward (6)-carboxy-X-rhodamine is higher compared to giant vesicles made of soyPC and molecular sitosterol. This fundamental effort contributes to the rapidly expanding understanding of the integration of natural membrane constituents with designed synthetic compounds to form hybrid membranes.

Spatially Confined Nanoreactors Designed for Biological Applications

The applications of nanoreactors in biology are becoming increasingly significant and prominent. Specifically, nanoreactors with spatially confined, due to their exquisite design that effectively limits the spatial range of biomolecules, attracted widespread attention. The main advantage of this structure is designed to improve reaction selectivity and efficiency by accumulating reactants and catalysts within the chambers, thus increasing the frequency of collisions between reactants. Herein, the recent progress in the synthesis of spatially confined nanoreactors and their biological applications is summarized, covering various kinds of nanoreactors, including porous inorganic materials, porous crystalline materials with organic components and self-assembled polymers to construct nanoreactors. These design principles underscore how precise reaction control could be achieved by adjusting the structure and composition of the nanoreactors to create spatial confined. Furthermore, various applications of spatially confined nanoreactors are demonstrated in the biological fields, such as biocatalysis, molecular detection, drug delivery, and cancer therapy. These applications showcase the potential prospects of spatially confined nanoreactors, offering robust guidance for future research and innovation.

Chimeric nanobody-decorated liposomes by self-assembly

Liposomes as drug vehicles have advantages, such as payload protection, tunable carrying capacity and improved biodistribution. However, due to the dysfunction of targeting moieties and payload loss during preparation, immunoliposomes have yet to be favoured in commercial manufacturing. Here we report a chemical modification-free biophysical approach for producing immunoliposomes in one step through the self-assembly of a chimeric nanobody (cNB) into liposome bilayers. cNB consists of a nanobody against human epidermal growth factor receptor 2 (HER2), a flexible peptide linker and a hydrophobic single transmembrane domain. We determined that 64% of therapeutic compounds can be encapsulated into 100-nm liposomes, and up to 2,500 cNBs can be anchored on liposomal membranes without steric hindrance under facile conditions. Subsequently, we demonstrate that drug-loaded immunoliposomes increase cytotoxicity on HER2-overexpressing cancer cell lines by 10- to 20-fold, inhibit the growth of xenograft tumours by 3.4-fold and improve survival by more than twofold.

Structural characterization of lateral phase separation in polymer-lipid hybrid membranes

Hierarchic self-assembly is the main mechanism used to create diverse structures using soft materials. This is a case for both synthetic materials and biomolecular systems, as exemplified by the non-covalent organization of lipids into membranes. In nature, lipids often assemble into single bilayers, but other nanostructures are encountered, such as bilayer stacks and tubular and vesicular aggregates. Synthetic block copolymers can be engineered to recapitulate many of the structures, forms, and functions of lipid systems. When block copolymers are amphiphilic, they can be inserted or co-assembled into hybrid membranes that exhibit synergistic structural, permeability, and mechanical properties. One example is the emergence of lateral phase separation akin to the raft formation in biomembranes. When higher-order structures, such as hybrid membranes, are formed, this lateral phase separation can be correlated across membranes in the stack. This chapter outlines a set of important methods, such as X-ray Scattering, Atomic Force Microscopy, and Cryo-Electron Microscopy, that are relevant to characterizing and evaluating lateral and correlated phase separation in hybrid membranes at the nano and mesoscales. Understanding the phase behavior of polymer-lipid hybrid materials could lead to innovative advancements in biomimetic membrane separation systems.

Degradable Polymer-Based Nanoassemblies for Precise Targeting and Drug Delivery to Breast Cancer Cells without Affecting Normal Healthy Cells

Stimuli-responsive amphiphilic polymers are known to be precursors to forming promising nanoarchitectonics with tunable properties for application in biomedical sciences. Currently, self-immolative polymers are widely recognized as an emerging class of responsive materials with excellent degradability, which is one of the crucial criteria for designing a robust drug delivery vehicle. Here, we design an amphiphilic polyurethane endowed with a redox-responsive self-immolative linker and a pH-responsive tertiary amine on the backbone, which forms entropy-driven nanoscale supramolecular assemblies (average hydrodynamic diameter ∼110 nm) and is programmed to disassemble in a redox environment (GSH) due to the degradation of the polymer in a self-immolative fashion. The nanoassembly shows efficient drug sequestration and release in a controlled manner in response to glutathione (10 mM). The tertiary amine residing on the surface of the nanoassembly becomes protonated in the tumor microenvironment (pH ∼ 6.4-6.8) and generates positively charged nanoassembly (ζ-potential = +36 mV), which enhances the cancer cell-selective cellular uptake. The biological evaluation of the drug-loaded nanoassembly revealed triple-negative breast cancer (MDAMB-231) selective internalization and cell death while shielding normal cells (RBCs or PBMCs) from off-targeting toxicity. We envision that polyurethane with a redox-responsive self-immolative linker might open up new opportunities for a completely degradable polyurethane-based nanocarrier for drug delivery and diagnosis applications.

Protein-Rich Rafts in Hybrid Polymer/Lipid Giant Unilamellar Vesicles

Considerable attention has been dedicated to lipid rafts due to their importance in numerous cell functions such as membrane trafficking, polarization, and signaling. Next to studies in living cells, artificial micrometer-sized vesicles with a minimal set of components are established as a major tool to understand the phase separation dynamics and their intimate interplay with membrane proteins. In parallel, mixtures of phospholipids and certain amphiphilic polymers simultaneously offer an interface for proteins and mimic this segregation behavior, presenting a tangible synthetic alternative for fundamental studies and bottom-up design of cellular mimics. However, the simultaneous insertion of complex and sensitive membrane proteins is experimentally challenging and thus far has been largely limited to natural lipids. Here, we present the co-reconstitution of the proton pump bo3 oxidase and the proton consumer ATP synthase in hybrid polymer/lipid giant unilamellar vesicles (GUVs) via fusion/electroformation. Variations of the current method allow for tailored reconstitution protocols and control of the vesicle size. In particular, mixing of protein-free and protein-functionalized nanosized vesicles in the electroformation film results in larger GUVs, while separate reconstitution of the respiratory enzymes enables higher ATP synthesis rates. Furthermore, protein labeling provides a synthetic mechanism for phase separation and protein sequestration, mimicking lipid- and protein-mediated domain formation in nature. The latter means opens further possibilities for re-enacting phenomena like supercomplex assembly or symmetry breaking and enriches the toolbox of bottom-up synthetic biology.

Synthetic Cells Revisited: Artificial Cells Construction Using Polymeric Building Blocks

The exponential growth of research on artificial cells and organelles underscores their potential as tools to advance the understanding of fundamental biological processes. The bottom-up construction from a variety of building blocks at the micro- and nanoscale, in combination with biomolecules is key to developing artificial cells. In this review, artificial cells are focused upon based on compartments where polymers are the main constituent of the assembly. Polymers are of particular interest due to their incredible chemical variety and the advantage of tuning the properties and functionality of their assemblies. First, the architectures of micro- and nanoscale polymer assemblies are introduced and then their usage as building blocks is elaborated upon. Different membrane-bound and membrane-less compartments and supramolecular structures and how they combine into advanced synthetic cells are presented. Then, the functional aspects are explored, addressing how artificial organelles in giant compartments mimic cellular processes. Finally, how artificial cells communicate with their surrounding and each other such as to adapt to an ever-changing environment and achieve collective behavior as a steppingstone toward artificial tissues, is taken a look at. Engineering artificial cells with highly controllable and programmable features open new avenues for the development of sophisticated multifunctional systems.

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.

Peptide-lipid hybrid vesicles with stimuli-responsive phase separation for controlled membrane functions

A disulfide-tethered peptide-lipid conjugate self-assembled into a homogeneously distributed peptide-lipid hybrid vesicle. Upon dithiothreitol treatment, the homogeneous peptide-lipid membrane spontaneously divided into lipid-rich and peptide-rich domains, while the vesicle retained its size and shape. Membrane phase separation enhanced temperature-dependent cargo release.

Performance of a Flow-Through Enzyme Reactor Prepared from a Silica Monolith and an α-Poly(D-Lysine)-Enzyme Conjugate

Horseradish peroxidase (HRP) is covalently bound in aqueous solution to polycationic α-poly(D-lysine) chains of ≈1000 repeating units length, PDL, via a bis-aryl hydrazone bond (BAH). Under the experimental conditions used, about 15 HRP molecules are bound along the PDL chain. The purified PDL-BAH-HRP conjugate is very stable when stored at micromolar HRP concentration in a pH 7.2 phosphate buffer solution at 4 °C. When a defined volume of such a conjugate solution of desired HRP concentration (i.e., HRP activity) is added to a macro- and mesoporous silica monolith with pore sizes of 20-30 µm as well as below 30 nm, quantitative and stable noncovalent conjugate immobilization is achieved. The HRP-containing monolith can be used as flow-through enzyme reactor for bioanalytical applications at neutral or slightly alkaline pH, as demonstrated for the determination of hydrogen peroxide in diluted honey. The conjugate can be detached from the monolith by simple enzyme reactor washing with an aqueous solution of pH 5.0, enabling reloading with fresh conjugate solution at pH 7.2. Compared to previously investigated polycationic dendronized polymer-enzyme conjugates with approximately the same average polymer chain length, the PDL-BAH-HRP conjugate appears to be equally suitable for HRP immobilization on silica surfaces.

Nanoconfinement-Enhanced Electrochemiluminescence for in Situ Imaging of Single Biomolecules

Direct imaging of electrochemical reactions at the single-molecule level is of potential interest in materials, diagnostic, and catalysis applications. Electrochemiluminescence (ECL) offers the opportunity to convert redox events into photons. However, it is challenging to capture single photons emitted from a single-molecule ECL reaction at a specific location, thus limiting high-quality imaging applications. We developed the nanoreactors based on Ru(bpy)₃²⁺-doped nanoporous zeolite nanoparticles (Ru@zeolite) for direct visualization of nanoconfinement-enhanced ECL reactions. Each nanoreactor not only acts as a matrix to host Ru(bpy)₃²⁺ molecules but also provides a nanoconfined environment for the collision reactions of Ru(bpy)₃²⁺ and co-reactant radicals to realize efficient in situ ECL reactions. The nanoscale confinement resulted in enhanced ECL. Using such nanoreactors as ECL probes, a dual-signal sensing protocol for visual tracking of a single biomolecule was performed. High-resolution imaging of single membrane proteins on heterogeneous cells was effectively addressed with near-zero backgrounds. This could provide a more sensitive tool for imaging individual biomolecules and significantly advance ECL imaging in biological applications.

Controlled Membrane Transport in Polymeric Biomimetic Nanoreactors

Polymersome-based biomimetic nanoreactors (PBNs) have generated great interest in nanomedicine and cell mimicry due to their robustness, tuneable chemistry, and broad applicability in biologically relevant fields. In this concept review, we mainly discuss the state of the art in functional polymersomes as biomimetic nanoreactors with membrane-controlled transport. PBNs that use environmental changes or external stimuli to adjust membrane permeability while maintaining structural integrity are highlighted. By encapsulating catalytic species, PBNs are able to convert inactive substrates into functional products in a controlled manner. In addition, special attention is paid to the use of PBNs as tailored artificial organelles with biomedical applications in vitro and in vivo, facilitating the fabrication of next-generation artificial organelles as therapeutic nanocompartments.

Phase separation in polymer-based biomimetic structures containing planar membranes

Phase separation in biological membranes is crucial for proper cellular functions, such as signaling and trafficking, as it mediates the interactions of condensates on membrane-bound organelles and transmembrane transport to targeted destination compartments. The separation of a lipid bilayer into phases and the formation of lipid rafts involve the restructuring of molecular localization, their immobilization, and local accumulation. By understanding the processes underlying the formation of lipid rafts in a cellular membrane, it is possible to reconstitute this phenomenon in synthetic biomimetic membranes, such as hybrids of lipids and polymers or membranes composed solely of polymers, which offer an increased physicochemical stability and unlimited possibilities of chemical modification and functionalization. In this article, we relate the main lipid bilayer phase transition phenomenon with respect to hybrid biomimetic membranes, composed of lipids mixed with polymers, and fully synthetic membranes. Following, we review the occurrence of phase separation in biomimetic hybrid membranes based on lipids and/or direct lipid analogs, amphiphilic block copolymers. We further exemplify the phase separation and the resulting properties and applications in planar membranes, free-standing and solid-supported. We briefly list methods leading to the formation of such biomimetic membranes and reflect on their improved overall stability and influence on the separation into different phases within the membranes. Due to the importance of phase separation and compartmentalization in cellular membranes, we are convinced that this compiled overview of this phenomenon will be helpful for any researcher in the biomimicry area.

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.

Single-component nanodiscs via the thermal folding of amphiphilic graft copolymers with the adjusted flexibility of the main chain

Nanodiscs have attracted considerable attention as structural scaffolds for membrane-protein research and as biomaterials in e.g. drug-delivery systems. However, conventional disc-fabrication methods are usually laborious, and disc fabrication via the self-assembly of amphiphiles is difficult. Herein, we report the formation of polymer nanodiscs based on the self-assembly of amphiphilic graft copolymers by adjusting the persistence length of the main chain. Amphiphilic graft copolymers with a series of different main-chain persistence lengths were prepared and these formed, depending on the persistence length, either rods, discs, or vesicles. Notably, polymer nanodiscs were formed upon heating a chilled polymer solution without the need for any additives, and the thus obtained nanodiscs were used to solubilize a membrane protein during cell-free protein synthesis. Given the simplicity of this disc-fabrication method and the ability of these discs to solubilize membrane proteins, this study considerably expands the fundamental and practical scope of graft-copolymer nanodiscs and demonstrates their utility as tools for studying the structure and function of membrane proteins.

Ferrostatin-1-loaded liposome for treatment of corneal alkali burn via targeting ferroptosis

Alkali burn is a potentially blinding corneal injury. During the progression of alkali burn-induced injury, overwhelmed oxidative stress in the cornea triggers cell damage, including oxidative changes in cellular macromolecules and lipid peroxidation in membranes, leading to impaired corneal transparency, decreased vision, or even blindness. In this study, we identified that ferroptosis, a type of lipid peroxidation-dependent cell death, mediated alkali burn-induced corneal injury. Ferroptosis-targeting therapy protected the cornea from cell damage and neovascularization. However, the specific ferroptosis inhibitor ferrostatin-1 (Fer-1) is hydrophobic and cannot be directly applied in the clinic. Therefore, we developed Fer-1-loaded liposomes (Fer-1-NPs) to improve the bioavailability of Fer-1. Our study demonstrated that Fer-1-NPs exerted remarkable curative effects regarding corneal opacity and neovascularization in vivo. The efficacy was comparable to that of dexamethasone, but without appreciable side effects. The significant suppression of ferroptosis (induced by lipid peroxidation and mitochondria disruption), inflammation, and neovascularization might be the mechanisms underlying the therapeutic effect of Fer-1-NPs. Moreover, the Fer-1-NPs treatment showed no signs of cytotoxicity, hematologic toxicity, or visceral organ damage, which further confirmed the biocompatibility. Overall, Fer-1-NPs provide a new prospect for safe and effective therapy for corneal alkali burn.

Kinetic Processes in Enzymatic Nanoreactors for In Vivo Detoxification

Enzymatic nanoreactors are enzyme-encapsulated nanobodies that are capable of performing biosynthetic or catabolic reactions. For this paper, we focused on therapeutic enzyme nanoreactors for the neutralization of toxicants, paying special attention to the inactivation of organophosphorus compounds (OP). Therapeutic enzymes that are capable of detoxifying OPs are known as bioscavengers. The encapsulation of injectable bioscavengers by nanoparticles was first used to prevent fast clearance and the immune response to heterologous enzymes. The aim of enzyme nanoreactors is also to provide a high concentration of the reactive enzyme in stable nanocontainers. Under these conditions, the detoxification reaction takes place inside the compartment, where the enzyme concentration is much higher than in the toxicant diffusing across the nanoreactor membrane. Thus, the determination of the concentration of the encapsulated enzyme is an important issue in nanoreactor biotechnology. The implications of second-order reaction conditions, the nanoreactor’s permeability in terms of substrates, and the reaction products and their possible osmotic, viscosity, and crowding effects are also examined.

Self-catalyzed synthesis of a nano-capsule and its application as a heterogeneous RCMP catalyst and nano-reactor

A nano-capsule synthesized via self-catalyzed RCMP and its use as a heterogeneous catalyst and a nano-reactor of RCMP to generate a multi-elemental particle.

Polymer-Lipid Hybrid Materials

Hierarchic self-assembly underpins much of the form and function seen in synthetic or biological soft materials. Lipids are paramount examples, building themselves in nature or synthetically in a variety of meso/nanostructures. Synthetic block copolymers capture many of lipid's structural and functional properties. Lipids are typically biocompatible and high molecular weight polymers are mechanically robust and chemically versatile. The development of new materials for applications like controlled drug/gene/protein delivery, biosensors, and artificial cells often requires the combination of lipids and polymers. The emergent composite material, a "polymer-lipid hybrid membrane", displays synergistic properties not seen in pure components. Specific examples include the observation that hybrid membranes undergo lateral phase separation that can correlate in registry across multiple layers into a three-dimensional phase-separated system with enhanced permeability of encapsulated drugs. It is timely to underpin these emergent properties in several categories of hybrid systems ranging from colloidal suspensions to supported hybrid films. In this review, we discuss the form and function of a vast number of polymer-lipid hybrid systems published to date. We rationalize the results to raise new fundamental understanding of hybrid self-assembling soft materials as well as to enable the design of new supramolecular systems and applications.

Computational Reverse Engineering Analysis for Scattering Experiments (CREASE) on Vesicles Assembled from Amphiphilic Macromolecular Solutions

In this paper we present the development and validation of the "Computational Reverse-Engineering Analysis for Scattering Experiments" (CREASE) method for analyzing scattering results from vesicle structures that are commonly found upon assembly of synthetic, biomimetic, or bioderived amphiphilic copolymers in solution. The two-step CREASE method takes the amphiphilic polymer chemistry and small-angle scattering intensity profile, I exp(q), as input and determines the vesicles' structural features on multiple length scales ranging from assembled vesicle wall's individual layer thicknesses to the monomer-level packing and distribution of polymer conformations. In the first step of CREASE, a genetic algorithm (GA) is used to determine the relevant vesicle dimensions from the input macromolecular solution information and I exp(q) by identifying the structure whose computed scattering profile best matches the input I exp(q). Then in the second step, the GA-determined dimensions are used for molecular reconstruction of the vesicle structure. To validate CREASE for vesicles, we test CREASE on input scattering intensity profiles generated mathematically (termed as in silico I exp(q) vs q) from a variety of vesicle sizes with known dimensions. We also test CREASE on in silico I exp(q) vs q generated from vesicles with dispersity in all relevant dimensions, resembling real experiments. After successful validation of CREASE, we compare the CREASE-determined dimensions against those obtained from the traditional approach of fitting the scattering intensity profile to relevant analytical model in SASVIEW package. We show that CREASE performs better than or as well as the core-multishell analytical model's fitting in SASVIEW in determining vesicle dimensions with dispersity. We also show that CREASE provides structural information beyond those possible from traditional scattering analysis using the core-multishell model, such as the distribution of solvophilic monomers between the vesicle wall's inner and outer layers in the vesicle wall and the chain-level packing within each vesicle layer.

Photo-triggered cargo release from liposome chlorin e6-bearing pullulan hybrid nanoparticles via membrane permeabilization

A liposome chlorin e6-bearing pullulan nanogel hybrid was prepared as a light-triggered payload release platform. The current system enabled manipulation of the release profile of model drugs encapsulated by liposomes. Gelatin hydrogels that comprised hybrid nanoparticles could successfully control the delivery of cargo molecules to human mesenchymal stem cells with light stimuli without injury to the cells.

Enhanced Sulfite-Selective Sensing and Cell Imaging with Fluorescent Nanoreactors Containing a Ratiometric Lipid Peroxidation Sensor

The detection of SO₂ and its derivatives is indispensable for monitoring atmospheric, water quality, and biological fluctuation of oxidative stress and metabolism of biothiols within native cellular contexts. In this article, the brush copolymer nanoreactors containing amine-terminated PDMS were used to encapsulate the fluorescent indicator C11-BDP, forming sulfite-sensitive nanoreactors (ssNRs). Surprisingly, the ssNRs were found to be highly selective to sulfite over a range of reactive oxygen/nitrogen/sulfur species and anions, which was not observed with freely dissolved indicators. The ssNRs showed a rapid response (t₉₅ = 65 s), an excellent detection limit (0.7 μM), and a very high sensitivity (ca. 1000-fold ratiometric intensity change) to sulfite. For cellular studies, the ssNRs exhibited negligible toxicity and could be endocytosed into endosomes and lysosomes. Finally, the ssNRs allowed us to visualize the different responses of three different types of cells (pre-adipocytes, RAW264.7, and HeLa cells) to external stimuli in the culture media with sulfites and lipopolysaccharides.

Polymer Vesicles for Antimicrobial Applications

Polymer vesicles, hollow nanostructures with hydrophilic cavity and hydrophobic membrane, have shown significant potentials in biomedical applications including drug delivery, gene therapy, cancer theranostics, and so forth, due to their unique cell membrane-like structure. Incorporation with antibacterial active components like antimicrobial peptides, etc., polymer vesicles exhibited enhanced antimicrobial activity, extended circulation time, and reduced cell toxicity. Furthermore, antibacterial, and anticancer can be achieved simultaneously, opening a new avenue of the antimicrobial applications of polymer vesicles. This review seeks to highlight the state-of-the-art of antimicrobial polymer vesicles, including the design strategies and potential applications in the field of antibacterial. The structural features of polymer vesicles, preparation methods, and the combination principles with antimicrobial active components, as well as the advantages of antimicrobial polymer vesicles, will be discussed. Then, the diverse applications of antimicrobial polymer vesicles such as wide spectrum antibacterial, anti-biofilm, wound healing, and tissue engineering associated with their structure features are presented. Finally, future perspectives of polymer vesicles in the field of antibacterial is also proposed.

Therapeutic nanoreactors for detoxification of xenobiotics: Concepts, challenges and biotechnological trends with special emphasis to organophosphate bioscavenging

The introduction of enzyme nanoreactors in medicine is relatively new. However, this technology has already been experimentally successful in cancer treatments, struggle against toxicity of reactive oxygen species in inflammatory processes, detoxification of drugs and xenobiotics, and correction of metabolic and genetic defects by using encapsulated enzymes, acting in single or cascade reactions. Biomolecules, e.g. enzymes, antibodies, reactive proteins capable of inactivating toxicants in the body are called bioscavengers. In this review, we focus on enzyme-containing nanoreactors for in vivo detoxification of organophosphorous compounds (OP) to be used for prophylaxis and post-exposure treatment of OP poisoning. A particular attention is devoted to bioscavenger-containing injectable nanoreactors operating in the bloodstream. The nanoreactor concept implements single or multiple enzymes and cofactors co-encapsulated in polymeric semi-permeable nanocontainers. Thus, the detoxification processes take place in a confined space containing highly concentrated bioscavengers. The article deals with historical and theoretical backgrounds about enzymatic detoxification of OPs in nanoreactors, nanoreactor polymeric enveloppes, realizations and advantages over other approaches using bioscavengers.

Large hybrid Polymer/Lipid Unilamellar vesicle (LHUV) at the nanoscale: An insight into the lipid distribution in the membrane and permeability control

Membrane structuration of Large Hybrid Unilamellar Polymer/Lipid Vesicle (LHUV) is an important parameter on the optimization of their properties and thus their valuation in various fields. However, this kind of information is hardly accessible. In this work, we will focus on the development of LHUV obtained from the self-assembly of diblock poly(dimethylsiloxane)-b-poly(ethylene oxide) (PDMS-b-PEO) of different molar masses combined with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at 15% and 25% w/w content. The hybrid character of the resulting vesicles as well as their membrane structure are characterized by the mean of different techniques such as small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). We show that hybrid vesicles with homogeneous membrane structure are obtained whatever the molar mass of the block copolymer (from 2500 to 4000 g/mol), with of a small number of tubular structures observed with the higher molar mass. We also demonstrate that the permeability of the LHUV, evaluated through controlled release experiments of fluorescein loaded in LHUV, is essentially controlled by the lipid/polymer composition.

Thermoresponsive Carbohydrate-b-Polypeptoid Polymer Vesicles with Selective Solute Permeability and Permeable Factors for Solutes

Solute-permeable polymer vesicles are structural compartments for nanoreactors/nanofactories in the context of drug delivery and artificial cells. We previously proposed design guidelines for polymers that form solute-permeable vesicles, yet we did not provide enough experimental verification. In addition, the fact that there is no clear factor for identifying permeable solutes necessitates extensive trial and error. Herein, we report solute-permeable polymer vesicles based on an amphiphilic copolymer, thermoresponsive oligosaccharide-block-poly(N-n-propylglycine). The introduction of a thermoresponsive polymer as a hydrophobic segment into amphiphilic polymers is a viable approach to construct solute-permeable polymer vesicles. We also demonstrate that the polymer vesicles are preferentially permeable to cationic and neutral fluorophores and are hardly permeable to anionic fluorophores due to the electrostatic repulsion between the bilayer and anionic fluorophores. In addition, the permeability of neutral fluorophores increases with the increasing log P value of the fluorophores. Thus, the electrical charge and log P value are important factors for membrane permeability. These findings will help researchers develop advanced nanoreactors based on permeable vesicles for a broad range of fundamental and biomedical applications.

Polymeric Nanoreactors as Emerging Nanoplatforms for Cancer Precise Nanomedicine

How to precisely detect and effectively cure cancer which is defined as precise nanomedicine has drawn great attention worldwide. Polymeric nanoreactors which can in situ catalyze inert species into activated ones, can greatly increase imaging quality and enhance therapeutic effects along with decreased background interference and reduced serious side effects. After a brief introduction, the design and preparation of polymeric nanoreactors are discussed from the following aspects, that is, solvent-switch, pH-tuning, film rehydration, hard template, electrostatic interaction, and polymerization-induced self-assembly (PISA). Subsequently, the biomedical applications of these nanoreactors in the fields of cancer imaging, cancer therapy, and cancer theranostics are highlighted. The last but not least, conclusions and future perspectives about polymeric nanoreactors are given. It is believed that polymeric nanoreactors can bring a great opportunity for future fabrication and clinical translation of precise nanomedicine.

Membrane reinforcement in giant hybrid polymer lipid vesicles achieved by controlling the polymer architecture

The physical properties of membranes of hybrid polymer lipid vesicles are so far relatively unknown. Since their discovery a decade ago, many studies have aimed to show their great potential in many fields of application, but so far, few systematic studies have been carried out to decipher the relationship between the molecular characteristics of the components (molar mass, chemical nature, and architecture of the copolymer), the membrane structure and its properties. In this work, we study the association of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and poly(dimethylsiloxane)-b-poly(ethylene oxide) (PDMS-b-PEO) diblock copolymers of different molar masses in giant hybrid vesicles and establish a complete phase diagram of the membrane structure. We also measured the mechanical properties of the giant hybrid unilamellar vesicle (GHUV) through micropipette aspiration at different lipid/polymer compositions. Thanks to a previous work using triblock PEO-b-PDMS-b-PEO copolymers, we were able to reveal the effect of the architecture of the block copolymer on membrane structure and properties. Besides, the association of diblock copolymers PDMS-b-PEO and POPC leads to the formation of hybrid vesicles with unprecedented membrane toughness.

Cell mimicry as a bottom-up strategy for hierarchical engineering of nature-inspired entities

Artificial biology is an emerging concept that aims to design and engineer the structure and function of natural cells, organelles, or biomolecules with a combination of biological and abiotic building blocks. Cell mimicry focuses on concepts that have the potential to be integrated with mammalian cells and tissue. In this feature article, we will emphasize the advancements in the past 3-4 years (2017-present) that are dedicated to artificial enzymes, artificial organelles, and artificial mammalian cells. Each aspect will be briefly introduced, followed by highlighting efforts that considered key properties of the different mimics. Finally, the current challenges and opportunities will be outlined. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Direct N-substituted N-thiocarboxyanhydride polymerization towards polypeptoids bearing unprotected carboxyl groups

Synthesis of poly(α-amino acid)s bearing carboxyl groups is a critical pathway to prepare biomaterials to simulate functional proteins. The traditional approaches call for carboxyl-protected monomers to prevent degradation of monomers or wrong linkage. In this contribution, we synthesize N-carboxypentyl glycine N-thiocarboxyanhydride (CPG-NTA) and iminodiacetic acid N-thiocarboxyanhydride (IDA-NTA) without protection. Initiated by amines, CPG-NTA directly polymerizes into polyCPG bearing unprotected carboxyl groups with controlled molecular weight (2.8-9.3 kg mol^-1) and low dispersities (1.08-1.12). Block and random copolymerizations of CPG-NTA with N-ethyl glycine N-thiocarboxyanhydride (NEG-NTA) demonstrate its versatile construction of complicated polypeptoids. On the contrary, IDA-NTA transforms amines into cyclic IDA dimer-capped species with carboxyl end group in decent yields (>89%) regio-selectively. Density functional theory calculation elucidates that IDA repeating unit is prone to cyclize to be the six-membered ring product with low ΔG. The polymer is a good adhesive reagent to various materials with adhesive strength of 33-229 kPa.

Interface Engineering in Multiphase Systems toward Synthetic Cells and Organelles: From Soft Matter Fundamentals to Biomedical Applications

Synthetic cells have a major role in gaining insight into the complex biological processes of living cells; they also give rise to a range of emerging applications from gene delivery to enzymatic nanoreactors. Living cells rely on compartmentalization to orchestrate reaction networks for specialized and coordinated functions. Principally, the compartmentalization has been an essential engineering theme in constructing cell-mimicking systems. Here, efforts to engineer liquid-liquid interfaces of multiphase systems into membrane-bounded and membraneless compartments, which include lipid vesicles, polymer vesicles, colloidosomes, hybrids, and coacervate droplets, are summarized. Examples are provided of how these compartments are designed to imitate biological behaviors or machinery, including molecule trafficking, growth, fusion, energy conversion, intercellular communication, and adaptivity. Subsequently, the state-of-art applications of these cell-inspired synthetic compartments are discussed. Apart from being simplified and cell models for bridging the gap between nonliving matter and cellular life, synthetic compartments also are utilized as intracellular delivery vehicles for nuclei acids and nanoreactors for biochemical synthesis. Finally, key challenges and future directions for achieving the full potential of synthetic cells are highlighted.

Near-Infrared-Induced Contractile Proteinosome Microreactor with a Fast Control on Enzymatic Reactions

Inspired by the compartmentalized structure of cells, self-regulating responsive hollow microcapsules are highly desirable for the modulation of enzymatic reactions. Here, we report a strategy to fabricate gold nanorod embedded proteinosomes by covalently grafting gold nanorods onto the surface of proteinosomes. The excellent photothermal conversion efficiency of the embedded gold nanorod and the thermal phase transition of the grafted PNIPAAm allow the constructed hybrid proteinosomes to show reversible contraction behaviors triggered by near-infrared light with the molecular weight cutoff of the membrane decreased to ca. 50 kDa, and importantly, the contraction frequency of the constructed proteinosomes could be as fast as 1 min and last for at least 15 cycles. Subsequently, the effective encapsulation of three cascade enzymes into the proteinosomes realizes the construction of a near-infrared responsive microreactor that allows control of the cascade reaction by near-infrared illumination, thereby enabling reversible on and off of the enzymatic reaction. Such microcapsule-based reactors demonstrate the potential to alter the membrane molecular weight cutoff, and it is believed that the development of such responsive microcapsules will have great potential for studying cellular responses and provide a platform for future applications in biosensing and drug delivery.

Polymer-Lipid Hybrid Vesicles and Their Interaction with HepG2 Cells

Polymer-lipid hybrid vesicles are an emerging type of nano-assemblies that show potential as artificial organelles among others. Phospholipids and poly(cholesteryl methacrylate)-block-poly(methionine methacryloyloxyethyl ester (METMA)-random-2-carboxyethyl acrylate (CEA)) labeled with a Förster resonance energy transfer (FRET) reporter pair are used for the assembly of small and giant hybrid vesicles with homogenous distribution of both building blocks in the membrane as confirmed by the FRET effect. These hybrid vesicles have no inherent cytotoxicity when incubated with HepG2 cells up to 1.1 × 10¹¹ hybrid vesicles per mL, and they are internalized by the cells. In contrast to the fluorescent signal originating from the block copolymer, the fluorescent signal coming from the lipids is barely detectable in cells incubated with hybrid vesicles for 6 h followed by 24 h in cell media, suggesting that the two building blocks have a different intracellular fate. These findings provide important insight into the design criteria of artificial organelles with potential structural integrity.

Thermoresponsive Polysaccharide Graft Polymer Vesicles with Tunable Size and Structural Memory

Controlling polymer vesicle size is difficult and a major obstacle for their potential use in biomedical applications, such as drug-delivery carriers and nanoreactors. Herein, we report size-tunable polymer vesicles based on self-assembly of a thermoresponsive amphiphilic graft copolymer. Unilamellar polymer vesicles form upon heating chilled polymer solutions, and vesicle size can be tuned in the range of 40-70 nm by adjusting the initial polymer concentration. Notably, the polymer can reversibly switch between a monomer state and a vesicle state in accordance with a cooling/heating cycle, which changes neither the size nor the size distribution of the vesicles. This lack of change suggests that the polymer memorizes a particular vesicle conformation. Given our vesicles' size tunability and structural memory, our research considerably expands the fundamental and practical scope of thermoresponsive amphiphilic graft copolymers and renders amphiphilic graft copolymers useful tools for synthesizing functional self-assembled materials.

Polypyrrole and polyaniline nanocomposites with high photothermal conversion efficiency

The simple and scalable synthesis of poly[2-(methacryloyloxy)ethyl phosphorylcholine] (PMPC)-coated conducting polymer (CP) nanocomposites is described. These functional nanocomposites exhibit tunable absorption in the near-infrared region with relatively high photothermal efficiencies. More importantly, their potential for bio-imaging and therapeutic treatment is proven by cellular uptake and cytotoxicity studies.

Manipulating Hybrid Nanostructures by the Cooperative Assembly of Amphiphilic Oligomers and Triblock Janus Nanoparticles

The cooperative assembly of nanoparticles and amphiphilic molecules has emerged as an appealing strategy for fabricating hybrid nanomaterials for a wide range of potential applications. However, it is challenging to precisely manipulate hybrid nanostructures. In this study, extensive dissipative particle dynamics simulations are carried out to investigate the cooperative assembly of amphiphilic oligomers and triblock Janus nanoparticles with different hydrophobic-hydrophilic patches. Three different hybrid nanostructures (networks, disks, and vesicles) are observed from the simulations. The structural characteristics and kinetic pathways are analyzed in detail. We reveal that the hydrophobic-hydrophilic patches in the triblock Janus nanoparticles significantly affect the arrangement of amphiphiles and nanoparticles, as well as the orientational degree of freedom between nanoparticles; therefore, the triblock Janus nanoparticles can function as a robust structure-directing agent to regulate the spatial organization of nanoparticles in networks, the curvature of disks, and the size of vesicles. This study demonstrates the cooperative assembly can serve as an efficient platform for the engineering of hybrid nanomaterials with tailored nanostructures.

Self-assembly of reversed bilayer vesicles through pnictogen bonding: water-stable supramolecular nanocontainers for organic solvents

A new air and moisture stable antimony thiolate compound has been prepared that spontaneously forms stable hollow vesicles. Structural data reveals that pnictogen bonding drives the self-assembly of these molecules into a reversed bilayer. The ability to make these hollow, spherical, and chemically and temporally stable vesicles that can be broken and reformed by sonication allows these systems to be used for encapsulation and compartmentalisation in organic media. This was demonstrated through the encapsulation and characterization of several small organic reporter molecules.