Protocells Featuring Membrane-Bound and Dynamic Membraneless Organelles

Living cells, especially eukaryotic ones, use multicompartmentalization to regulate intra- and extracellular activities, featuring membrane-bound and membraneless organelles. These structures govern numerous biological and chemical processes spatially and temporally. Synthetic cell models, primarily utilizing lipidic and polymeric vesicles, have been developed to carry out cascade reactions within their compartments. However, these reconstructions often segregate membrane-bound and membraneless organelles, neglecting their collaborative role in cellular regulation. To address this, we propose a structural design incorporating microfluidic-produced liposomes housing synthetic membrane-bound organelles made from self-assembled poly(ethylene glycol)-block-poly(trimethylene carbonate) nanovesicles and synthetic membraneless organelles formed via temperature-sensitive elastin-like polypeptide phase separation. This architecture mirrors natural cellular organization, facilitating a detailed examination of the interactions for a comprehensive understanding of cellular dynamics.

Frontier in gellan gum-based microcapsules obtained by emulsification: Core-shell structure, interaction mechanism, intervention strategies

As a translucent functional gel with biodegradability, non-toxicity and acid resistance, gellan gum has been widely used in probiotic packaging, drug delivery, wound dressing, metal ion adsorption and other fields in recent years. Because of its remarkable gelation characteristics, gellan gum is suitable as the shell material of microcapsules to encapsulate functional substances, by which the functional components can improve stability and achieve delayed release. In recent years, many academically or commercially reliable products have rapidly emerged, but there is still a lack of relevant reports on in-depth research and systematic summaries regarding the process of microcapsule formation and its corresponding mechanisms. To address this challenge, this review focuses on the formation process and applications of gellan gum-based microcapsules, and details the commonly used preparation methods in microcapsule production. Additionally, it explores the impact of factors such as ion types, ion strength, temperature, pH, and others present in the solution on the performance of the microcapsules. On this basis, it summarizes and analyzes the prospects of gellan gum-based microcapsule products. The comprehensive insights from this review are expected to provide inspiration and design ideas for researchers.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Dual-Drug Delivery by Anisotropic and Uniform Hybrid Nanostructures: A Comparative Study of the Function and Substrate-Drug Interaction Properties

By utilizing nanoparticles to upload and interact with several pharmaceuticals in varying methods, the primary obstacles associated with loading two or more medications or cargos with different characteristics may be addressed. Therefore, it is feasible to evaluate the benefits provided by co-delivery systems utilizing nanoparticles by investigating the properties and functions of the commonly used structures, such as multi- or simultaneous-stage controlled release, synergic effect, enhanced targetability, and internalization. However, due to the unique surface or core features of each hybrid design, the eventual drug-carrier interactions, release, and penetration processes may vary. Our review article focused on the drug's loading, binding interactions, release, physiochemical, and surface functionalization features, as well as the varying internalization and cytotoxicity of each structure that may aid in the selection of an appropriate design. This was achieved by comparing the actions of uniform-surfaced hybrid particles (such as core-shell particles) to those of anisotropic, asymmetrical hybrid particles (such as Janus, multicompartment, or patchy particles). Information is provided on the use of homogeneous or heterogeneous particles with specified characteristics for the simultaneous delivery of various cargos, possibly enhancing the efficacy of treatment techniques for illnesses such as cancer.

Poly(vinylpyridine)-Containing Block Copolymers for Smart, Multicompartment Particles

Multicompartment particles generated by the self-assembly of block copolymers (BCPs) have received considerable attention due to their unique morphologies and functionalities. A class of important building blocks for multicomponent particles...

Molecular modeling of interfacial layer-by-layer assembly towards functionalized capsule materials

Encapsulated nanomaterials, such as polymer-coated nanoemulsions, have highly tunable properties leading to versatile applications. A current lack of understanding of the fundamentals governing the choice of "capsule" materials (polyelectrolyte + surfactant) and its ensuing performance effectively precludes their widespread use. Computational methods can start to redress this by discovering molecule-scale attributes that significantly control the design of capsule materials tuned to fit desired properties. We use molecular dynamics (MD) to carry out the layer-by-layer (LbL) assembly of six unique polyelectrolyte bilayer systems at a surfactant-mediated interface, modeling early-stage capsule synthesis. Monolayer thickness is related to layer density and polyelectrolyte/surfactant interaction energy through polyelectrolyte molecular weight and radius of gyration, respectively, yielding a simple relationship between absorption kinetics and layer structure. For the second monolayer, faster absorption kinetics are observed for pairings of polyelectrolytes with similarly sized functional groups. Surfactants with a more delocalized charge on the head-group catalyze the build-up of ions at the interface, resulting in faster absorption kinetics and greater confinement of the encapsulated material but leading to thicker, less uniform bilayers. These relationships between capsule building block molecules and nanomaterial capsule properties provide a foundation for property prediction and rational design of optimized multi-functional capsule materials.

Organic/Inorganic Self-Assembled Hybrid Nano-Architectures for Cancer Therapy Applications

Since the conceptualization of nanomedicine, numerous nanostructure-mediated drug formulations have progressed into clinical trials for treating cancer. However, recent clinical trial results indicate such kind of drug formulations has a limited improvement on the antitumor efficacy. This is due to the biological barriers associated with those formulations, for example, circulation stability, extravasation efficiency in tumor, tumor penetration ability, and developed multi-drug resistance. When employing for nanomedicine formulations, pristine organic-based and inorganic-based nanostructures have their own limitations. Accordingly, organic/inorganic (O/I) hybrids have been developed to integrate the merits of both, and to minimize their intrinsic drawbacks. In this context, the recent development in O/I hybrids resulting from a self-assembly strategy will be introduced. Through such a strategy, organic and inorganic building blocks can be self-assembled via either chemical covalent bonds or physical interactions. Based on the self-assemble procedure, the hybridization of four organic building blocks including liposomes, micelles, dendrimers, and polymeric nanocapsules with five functional inorganic nanoparticles comprising gold nanostructures, magnetic nanoparticles, carbon-based materials, quantum dots, and silica nanoparticles will be highlighted. The recent progress of these O/I hybrids in advanced modalities for combating cancer, such as, therapeutic agent delivery, photothermal therapy, photodynamic therapy, and immunotherapy will be systematically reviewed.

Preparation of Salt-Responsive Hollow Hydrophilic Polymer Particles by Inverse Suspension Polymerization

Hydrophilic polymer particles with a hollow structure have potential applications such as carriers for hydrophilic drugs. However, there are few reports on preparation and morphology control of such particles via a simple method. In this study, hollow hydrophilic polymer particles were prepared by inverse suspension polymerization for water droplets containing 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) anions, 1-vinylimidazole (VIm) cations, oligo(ethylene glycol) diacrylate (OEGDA), dextran, and an initiator via the self-assembling phase-separated polymer (SaPSeP) method developed in our lab. The inner morphology of the particle could be controlled (as single- or multi-hollow structures) by changing the concentrations of the OEGDA and the dextran. The obtained hollow particles could encapsulate a hydrophilic fluorescent substance in their hollow region when the substance was added to the primary droplets before polymerization. In addition, the poly(AMPS-co-VIm-co-OEGDA) shell of the particles exhibited an ionic cross-linked structure, which could be stimulated by salt. The poly(AMPS-co-VIm-co-OEGDA) hollow particles with the encapsulated substance released the substance when salt was added to the dispersion. These results indicated that the applicability of the SaPSeP method can be broadened for morphology control of the hydrophilic polymer particles encapsulating water-soluble materials.

An investigation of alkaline phosphatase enzymatic activity after electrospinning and electrospraying

The high target specificity and multifunctionality of proteins has led to great interest in their clinical use. To this end, the development of delivery systems capable of preserving their bioactivity and improving bioavailability is pivotal to achieve high effectiveness and satisfactory therapeutic outcomes. Electrohydrodynamic (EHD) techniques, namely electrospinning and electrospraying, have been widely explored for protein encapsulation and delivery. In this work, monoaxial and coaxial electrospinning and electrospraying were used to encapsulate alkaline phosphatase (ALP) into poly(ethylene oxide) fibres and particles, respectively, and the effects of the processing techniques on the integrity and bioactivity of the enzyme were assessed. A full morphological and physicochemical characterisation of the blend and core-shell products was performed. ALP was successfully encapsulated within monolithic and core-shell electrospun fibres and electrosprayed particles, with drug loadings and encapsulation efficiencies of up to 21% and 99%, respectively. Monoaxial and coaxial electrospinning were equally effective in preserving ALP function, leading to no activity loss compared to fresh aqueous solutions of the enzyme. While the same result was observed for monoaxial electrospraying, coaxial electrospraying of ALP caused a 40% reduction in its bioactivity, which was attributed to the high voltage (22.5 kV) used during processing. This demonstrates that choosing between blend and coaxial EHD processing for protein encapsulation is not always straightforward, being highly dependent on the chosen therapeutic agent and the effects of the processing conditions on its bioactivity.

Formulation of Next-Generation Multicompartment Microcapsules by Reversible Electrostatic Attraction

The combination of several active substances into one carrier is often limited due to solubility, stability and phase-separation issues. These issues have been addressed by an innovative capsule design, in which nanocapsules are assembled on the microcapsule surface by electrostatic forces to form a pH-responsive hierarchical capsule@capsule system. Here, melamine-formaldehyde (MF) microcapsules with a negative surface charge were synthesized and coated with a novel MF-polyethyleneimine (PEI) copolymer to achieve a positive charge of ζ=+28 mV. This novel coating procedure allows the electrostatic assembly of negatively charged poly-l-lactide (PLLA, ζ=-19 mV) and poly-(lactide-co-glycolide) (PLGA, ζ=-56 mV) nanocapsules on the microcapsule surface. Assembly studies at pH 7 gave a partial surface coverage of PLLA nanocapsules and full surface coverage for PLGA nanocapsules. The pH-responsive adsorption and desorption of nanocapsules was shown at pH 7 and pH 3.

Hetero-network hydrogels crosslinked with silica nanoparticles for strategic control of thermal responsive property

Two thermoresponsive copolymers with different lower critical solution temperatures (LCSTs) were crosslinked using silica nanoparticles to afford hybrid hydrogels exhibiting two distinct thermo-responsivities. The thermo-responsive copolymers were synthesised by free radical polymerisation from a monomer with a reactive side chain (3-methacryloxypropyl trimethoxysilane (S)) and water-soluble monomers with different thermo-responsivities (N-isopropyl acrylamide (N) or N-(3-methoxy propyl)acrylamide (M)). The obtained reactive copolymers, poly(N-isopropyl acrylamide-co-3-methacryloxypropyl trimethoxysilane) (pNS) and poly(N-(3-methoxy propyl acrylamide-co-3-methacryloxypropyl trimethoxysilane)) (pMS), were characterized by multiple techniques including 1H NMR and FTIR spectroscopy. The hetero-network hybrid hydrogels were easily prepared by mixing aqueous solutions of the copolymer with an aqueous colloidal silica suspension; their gelation properties could be tuned by varying the amounts of pNS, pMS, and Si. Differential scanning calorimetric analysis showed that the hetero-network hydrogel exhibited a critical two-step phase transition at temperatures around the LCST of each copolymer (33 °C for pNS, 73 °C for pMS), indicating that each polymer does not disturb the phase transitions of the other. The deswelling of the hetero-network hydrogel could be controlled with respect to temperature and time.

Robust Damage-Reporting Strategy Enabled by Dual-Compartment Microcapsules

Dye-filled microcapsules are an attractive way to identify microscopic damage of materials by the naked eye. However, there are many disadvantages in traditional microcapsule-based self-reporting materials, such as a poor self-reporting effect. A new concept for the design of self-reporting microcapsules is presented here. Our work develops a novel kind of dual-compartmental microcapsule via Pickering emulsion photopolymerization, which can encapsulate two interacting species ("pro-dye" and "developer") separately in a single microcapsule. In our strategy, SiO₂ microspheres encapsulating polyetheramine (PEA, developer) were first prepared and employed as a Pickering emulsifier to stabilize oil-in-water emulsions, in which the oil phase consisted of 2',7'-dichlorofluorescein (DCF, pro-dye) and a monomer. After the monomer polymerization, a dual-compartment microcapsule, which encapsulated the pro-dye in the core and the developer in the shell, was obtained. Upon the rupture of the microcapsule, the pro-dye and the developer were released simultaneously and reacted to yield a pronounced chromogenic response. Compared with traditional double-microcapsule systems, this dual-compartment microcapsule system demonstrated a more efficient and pronounced self-reporting effect. This is the first time that a double-encapsulation scheme involving the compartmentalized release of two interacting species within a single microcapsule has been demonstrated for self-reporting, which overcomes the tough problems of the uneven distribution of the traditional double-microcapsule systems.

A novel self-templating strategy for facile fabrication of monodisperse polymeric microporous capsules with a tunable hollow structure

The self-templating fabrication of monodisperse polymeric microporous capsules with a tunable hollow structure for gas storage, efficient iodine capture and heterogeneous catalysis.

Construction of coacervate-in-coacervate multi-compartment protocells for spatial organization of enzymatic reactions

Coacervate microdroplets, formed via liquid–liquid phase separation, have been extensively explored as a compartment model for the construction of artificial cells or organelles. In this study, coacervate-in-coacervate multi-compartment protocells were constructed using four polyelectrolytes, in which carboxymethyl-dextran and diethylaminoethyl-dextran were deposited on the surface of as-prepared polydiallyldimethyl ammonium/deoxyribonucleic acid coacervate microdroplets through layer-by-layer assembly. The resulting multi-compartment protocells were composed from two immiscible coacervate phases with distinct physical and chemical properties. Molecule transport experiments indicated that small molecules could diffuse between two coacervate phases and that macromolecular enzymes could be retained. Furthermore, a competitive cascade enzymatic reaction of glucose oxidase/horseradish peroxidase–catalase was performed in the multi-compartment protocells. The different enzyme organization and productions of H₂O₂ led to a distinct polymerization of dopamine. The spatial organization of different enzymes in immiscible coacervate phases, the distinct reaction fluxes between coacervate phases, and the enzymatic cascade network led to distinguishable signal generation and product outputs. The development of this multi-compartment structure could pave the way toward the spatial organization of multi-enzyme cascades and provide new ideas for the design of organelle-containing artificial cells.

A coacervate-in-coacervate micro-architecture is constructed as a multi-compartment protocell model, in which a multi-enzyme cascade is spatially organized for competitive enzymatic reactions.

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.

Microfluidics for Biosynthesizing: from Droplets and Vesicles to Artificial Cells

Fabrication of artificial biomimetic materials has attracted abundant attention. As one of the subcategories of biomimetic materials, artificial cells are highly significant for multiple disciplines and their synthesis has been intensively pursued. In order to manufacture robust "alive" artificial cells with high throughput, easy operation, and precise control, flexible microfluidic techniques are widely utilized. Herein, recent advances in microfluidic-based methods for the synthesis of droplets, vesicles, and artificial cells are summarized. First, the advances of droplet fabrication and manipulation on the T-junction, flow-focusing, and coflowing microfluidic devices are discussed. Then, the formation of unicompartmental and multicompartmental vesicles based on microfluidics are summarized. Furthermore, the engineering of droplet-based and vesicle-based artificial cells by microfluidics is also reviewed. Moreover, the artificial cells applied for imitating cell behavior and acting as bioreactors for synthetic biology are highlighted. Finally, the current challenges and future trends in microfluidic-based artificial cells are discussed. This review should be helpful for researchers in the fields of microfluidics, biomaterial fabrication, and synthetic biology.

Fabrication and application of complex microcapsules: a review

The development of new functional materials requires cutting-edge technologies for incorporating different functional materials without reducing their functionality. Microencapsulation is a method to encapsulate different functional materials at nano- and micro-scales, which can provide the necessary protection for the encapsulated materials. In this review, microencapsulation is categorized into chemical, physical, physico-chemical and microfluidic methods. The focus of this review is to describe these four categories in detail by elaborating their various microencapsulation methods and mechanisms. This review further discusses the key features and potential applications of each method. Through this review, the readers could be aware of many aspects of this field from the fabrication processes, to the main properties, and to the applications of microcapsules.

The construction of thiol-functionalized DNAsomes with small molecules response and protein release

In this work, a poly(N-isopropylacrylamide) polymer (PNIPAAm) was prepared via the photoinduced reversible addition-fragmentation chain transfer (RAFT) polymerization using Ru(bpy)₃Cl₂·6H₂O as photoinitiator. The design and spontaneous assembly of thiol-functionalized DNA-Thiol/PNIPAAm polymeric capsule (DNAsomes) by water-in-oil Pickering emulsion method and effective response with small molecules (Sybr green and phenanthrene) were described. The intermediate product, DNA-Thiol/PNIPAAm conjugates and DNAsomes were characterized by using ¹H NMR, dynamic light scattering (DLS), SEM, TEM and UV-vis methods. The obtained results indicated that DNA-Thiol/PNIPAAm constructs assembled in a Pickering emulsion could produce DNA-based spherical DNAsomes with typically 3.3-267.7 μm in diameter. The DNAsomes showed a vesicle formation approximately 2 μm in diameter, resulting in phenanthrene molecule intercalating with DNAsomes. The phenomenon indicated that the DNA-Thiol/PNIPAAm conjugates may have potential applications in recognition polycyclic aromatic hydrocarbon molecules. The membrane of the DNAsomes could effective response toward small molecules such as Sybr green or phenanthrene, and DNAsomes has release capability of protein (BSA) under reductive agent glutathione (GSH). Our results highlight the potential of integrating aspects of supramolecular and polymer chemistry into the design and construction of DNA-polymeric capsule, guest molecule encapsulation, control delivery of drugs, recognition organic polycyclic aromatic hydrocarbon molecules and gene-directed capsule synthesis.

Reductively Responsive Gel Capsules Prepared Using a Water-Soluble Zwitterionic Block Copolymer Emulsifier

Utilizing the unique solubility of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), which is soluble in only water and alcohol, we synthesized a water-soluble block copolymer emulsifier composed of a hydrophilic PMPC block and an amphiphilic poly[oligo(ethylene glycol) methacrylate] (POEGMA) block via reversible addition-fragmentation chain transfer (RAFT) polymerization. Water-in-oil (W/O) emulsions were successfully formed in the presence of the resulting PMPC- b-POEGMA, which acted as a stabilizer of water droplets in a chloroform continuous phase because the PMPC and POEGMA blocks were distributed to the water and chloroform phases, respectively. Next, the amphiphilic poly[poly(ethylene glycol) methacrylate] (PPEGMA) gel layer, which contained bis(2-methacryloyl)oxyethyl disulfide as a reductively responsive cross-linker, was prepared by inverse miniemulsion periphery RAFT polymerization from the PMPC- b-POEGMA that stabilized the W/O emulsions. The resulting PPEGMA gel capsules were colloidally stable in not only chloroform but also water without additional hydrophilic surface modification. The drug-release behavior from the PPEGMA gel capsules in response to dithiothreitol (DTT), which is a reducing agent, was investigated using fluorescein-conjugated dextran (FITC-Dex) as a model drug. The FITC-Dex release rate from the gel capsules in a phosphate buffer solution (pH 7.4, 20 mM) with DTT was fast compared to that without DTT. The reductively responsive FITC-Dex release is attributed to the cleavage of disulfide bonds that act as cross-links in the PPEGMA gel layer. The fascinating properties of the PPEGMA gel capsules suggest that they can provide a useful platform for designing drug carriers for protein and gene delivery and nanobioreactors.

Recent Trends in Metallopolymer Design: Redox-Controlled Surfaces, Porous Membranes, and Switchable Optical Materials Using Ferrocene-Containing Polymers

Metallopolymers with metal functionalities are a unique class of functional materials. Their redox-mediated optoelectronic and catalytic switching capabilities, their outstanding structure formation and separation capabilities have been reported recently. Within this Minireview, the scope and limitations of intriguing ferrocene-containing systems will be discussed. In the first section recent advances in metallopolymer design will be given leading to a plethora of novel metallopolymer architectures. Discussed synthetic pathways comprise controlled and living polymerization protocols as well as surface immobilization strategies. In the following sections, we focus on recent advances and new applications for side-chain and main-chain ferrocene-containing polymers as (i) remote-switchable materials, (ii) smart surfaces, (iii) redox-responsive membranes, and some recent trends in (iv) photonic structures and (v) other optical applications.

Biomimetic Membranes as a Technology Platform: Challenges and Opportunities

Biomimetic membranes are attracting increased attention due to the huge potential of using biological functional components and processes as an inspirational basis for technology development. Indeed, this has led to several new membrane designs and applications. However, there are still a number of issues which need attention. Here, I will discuss three examples of biomimetic membrane developments within the areas of water treatment, energy conversion, and biomedicine with a focus on challenges and applicability. While the water treatment area has witnessed some progress in developing biomimetic membranes of which some are now commercially available, other areas are still far from being translated into technology. For energy conversion, there has been much focus on using bacteriorhodopsin proteins, but energy densities have so far not reached sufficient levels to be competitive with state-of-the-art photovoltaic cells. For biomedical (e.g., drug delivery) applications the research focus has been on the mechanism of action, and much less on the delivery 'per se'. Thus, in order for these areas to move forward, we need to address some hard questions: is bacteriorhodopsin really the optimal light harvester to be used in energy conversion? And how do we ensure that biomedical nano-carriers covered with biomimetic membrane material ever reach their target cells/tissue in sufficient quantities? In addition to these area-specific questions the general issue of production cost and scalability must also be treated in order to ensure efficient translation of biomimetic membrane concepts into reality.

Nanoencapsulation of phase change materials for advanced thermal energy storage systems

Phase change materials (PCMs) allow the storage of large amounts of latent heat during phase transition. They have the potential to both increase the efficiency of renewable energies such as solar power through storage of excess energy, which can be used at times of peak demand; and to reduce overall energy demand through passive thermal regulation. 198.3 million tons of oil equivalent were used in the EU in 2013 for heating. However, bulk PCMs are not suitable for use without prior encapsulation. Encapsulation in a shell material provides benefits such as protection of the PCM from the external environment and increased specific surface area to improve heat transfer. This review highlights techniques for the encapsulation of both organic and inorganic PCMs, paying particular attention to nanoencapsulation (capsules with sizes <1 μm). We also provide insight on future research, which should focus on (i) the development of multifunctional shell materials to improve lifespan and thermal properties and (ii) advanced mass manufacturing techniques for the economically viable production of PCM capsules, making it possible to utilize waste heat in intelligent passive thermal regulation systems, employing controlled, "on demand" energy release/uptake.

Preparation and application of flavor and fragrance capsules

The preparation methods and applications of flavor and fragrance capsules based on polymeric, inorganic and polymeric–inorganic wall materials are summarized.

Fabrication of polymer capsules by an original multifunctional, active, amphiphilic macromolecule, and its application in preparing PCM microcapsules

Based on our recent discovery that D-PGMA solution showed excellent amphiphilic and reinitiation properties, an eco-friendly, facile and scalable method to prepare polymeric capsules was proposed.

Dual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) copolymer micromicelles: surface RAFT synthesis, self-assembly and drug release applications

BACKGROUND

Stimuli-responsive polymer materials are a new kind of intelligent materials based on the concept of bionics, which exhibits more significant changes in physicochemical properties upon triggered by tiny environment stimuli, hence providing a good carrier platform for antitumor drug delivery.

RESULTS

Dual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) block copolymers (Fe3O4-g-PAA-b-PMAEFC) were engineered and synthesized through a two-step sequential reversible addition-fragmentation chain transfer polymerization route. The characterization was performed by FTIR, 1H NMR, SEC, XRD and TGA techniques. The self-assembly behavior in aqueous solution upon triggered by pH, magnetic and redox stimuli was investigated via zeta potentials, vibration sample magnetometer, cyclic voltammetry, fluorescent spectrometry, dynamic light scattering, XPS, TEM and SEM measurements. The experimental results indicated that the Fe3O4-g-PAA-b-PMAEFC copolymer materials could spontaneously assemble into hybrid magnetic copolymer micromicelles with core-shell structure, and exhibited superparamagnetism, redox and pH stimuli-responsive features. The hybrid copolymer micromicelles were stable and nontoxic, and could entrap hydrophobic anticancer drug, which was in turn swiftly and effectively delivered from the drug-loaded micromicelles at special microenvironments such as acidic pH and high reactive oxygen species.

CONCLUSION

This class of stimuli-responsive copolymer materials is expected to find wide applications in medical science and biology, etc., especially in drug delivery system.

Tunable Permeability of Cross-Linked Microcapsules from pH-Responsive Amphiphilic Diblock Copolymers: A Dissipative Particle Dynamics Study

Using dissipative particle dynamics simulation, we probe the tunable permeability of cross-linked microcapsules made from pH-sensitive diblock copolymers poly(ethylene oxide)-b-poly(N,N-diethylamino-2-ethyl methacrylate) (PEO-b-PDEAEMA). We first examine the self-assembly of non-cross-linked microcapsules and their pH-responsive collapse and then explore the effects of cross-linking and block interaction on the swelling or deswelling of cross-linked microcapsules. Our results reveal a preferential loading of hydrophobic dicyclopentadiene (DCPD) molecules in PEO-b-PDEAEMA copolymers. Upon reduction of pH, non-cross-linked microcapsules fully decompose into small wormlike clusters as a result of large self-repulsions of protonated copolymers. With increasing degree of cross-linking, the morphology of the microcapsule becomes more stable to pH change. The highly cross-linked microcapsule shell undergoes significant local polymer rearrangement in acidic solution, which eliminates the amphiphilicility and therefore enlarges the permeability of the shell. The responsive cross-linked shell experiences a disperse-to-buckle configurational transition upon reduction of pH, which is effective for the steady or pulsatile regulation of shell permeability. The swelling rate of the cross-linked shell is dependent on both electrostatic and nonelectrostatic interactions between the pH-sensitive groups as well as the other groups. Our study highlights the combination of cross-linking structure and block interactions in stabilizing microcapsules and tuning their selective permeability.

Hollow polymer particles: a review

Herein, the basic principles, such as the definitions, classifications, and properties, of hollow polymer particles (HPPs) are critically investigated.

Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields.

Multi-stimuli responsive block copolymers as a smart release platform for a polypyridyl ruthenium complex

An efficient protocol for the preparation of poly(N,N-dimethylaminoethyl methacrylate)(PDMAEMA)-based multi-stimuli responsive block copolymers (BCPs) with poly(methyl methacrylate) (PMMA)viaanionic polymerization protocols is presented.

Programmable Modulation of Membrane Permeability of Proteinosome upon Multiple Stimuli Responses

Membrane permeability is a necessary and overarching attribute for all the hollow microcompartments toward the application as nanoreactors or artificial cells. Differing from the widely reported various stimuli models, in this study we describe a way to generate a multistimuli proteinosome capable of being triggered in sequence of temperature, redox species, and pH, thus, showing a continuous modulation on the membrane permeability. Studies showed that the molecular weight cutoff of the constructed proteinosome membrane could be continuously turned up from 78 to 102 kDa and to 142 kDa, and then turned down to 35.2 kDa upon different stimuli. As a proof of concept, such continuous modulated behavior allows a well-controlled programmed release upon the encapsulation of a FITC-labeled dextran into proteinosomes. It is anticipated that such designed proteinosomes equipped with programmed modulation of membrane permeability are promising candidates for the further development of artificial model design, such as cellular communication or metabolism in which stuff exchange is required to support in situ procedures.

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.

Controllable Multicompartmental Capsules with Distinct Cores and Shells for Synergistic Release

A facile and flexible approach is developed for controllable fabrication of novel multiple-compartmental calcium alginate capsules from all-aqueous droplet templates with combined coextrusion minifluidic devices for isolated coencapsulation and synergistic release of diverse incompatible components. The multicompartmental capsules exhibit distinct compartments, each of which is covered by a distinct part of a heterogeneous shell. The volume and number of multiple compartments can be well-controlled by adjusting flow rates and device numbers for isolated and optimized encapsulation of different components, while the composition of different part of the heterogeneous shell can be individually tailored by changing the composition of droplet template for flexibly tuning the release behavior of each component. Two combined devices are first used to fabricate dual-compartmental capsules and then scaled up to fabricate more complex triple-compartmental capsules for coencapsulation. The synergistic release properties are demonstrated by using dual-compartmental capsules, which contain one-half shell with a constant release rate and the other half shell with a temperature-dependent release rate. Such a heterogeneous shell provides more flexibilities for synergistic release with controllable release sequence and release rates to achieve advanced and optimized synergistic efficacy. The multicompartmental capsules show high potential for applications such as drug codelivery, confined reactions, enzyme immobilizations, and cell cultures.

A triblock terpolymer vs. blends of diblock copolymers for nanocapsules addressed by three independent stimuli

The chemical structure of triblock terpolymers is exploited to achieve polymer nanocapsules responsive to three different stimuli.

Synthesis of amphiphilic block-type macromolecular brushes with cleavable pendant chains and fabrication of micelle-templated polymer nanocapsules

Macromolecular brushes with cleavable pendant chains were synthesized by controlled free radical polymerizations and functional nanocapsules were fabricated on the basis of the brush polymers.