Responsive Microcapsules Research Articles

Effect of thermal processing on the integrity of polyurea microcapsules for underwater adhesives

Adhesives that rely on a curing mechanism struggle to function in underwater environments due to detrimental interactions with water. One strategy to overcome this involves protecting sensitive components in mechanically responsive microcapsules. In this way, a two-part adhesive can be achieved via a single mixture, applied as one would apply a pressure sensitive adhesive. This work focused on improving polyurea microcapsule shell integrity, specifically focusing on the effect of additional thermal processing. The improved microcapsule shells displayed limited payload leakage with only an 8 % loss in pot life compared to the base isocyanate resin alone. A mixture of optimized microcapsules and isocyanate resin was evaluated against a wide range of substrates and conditions, including dry and wet environments. When microcapsules were intentionally ruptured to release the catalyst and crosslinker payload, the microcapsule-isocyanate mixture had improved adhesive strength (506 %) compared to the base isocyanate resin without microcapsules.

Fabrication of dual responsive microcapsules based on starch with enhanced foliar adhesion and photostability for improving control efficacy and reducing environmental risks

Stimuli-responsive controlled release formulations offer a promising avenue for enhancing effective utilization and mitigating environmental risks of pesticides. Herein, pH and enzyme-responsive pesticide microcapsules (AVE@CPS-Fe-TA) were constructed by encapsulating carboxylated porous starch (CPS) loaded with avermectin (AVE) within tannic acid-iron complexes (Fe-TA) to improve the insecticidal efficacy and reduce toxicity to non-targets of AVE. The results showed that the loading content of AVE in the modified starch-based microcapsules could be precisely adjusted by the enzymatic hydrolysis time of starch. The prepared AVE@CPS-Fe-TA had pH and α-amylase dual responsive release properties and exhibited superior photostability, and its photolysis half-life was extended by 15.57-fold compared to AVE technical. Additionally, the leaf retention rate of AVE@CPS-Fe-TA after being rinsed by simulated rainwater was 6.08 times higher than that of commercial formulation AVE EC. In greenhouse insecticidal activity experiment, AVE@CPS-Fe-TA demonstrated a high control efficacy against Ostrinia furnacalis and had a prolonged effective duration. Moreover, AVE@CPS-Fe-TA significantly reduced the acute toxicity of AVE to zebrafish and promoted the growth of maize seedlings. Therefore, this work would provide eco-friendly stimuli-responsive microcapsules of pesticides for improving the efficiency of utilization and reducing environmental risks.

Multistimuli responsive microcapsules produced by the prilling/vibration technique for targeted colonic delivery of probiotics

This study aimed to microencapsulate the probiotic strain Lactiplantibacillus plantarum 4S6R (basonym Lactobacillus plantarum) in both microcapsules and microspheres by prilling/vibration technique. A specific polymeric mixture, selected for its responsiveness to parallel colonic stimuli, was individuated as a carrier of microparticles. Although the microspheres were consistent with some critical quality parameters, they showed a low encapsulation efficiency and were discarded. The microcapsules produced demonstrated high yields (97.52%) and encapsulation efficiencies (90.06%), with dimensional analysis and SEM studies confirming the desired size morphology and structure. The results of thermal stress tests indicate the ability of the microcapsules to protect the probiotic. Stability studies showed a significant advantage of the microcapsules over non-encapsulated probiotics, with greater stability over time. The release study under simulated gastrointestinal conditions demonstrated the ability of the microcapsules to protect the probiotics from gastric acid and bile salts, ensuring their viability. Examination in a simulated faecal medium revealed the ability of the microcapsules to release the bacteria into the colon, enhancing their beneficial impact on gut health. This research suggests that the selected mixture of reactive polymers holds promise for improving the survival and efficacy of probiotics in the gastrointestinal tract, paving the way for the development of advanced probiotic products.

Tailored synthesis of pH-responsive biodegradable microcapsules incorporating gelatin, alginate, and hyaluronic acid for effective-controlled release

In response to escalating environmental concerns and the urgent need for sustainable drug delivery systems, this study introduces biodegradable pH-responsive microcapsules synthesized from a blend of gelatin, alginate, and hyaluronic acid. Employing the coacervation process, capsules were created with a spherical shape, multicore structure, and small sizes ranging from 10 to 20 μm, which exhibit outstanding vitamin E encapsulation efficiency. With substantial incorporation of hyaluronic acid, a pH-responsive component, the resulting microcapsules displayed noteworthy swelling behavior, facilitating proficient core ingredient release at pH 5.5 and 7.4. Notably, these capsules can effectively deliver active substances to the dermal layer under specific skin conditions, revealing promising applications in topical medications and cosmetics. Furthermore, the readily biodegradable nature of the designed capsules was demonstrated through Biochemical Oxygen Demand (BOD) testing, with over 80 % of microcapsules being degraded by microorganisms after one week of incubation. This research contributes to the development of responsive microcapsules and aligns with broader environmental initiatives, offering a promising pathway to mitigate the impact of microplastics while advancing various applications.

Programmable Photoswitchable Microcapsules Enable Precise and Tailored Drug Delivery from Microfluidics.

The development of precision personalized medicine poses a significant need for the next generation of advanced diagnostic and therapeutic technologies, and one of the key challenges is the development of highly time-, space-, and dose-controllable drug delivery systems that respond to the complex physiopathology of patient populations. In response to this challenge, an increasing number of stimuli-responsive smart materials are integrated into biomaterial systems for precise targeted drug delivery. Among them, responsive microcapsules prepared by droplet microfluidics have received much attention. In this study, we present a UV-visible light cycling mediated photoswitchable microcapsule (PMC) with dynamic permeability-switching capability for precise and tailored drug release. The PMCs were fabricated using a programmable pulsed aerodynamic printing (PPAP) technique, encapsulating an aqueous core containing magnetic nanoparticles and the drug doxorubicin (DOX) within a poly(lactic-co-glycolic acid) (PLGA) composite shell modified by PEG-b-PSPA. Selective irradiation of PMCs with ultraviolet (UV) or visible light (Vis) allows for high-precision time-, space-, and dose-controlled release of the therapeutic agent. An experimentally validated theoretical model was developed to describe the drug release pattern, holding promise for future customized programmable drug release applications. The therapeutic efficacy and value of patternable cancer cell treatment activated by UV radiation is demonstrated by our experimental results. After in vitro transcatheter arterial chemoembolization (TACE), PMCs can be removed by external magnetic fields to mitigate potential side effects. Our findings demonstrate that PMCs have the potential to integrate embolization, on-demand drug delivery, magnetic actuation, and imaging properties, highlighting their immense potential for tailored drug delivery and embolic therapy.

Pancreatic cancer cell line in responsive hydrogel microcapsules for drug evaluation

AbstractDrug therapies are the cornerstone of systemic treatment for pancreatic cancer patients. However, the relative outcome of drug evaluation is often hampered by the complex microenvironment of pancreatic cancer due to the lack of reasonable tumor models. Here, we proposed a novel platform that integrated pancreatic adenocarcinoma cells encapsulated into hydrogel microcapsules for three‐dimensional (3D) tumor cultivation and antitumor agent evaluation. These hydrogel microcapsules contain alginate/poly (N‐isopropyl acrylamide) (alginate/PNIPAM) shells and carboxymethyl cellulose cores, which are generated through the microfluidic electrospray technique. The microcapsules have the feature of rapid response to temperature, by which they can regulate the internal pressure environment. Besides, benefiting from good monodispersity, precise size control, and biocompatibility of these microcapsules, these wrapped tumor cells have the capacity for proliferating spontaneously and forming 3D tumor spheroids with good cell viability. We have demonstrated that pancreatic adenocarcinoma cells encapsulated in the composite microcapsules with different PNIPAM concentrations showed different drug sensitivity, which could be ascribed to the influence of external pressures environment. These results indicate that the tumor spheroids coated in these responsive microcapsules have great potential in the analysis of antitumor drug sensitivity.

Smart antibacterial nanocellulose packaging film based on pH-stimulate responsive microcapsules synthesized by Pickering emulsion template

Spoilage results in food waste and endangers consumer health, and the smart antibacterial packaging can effectively inhibit bacterial growth and reduce food spoilage. In this study, the smart antibacterial nanocellulose packaging films were developed by adding the pH-stimulated responsive microcapsules into cellulose nanofibril (CNF) film-forming. The microcapsules were synthesized by interfacial polymerization of Pickering emulsion. Carboxylated cellulose nanocrystals as solid particles stabilized the composited oil phase to prepare the oil-in-water Pickering emulsion. The emulsion with the particle concentration of 1.25 wt% and the oil phase mass fraction of 7.5 % processes excellent stability and uniform particle size, was chosen to synthesize microcapsules. The cinnamaldehyde in the film with the addition amount of microcapsules 0.6 g burst released in the first 1 h and then slowly, and the cumulative release at pH 2.0, 4.0, 5.5 and 7.2 was 28.43 μg/cm2, 18.84 μg/cm2, 16.52 μg/cm2 and 12.89 μg/cm2, respectively. The inhibitory rate of film against both E. coli and L. monocytogenes reached 99 % at pH 4.0. The shelf life of pork packed by the film prolonged to nearly 9 d at room temperature. The developed films have the potential to be used in food packaging.

10-hydroxycamptothecin-loaded starch-based microcapsules with the stepwise responsive release strategy for targeted controlled release

Controlled and accurate drug release at the target site have been the focus of research. Especially in cancer therapy, economical, convenient and accurate delivery strategies could help to reduce the toxic effects of drugs on normal tissues and improve drug availability. In the study, glutathione (GSH)-responsive microcapsules (FA-RSMCs) were prepared by sonochemical method based on thiolated modified starch. 10-Hydroxycamptothecin (HCPT) was designed as a reactive oxygen species (ROS)-responsive polyprodrug (polyHCPT), which was loaded into the core of the microcapsules to obtain stepwise released drug delivery carriers. In the tumor microenvironment, FA-RSMCs first triggered GSH-responsive cleavage to release polyHCPT, followed by ROS-responsive cleavage of polyHCPT to release intact HCPT drug molecules. The results of experiments in simulated tumor microenvironment showed that FA-RSMCs exhibited good cascade-response release properties in vitro. It exhibited good anti-tumor ability and protection of normal cells in cytotoxicity in vitro. This strategy enhanced the accuracy and safety of targeted delivery of HCPT via microcapsules, which has potential for clinical application.

Dual-responsive microcapsules with tailorable shells from oppositely charged biopolymers for precise pesticide release

pH/Laccase responsive microcapsules with tailorable shells were prepared by the layer-by-layer deposition of sodium lignosulfonate and chitosan for protecting photosensitive avermectin.

Ultrasound responsive microcapsules for antibacterial nanodrug delivery

Ultrasound responsive microcapsules for antibacterial nanodrug delivery

Stimulus responsive microcapsules and their aromatic applications

Fragrances and essential oils are promising for a wide range of applications due to their pleasant odors and diverse effects. However, direct addition to consumer products has the disadvantages of short retention time and easy deterioration of odor. At the same time, releasing a large amount of odor in a short time may be an unpleasant experience, which severely limits the practical application of aromatic substances. Microencapsulation perfectly solves these problems. Stimuli-responsive microcapsules, which combine environmental stimulation with microencapsulation, can not only effectively prevent the rapid decomposition and evaporation of aroma components, but also realize the "on-off" intelligent release of aroma substances to environmental changes, which have great promise in the field of fragrances. In this review, the application of stimuli-responsive microcapsules in fragrances is highlighted. Firstly, various encapsulation materials used to prepare stimuli-responsive aromatic microcapsules are described, mainly including some natural polymers, synthetic polymers, and inorganic materials. Subsequently, there is a detailed description of the common release mechanisms of stimuli-responsive aromatic microcapsules are described in detail. Finally, the application and future research directions are given for stimuli-responsive aromatic microcapsules in new textiles, food, paper, and leather.

Facile preparation of pH/pectinase responsive microcapsules based on CaCO3 using fungicidal ionic liquid as a nucleating agent for sustainable plant disease management

Controlled release formulation of pesticides based on microcapsules is a promising strategy for improving utilization efficiency and reducing adverse effects caused by conventional pesticide formulations. However, the complex preparation process and use of toxic additives limit the development of microcapsules. Herein, a simple and green method was developed to prepare double-shelled CaCO3 microcapsules of pesticide using the newly prepared prochloraz ionic liquid (PRO IL) as a nucleating agent to precipitate CaCO3 on the surface of PRO IL micelles in situ and pectin as a coating agent without a complex post-loading process. The results showed that the obtained spherical microcapsules had pectinase and pH dual responsive release properties. The release of PRO from microcapsules belonged to a non-Fickian behavior controlled by the dissolution and diffusion. The photostability of obtained microcapsules was 1.58 times better than that of PRO EW. The fungicidal tests showed that microcapsules had a long-term efficacy against Sclerotinia sclerotiorum and the control efficacy was 1.65 times that of PRO EW at the same concentration. The genotoxicity tests showed that PRO IL@CaCO3@pectin microcapsules did not increase genotoxicity to cells of Vicia faba compared with PRO EW and encapsulation of pesticides in carriers could reduce genotoxicity of PRO IL to plants. These findings would provide a new strategy for the development of calcium carbonate-based microcapsules which could effectively increase the utilization efficiency of pesticides by improving the photostability and durability in environment.

Facile Preparation of Ph/Pectinase Responsive Microcapsules Based on Caco3 Using Fungicidal Ionic Liquid as a Nucleating Agent for Sustainable Plant Disease Management

Facile Preparation of Ph/Pectinase Responsive Microcapsules Based on Caco3 Using Fungicidal Ionic Liquid as a Nucleating Agent for Sustainable Plant Disease Management

Materials Microencapsulation Applications in Oil Drilling and Production

Advancing the materials used in oil drilling and production has significantly augmented the industry’s efforts to improving the processes and preventing the operations failures. Presently, oil drilling and production demand that materials do not simply demonstrate better performance, but also possess some degree of intelligence. The intelligence is induced to the materials by preprogramming a certain response to a change in the surrounding conditions to trigger the function of the used materials. This improves the performance and prevents possible physical damage or mitigates negative changes in the downhole environment during production. Smart responsive microcapsules, with the ability to self-heal the materials, delayed and targeted active release, and could become a viable solution for the challenges the oil drilling and production industry is currently facing. This paper provides an overview of the benefits that a microencapsulation technique has demonstrated when applied to the materials involved in oil drilling and production. It outlines possibilities for improving the well drilling process when products containing microcapsules are applied. Several examples demonstrating the ability to perform downhole treatment seamlessly with pre-designed microcapsules are embedded. The paper puts emphasis on developing smart self-healing materials by integrating microcapsules into the cement sheath as well as the coatings of steel pipes to mitigate costly failures. Finally, the paper shows examples of some outstanding results of microencapsulated materials when applied to the most advanced research areas in the oil industry such as enhanced oil recovery (EOR) and hydraulic fracturing.

PH-Responsive Capsules with a Fibril Scaffold Shell Assembled from an Amyloidogenic Peptide.

Peptides and proteins have evolved to self-assemble into supramolecular entities through a set of non-covalent interactions. Such structures and materials provide the functional basis of life. Crucially, biomolecular assembly processes can be highly sensitive to and modulated by environmental conditions, including temperature, light, ionic strength and pH, providing the inspiration for the development of new classes of responsive functional materials based on peptide building blocks. Here, it is shown that the stimuli-responsive assembly of amyloidogenic peptide can be used as the basis of environmentally responsive microcapsules which exhibit release characteristics triggered by a change in pH. The microcapsules are biocompatible and biodegradable and may act as vehicles for controlled release of a wide range of biomolecules. Cryo-SEM images reveal the formation of a fibrillar network of the capsule interior with discrete compartments in which cargo molecules can be stored. In addition, the reversible formation of these microcapsules by modulating the solution pH is investigated and their potential application for the controlled release of encapsulated cargo molecules, including antibodies, is shown. These results suggest that the approach described here represents a promising venue for generating pH-responsive functional peptide-based materials for a wide range of potential applications for molecular encapsulation, storage, and release.

Low intensity focused ultrasound responsive microcapsules for non-ablative ultrafast intracellular release of small molecules.

Focused ultrasound (FU) is in demand for clinical cancer therapy, but the possible thermal injury to the normal peripheral tissues limits the usage of the ablative FU for tumors with a large size; therefore research efforts have been made to minimize the possible side effects induced by the FU treatment. Non-ablative focused ultrasound assisted chemotherapy could open a new avenue for the development of cancer therapy technology. Here, low intensity focused ultrasound (LIFU) for controlled quick intracellular release of small molecules (Mw ≤ 1000 Da) without acute cell damage is demonstrated. The release is achieved by a composite poly(allylamine hydrochloride) (PAH)/poly-(sodium 4-styrenesulfonate) (PSS)/SiO2 microcapsules which are highly sensitive to LIFU and can be effectively broken by weak cavitation effects. Most PAH/PSS/SiO2 capsules in B50 rat neuronal cells can be ruptured and release rhodamine B (Rh-B) into the cytosol within only 30 s of 0.75 W cm-2 LIFU treatment, as demonstrated by the CLSM results. While the same LIFU treatment shows no obvious damage to cells, as proved by the live/dead experiment, showing that 90% of cells remain alive.

Broaden reflection bandwidth of chiral nematic liquid crystals by chiral compound-loaded thermally responsive microcapsules

ABSTRACT Controllable broadband reflection of cholesteric liquid crystal (N*-LC) materials has sparked enormous interests due to its significance in areas such as infrared shielding glass films and LC displays. In this study, we report a novel method to broaden the bandwidth of the chiral nematic liquid crystal (N*-LC) by a thermally responsive microcapsule (TRMC) loaded with chiral compound. Diffusion of chiral compound loaded in the microcapsules triggered by heating resulted in non-uniform pitch distribution, which were locked by UV-radical polymerisation. The results showed that the reflection bandwidth could be broadened by adjusting mass of the microcapsules, heating time, UV intensity, concentration of UV-polymerisable free radical monomer and polymerisation temperature. The reflection bandwidth was broadened from 240 nm to 374 nm by optimising the above factors.

Preparation and properties of NIR-Responsive microcapsules

In this paper, near infrared (NIR) absorbing dye and fluorane dye (FD) was successfully encapsulated into microcapsules with NIR light responsive performance. The NIR responsive microcapsules are able to be utilized in information recording and anti-counterfeiting fields. Specifically, the factors effecting on synthesis of NIR responsive microcapsules were studied in detail. Microcapsules with an average particle size of 0.2 ∼ 0.5 μm were prepared by adjusting the mass ratio of shell/core material, the viscosity of oil phase and the mass ratio of water/oil (W/O) phase. It was found that the preferred reaction condition was the feeding mass ratio of shell/core materiel at 1:2 and the W/O phase mass ratio of 2:1. When the feeding mass ratio of NIR absorbing dye and FD is 1/10, the NIR responsive microcapsules have the best coloration performance. Then the NIR responsive microcapsules were coated on aluminum substrate and scanned by 808 nm near-infrared laser, the image precision reached 20 μm.

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

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

Synthesis of Temperature/pH Dual-Stimuli-Response Multicompartmental Microcapsules via Pickering Emulsion for Preprogrammable Payload Release.

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.