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While ultrasound represents a facile, portable, and noninvasive trigger for drug delivery vehicles, most reported ultrasound-triggered drug delivery vehicles predominately present "burst" release profiles that are hard to control after the initial activation stimulus. Herein, we report a submerged electrospraying technique to fabricate protein-loaded microcapsules in which silica "corks" are embedded within the microcapsule shell. Upon the application of an ultrasound trigger, the corks can be perturbed within the shell, allowing for the release of the protein payload through a phantom tissue mimic to a degree proportional to the number/time of pulses applied. Specifically, multiple ultrasound pulses were shown to enable a 15- to 23-fold increase in the rate of release of the model bovine serum albumin protein payload relative to no ultrasound being applied, with release returning to a lower level when the ultrasound stimulus was removed. Coupled with the low cytotoxicity of the vehicle components, the corked microcapsules show promise for expanding the potential to use ultrasound to facilitate both on-demand and pulsatile release profiles.

We report a comprehensive investigation of the synthetic conditions leading to the formation of tunable plasmonic microcapsules (MCs) made of a hydrophobic liquid core encapsulated into a hard silica shell embedding plasmonic metallic nanoparticles (NPs). The distinctive and remarkable features of the prepared MCs are the inert nanometer-thin silica shell and the small plasmonic NPs embedded in it, which confer interesting optical absorbance properties. We tie the mechanical robustness of the MCs to the thickness of their silica shell. We show that several oils can be used for the synthesis of MCs and we evidence how the relative solubility of the silica precursor and the polarity of the oil phase influence the final MC characteristics. We also evidence the synthesis of "monoflavor" or "multiflavor" MCs with, respectively, a single type of NPs or a mixture of metallic NPs, respectively, embedded in the silica shell. Using experiments and simulations, we demonstrate that the optical response of the MCs can be finely tuned by choosing the right ratio between Ag and Au NPs initially suspended in the solution. Our heterogeneous hybrid MCs exhibit optical properties directly resulting from the choice of NP composition and shell thickness, making them of great interest not only for mechanical and chemical microsensing but also for applications in photothermal therapy, surface-enhanced Raman spectroscopy studies, microreactor vesicles for interfacial electrocatalysis, antimicrobial activity, and drug delivery. Our simple and versatile emulsion template method holds great promise for the tailored design of a generation of multifunctional MCs consisting of modular nanoscale building blocks. [ABSTRACT FROM AUTHOR]

Maintaining the differentiated phenotype and function of primary hepatocytes in vitro and in vivo represents a distinct challenge. Our paper describes microcapsules comprised of a bioactive polymer and overcoated with an ultrathin film as a means of maintaining the function of entrapped hepatocytes for at least two weeks. We previously demonstrated that heparin (Hep)-based microcapsules improved the function of entrapped primary hepatocytes by capturing and releasing cell-secreted inductive signals, including hepatocyte growth factor (HGF). Further enhancement of hepatic function could be gained by loading exogenous HGF into microcapsules. In this study, we demonstrate that an ultrathin coating of tannic acid (TA) further enhances endogenous HGF signaling for entrapped hepatocytes and increases by 2-fold the rate of uptake of exogenous HGF by Hep microcapsules. Hepatocytes in overcoated microcapsules exhibited better function and hepatic gene expression than in capsules without a TA coating. Our study showcases the potential application of ultrathin coatings to modulate the bioactivity of microcapsules and may enable the use of encapsulated hepatocytes for modeling drug toxicity or treating liver diseases.

Flame retardants could improve the safety properties of lithium batteries (LBs) with the sacrifice of electrochemical performance due to parasitic reactions. To concur with this, we designed thermal-response clothes for hexachlorophosphazene (HCP) additives by the microcapsule technique with urea-formaldehyde (UF) resin as the shell. HCP@UF combines with polyacrylonitrile (PAN) by hydrogen bonds successfully to form PAN-HCP@UF as the flame-retardant solid polymer electrolyte. The hydrogen bonds ensure excellent mechanical properties of the polymer electrolyte. The multiscale free radical-annihilating agent HCP effectively eliminates hydrogen free radicals of electrolytes under high temperature, showing excellent flame retardation. During the operation of the battery, functional groups on the UF resin act as active sites to promote the migration of lithium ions, while the internal HCP is protected from electrochemical reaction. With 25% HCP@UF addition, the limiting oxygen index of the PAN-HCP@UF increases to 28% and the Li + transfer number up to 0.80. By UF protection, the initial capacity retention rate of the Li||LFP battery that assembles with PAN-HCP@UF is 88.8% after 500 cycles at 0.5 C. Thus, the microcapsule-encapsulated approach is deemed to provide an innovative strategy to prepare high-safety solid-state LB with a stable long cycle life.

The protective efficacy of chemically bonded phosphate ceramic coatings (CBPC) is notably diminished owing to the presence of micropores and inadequate self-healing capacity in prolonged corrosive environments. Consequently, it is imperative to augment the corrosion and wear resistance of phosphate ceramic coatings while imbuing them with self-healing capabilities. In this work, a novel self-healing phosphate ceramic coating (MC-PT x @CBPC, x = 0.5, 1.0, 1.5) is designed by urea-formaldehyde (UF) in situ polymerization of nanoscale microcapsules encapsulated with 1 H ,1 H ,2 H ,2 H -perfluorodecyltriethoxysilane (PFDTES) and evaluated in detail for corrosion and wear resistance. The corrosion inhibition efficiencies of all formulated MC-PT x @CBPC ( x = 0.5, 1.0, 1.5) coatings exceed 90%, with the impedance modulus at the lowest frequency (| Z | f =0.01 ) showing enhancements of 1-2 orders of magnitude compared to pure CBPC. Moreover, the self-healing function becomes active during prolonged immersion. This can be primarily ascribed to the formation of a unique micronanostructure facilitated by nanoscale microcapsules and micrometer-sized alumina ceramics, bonded via the AlPO 4 phase. This structure enhances both the hydrophobicity and the bonding strength of the coating. Specifically, following prolonged immersion, the encapsulated PFDTES is liberated from the microcapsules, undergoing hydrolysis and subsequent polymerization upon contact with the electrolyte to form a protective thin film. This film efficiently obstructs the ingress of corrosive agents. Furthermore, the special micronanostructure enhances the hardness of the coating and the releasing PFDTES can form a lubricating film at the interface of abrasion, thus reducing the wear rate and friction coefficient of the MC-PT x @CBPC ( x = 0.5, 1.0, 1.5). Therefore, MC-PT x @CBPC ( x = 0.5, 1.0, 1.5) possesses excellent corrosion protection, tribological properties, and self-healing capabilities, which provide thought-provoking ideas for phosphate ceramic coatings to protect metals in harsh environments.

Tumor heterogeneity requires development of an anticancer system equipped with both chemical and physical therapeutics to eradicate cancer exhibiting drug resistance and clonal evolution into diverse tumor cells. Assortment of various toxic components into one platform without compromising their individual toxic activity remains a formidable task. Herein, a novel drug delivery system (DDS) exerting potent cytotoxicity toward cancer cells was fabricated with gold nanoparticles (AuNPs) coated with an innocuous self-assembly protein of κ-casein (κC). Pickering emulsions of the κC-AuNP conjugates in the presence of chloroform inside led to the κC-AuNP microcapsules being stabilized via robust β-sheet formation between κC molecules located on the single-layered shell made of κC-AuNPs. Phase change material (PCM) comprising a eutectic mixture of lauric acid and myristic acid with the melting point of 43 °C was encapsulated in the presence of a hydrophilic anticancer drug of doxorubicin (Dox), in which the PCM has played multiple functions such as drug-holding matrix and thermoresponsive gating material for drug release. Once liberated with the heat generated by the AuNPs upon a near-infrared (NIR) irradiation at 808 nm, the PCM by itself exhibited not only chemical cytotoxicity but also physical toxic effects such as membrane destabilization of the cells and a possible cellular fixative effect toward cancer cells by the solidified PCM at body temperature. Moreover, the PCM was shown to facilitate the intranuclear localization of Dox. As a result, the DDS comprising κC-AuNP microcapsules containing Dox-loaded PCM was demonstrated to show a powerful anticancer effect upon the NIR irradiation, which unleashed several toxic agents such as Dox, PCM, heat-generating AuNPs, and tissue-immobilizing solidified PCM. Therefore, the κC-AuNP microcapsules would serve as an anticancer system into which diverse chemical and physical therapeutic agents could be combined to effectively remove the heterogeneous and drug resistant cancer cells.

The long-term operation of power equipment and power electronics can cause local overheating and discharges in the insulation material, resulting in irreversible insulation damage. Further development of such damage can eventually lead to equipment failure, but this problem is very difficult to solve. In this paper, inspired by how the petals of morning glory change color with the environment due to the presence of pigmented globules, a dual-function heat alert in the form of a self-healing (HASH) microcapsule with a nested structure is prepared by using microfluidic technology. By combination of the microcapsule with the insulation material, the local overheating in equipment can be detected promptly under live operating conditions without manual external intervention, and the defects that occur can be repaired autonomously. These HASH microcapsules can be pre-embedded in places at which the material is prone to overheating using artificial magnetic targeting. The doping of the matrix material with microcapsules does not cause any deterioration in its electrical or mechanical properties. This technology is expected to be applied to electrical equipment and electronic devices to allow for the early detection of local overheating and the autonomous repair of defects, thereby ensuring the safety of the equipment and improving its service life.

The synthesis of microcapsules via in situ polymerization is a labor-intensive and time-consuming process, where many composition and process factors affect the microcapsule formation and its morphology. Herein, we report a novel combinatorial technique for the preparation of melamine-formaldehyde microcapsules, using a custom-made and automated high-throughput platform (HTP). After performing validation experiments for ensuring the accuracy and reproducibility of the novel platform, a design of experiment study was performed. The influence of different encapsulation parameters was investigated, such as the effect of the surfactant, surfactant type, surfactant concentration and core/shell ratio. As a result, this HTP-platform is suitable to be used for the synthesis of different types of microcapsules in an automated and controlled way, allowing the screening of different reaction parameters in a shorter time compared to the manual synthetic techniques. [ABSTRACT FROM AUTHOR]

Implantable sensors that detect biomarkers in vivo are critical for early disease diagnostics. Although many colloidal nanomaterials have been developed into optical sensors to detect biomolecules in vitro, their application in vivo as implantable sensors is hindered by potential migration or clearance from the implantation site. One potential solution is incorporating colloidal nanosensors in hydrogel scaffold prior to implantation. However, direct contact between the nanosensors and hydrogel matrix has the potential to disrupt sensor performance. Here, we develop a hollow-microcapsule-based sensing platform that protects colloidal nanosensors from direct contact with hydrogel matrix. Using microfluidics, colloidal nanosensors were encapsulated in polyethylene glycol microcapsules with liquid cores. The microcapsules selectively trap the nanosensors within the core while allowing free diffusion of smaller molecules such as glucose and heparin. Glucose-responsive quantum dots or gold nanorods or heparin-responsive gold nanorods were each encapsulated. Microcapsules loaded with these sensors showed responsive optical signals in the presence of target biomolecules (glucose or heparin). Furthermore, these microcapsules can be immobilized into biocompatible hydrogel as implantable devices for biomolecular sensing. This technique offers new opportunities to extend the utility of colloidal nanosensors from solution-based detection to implantable device-based detection. [ABSTRACT FROM AUTHOR]

Fragrances, which are commonly used in food, textiles, consumer products, and medical supplies, are volatile compounds that require stabilization and controlled release due to their sensitivity to environmental conditions such as light, oxygen, temperature, and humidity. Encapsulation in various material matrices is a desired technique for these purposes, and there is a growing interest in using sustainable natural materials to reduce environmental impact. In this study, fragrance encapsulation in microspheres made from silk fibroin (SF) was investigated. Fragrance-loaded silk fibroin microspheres (Fr-SFMSs) were prepared by adding fragrance/surfactant emulsions to silk solutions, followed by mixing them with polyethylene glycol under ambient conditions. The study investigated eight different fragrances, where citral, beta-ionone, and eugenol showed higher binding affinities to silk than the other five fragrances, resulting in better microsphere formation with uniform sizes and higher fragrance loading (10-30%). Citral-SFMSs showed characteristic crystalline β-sheet structures of SF, high thermal stability (initial weight loss at 255 °C), long shelf life at 37 °C (>60 days), and sustained release (∼30% of citral remained after incubation at 60 °C for 24 h). When citral-SFMSs with different sizes were used to treat cotton fabrics, about 80% of the fragrance remained on the fabrics after one wash, and the duration of release from the treated fabrics was significantly longer than that of control samples treated with citral alone (no microspheres). This method of preparing Fr-SFMSs has potential applications in textile finishing, cosmetics, and the food industry.

High supercooling and single functionalization are the main barriers to the large-scale application of microencapsulated phase-change materials (PCMs) in the construction industry. To address these issues, we propose a new inorganic microencapsulated PCM, PW@CaWO 4 , which was synthesized via the in situ polymerization method using inorganic CaWO 4 as shell and phase-change paraffin wax (PW) as core. We investigated the effects of different emulsifiers and core-to-shell ratios on microcapsule properties and found that the PW@CaWO 4 microcapsules have regular spherical topography and good uniformity in particle size. During the synthesis process, the CaWO 4 shell provides convenient conditions for heterogeneous nucleation of PW and effectively reduces the supercooling degree. The minimum supercooling degree of the PW@CaWO 4 microcapsules is only 1.00 ± 0.08 °C, which is 3.41 °C lower than that of PW. Moreover, the PW@CaWO 4 microcapsules can absorb ultraviolet radiation and exhibit fluorescence, which originates from the peculiar WO 4 2- shell, eliminating the need for doping other light-activating ions into the shell. The newly prepared microcapsules possess several advantages, including suitable particle size, low supercooling, good heat storage, high thermal conductivity, good short-wave ultraviolet absorption, peculiar fluorescence, excellent proof of leakage, and so on. The microcapsules can be applied to fluorescent architectural energy-saving coatings.4 shell, eliminating the need for doping other light-activating ions into the shell. The newly prepared microcapsules possess several advantages, including suitable particle size, low supercooling, good heat storage, high thermal conductivity, good short-wave ultraviolet absorption, peculiar fluorescence, excellent proof of leakage, and so on. The microcapsules can be applied to fluorescent architectural energy-saving coatings.

Dielectric polymers are playing important roles in electrical and electronic industries. However, aging under high electric stress is a main threat to the reliability of polymers. In this work, we demonstrate a self-healing method for electrical tree damage based on radical chain polymerization, which is initiated by in situ radicals that are generated during electrical aging. Acrylate monomers contained in microcapsules will be released and flow into hollow channels after the capsules are punctured by electrical trees. Autonomous radical polymerization of the monomers will heal the damaged regions, which is triggered by radicals resulting from polymer chain scissions. After optimizing the healing agent compositions by evaluating their polymerization rate and dielectric properties, the fabricated self-healing epoxy resins showed effective recovery from treeing in multiple aging-healing cycles. We also expect the great potential of this method to heal tree defects autonomously without the need to switch off operating voltages. This novel self-healing strategy will shed light on building smart dielectric polymers with its broad applicability and online healing competence.

Selective ion separations are increasingly needed to combat water scarcity, recover resources from wastewater, and enable the efficient recycling of electronics waste. Emulsion liquid membranes (ELMs) have received interest due to rapid kinetics, high selectivities, and low solvent requirements but are too unstable for industrial usage. We demonstrate that polymeric microcapsules can serve as robust, solvent-free mimics of ELMs. As a proof of concept, we incorporated the copper-selective ligand Lix 84-I in the walls of microcapsules formed from a commercial polystyrene- b -polybutadiene- b -polystyrene triblock polymer. The microcapsules were formed from a double-emulsion template, resulting in particles typically 20-120 μm in diameter that encapsulated even smaller droplets of a dilute (≤0.5 M) H 2 SO 4 solution. Batch experiments demonstrated facilitated-transport behavior, with equilibrium reached in as little as 10 min for microcapsules with 1% ligand, and with ∼15-fold selectivity for Cu 2+ over Ni 2+ . Furthermore, the microcapsules could be packed readily in columns for flow-through operation, thus enabling near-complete Cu 2+ removal in ∼2 min under certain conditions, recovery of Cu 2+ by flowing through fresh dilute H 2 SO 4 , and reuse for at least 10 cycles. The approach in this work can serve as a template for using selective ligands to enable robust and simple flow-through processes for a variety of selective ion separations.

A new promising trend in personalized medicine is the use of autologous cells (macrophages or stem cells) for cell-based therapy and also as a "Trojan horse" for targeted delivery of a drug carrier. The natural ability of macrophages for chemotaxis allows them to deliver cargo to the damaged area, significantly reducing side effects on healthy organ tissues. Therefore, it is important to develop tools to track their behavior in the organism. While labeled containers can serve as anchored tags for imaging macrophages in vivo , they can affect the properties and functions of macrophages. This work demonstrates that 3 μm sized capsules based on biocompatible polyelectrolytes and fluorescently labeled with both Cy7 and RITC dyes do not affect cell functionalization in vitro , such as viability, proliferation, and movement of transformed monocyte/macrophage-like cells (RAW 264.7) and primary bone marrow derived macrophages (BMDM) at maximal loading of five capsules per cell. In addition, capsules allowed fluorescent detection of ex vivo loaded cells 24 h after the tail vein injection in vivo and visualization of microcapsule-laden macrophages ex vivo using confocal microscopy. We have delivered about 62.5% of injected BMDM containing 12.5 million capsules with 3.75 μg of high-molecular-weight cargo (0.3 pg/capsule) to the liver. Our results demonstrate that 3 μm polyelectrolyte fluorescently labeled microcapsules can be used for safe macrophage loading, allowing cell tracking and drug delivery, which will facilitate development of macrophage-based cell therapy protocols.

Wound healing involves multiple stages of body responses, including hemostasis, inflammation, cell proliferation, and tissue remodeling. New material design satisfying all demands throughout different stages of wound healing is cherished but rarely discussed. Here we introduce all-aqueous multiphase microfluidics as a novel strategy to fabricate self-assembled, multifunctional alkylated chitosan/alginate microcapsules (SAAMs) as novel therapeutic materials for rapid blood coagulation and wound healing. SAAMs are structurally distinguished by their ultrathin shells with polycationic surface for rapid activation of clotting cascade and their internal porous dextran-rich cores for fast absorption of blood and exudate. These features endow SAAMs with excellent hemostatic properties for acute hemorrhage. Moreover, the alkylated chitosan within the microcapsules exhibits persistent antimicrobial activities against bactericidal infections due to their amphiphilic and cationic surfaces. Besides, cytokines can be safely loaded into the organic-solvent-free microcapsules and released precisely to promote the proliferation of epidermal cells, supporting the subsequent development of granulation tissue and suppression of inflammation in the last stages of wound healing. With the ability to fabricate size-tailored soft microcapsules and to realize time-sequential functions for tissue repairing, the presented "all-aqueous microfluidics generation of multifunctional bioactive SAAMs" create a versatile and robust paradigm for wound treatment.

The regulatory functions of plant miRNAs on mammalian bodies are controversial, mainly because stability of the miRNAs in the digestive tract, as the prerequisite for their cross-kingdom effects, has somehow been overlooked. Hence, as the first stage of food ingestion, stability of plant miRNAs in human saliva has been investigated. The results show that plant miRNAs are of considerable resistance against salivary digestion, as surviving miRNAs more than 20 fM are detected. The stability varies dramatically, which can be explained by the difference in tertiary structure, governing their affinities to RNase. Surprisingly, miRNAs of low initial concentrations can end up with high survival rates after digestion. Plant miRNAs can be loaded into exosome-like nanoparticles (ELNs) and microcapsules formed by food components, both of which protect the miRNAs from being degraded in human saliva. Overall, plant miRNAs can apply certain strategies to maintain constant concentrations, paving the way for their potential cross-kingdom effects.

Thermochromic coatings that can change their color in response to variations in ambient temperature have various potential applications. Cholesteric liquid crystals (CLCs) are promising thermochromic materials due to their selective light reflection and wide regulation range. However, it remains a challenge to fabricate thermochromic coatings that combine good responsivity, mechanical strength, fabrication feasibility, and flexibility. In this study, CLC microcapsules containing cellulose nanocrystals (CNCs) and a melamine-formaldehyde (MF) resin hybrid shell were fabricated via in situ polymerization using CNC-stabilized Pickering emulsions as templates. The CNCs were employed as both Pickering emulsifiers and alignment agents of CLCs to prepare CLC Pickering emulsions. The CLC microcapsules were mixed with curable binders to obtain coating slurries, and thermochromic coatings were prepared by painting the slurries on substrates and drying. The thermochromic coatings could adjust their color in the visible wavelength range in a temperature range of 12 to 42 °C. Moreover, the obtained thermochromic coatings displayed a relatively high reflectance of up to 30-40% and can even be applied to flexible substrates. The CLC microcapsules with CNCs and an MF hybrid shell are promising in the field of smart decorative paints, anti-counterfeit labels, and artificial skins.

By designing and preparing multifunctional materials exhibiting self-healing ability, problems related to their durability outdoors can be solved. This study, inspired by the self-healing mechanism of natural creatures, successfully prepared a dual self-healing multifunctional coating using temperature stimuli-responsive multicompartment microcapsules. Phase change materials (PCMs) were employed to load multicompartment microcapsules that were produced through Pickering emulsion polymerization by applying hydrophobic materials encapsulated by titanium dioxide (TiO 2 ) nanocapsules as Pickering emulsifiers. The multifunctional coating produced using microcapsules and self-healing waterborne polyurethane (WPU) exhibited thermal insulation and antireflection properties, which was attributed to the application of PCMs and TiO 2 , and it also achieved remarkable superhydrophobicity. Moreover, this coating exhibited the intrinsic and superficial dual self-healing ability, which was attributed to the release of hydrophobic materials from microcapsules and the self-healing ability of WPU. This study can be referenced to guide the fabrication of high-performance self-healing materials, and it can contribute to the long-term use of multifunctional coatings.

Smart polymeric composite coatings demonstrating multilevel self-healing characteristics were developed and characterized. The pH-responsive smart carriers were synthesized by loading halloysite nanotubes (HNTs) with the benzotriazole corrosion inhibitor (BTA) using the vacuum cycling method, referred to as (BTA-loaded HNTs). Similarly, mechanically triggered melamine urea-formaldehyde microcapsules encapsulated with the boiled linseed oil-self-healing agent (LO) denoted as (MUFMCs) having an average size of a ∼120 μm diameter with a wall thickness of ∼1.84 μm were synthesized by the in situ polymerization technique. The newly designed double-layered smart polymeric composite coatings (DLPCs) were developed by mixing 3 wt % BTA-loaded HNTs with epoxy and applying it on the clean steel substrate to form a primer layer. After its complete curing, a top layer of epoxy containing 5 wt % of MUFMCs was deposited on it. For an exact comparison, single-layer polymeric composite coatings (SLPCs) containing 3 wt % BTA-loaded HNTs were also developed. The Fourier transform infrared radiation spectra of MUFMCs and BTA-loaded HNTs indicate the existence of all desired functional groups, confirming the presence of loaded chemical species such as LO and BTA into the smart carriers. Thermogravimetric analysis (TGA) indicates that ∼18% BTA is successfully loaded into HNTs. Quantitative UV-spectroscopic analysis indicates a pH-responsive release of BTA from BTA-loaded HNTs, which is time-dependent, attaining its maximum value of ∼ 90% in an acidic medium after 30 h. Electrochemical impedance spectroscopy analysis conducted in 3.5 wt % NaCl solution at room temperature for different immersion times reveals that SLPC exhibits the maximum charge-transfer resistance ( R ct ) of 55.47 GΩ cm 2 after the 7th day of immersion, and then, a declining trend is observed, reaching 26.6 GΩ cm 2 after the 9th day. However, in the case of DLPC, the R ct values show a continuous increment, attaining a maximum value of 82.11 GΩ cm 2 after the 9th day of immersion. The improved performance of DLPC can be ascribed to the efficient triggering of the individual carriers in the isolated matrices, resulting in the release of LO and BTA to form individual protective films at the damaged area due to the oxidative polymerization process and triazoles' ability of passive film formation on the substrate, respectively. The tempting self-healing properties of DLPCs justify their decent role for long-term corrosion protection in many industrial applications.

We report that micrometer-scale droplets of thermotropic liquid crystals (LCs) can be positioned inside living mammalian cells and deployed as chemical sensors to report the presence of toxins in extracellular environments. Our approach exploits droplets of LC enclosed in semi-permeable polymer capsules that enable internalization by cells. The LC droplets are stable in intracellular environments, but undergo optical changes upon exposure of cells to low, sub-lethal concentrations of toxic amphiphiles. Remarkably, LC droplets in intracellular environments respond to extracellular analytes that do not generate an LC response in the absence of cellular internalization. They also do not respond to other chemical stimuli or processes associated with cell growth or manipulation in culture. Our results suggest that droplet activation involves the transport and co-adsorption of amphiphilic toxins and other lipophilic cell components to the surfaces of internalized droplets. This work provides fundamentally new designs of biotic-abiotic systems that can report sensitively and selectively on the presence of select chemical agents outside cells and provides a foundation for the design of structured liquid droplets that can sense and report on other biochemical or metabolic processes inside cells.

We present a microfluidic approach that utilizes temperature-responsive and biocompatible palm oil as the shell material in microcapsules to simultaneously achieve hermetic sealing as well as on-demand temperature-triggered release of the encapsulated actives. Unlike common paraffin waxes (e.g., eicosane), microcapsule shells comprising palm oil do not form pores or cracks during freezing and provide a hermetic seal, a nearly perfect seal that separates the core containing the actives from the surrounding environment over a prolonged period of time. This allows effective isolation and protection of complex cargoes such as small molecules with high diffusivity, strong acids, and cosmetic actives including niacinamide. Moreover, the palm oil shell melts above the defined melting temperature, allowing the on-demand release of the encapsulated actives. Furthermore, palm oil is biocompatible, is edible, and leaves a minimal footprint when used in personal care and cosmetic products, offering new perspectives in the design of microcapsules for cosmetic applications.

A novel polymer microcapsule-filled dye-doped liquid crystal (DDLC) and phase-change material (PCM) system inspired by biological materials was first proposed, which was further encapsulated into a calcium alginate substrate by wet spinning for making an electrochromic fiber with both bistable electric-optical capability and knitting characteristics. Results show that the optical appearance of the optimized microcapsules and fiber can be reversibly changed between colored and colorless states according to the electric field by switching the DDLCs between isotropic (I) and anisotropic (A) states. Moreover, both I and A states can remain stable for more than 1 week after removing the electric field, due to the synergy of the greatly increased spatial hindrance of the PCM with core loading of 22.58% and the confinement effect from the polymer microcapsule shell material. Aside from the long-term optical stability, the high content of the densely packed DDLCs also endows the electrochromic fiber with a satisfactory driving voltage of 9.7 V, which is below the human safe voltage, showing great potential in a wide range of applications, such as flexible displays, energy-saving smart windows, and wearable advanced textiles.

Microcapsules made of synthetic polymers are used for the release of cargo in agriculture, food, and cosmetics but are often difficult to be degraded in the environment. To diminish the environmental impact of microcapsules, we use the biofilm-forming ability of bacteria to grow cellulose-based biodegradable microcapsules. The present work focuses on the design and optimization of self-grown bacterial cellulose capsules. In contrast to their conventionally attributed pathogenic role, bacteria and their self-secreted biofilms represent a multifunctional class of biomaterials. The bacterial strain used in this work, Gluconacetobacter xylinus , is able to survive and proliferate in various environmental conditions by forming biofilms as part of its lifecycle. Cellulose is one of the main components present in these self-secreted protective layers and is known for its outstanding mechanical properties. Provided enough nutrients and oxygen, these bacteria and the produced cellulose are able to self-assemble at the interface of any given three-dimensional template and could be used as a novel stabilization concept for water-in-oil emulsions. Using a microfluidic setup for controlled emulsification, we demonstrate that bacterial cellulose capsules can be produced with tunable size and monodispersity. Furthermore, we show that successful droplet stabilization and bacterial cellulose formation are functions of the bacteria concentration, droplet size, and surfactant type. The obtained results represent the first milestone in the production of self-assembled biodegradable cellulose capsules to be used in a vast range of applications such as flavor, fragrance, agrochemicals, nutrients, and drug encapsulation.

In modern biomedical science and developmental biology, there is significant interest in optical tagging to study individual cell behavior and migration in large cellular populations. However, there is currently no tagging system that can be used for labeling individual cells on demand in situ with subsequent discrimination in between and long-term tracking of individual cells. In this article, we demonstrate such a system based on photoconversion of the fluorescent dye rhodamine B co-confined with carbon nanodots in the volume of micron-sized polyelectrolyte capsules. We show that this new fluorescent convertible capsule coding system is robust and is actively uptaken by cell lines while demonstrating low toxicity. Using a variety of cellular lines, we demonstrate how this tagging system can be used for code-like marking and long-term tracking of multiple individual cells in large cellular populations.

Microgels of biopolymers such as alginate are widely used to encapsulate cells and other biological payloads. Alginate is an attractive material for cell encapsulation because it is nontoxic and convenient: spherical alginate gels are easily created by contacting aqueous droplets of sodium alginate with divalent cations such as Ca 2+ . Alginate chains in the gel become cross-linked by Ca 2+ cations into a 3-D network. When alginate gels are placed in a buffer, however, the Ca 2+ cross-links are eliminated by exchange with Na + , thereby weakening and degrading the gels. With time, encapsulated cells are released into the external solution. Here, we describe a simple solution to the above problem, which involves forming alginate gels enveloped by a thin shell of a covalently cross-linked gel . The shell is formed via free-radical polymerization using conventional monomers such as acrylamide (AAm) or acrylate derivatives, including polyethylene glycol diacrylate (PEGDA). The entire process is performed in a single step at room temperature (or 37 °C) under mild, aqueous conditions. It involves combining the alginate solution with a radical initiator, which is then introduced as droplets into a reservoir containing Ca 2+ and monomers. Within minutes of either simple incubation or exposure to ultraviolet (UV) light, the droplets are converted into alginate-polymer microcapsules with a core of alginate and a shell of the polymer (AAm or PEGDA). The microcapsules are mechanically more robust than conventional alginate/Ca 2+ microgels, and while the latter swell and degrade when placed in buffers or in chelators like sodium citrate, the former remain stable under all conditions. We encapsulate both bacteria and mammalian cells in these microcapsules and find that the cells remain viable and functional over time. Lastly, a variation of the synthesis technique is shown to generate multilayered microcapsules with a liquid core surrounded by concentric layers of alginate and AAm gels. We anticipate that the approaches presented here will find application in a variety of areas including cell therapies, artificial cells, drug delivery, and tissue engineering.

Capsules are often used to protect chemical and biological entities from the environment, to control the timing and location of their release, or to facilitate the collection of waste. Their performance depends on the thickness and composition of their shells, which can be closely controlled if capsules are made from double emulsion drops that are produced with microfluidics. However, the fabrication of such double emulsions is delicate, limiting throughput and increasing costs. Here, a fast, scalable method to produce monodisperse microcapsules possessing mechanically robust, thin, semipermeable hydrogel shells from single emulsion drops is introduced. This is achieved by selectively polymerizing reagents in close proximity to the drop surface to form a biocompatible 1.6 μm-thick hydrogel shell that encompasses a liquid core. The size-selective permeability of the shell enables the growth of living yeast and bacteria in their cores. Moreover, if capsules are loaded with adsorbents, they can repetitively remove waste products from water. The simplicity and robustness of the capsule fabrication makes the process scalable and cost effective. It has thus the potential to extend the use of calibrated capsules possessing well-defined dimensions to cost sensitive fields, including food, waste water treatment, or oil recovery.

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, SiO 2 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.

Electrochromic materials have great application in soft displays and devices, but the application of ideal electrochromic textiles still faces challenges owing to the inconvenience of a continuous power supply. Here, electrochromic color-memory microcapsules (ECM-Ms-red, -yellow, and -blue) with a low drive voltage (2.0 V), coloration efficiency (921.6 cm 2 C -1 ), a practical response rate (34.4 s -1 ), multistage response discoloration, and good color-memory performance (>72 h) and reversibility (≥1000 cycles) are developed. The color-memory performance is controlled by the energy difference of oxidation-reduction reactions. A multicolor and multistage response electrochromic color-memory wearable smart textile and flexible display are developed that are convenient and energy-efficient for application. The design philosophy of color-memory based on controllable energy difference of reactions has great potential application in sensors and smart textiles.

Sequence-specific nucleic acids recognizing low-molecular-weight ligands or macromolecules (aptamers) have found growing interest for biomedical applications. The present review article summarizes recent applications of aptamers as stimuli-responsive gating units of drug (or dye)-loaded nano- or microcarriers for controlled and targeted drug release. In the presence of cellular biomarkers, the nano-/microcarriers are unlocked by forming aptamer-ligand complexes. Different aptamer-functinalized nano-/microcarriers are presented, including inorganic nanomaterials, metal-organic framework nanoparticles, and soft materials. The chemistries associated with the preparation of the carriers and the mechanisms to unlock the carriers are discussed. Stimuli-responsive gated drug-loaded micro-/nanocarriers hold great promise as functional sense-and-treat materials for the targeted and selective release of drugs.

The fungicide pyraclostrobin is highly toxic to aquatic organisms. Microencapsulation is an effective way to reduce the exposure of pyraclostrobin to aquatic organisms but it also reduces the contact probability between the fungicide and plant pathogens. Hence, winning a balance between the toxicity and bioactivity of pyraclostrobin is very necessary. In this study, triethylenetetramine (TETA), ethylenediamine (EDA), hexamethylenediamine (HAD), and isophoronediamine (IPDA) were selected as cross-linkers to prepare the pyraclostrobin-loaded polyurea microcapsules (PU-MCs) by interfacial polymerization. TETA formed the shells with the highest degree of cross-linking, the slowest release profile, and the best protection against ultraviolet (UV). In terms of MCs fabricated by diamines, higher leaking, weaker UV resistance of the shells was observed with increasing carbon skeleton. TETA-MCs showed the highest safety to zebrafish (LC 50 of 10.086 mg/L), whereas EDA-MCs, HAD-MCs, and IPDA-MCs were 5.342, 3.967, and 0.767 mg/L, respectively. TETA-MCs had the best long-term disease management, while the control efficacies of other MCs were higher at the early stage of disease development. Overall, a balance between the aquatic toxicities and fungicidal activities of pyraclostrobin-loaded PU-MCs could be reached through a simple selection of polyamines in the fabrication.

This work demonstrates the fabrication of surface-textured microcapsules formed from emulsion droplets, which are stabilized by an interlocking mesh of needle-like crystals. Crystals of the small-organic-compound decane-1,10-bis(cyclohexyl carbamate) are formed within the geometric confinement of the droplets, through precipitation from a binary-solvent-dispersed phase. This binary mixture consists of a volatile solvent and nonvolatile carrier oil. Crystallization is facilitated upon supersaturation due to evaporation of the volatile solvent. Microcapsule diameter can be easily tuned using microfluidics. This approach also proves to be scalable when using conventional mixers, yielding spikey microcapsules with diameters in the range of 10-50 μm. It is highlighted that the capsule shape can be molded and arrested by jamming using recrystallization in geometric confinement. Moreover, it is shown that these textured microcapsules show a promising enhanced deposition onto a range of fabric fibers.

Currently, smart and functional textiles have attracted increasing attention for the research on their application in various fields. In this paper, perfluorooctyltriethoxysilane (FAS13)-loaded silica nanocapsules taken as the Pickering emulsifier was applied to stabilize O/W emulsion for obtaining pH-responsive dual-compartmental microcapsules which show a strawberry-like structure with jasmine essence as the core and pH-responsive polymers and silica nanocapsules as the shell. These microcapsules could endow it with multifunctions by functionalizing the fabric, while the preparation and functionalization process is effortless and environmental friendly. Not only does the treated fabric demonstrate the self-healing superhydrophobicity and ultraviolet (UV) resistance because of the hydrophobic FAS13 getting loaded into silica nanocapsules and the surface modification of UV absorbent, it is also capable of the pH control jasmine essence-releasing performance, which allows over 40% of the fragrance to be preserved for three months through the controlled release of jasmine essence from the microcapsules.

The poor ultraviolet (UV) resistance and insufficient solvent compatibility are challenges for long-term storage and service of oil-water separation materials in practical applications. Herein, a superhydrophobic/superoleophilic surface with nano- to microscale hierarchical structures was formed spontaneously on robust microcapsules (MCs) via in situ polymerization and a sol-gel surface treatment. The resultant MCs possessed superior UV-resistant and solvent-proof superhydrophobicity. The water contact angles (WCAs) of the MC coating remained above 160° and the sliding angles (SAs) were below 3° after 9 days of UV aging test or 20 days of nonpolar and polar aprotic solvent immersion tests. More interestingly, these MCs can be used to separate the oil phase from its aqueous emulsion effectively, achieving a high and reusable separation efficiency with over 90% oil purity after 10 cycles of filtrations even after 13 days of UV aging. Therefore, these novel MCs will exhibit effective oil-water separation performance, superior chemical stability, outstanding reusability, and long-term storage stability for promising practical applications.

In this work, a simple and flexible method for the fabrication of chitosan microcapsules with controllable structures and functions via the interfacial cross-linking reaction of the water-in-oil (W/O) emulsion templates is developed. The interfacial cross-linking reactions of chitosan and terephthalaldehyde (TPA) in W/O emulsion templates are comprehensively studied. The interfacial cross-linking reactions of the droplet templates in both batchwise and continuous conditions are studied. A poly(dimethylsiloxane) (PDMS) droplet-capture microfluidic chip is fabricated to investigate the interfacial reaction in continuous conditions online. In this study, the size and shell thickness of the microcapsules are affected by the preparation condition, such as the template size, emulsifier concentration, TPA concentration, and cross-linking time. Moreover, the size and shell thickness changes of chitosan microcapsules prepared in continuous conditions are much faster than those prepared in batchwise conditions. By regulating the preparation parameters, the microcapsules with controllable structures are fabricated in both batchwise and continuous conditions. The drug release behaviors of the microcapsules with controllable structures are studied. Furthermore, by adding magnetic nanoparticles to the aqueous solution, magnetic-responsive microcapsules are fabricated easily. This work provides valuable guidance for the controllable fabrication of chitosan microcapsules with designed structures and functions via single emulsion templates.

Self-assembly of block copolymers (BCPs) has been developed as a promising approach for constructing photonic crystal (PC) microspheres for dynamic optical modulation. However, high curvature in the center of microspheres usually distorts the periodic core structure, leading to an inconsistency of photonic bandgap and poor monochromaticity of structural color. Herein, we report a simple yet robust strategy for fabricating responsive PC microcapsules of polystyrene- b -poly(2-vinylpyridine) through self-emulsification strategy. Interestingly, the microcapsules exhibit bright structural color with significantly enhanced monochromaticity, compared to their solid counterpart, since the microcapsules have no irregular cores. The structural colors of the PC microcapsules not only exhibit a variability through binary mixing of BCPs but also show a responsiveness to pH value. As a colored microcarrier, the PC microcapsules show a potential for visualizing the pH-dependent release behavior of encapsulated hydrophilic cargos on account of pH-responsive structural color.

Self-healing superhydrophobic coatings are attracting interest, but it still remains a great challenge to develop facile and fast self-healing strategies for superhydrophobic coatings. In this work, a novel environmentally friendly self-healing superhydrophobic coating based on an ultraviolet (UV)/near-infrared light (NIR) dual-responsive action was fabricated by blending UV-responsive microcapsules with NIR-responsive carbon nanoparticles (NPs), hydrophobic silica NPs, and waterborne silicone latex. The UV-responsive microcapsules were simply prepared through the electrostatic adsorption of negatively charged TiO 2 NPs onto a positively charged microcapsule surface. The UV-NIR dual-responsive properties were mainly reflected in the healing of the superhydrophobic property for coatings through NIR or UV light irradiation. The self-healing process could be repeated many times, which can be attributed to the continued release of fluorine silane (FAS-13) loaded in the UV-responsive microcapsules to the coating surface. The combinations of NIR and UV responses endow the coating with the characteristics of fast healing and large-area healing when damaged by the external environment. In addition, the self-healing superhydrophobic coating film has excellent oil, corrosion, and wear resistance, satisfying the requirements for realistic outdoor applications.

Herein, pH-sensitive microcapsules containing NaNO 2 corrosion inhibitors for protection of steel reinforced concrete were synthesized via water-in-oil-in-water (W/O/W) double emulsion using colophony as the wall material. The average microcapsule size was 79.07 μm in diameter and exhibited a high encapsulation efficiency of 83.2%. Study of the release of corrosion inhibitors from microcapsules in deionized water (DI water, pH 6.8), carbonate/bicarbonate buffer solution (CBS, pH 9.1), and simulated concrete pore solution (SCPS, pH 12.6) demonstrates that the microcapsules are sensitive to pH and display higher release in alkaline media. This is the first study of colophony as an encapsulating agent for corrosion inhibitors. Furthermore, the alkaline pH-triggered release shows the suitability of its use in reinforced concrete systems. A wide thermal stability range was also found for the colophony microcapsules up to 100 °C. These high pH environments (CBS and SCPS) present pH values above the p K a of colophony (7.2), thus triggering enhanced inhibitor release by the ionization and deprotonation of colophony shell. The higher release in CBS and SCPS is demonstrated by the increases of the corrosion inhibitor diffusion coefficient by an order of magnitude from 3.30 × 10 -17 m 2 /s in DI water up to 1.66 × 10 -16 /s for SCPS. The release performance indicates that the proposed approach can be used to encapsulate a variety of inhibitors for the protection of steel reinforcements. After immersion in different pH solutions, the corrosion potentials of a carbon steel substrate with microcapsules containing nitrite were more noble than when immersed without microcapsules and the corrosion current densities showed comparable values to free corrosion inhibitors. The formation of a passive ferric oxide layer was confirmed by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy.2 /s for SCPS. The release performance indicates that the proposed approach can be used to encapsulate a variety of inhibitors for the protection of steel reinforcements. After immersion in different pH solutions, the corrosion potentials of a carbon steel substrate with microcapsules containing nitrite were more noble than when immersed without microcapsules and the corrosion current densities showed comparable values to free corrosion inhibitors. The formation of a passive ferric oxide layer was confirmed by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy.

Microcapsules have attracted widespread interest for their unique properties in encapsulation, protection, and separation of active ingredients from the surrounding environment. However, microcapsule carriers with controllable shell thickness, permeability, good mechanical properties, and thermostability are challenging to obtain. Herein, robust and versatile composite microcapsules were fabricated using SiO 2 nanoparticle-stabilized (Pickering) oil emulsions as core templates, while silk fibroin (SF) was assembled at the oil/water interface. This process resulted in the formation of physically and chemically stable microcapsules with a thick (∼800 nm) shell that protected the encapsulated ingredient from high shear forces and high temperatures during spray-drying. SiO 2 nanoparticles were randomly distributed in the shell matrix after preparation, making the microcapsules mechanically robust (4.48 times higher than control samples prepared using surfactant Tween 80 instead of the SiO 2 nanoparticles), as well as thermostable (retained shape to 900 °C). The microcapsules displayed tunable drug release by adjusting the SF content in the shell. Under optimal conditions (weight ratio of SiO 2 /SF = 7:10, corn oil content about 55 wt %), a model drug (curcumin) was encapsulated in the SF microcapsules with an encapsulation efficiency up to 95%. The in vitro drug release from these SF microcapsules lasted longer than control microcapsules, demonstrating the capability of these novel microcapsules in sustaining drug release.

Glioblastoma (GBM) is the most common primary brain tumor and has a poor prognosis; as such, there is an urgent need to develop innovative new therapies. Tumoricidal stem cells are an emerging therapy that has the potential to combat limitations of traditional local and systemic chemotherapeutic strategies for GBM by providing a source for high, sustained concentrations of tumoricidal agents locally to the tumor. One major roadblock for tumoricidal stem cell therapy is that the persistence of tumoricidal stem cells injected as a cell suspension into the GBM surgical resection cavity is limited. Polymeric biomaterial scaffolds have been utilized to enhance the delivery of tumoricidal stem cells in the surgical resection cavity and extend their persistence in the brain, ultimately increasing their therapeutic efficacy against GBM. In this review, we examine three main scaffold categories explored for tumoricidal stem cell therapy: microcapsules, hydrogels, and electrospun scaffolds. Furthermore, considering the significant impact of surgery on the brain and recurrent GBM, we survey a brief history of orthotopic models of GBM surgical resection.

A new system of yolk-shell microcapsules containing two types of dye-doped liquid crystals was prepared via seed emulsion polymerization in which the synthetic process was mimicking plant respiration. The resulting system demonstrated reversible low voltage-driven switching between multispectral colored and transparent states. Moreover, wearable multicolor electrochromic fibers based on calcium alginate were produced via wet spinning to expand the application of yolk-shell dye-doped liquid crystal microcapsules. In addition to its long-term optical stability, the proposed cells and fibers also have satisfactory driving voltage values of color change (4.8 and 9.0 V), which are far lower than the human body safety voltage (12 V). We believe that the prepared microcapsules and fibers are potentially widely applicable in smart windows, electronic paper, and military camouflage clothing.

Proanthocyanidins are sustainable materials with amphiphilic characteristic, network-forming capacity, and health benefits, which give them possibility as encapsulating biomaterials. We found that proanthocyanidins from Chinese bayberry leaves and grape seeds (BLPs and GSPs) were able to encapsulate oil to form spherical microcapsules of controlled size and architecture. Microcapsules encapsulated with BLPs and GSPs (BMs and GMs) exhibited different physical stability when subjected to environmental stresses. BMs showed higher physical stability to environmental stresses than GMs. The proanthocyanidin shell could protect β-carotene from chemical degradation. Subsequently, varied gastrointestinal behaviors of the microcapsules were observed in simulated digestion. GMs with low stability reduced the lipid digestion and β-carotene bioaccessibility. BMs with high stability retarded lipid digestion but did not change the amount of hydrolyzed lipids and β-carotene bioaccessibility. Our study demonstrates that BLPs rather than GSPs can be used alone as encapsulating material for protection and targeted delivery of lipophilic bioactive compounds.

Polyelectrolyte microcapsules can be produced either by the layer-by-layer assembly technique or the formation of polyelectrolyte complexes at the liquid-liquid interface. Here, we describe the design and construction of DNA microcapsules using the cooperative assembly of DNA and amine-functionalized polyhedral oligomeric silsesquioxane (POSS-NH 2 ) at the oil-water interface. "Janus-like" DNA surfactants (DNASs) assemble in situ at the interface, forming an elastic film. By controlling the jamming and unjamming behavior of DNASs, the interfacial assemblies can assume three different physical states: solid-like, elastomer-like, and liquid-like, similar to that seen with thermoplastics upon heating, that change from a glassy to a rubbery state, and then to a viscous liquid. By the interfacial jamming of DNASs, the liquid structures can be locked-in and reconfigured, showing promising potentials for drug delivery, biphasic reactors, and programmable liquid constructs.

Stimuli-responsive microcapsules, which can release the encapsulated payload under various environmental stimuli, have attracted great interests of the food, pharmaceutical, cosmetics, and agricultural fields in recent years. However, most reported responsive microcapsules normally have a single storage area and thus load/release only one type of payload under one stimulus. In this work, we fabricated a novel kind of multicompartmental intelligent microcapsule with two storage areas and independently controlled (preprogrammable) releasing behavior under different stimuli via rapid photopolymerization of Pickering emulsions. In our strategy, a temperature-sensitive polymeric ( N -isopropyl acrylamide, pNIPAM) particle was prepared and loaded with Nile Red (NR), which was then employed as a Pickering emulsifier to stabilize oil-in-water droplets. The oil was composed of pH-responsive monomers and oil-soluble fluorescent green (OG). Upon exposure to photoirradiation, pH-responsive monomers were polymerized along the interior of the droplets and converted into microcapsules. With NR in the temperature-sensitive pNIPAM@NR particles and OG in the interior of the microcapsules, the as-prepared microcapsules possess dual-carrier capability with two payloads encapsulated dependently in two different compartments. In addition, the microcapsules could respond to two different external stimuli (temperature and pH) and realize the selective and independent release of encapsulated molecules (NR and OG) from the shell and core without any mutual interference. More importantly, the release of NR and OG can be programmed by preprogramming the order of the stimulus responses, which can be altered. Our work develops a simple and effective strategy to fabricate responsive multicompartment microcapsules with preprogrammable release of different molecules.

Polyelectrolyte microcapsules and other targeted drug delivery systems could substantially reduce the side effects of drug and overall toxicity. At the same time, the cardiovascular system is a unique transport avenue that can deliver drug carriers to any tissue and organ. However, one of the most important potential problems of drug carrier systemic administration in clinical practice is that the carriers might cause circulatory disorders, the development of pulmonary embolism, ischemia, and tissue necrosis due to the blockage of small capillaries. Thus, the presented work aims to find out the processes occurring in the bloodstream after the systemic injection of polyelectrolyte capsules that are 5 μm in size. It was shown that 1 min after injection, the number of circulating capsules decreases several times, and after 15 min less than 1% of the injected dose is registered in the blood. By this time, most capsules accumulate in the lungs, liver, and kidneys. However, magnetic field action could slightly increase the accumulation of capsules in the region-of-interest. For the first time, we have investigated the real-time blood flow changes in vital organs in vivo after intravenous injection of microcapsules using a laser speckle contrast imaging system. We have demonstrated that the organism can adapt to the emergence of drug carriers in the blood and their accumulation in the vessels of vital organs. Additionally, we have evaluated the safety of the intravenous administration of various doses of microcapsules.

Efforts to develop microcapsules that respond to different stimuli derive from the incorporation of multiple dynamic assemblies of diverse functional species to the capsule shells. However, this usually involves complicated preparation processes that ultimately hinder the integration of multiple functionalities in a single material. This is addressed in the present work by proposing a multilevel interfacial assembly approach involving polymeric complexes that facilitate the fabrication of multistimuli-responsive microcapsules based on one-step Pickering emulsification using oppositely charged polycation-graphene oxide (GO) and polyanion-surfactant complexes prepared in immiscible liquid solutions. The complexes initially stabilize the emulsion based on electrostatic interactions. Subsequently, the highly dynamic bonding between the polymeric complexes facilitates the rearrangement of components at the oil/water interface to form a continuous interfacial shell membrane. The integrity of the microcapsule shells is sensitive to near-infrared irradiation owing to the GO component and is also sensitive to NaCl content because the assemblies between nanoparticles and polyelectrolytes are bonded through electrostatic interactions. The generality of the proposed strategy is demonstrated by the interfacial assembly of polycation-Fe 3 O 4 complexes and polyanion-surfactant complexes. The resulting microcapsules exhibit salt responsiveness, pH responsiveness, and the ability to be positioned controllably by the application of an external magnetic field. This work provides a promising approach for the preparation of multistimuli-responsive microcapsules.

Microcapsules with two distinct layers of shells were fabricated using an approach combining microfluidics and photopolymerization. Unlike conventional microcapsules with a single shell, a fluorinated oil layer was introduced between the lumen and the outer polymer shell. The fluorinated oil layer significantly suppresses the leakage of the encapsulated ingredients in the lumen and consequently gives the microcapsules remarkable slow release capability for hydrophilic small molecule-based payloads, such as Rhodamine 6G. The release period of Rhodamine 6G can be up to 4 months when using a photocurable resin as the shell material, and the release of Rhodamine 6G can be regulated via the osmolality of the incubation solution for porous hydrogel microcapsules. Even under maximum hypotonic conditions, the release period of Rhodamine 6G in the hydrogel microcapsules is at least 10 days. The slow release capability can be significantly enhanced (6 weeks or longer) by increasing the thicknesses of the hydrogel shell and fluorinated oil layer.

Phase separation driven by solvent evaporation of emulsions can be used to create polymeric microcapsules. The combination of emulsion solvent evaporation with ink-jet printing allows the rapid fabrication of polymeric microcapsules at a target location on a surface. The ink is an oil-in-water emulsion containing in the dispersed phase a shell-forming polymer, a core-forming fluid that is a poor solvent for the polymer, and a low-boiling good solvent. After the emulsion is printed onto the substrate, the good solvent evaporates by diffusion through the aqueous phase, and the polymer and the poor solvent phase separate to form microcapsules. The continuous aqueous phase contains polyvinyl alcohol that serves as an emulsifier and a binder of the capsules to the substrate. This method is demonstrated for microcapsules with various shell-forming polymers (polystyrene, poly(methylmethacrylate) and poly(l-lactide)) and core-forming poor solvents (hexadecane and a 4-heptanone/sunflower oil mixture). Cargoes such as fluorescent dyes (Nile Red and tetracyanoquinodimethane) or active ingredients (e.g., the fungicide tebuconazole) can be encapsulated. Uniform microcapsules are obtained by printing emulsions containing monodisperse oil droplets produced in a microfluidic device. We discuss the physical parameters that need to be controlled for the successful fabrication of microcapsules in inkjet printing. The method for rapid, in situ encapsulation could be useful for controlled-release applications such as in agrochemical sprays, fragrances, functional coatings, and topical medicines.

In this work, surface-functionalized microcapsules from porous carbon nanospheres (PCNs) were successfully prepared by mussel-inspired chemistry with polydopamine (PDA) and metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP). These functional microcapsules are introduced into self-healing hydrogels to enhance their mechanical strength. The PCNs synthesized by a simple soft template method are mixed with linseed oil for loading of the biomass healing agent, and the microcapsules are first prepared by coating PDA. PDA coatings were used to immobilize the ATRP initiator for initiating 4-vinylpyridine on the surface of microcapsules by PET-ATRP. Using these functional microcapsules, the self-healing efficiency was about 92.5% after 4 h at ambient temperature and the healed tensile strength can be held at 2.5 MPa with a fracture strain of 625.2%. All results indicated that the surface-functionalized microcapsules for self-healing hydrogels have remarkable biocompatibility and mechanical properties.

An innovative design of a molecularly imprinted phase-change microcapsule (MIM) system for bifunctional applications in waste heat recovery and targeted pollutant removal was reported in this work. This molecularly imprinted system was successfully constructed by encapsulating n -eicosane with a SiO 2 base shell through emulsion-templated interfacial polycondensation and then coating a molecularly imprinted polymeric layer with bisphenol A (BPA) as a template molecule through surface free-radical polymerization. The morphology, microstructure, and chemical structure of the resultant molecularly imprinted phase-change microcapsules (MIMs) were characterized, and their phase-change behavior, thermal energy-storage performance, and selective adsorption capability were investigated intensively. The MIMs developed in this study achieved an outstanding latent heat-storage capability with a high capacity more than 165 J/g and also showed an excellent phase-change reliability with a very small fluctuation in phase-change temperatures and enthalpies after 500 thermal cycles. Moreover, the MIMs also presented a high thermal stability over 200 °C and good shape stability up to 120 °C. Most of all, an effective specific recognition capability and high recognition efficiency were achieved for the MIMs due to the formation of BPA-molecular imprinting sites on their surface. As a result, the MIMs exhibited good adsorption selectivity toward the BPA molecules and satisfactory reusability for targeted removal of BPA with a removal efficiency of 61.7% after 10 cycles of the rebinding-elution procedure. In view of a smart combination of thermal energy-storage and selective adsorption functions, the MIMs developed in this study demonstrate a great potential in applications for waste heat recovery and targeted pollutant removal of industrial and domestic wastewaters.