Hybrid nanostructured particles via surfactant-free double miniemulsion polymerization

Morphology Control of Polymer-Inorganic Hybrid Nanomaterials Prepared in Miniemulsion: From Solid Particles to Capsules

The preparation of so-called hybrid nanomaterials has been widely developed in terms of functional and morphological complexity. However, the specific control of the arrangement of organic and inorganic species, which determines the properties of the final material, still remains a challenge. This article offers a review of the strategies that have been used for the preparation of polymer-inorganic hybrid nanoparticles and nanocapsules via processes involving miniemulsions. Different polymer-inorganic nanostructures are classified into four main groups according to the sequential order followed between the synthesis of the polymer and the inorganic species, and the presence or not of their counterpart precursors. The minimization of the energy of the system governs the self-assembly of the different material components and can be addressed by the miniemulsion formulation to reduce the interfacial tensions between the phases involved. The state of the art in the preparation of hybrid nanoparticles is reviewed, offering insight into the structural possibilities allowed by miniemulsion as a versatile synthetic technique.

High-Performance Membranes Based on Spherical-Beaded Nanofibers and Nanoarchitectured Networks for Water-in-Oil Emulsion Separation

High-performance separation materials for oil-water emulsions are crucial to environmental protection and resource recovery; however, most existing fibrous separation materials are subject to large pore size and low porosity, resulting in limited separation performance. Herein, we create high-performance membranes consisting of spherical-beaded nanofibers and nanoarchitectured networks (nano-nets) using electrostatic spinning/netting technology, for water-in-oil emulsion separation. By manipulating the nonequilibrium stretching of jets, spherical-beaded nanofibers capable of generating a robust microelectric field are fabricated as scaffolds, on which charged droplets are induced to eject and phase separate to self-assemble nano-nets with small pores. Benefiting from 3D undulating networks with cavities originating from 2D nano-nets supported by 1D spherical-beaded nanofibers, the membranes exhibit under-oil superhydrophobicity (>152°), a striking separation performance with an efficiency of >99.2% and a flux of 5775 L m-2 h-1, together with wide pressure applicability, antifouling, and reusability. This work may open up new horizons in developing fibrous materials for separation and purification.

Pickering Emulsions Biocatalysis: Recent Developments and Emerging Trends

Biocatalysis within biphasic systems is gaining significant attention in the field of synthetic chemistry, primarily for its ability to solve the problem of incompatible solubilities between biocatalysts and organic compounds. By forming an emulsion from these two-phase systems, a larger surface area is created, which greatly improves the mass transfer of substrates to the biocatalysts. Among the various types of emulsions, Pickering emulsions stand out due to their excellent stability, compatibility with biological substances, and the ease with which they can be formed and separated. This makes them ideal for reusing both the emulsifiers and the biocatalysts. This review explores the latest developments in biocatalysis using Pickering emulsions. It covers the structural features, methods of creation, innovations in flow biocatalysis, and the role of interfaces in these processes. Additionally, the challenges and future directions are discussed in combining chemical and biological catalysts within Pickering emulsion frameworks to advance synthetic methodologies.

Nucleation-Inhibited Emulsion Interfacial Assembled Polydopamine Microvesicles as Artificial Antigen-Presenting Cells

Albeit microemulsion systems have emerged as efficient platforms for fabricating tunable nano/microstructures, lack of understanding on the emulsion-interfacial assembly hindered the control of fabrication. Herein, a nucleation-inhibited microemulsion interfacial assembly method is proposed, which deviates from conventional interfacial nucleation approaches, for the synthesis of polydopamine microvesicles (PDA MVs). These PDA MVs exhibit an approximate diameter of 1 µm, showcasing a pliable structure reminiscent of cellular morphology. Through modifications of antibodies on the surface of PDA MVs, their capacity as artificial antigen presentation cells is evaluated. In comparison to solid nanoparticles, PDA MVs with cell-like structures show enhanced T-cell activation, resulting in a 1.5-fold increase in CD25 expression after 1 day and a threefold surge in PD-1 positivity after 7 days. In summary, the research elucidates the influence of nucleation and interfacial assembly in microemulsion polymerization systems, providing a direct synthesis method for MVs and substantiating their effectiveness as artificial antigen-presenting cells.

Polymerization-Induced Hierarchical Hybrid Particles from Siloxane Emulsification Endowing Polyurethane Composite Coating with Superhydrophobicity, Thermal Insulation, and Fluorescence

Hierarchically structural particles (HSPs) are highly regarded as favorable nanomaterials for superhydrophobic coating due to their special multiscale structure and surface physicochemical properties. However, most of the superhydrophobic coatings constructed from HSPs are monofunctional, constraining their broader applications. Moreover, traditional methods for constructing HSPs mostly rely on complicated chemical routes and template removal. Herein, we propose an innovative strategy (one-pot method) for producing multifunctional hierarchical hybrid particles (HHPs). Polysilsesquioxane (PSQ), generated from hydrolysis condensation of methyltriethoxylsilane, is used as the sole stabilizer to anchor on the surface of styrene and short fluoroalkyl compound tridecafluorooctyl acrylate comonomers droplets, forming a mesoporous PSQ shell. Subsequently, the comonomers inside of the shell perform restricted polymerization to generate the HHP due to the driving of the mesoporous capillary force. The HHP is then mixed with waterborne polyurethane (WPU) to develop a robust nanocomposite coating (WPU-HHP). Through the deliberate design of the HHP components, the WPU-HHP coating has thermal insulation, photoluminescence properties, and the ability to achieve a wettability transition during abrasion. Our research has achieved the integration of multifunctionality in one waterborne hybrid system, broadening the application areas of nanocomposite coatings.

Shape-Tunable Hollow Polysiloxane Nanoparticles Based on a Surfactant-Free Soft Templating Method and Their Application as a Drug Carrier

A surfactant-free soft-templating method has been used to prepare polysiloxane hollow nanoparticles with a controllable shape. This method is simple and has the potential for large-scale preparation. For the first time, we successfully obtained hollow polysiloxane nanoparticles with different shapes, including eccentric hollow polysiloxane microspheres (EHPM), apple-like hollow polysiloxane microparticles (AHPM), and bowl-like hollow polysiloxane microparticles (BHPM), by simply changing the solvent. In this method, the hydrolyzed methyltriethoxysilane (MTES) not only stabilizes the system as a surfactant but also acts as a reactant for subsequent reactions, so no additional surfactant is needed. In addition, the formation mechanism of hollow polysiloxane microparticles with different shapes is also proposed: that is, MTES hydrolyzed under acidic conditions to form a surfactant, which changes the system from suspension to a stable oil-in-water emulsion. Then, under alkaline conditions, the hydrolyzed MTES polycondenses and nucleates at the oil-water interface. At the same time, with the process of polycondensation, the hydrolyzed MTES will migrate to the nucleation site driven by surface tension, thus forming an eccentric core/shell (solvent/polysiloxane) structure. Due to the different forces between hydrolyzed MTES and different solvents, the deviation degree of hollow in microspheres is different, thus forming particles with various morphologies. This synthesis method provides a new idea for the preparation of shapeable anisotropic hollow structures. Finally, we use AHPM to study the application of the drug load. The results show that the prepared hollow polysiloxane particles have a good drug loading capacity and release performance. It can be predicted that the shape-tunable hollow polysiloxane particles prepared by this method have broad application prospects in the field of drug delivery.

Surface Tension-Induced Eccentric Hollow Polysiloxane Microspheres in a Surfactant-Free System and Their Applications as a Nanoreactor and Nanomotor

Eccentric hollow polysiloxane microspheres (EHPMs) have attracted significant attention due to their potential in energy storage, drug delivery, and heterogeneous catalysis applications. However, their preparation pathways are often particularly complex. Therefore, it is critical to find a simple method for preparing EHPMs. In this study, a surfactant-free emulsification method is proposed to prepare EHPM. Under acidic conditions, methyl triethoxysilane (MTES) is hydrolyzed at the oil-water interface, with the hydrolyzed MTES demonstrating amphiphilic properties, and it could be anchored on the xylene surface to form an oil-in-water emulsion. The solution, when adjusted to alkaline, nucleated from a point at the oil-water interface. Driven by the surface tension, the hydrolyzed MTES migrated to the nucleation site with decreasing hydrophilicity. As a result, an EHPM formed. This process provides a simple, low cost, and environmentally friendly strategy for the preparation of EHPM, which demonstrated potential in catalytic and nanomotor applications.

pH-Switchable Pickering miniemulsion enabled by carbon quantum dots for quasi-homogenized biphasic catalytic system

A quasi-homogenized miniemulsion system enabled by carbon quantum dot solid nanoparticles for biphasic catalysis is proposed, which breaks existing limits for an immiscibly biphasic system and overcomes issues for large-sized solid particle-stabilized emulsion droplets. The presented Pickering miniemulsion features pH-responsive behavior, finally triggering facile product separation and catalyst recycling in one reaction vessel.

Steric Effects in the Deposition Mode and Drug-Delivering Efficiency of Nanocapsule-Based Multilayer Films

Using surface-initiated atom transfer radical polymerization (ATRP), block polymers with a series of quaternization degrees were coated on the surface of silica nanocapsules (SNCs) by the "grafting-from" technique. Molnupiravir, an antiviral medicine urgently approved for the treatment of SARS-CoV-2, was encapsulated in polymer-coated SNCs and further incorporated into well-defined films with polystyrene sulfonate (PSS) homopolymers by layer-by-layer (LBL) self-assembly via electrostatic interactions. We investigated the impact of the quaternization degree of the polymers and steric hindrance of functional groups on the growth mode, swelling/deswelling transition, and drug-delivering efficiency of the obtained LBL films. The SNCs were derived from coronas of parent block polymers of matched molecular weights-poly(N-isopropylacrylamide)-block-poly(N,N-dimethylaminoethyl methacrylate) (PNIPAM-b-PDMAEMA)-by quaternization with methyl sulfate. As revealed by the data results, SNCs with coronas with higher quaternization degrees resulted in a larger layering distance of the film structure because of weaker ionic pairing (due to the presence of a bulky methyl spacer) between SNCs and PSS. Interestingly, when comparing the drug release profile of the encapsulated drugs from SNC-based films, the release rate was slower in the case of capsule coronas with higher quaternization degrees because of the larger diffusion distance of the encapsulated drugs and stronger hydrophobic-hydrophobic interactions between SNCs and drug molecules.

Rapid and efficient oil removal from O/W emulsions by hydrophobic porous polystyrene microspheres embedded with hydrophilic surface micro-regions

Inspired by Namib Desert beetle's back which is patterned with different wetting properties, hydrophobic porous polystyrene microspheres embedded with hydrophilic surface micro-regions (HPHs) were designed and fabricated by the radical copolymerization in the W₁/O/W₂ double Pickering emulsions with high internal water phase. The synergistic effect of the hydrophobic surface and the hydrophilic surface micro-regions results in HPHs exhibiting superior performances for separating both surfactant-free and surfactant-stabilized O/W emulsions. After 60 s hand-shaking, the oil was absorbed and stored within HPHs which could be separated from the water using a 600-mesh sieve, and the TOC values of purified water could be reduced to 2.06 ± 0.06-67.38 ± 2.02 ppm when the initial oil content was 1 vol%. Meanwhile, HPHs could be recovered and reused through a simple treatment. The excellent oil removal efficiency was kept even after 50 cycles. High oil removal efficiency, general applicability, easy operation and excellent recyclability endow HPHs with great potential for practical applications. And this work provides a facile and general way to prepare porous polymer microspheres with wettability contrast surfaces.

Immunoprofiling of Severity and Stage of Bacterial Infectious Diseases by Ultrabright Fluorescent Nanosphere-Based Dyad Test Strips

Bacterial infectious diseases are common clinical diseases that seriously threaten human health, especially in countries and regions with poor environmental hygiene. Due to the lack of characteristic clinical symptoms and signs, it is a challenge to distinguish a bacterial infection from other infections, leading to misdiagnosis and antibiotic overuse. Therefore, there is an urgent need to develop a specific method for detection of bacterial infections. Herein, utilizing ultrabright fluorescent nanospheres (FNs) as reporters, immunochromatographic dyad test strips are developed for the early detection of bacterial infections and distinction of different stages of bacterial infectious diseases in clinical samples. C-reactive protein (CRP) and heparin-binding protein (HBP) are quantified and assayed because their levels in plasma are varied dynamically and asynchronously during the progression of the disease. The detection limits of CRP and HBP can reach as low as 0.51 and 0.65 ng/mL, respectively, due to the superior fluorescence intensity of each FN, which is 570 times stronger than that of a single quantum dot. The assay procedure can be achieved in 22 min, fully meeting the needs of rapid and ultrasensitive detection in the field. This constructed strip has been successfully used to profile the stage and severity of bacterial infections by monitoring the levels of CRP and HBP in human plasma samples, showing great potential as a point-of-care biosensor for clinical diagnosis. In addition to bacterial infections, the developed ultrabright FN-based point-of-care testing can be readily expanded for rapid, quantitative, and ultrasensitive detection of other trace substances in complex systems.

Silica-Based Core-Shell Nanocapsules: A Facile Route to Functional Textile

In this work, we present a surfactant-free miniemulsion approach to obtain silica-based core-shell nanocapsules with a phase change material (PCM) core via in-situ hydrolytic polycondensation of precursor hyperbranched polyethoxysiloxanes (PEOS) as silica shells. The obtained silica-based core-shell nanocapsules (PCM@SiO2), with diameters of ~400 nm and silica shells of ~14 nm, reached the maximum core content of 65%. The silica shell had basically no significant influence on the phase change behavior of PCM, and the PCM@SiO2 exhibited a high enthalpy of melt and crystallization of 123–126 J/g. The functional textile with PCM@SiO2 has been proposed with thermoregulation and acclimatization, ultraviolet (UV) resistance and improved mechanical properties. The thermal property tests have shown that the functional textile had good thermal stability. The functional textile, with a PCM@SiO2 concentration of 30%, was promising, with enthalpies of melting and crystallization of 27.7 J/g and 27.8 J/g, and UV resistance of 77.85. The thermoregulation and ultraviolet protection factor (UPF) value could be maintained after washing 10 times, which demonstrated that the functional textile had durability. With good thermoregulation and UV resistance, the multi-functional textile shows good prospects for applications in thermal comfort and as protective and energy-saving textile.

Microemulsions: Unique Properties, Pharmacological Applications, and Targeted Drug Delivery

Microemulsions, comprising oil, water and a surfactant, in association with some co-surfactant, are thermodynamically stable systems. They have found applications in a large number of chemical and pharmacological processes due to their unique properties such as large interfacial area, low interfacial tension, and most importantly, the ability to solubilize and deliver hydrophobic drugs. In addition to the oral and intravenous route, they are suitable for drug delivery through the ophthalmic, vaginal, pulmonary, dental, and topical routes. This review highlights the properties and several recent developments in the use of microemulsions for medical treatment purposes including targeted drug delivery.

Fundamentals and Design-Led Synthesis of Emulsion-Templated Porous Materials for Environmental Applications

Emulsion templating is at the forefront of producing a wide array of porous materials that offers interconnected porous structure, easy permeability, homogeneous flow-through, high diffusion rates, convective mass transfer, and direct accessibility to interact with atoms/ions/molecules throughout the exterior and interior of the bulk. These interesting features together with easily available ingredients, facile preparation methods, flexible pore-size tuning protocols, controlled surface modification strategies, good physicochemical and dimensional stability, lightweight, convenient processing and subsequent recovery, superior pollutants remediation/monitoring performance, and decent recyclability underscore the benchmark potential of the emulsion-templated porous materials in large-scale practical environmental applications. To this end, many research breakthroughs in emulsion templating technique witnessed by the recent achievements have been widely unfolded and currently being extensively explored to address many of the environmental challenges. Taking into account the burgeoning progress of the emulsion-templated porous materials in the environmental field, this review article provides a conceptual overview of emulsions and emulsion templating technique, sums up the general procedures to design and fabricate many state-of-the-art emulsion-templated porous materials, and presents a critical overview of their marked momentum in adsorption, separation, disinfection, catalysis/degradation, capture, and sensing of the inorganic, organic and biological contaminants in water and air.

Fabrication of microcapsules with core-shell structure for oral delivery of dual drugs and real-time computed tomography imaging

Although multidrug combinations are an effective therapeutic strategy for serious disease in clinical practice, their therapeutic effect may be reduced because they conflict with each other medicinally in certain cases. Hence, there is an urgent need to develop a single drug carrier for precise multidrug delivery to avoid this interference. A reverse coordination method is reported that fabricates a double‐layer barium sulphate microcapsule (DL@BS MS) for two drugs separately loading simultaneously. In addition, BS nanoclusters were synthesised in situ inside the DL@BS MSs for real‐time computed tomography (CT) imaging. The results showed that the DL@BS MSs with a particle size of approximately 2 mm exhibited a uniform sphere. Because BS nanoclusters have a high X‐ray attenuation coefficient, the retention of DL@BS MSs in the digestive tract could be monitored through CT imaging in real time. More important, the core‐shell structure of DL@BS MSs encapsulating two different drugs could be released in spatiotemporal order in an acidic stomach environment. The as‐synthesis DL@BS MSs with a core‐shell structure and real‐time imaging performance provide an ideal carrier for the oral administration of multiple drugs simultaneously loaded but sequentially released.

In vivo targeted delivery of nucleic acids and CRISPR genome editors enabled by GSH-responsive silica nanoparticles

The rapid development of gene therapy and genome editing techniques brings up an urgent need to develop safe and efficient nanoplatforms for nucleic acids and CRISPR genome editors. Herein we report a stimulus-responsive silica nanoparticle (SNP) capable of encapsulating biomacromolecules in their active forms with a high loading content and loading efficiency as well as a well-controlled nanoparticle size (~50 nm). A disulfide crosslinker was integrated into the silica network, endowing SNP with glutathione (GSH)-responsive cargo release capability when internalized by target cells. An imidazole-containing component was incorporated into the SNP to enhance the endosomal escape capability. The SNP can deliver various cargos, including nucleic acids (e.g., DNA and mRNA) and CRISPR genome editors (e.g., Cas9/sgRNA ribonucleoprotein (RNP), and RNP with donor DNA) with excellent efficiency and biocompatibility. The SNP surface can be PEGylated and functionalized with different targeting ligands. In vivo studies showed that subretinally injected SNP conjugated with all-trans-retinoic acid (ATRA) and intravenously injected SNP conjugated with GalNAc can effectively deliver mRNA and RNP to murine retinal pigment epithelium (RPE) cells and liver cells, respectively, leading to efficient genome editing. Overall, the SNP is a promising nanoplatform for various applications including gene therapy and genome editing.

Study on a Novel Filter Media Incorporating with Core Shell Nanoencapsulated Phase Change Material: Fabrication and Evaluation

Thermal performance of filter media plays a significant effect on the filtration efficiency of baghouse, especially its tolerance of high temperature air and chemical erosion. In this study, nano-encapsulated phase change material within the silica shell (NPCMs) is synthesized through a self-assembly method based on polymer—hyperbranched precursor polyethoxysiloxane (PEOS). Filter media is fabricated by NPCMs through a facile dip-dry-cure process to enhance its thermal regulation and serving durability. Filter media acts as frame-supporting of the functional structure NPCMs. Incorporating NPCMs into filter media optimizes the microstructure and filtration efficiency of baghouse. The penetration rate was reduced from 457 × 10−4% of the control filter media to 5 × 10−4%. Meanwhile, the novel filter media lowers the temperature up to 20 °C than the surroundings. The novel filter media exhibits not only better mechanical properties, but also much less tensile strength loss after suffering 100 thermal shock cycles with simultaneous chemical exposure, from 37.58% to 20.37%. Overall, the filter media incorporated with NPCMs demonstrates excellent performances on filter efficiency, thermal regulation, and environmental endurance, which has the potential for extending lifespans and enhancing operation stability of filter bags in industrial air pollutant control.

Out-of-the-Box Nanocapsules Packed with On-Demand Hydrophobic Anticancer Drugs for Lung Targeting, Esterase Triggering, and Synergy Therapy

Most anticancer drugs, particularly paclitaxel (PTX), are suffering the challenges of cancer chemotherapy due to their poor water-solubility, high toxicity under effective therapeutic dosages, and multi-drug resistance. Currently, nanoscale drug delivery systems (DDSs) represent an efficient platform to overcome the above challenges. However, those DDSs generally need a careful design of conjugation, complexation, or co-self-assembly. Herein, a facile out-of-the-box nanocapsule is developed not only to be easily packed with on-demand hydrophobic anticancer drugs (up to 76% of loading efficiency for PTX), but also to be loaded with other concomitant drugs for synergy therapy (Itraconazole (ITA) here as P-glycoprotein inhibitor for drug resistance and antiangiogenic agent for combination therapy with PTX). Three kinds of biocompatible poly(ethylene glycol) dimethacrylates (PEGDM) derivatives usually as cross-linking agents are selected and successfully constructed adequate nanocapsules with single monomer as shell materials. More importantly, as-prepared nanocapsules have abilities of esterase triggering and lung targeting. Both in vitro and in vivo studies showed that the drug-loaded nanocapsules can effectively inhibit tumor growth and vascular proliferation in PTX-resistant tumor models without apparent systemic toxicity. The above results demonstrate that the nanocapsule system provides an effective and universal strategy for lung targeting, esterase triggering, and synergy therapy.

Capillary Action-Inspired Nanoengineering of Spheres-on-Sphere Microspheres with Hollow Core and Hierarchical Shell

The current syntheses of spheres-on-sphere (SOS) microsphere, which possesses both hollow cavity and hierarchical structure, mainly rely on complicated routes and template removal. In this study, a one pot nanoengineering strategy inspired by the automatic transport behavior of water in plants is successfully developed to fabricate SOS microsphere in tandem with a traditional soft template method in the preparation of hollow structure. Amphiphilic siloxane oligomers generated in situ from methyltriethoxylsilane (MTES) under acidic conditions are anchored on the surface of soft template St monomer droplets, sequentially completing hydrolysis-polycondensation and forming a mesoporous polysilsesquioxane (PSQ) shell. Then, the St monomers located in cavity migrate outward under the combined action of capillary force stemming from mesoporous and osmotic pressure generating from inside-outside of the PSQ shell and polymerize on the outside of the hollow PSQ shell, in which residual siloxane oligomers further anchor on the polystyrene (PS) surface to reduce the surface energy of the system, finally resulting in the successful formation of SOS particles. To reduce thermal insulation coefficient of the material, the PS phase in SOS particles is removed to obtain the particles with multiscale hollow structure (SOS-MH), which have more hollow cavities to encapsulate more air. The presence of a much hollow structure in SOS-MH particles enables the thermal conductivity of polyacrylonitrile (PAN)/SOS-MH composite fibrous membranes (0.0307 W m^-1 K^-1) to decrease by about 40% compared to that of pure PAN fibrous films (0.0520 W m^-1 K^-1) at the same thickness of 1 mm, and the material also has moisture resistance due to the existence of a hierarchical shell.

Cross-Linker-Controlled Ostwald Ripening in Emulsion Polymerization of Hollow Copolymer Nanoparticles

We propose a synthesis method for hollow copolymer nanoparticles, in which the size is controllable by the wettability of the materials designed by relative energy difference (RED). We investigated the influence of cross-linkers in RED and the hollow polymer nanoparticle synthesis. The size of the nanoparticles was characterized by scanning electron microscopy and transmission electron microscopy images. The diameter size of the hollow copolymer (styrene-co-methyl methacrylate) changes from 400 to 141 nm and the average core-vacancy sizes changes from 330 to 71 nm as increasing the feed ratio of the cross-linker, divinyl benzene, from 0.07 to 0.43. Cross-linkers in polymerization precipitates a polymerization reaction to produce seed copolymer particles quickly. The seed copolymer is a more transferrable medium through the surfactants across emulsion droplets and inhibits emulsion growth by unstable concentration variations of seed copolymers in emulsions. Therefore, Ostwald ripening was reduced by a higher feeding ratio of the cross-linker in the copolymer, which tends to produce smaller sized hollow nanoparticles.

Polymer Brush-Induced Hollow Colloids via Diffusion-Controlled Silication

We report on a new strategy to synthesize asymmetrical hollow colloidal particles by exploiting limited chemical diffusion that occurs at the periphery of a solvated polymer brush on the particle surface. The polymer brush-in our case poly(glycidyl methacrylate)-bears hydroxyl groups upon hydrolysis and is partially cross-linked under the Stöber condition of silication. Desolvation of the polymers creates a cavity. While elucidating this new mechanism, we demonstrate that particles with various types of cavities and tunable properties can be synthesized, including the ones bearing hemispherical and crescent shapes, as well as particles with wrinkled surfaces. Furthermore, we show that the hollow particles adopt preferred orientations because of their shape and composition attributes, which is further explored to facilitate the confined synthesis of nanocrystals.

One-pot synthesis of polymer-reinforced silica aerogels from high internal phase emulsion templates

HYPOTHESIS

Conventional strategies for strengthening silica aerogels through polymer modification always lead to a significant density increase and an obvious sacrifice of thermal insulation performance. In this work, we propose a facile one-pot method for the preparation of polymer-reinforced silica aerogels via polymerization of water-in-oil high internal phase emulsion (HIPE) templates.

EXPERIMENTS

Hyperbranched vinyl-modified polyethoxysiloxane (VPEOS) is used as both emulsion stabilizer and silica source. FT-IR spectra of VPEOS are recorded to confirm the successful incorporation of vinyl groups. The pore structure of polymer-functionalized silica aerogels is characterized by a scanning electron microscope (SEM), nitrogen adsorption-desorption and mercury intrusion porosimetry.

FINDINGS

The Young's modulus is increased from 0.69 to 19.28 MPa, nearly 28 times that of unmodified silica aerogels. Moreover, the silica aerogels present a superhydrophobicity with a water contact angle of 152.4° and good thermal insulation. The superior performance properties of the polymer-reinforced silica aerogels over pure silica aerogels may guarantee their wide applications in energy and aerospace fields.

Redox-Driven Spontaneous Double Emulsion

The formation of spontaneous double emulsions is a peculiar phenomenon in emulsion systems. When compared to the traditional one-step and two-step methods for preparing double emulsions, spontaneous emulsification can not only steadily load uniform water droplets into an oil phase, but can also facilitate the preparation of emulsions with higher stability. However, the limited solubility of salts, which are typically used to modify osmotic pressure, in organic oils has inhibited the viability of this method for the preparation of W/O/W double emulsions. In this paper, a redox-driven spontaneous emulsification method is developed and investigated. Instead of employing oil-soluble salts, an oxidation reaction is implemented in the oil phase, which produces cation radicals and iodide counterions to generate osmotic pressure. Additionally, amphiphilic polymer chains are harnessed as stabilizers for the newly formed W/O interfaces. Various characterization methods have been used to elucidate the mechanism of both the oxidation reaction and the spontaneous formation of double emulsions.

One-Step Dynamic Imine Chemistry for Preparation of Chitosan-Stabilized Emulsions Using a Natural Aldehyde: Acid Trigger Mechanism and Regulation and Gastric Delivery

Chitosan is a polysaccharide widely used as a structuring agent in foods and other materials because of its positive charge (amino groups). At present, however, it is difficult to form and stabilize emulsions using chitosan due to its high hydrophilicity. In this study, oil-in-water emulsions were prepared using a one-pot green-chemistry method. The chitosan and aldehyde molecules were in situ interfacially conjugated during homogenization, which promoted the adsorption of chitosan onto the oil droplet surfaces where they created a protective coating. The universality of this method was verified by using chitosan with different molecular weights and four kinds of natural aldehydes [cinnamaldehyde (CA), citral (CT), citronella (CN), and vanillin (VL)]. Chitosan with higher molecular weight facilitated the formation of emulsions. By harnessing the dynamic covalent nature of imine bonds, chitosan emulsions with an imine link display dynamic behavior with acid-catalyzed hydrolysis. The aldehyde structure could control the pH point of trigger for breakdown of emulsions, which was 1.0, 3.0, 4.0, and 4.0 for CA emulsion, CT emulsion, CN emulsion, and VL emulsion, respectively. At pH 6.5, aldehyde helped to decrease the interfacial tension of chitosan to about 10 mN/m, while this value would increase if the pH decreased by adding acid during the measurement. Chemical kinetics studies indicated that the hydrophobicity and conjugation effect of the aldehyde together determined the trigger points and properties of the emulsion. Finally, we used the optimized emulsions to encapsulate and control the release of curcumin. The gastric release behavior of the curcumin depended on aldehyde structure: VL > CN > CT ≈ CA. Hence, a tailor-made trigger release emulsion system can be achieved by rational selection and design of aldehyde structure to control hydrophobicity and conjugation effect of aldehydes.

Programmable droplet manipulation by a magnetic-actuated robot

Droplet manipulations are fundamental to numerous applications, such as water collection, medical diagnostics, and drug delivery. Structure-based liquid operations have been widely used both in nature and in artificial materials. However, current strategies depend mainly on fixed structures to realize unidirectional water movement, while multiple manipulation of droplets is still challenging. Here, we propose a magnetic-actuated robot with adjustable structures to achieve programmable multiple manipulations of droplets. The adjustable structure redistributes the resisting forces from the front and rear ends of the droplets, which determine the droplet behaviors. We can transport, split, release, and rotate the droplets using the robot. This robot is universally applicable for manipulation of various fluids in rough environments. These findings offer an efficient strategy for automated manipulation of droplets.

Cold-Responsive Nanoparticle Enables Intracellular Delivery and Rapid Release of Trehalose for Organic-Solvent-Free Cryopreservation

Conventional cryopreservation of mammalian cells requires the use of toxic organic solvents (e.g., dimethyl sulfoxide) as cryoprotectants. Consequently, the cryopreserved cells must undergo a tedious washing procedure to remove the organic solvents for their further applications in cell-based medicine, and many of the precious cells may be lost or killed during the procedure. Trehalose has been explored as a nontoxic alternative to traditional cryoprotectants. However, mammalian cells do not synthesize trehalose or express trehalose transporters in their membranes, and the lack of an approach for the efficient intracellular delivery of trehalose has been a major hurdle for its use in cell cryopreservation. In this study, a cold-responsive polymer (poly(N-isopropylacrylamide-co-butyl acrylate)) is utilized to synthesize nanoparticles for the encapsulation and intracellular delivery of trehalose. The trehalose-laden nanoparticles can be efficiently taken up by mammalian cells. The nanoparticles quickly and irreversibly disassemble upon cold treatment, enabling the controlled and rapid release of trehalose from the nanoparticles inside cells. The latter is confirmed by an evident increase in cell volume upon cold treatment. This rapid cold-triggered intracellular release of trehalose is crucial to developing a fast protocol to cryopreserve cells using trehalose. Cells with intracellular trehalose delivered using the nanoparticles show comparable postcryopreservation viability compared to that of cells treated with DMSO, eliminating the need for the tedious and cell-damaging washing procedure required for using the DMSO-cryopreserved cells in vivo. This cold-responsive nanoparticle may greatly facilitate the use of trehalose as a nontoxic cryoprotectant for banking cells and tissues to meet their high demand by modern cell-based medicine.

Novel Polymeric Organosilica Precursor and Emulsion Stabilizer: Toward Highly Elastic Hollow Organosilica Nanospheres

The fabrication of hollow organosilica nanoparticles with high elasticity is greatly desirable but still challenging. Herein, we present a new and simple strategy to prepare such nanoparticles by using hyperbranched polyvinylpolytrimethoxysilane (PVPMS) via a soap-free oil in water (O/W) emulsion system. PVPMS was synthesized through the radical polymerization of vinyltrimethoxysilane (VMS) followed by the acid-catalyzed hydrolytic polycondensation of trimethoxysilyl groups, which works not only as an organosilica precursor but also as a sole emulsion stabilizer due to its hydrolysis-induced amphiphilicity at the oil/water interface. When styrene was used as the oil phase and initiated to polymerize, hybrid polystyrene (PS) core-organosilica shell (PS@organosilica) nanoparticles were obtained by controlling the reaction conditions. Furthermore, highly elastic hollow organosilica nanospheres with low Young's modulus (∼220 MPa) were yielded through solvent etching of the core. This study expands the scope of organosilica precursor from small molecule organosilane to polymeric macromolecule and provides useful guidance for application in other polyorganosilsesquioxane related hybrid organosilica particles and functional hollow nanoparticles.

A Robust Aqueous Core-Shell-Shell Coconut-like Nanostructure for Stimuli-Responsive Delivery of Hydrophilic Cargo

Conventional delivery systems for hydrophilic material still face critical challenges toward practical applications, including poor retention abilities, lack of stimulus responsiveness, and low bioavailability. Here, we propose a robust encapsulation strategy for hydrophilic cargo to produce a wide class of aqueous core-shell-shell coconut-like nanostructures featuring excellent stability and multifunctionality. The numerous active groups (-SH, -NH₂, and -COOH) of the protein-polysaccharide wall material enable the formation of shell-cross-linked nanocapsules enclosing a liquid water droplet during acoustic cavitation. A subsequent pH switch can trigger the generation of an additional shell through the direct deposition of non-cross-linked protein back onto the cross-linked surface. Using anthocyanin as a model hydrophilic bioactive, these nanocapsules show high encapsulation efficiency, loading content, tolerance to environmental stresses, biocompatibility, and high cellular uptake. Moreover, the composite double shells driven by both covalent bonding and electrostatics provide the nanocapsules with pH/redox dual stimuli-responsive behavior. Our approach is also feasible for any shell material that can be cross-linked via ultrasonication, offering the potential to encapsulate diverse hydrophilic functional components, including bioactive molecules, nanocomplexes, and water-dispersible inorganic nanomaterials. Further development of this strategy should hold promise for designing versatile nanoengineered core-shell-shell nanoplatforms for various applications, such as the oral absorption of hydrophilic drugs/nutraceuticals and the smart delivery of therapeutics.

Ultralight Silica Foams with a Hierarchical Pore Structure via a Surfactant-Free High Internal Phase Emulsion Process

An ultralight silica aerogel is among the most versatile materials available for technical applications; however, it remains a huge challenge to reduce its manufacturing cost. Here, we report on a simple approach for the preparation of silica foam monoliths with ultrahigh porosity up to 99.5% and specific surface area as high as 755 m² g^-1, which are similar to those of an aerogel. Our strategy is based on the effective stabilization of water-in-oil high internal phase emulsions by a hydrophobic silica precursor polymer, hyperbranched polyethoxysiloxane because of its hydrolysis-induced amphiphilicity. After conversion of this precursor polymer to silica, the emulsions are solidified without significant volume shrinkage. Thus, mechanically strong macroporous silica monoliths are obtained after removal of its liquid components. According to nitrogen sorption data, the resulting silica foams exhibit a high specific surface area and a foam skeleton consisting of both micropores (<2 nm) and mesopores (2-50 nm). The pore size, porosity, and surface area can be regulated by varying pH as well as the concentration of the silica precursor in the oil phase. In addition, the pore size can be adjusted by controlling shear force during emulsification. This work opens a new avenue for producing ultralight porous materials amenable to numerous applications.

Inclusion of Phase-Change Materials in Submicron Silica Capsules Using a Surfactant-Free Emulsion Approach

Microencapsulation of phase-change materials is of great importance for thermal energy-storage applications. In this work, we report on a facile approach to enclose paraffin in mechanically strong submicron silica capsules without the addition of any classical organic surfactants. A liquid silica precursor polymer, hyperbranched polyethoxysiloxane (PEOS), is used as both silica source and stabilizer of oil-in-water emulsions because of its hydrolysis-induced interfacial activity. Hydrophobic paraffin is microencapsulated in silica with quantitative efficiency simply by emulsifying the mixture of molten paraffin and PEOS in water under ultrasonication or high-shear homogenization. The size of the capsules can be controlled by emulsification energy and rate of subsequent stirring. The silica shell, whose thickness can be easily tuned by varying the paraffin to PEOS ratio, acts as an effective barrier layer retarding significantly the evaporation of enclosed substances; meanwhile, the microencapsulated paraffin maintains the excellent phase-change performance. This technique offers a low-cost, highly scalable, and environmentally friendly process for microencapsulation of paraffin phase-change materials.