Polymeric Microcapsules Research Articles

Self-healing coatings based on poly(urea-formaldehyde) microcapsules: In situ polymerization, capsule properties and application

Protective coating failure can lead to excessive substrate wear increasing the need for maintenance. Polymeric microcapsules loaded with a healing agent can offer self-healing properties when embedded to a coating, repairing the microcracks produced. Epoxy loaded microcapsules with a poly(urea-formaldehyde) shell were successfully prepared within the current study, using in situ polymerization. Microcapsules were obtained as colorless free-flowing powder with a diameter ranging from 37 to 66 μm and high encapsulation efficiency (up to 75%). Microcapsule characteristics, such as morphology, particle size, encapsulation efficiency, thermal stability, were correlated to in situ polymerization conditions, and efficiently induced self-healing ability to an alkyd-based coating.

Encapsulation and characterisation of grape seed proanthocyanidin extract using sodium alginate and different cellulose derivatives

SummaryGrape seed proanthocyanidin extract (GSPE) has health benefits. However, these phenolic compounds undergo degradation reactions and have undesirable sensorial characteristics. GSPE was encapsulated using sodium alginate (SA), SA‐methyl cellulose (MC) and SA‐hydroxypropyl methylcellulose (HPMC) for promoting controlled release, pH stability, temperature and storage period tolerance of GSPE. The microcapsules were characterised using scanning electron microscopy (SEM) and Fourier transform infra‐red (FTIR) analysis. The SA‐MC and SA‐HPMC microcapsules appeared to have a more compact surface than SA‐alone microcapsules. FTIR analysis indicated successful immobilisation of GSPE into the polymeric microcapsules. Moreover, the SA‐MC and SA‐HPMC microcapsules showed higher thermal stability. The microcapsules showed a relatively higher amount of released GSPE at a pH above six than at a lower pH. The SA‐MC and SA‐HPMC microcapsules could be used to retain more GSPE content in the gastric phase and to release it in the intestinal phase for possible absorption. Furthermore, after 28 days of storage at 25 °C, the GSPE retention rate of the microcapsules was still higher than 80%. GSPE encapsulated in SA‐MC and SA‐HPMC microcapsules results in lesser degradation and can be absorbed more effectively. This method has potential for the delivery of colon‐specific materials while exhibiting a sustained‐release characteristic.

Biomimetic Solid-Liquid Transition Structural Dye-Doped Liquid Crystal/Phase-Change-Material Microcapsules Designed for Wearable Bistable Electrochromic Fabric.

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.

Triphenylphosphine‐containing microcapsules fabricated from Pickering emulsions as a thermal latent curing accelerator for an epoxy/anhydride system

AbstractLatent curing accelerators are essential for application to one‐component epoxy systems in various industries, such as coatings, adhesives and electronic packaging. Herein, we developed organic–inorganic hybrid microcapsules encapsulating triphenylphosphine (TPP) by Pickering emulsion polymerization of styrene and methoxyethyl methacrylate with dimethoxydiphenylsilane‐modified silica nanoparticles as emulsifiers. The microcapsules were further surface‐modified by epoxy silane and employed as a thermal latent curing accelerator for an epoxy/anhydride system. Good dispersibility and interfacial bonding of the hybrid microcapsules with the resin matrix were observed. Compared with TPP, the microcapsule‐type accelerator endowed the one‐component epoxy curing system with significantly enhanced storage stability at room temperature of 25 °C (a pot life of 20 days) and a comparable curing activity at high temperature. The activity of the encapsulated accelerator can be blocked and released rapidly and effectively with increasing temperature to trigger the segmental motion of the polymeric microcapsules. Furthermore, the addition of microcapsules increased the glass transition temperature and thermal stability of the epoxy thermosets owing to the organic–inorganic hybrid character. Moreover, the toughness of the cured resin was also improved. Therefore, the latent curing accelerator demonstrated a promising prospect for application in high‐performance one‐pot epoxy formulations. © 2021 Society of Industrial Chemistry.

Living fabrication of functional semi-interpenetrating polymeric materials

Cell-mediated living fabrication has great promise for generating materials with versatile, programmable functions. Here, we demonstrate the engineering of living materials consisting of semi-interpenetrating polymer networks (sIPN). The fabrication process is driven by the engineered bacteria encapsulated in a polymeric microcapsule, which serves as the initial scaffold. The bacteria grow and undergo programmed lysis in a density-dependent manner, releasing protein monomers decorated with reactive tags. Those protein monomers polymerize with each other to form the second polymeric component that is interlaced with the initial crosslinked polymeric scaffold. The formation of sIPN serves the dual purposes of enhancing the mechanical property of the living materials and anchoring effector proteins for diverse applications. The material is resilient to perturbations because of the continual assembly of the protein mesh from the monomers released by the engineered bacteria. We demonstrate the adoption of the platform to protect gut microbiota in animals from antibiotic-mediated perturbations. Our work lays the foundation for programming functional living materials for diverse applications.

Antibacterial self‐healing anticorrosion coatings from single capsule system

AbstractIt is highly desirable to develop self‐healing anticorrosion coatings with enhanced antibacterial function to prevent the scratched area to be fouled or corroded in harsh environments. Herein, we report antibacterial self‐healing anticorrosion coatings via the simple incorporation of the easily synthesized single polymer microcapsule system. Well‐defined polymer microcapsules containing isophorone diisocyanate (IPDI) as a healing agent and 4,5‐dichloro‐2‐n‐octyl‐4‐isothiazolin‐3‐one (DCOIT) as antibacterial molecules were synthesized by one‐pot polymerization. The diameter and core fraction were around 30 μm and 90%, respectively. The active DCOIT content in the core material could be precisely controlled by adjusting the DCOIT/IPDI feeding ratio. The DCOIT/IPDI microcapsules‐embedded protective coating exhibits an adaptive self‐healing anticorrosion property, as shown by electrochemical test under the condition of the salt‐water immersion. Furthermore, the self‐healing coating showed efficient antibacterial function against Escherichia coli and Pseudomonas aeruginosa, which is due to the released active biocide molecules on the damaged surfaces. In contrast to other systems, this single capsule system without any catalyst is perspective for extending the service time of the antibacterial self‐healing materials in harsh environment.

Facile preparation of amino-functionalized polymeric microcapsules as efficient adsorbent for heavy metal ions removal

Herein, amino-functionalized monodisperse polymeric microcapsules were prepared via Schiff-base reaction between polyethyleneimine (PEI) and glutaraldehyde (GA) using a microfluidic approach. The GA encapsulated in the microcapsules leaked through thermal-induced microcracks at the shell of the microcapsules, and then the leaked GA caused crosslinking of the PEI molecules onto the shell without any further treatments. The success of amino-functionalization and the surface morphology of the microcapsules were demonstrated by Fourier transform infrared spectroscopy, scanning electron microscopy, and optical microscopy. Due to the presence of abundant amine groups in the PEI molecules on the shell, the amino-functionalized microcapsules serve as an effective adsorbent for heavy metal ions (HMI). The as-prepared microcapsules were evaluated as adsorbents to remove Cu2+, Cd2+, and Zn2+ ions from the aqueous solution under varying process parameters such as pH, contact time, and metal ion concentration. The adsorption capacity of the microcapsules for Cu2+, Cd2+, and Zn2+ was measured and fitted using the Sips isotherm model. After completion of HMI adsorption, the microcapsules were readily separated from the aqueous suspension by an external magnetic field. In addition, the cyclic adsorption–desorption efficiency of the amino-functionalized microcapsules was almost maintained for five times.

(Invited) On-Chip Characterization of Microcapsules Using a Capacitive Sensor for Microencapsulation and Single-Cell Analysis Applications

Introduction Droplet microfluidics has emerged as a versatile tool for a wide range of biomedical applications. Recently, various types of microfluidic droplet-generation platforms such as T-junction, flow-focusing, and co-flow, have been used for high throughput generation of microcapsules containing cells, drugs and biomolecules. microfluidic microencapsulation is a fast and well-controlled method for the generation of uniform microcapsules with the capability of tuning the size and physicochemical properties of microcapsules during the encapsulation process [1,2].In a microfluidic droplet generation system, droplet formation can be widely classified into three regimes (squeezing, dripping, and jetting). The quality of the generated droplets in terms of stability and uniformity can be highly affected by the type of flow regimes. Since the flow regime and size of the droplets can be influenced by a small change in the system variables (such as the flow rate ratio of the dispersed and continuous phase), real-time monitoring of the droplet generation is vital especially for biomedical applications [3,4].To address the above challenges, in this work we developed microfluidic droplet generation devices (T-junction and flow-focusing) for a well-controlled encapsulation of probiotic bacteria. In order to characterize microcapsules, a capacitive sensor was designed and integrated into the chip. Finally, the performance of the fabricated microfluidic device for on-chip monitoring of the encapsulating process was evaluated. Materials and Methods The device is made out of gold microelectrodes integrated into a polydimethylsiloxane (PDMS) chip. The microfluidic chip was fabricated in a cleanroom facility using a glass substrate with electrodes patterned by photolithography and wet etching process. A microfluidic channel was then fabricated with inlets and outlets by pouring PDMS over a mold followed by bonding the PDMS channel to the glass slide via plasma treatment machine. The dispersion phase (DP) containing alginate and Escherichia coli DH5-alpha (E. coli DH5a), as a bacterial model, was injected through a central channel. The continuous phase (CP) was the mixture solution of mineral oil and span 80 that injected through the other channel. To characterize the generated microcapsules, the change in capacitance between the electrodes was recorded using a potentiostat as probiotic bacteria were encapsulated on the chip. Results and Conclusions E.coli cells were encapsulated inside of hydrogel microcapsules using the microfluidic device. The polymeric microcapsules, once ingested, will protect the probiotics in the acidic pH of the stomach and dissolve or swell in the intestine where the pH increases above 7 to release the entrapped probiotics. The proposed microfluidic microencapsulation method can be used for the high-throughput production of microencapsulates containing probiotic cells as new drug delivery systems.The size and shape of the generated microcapsules was precisely tuned by changing the flow rate ratio of the dispersed and continuous phases followed by measuring the capacitance between the microelectrodes. The results show that the size and shape of microcapsules, as well as the flow regime, can be determined by the sensors signal (Fig 1).Individual microcapsules can be identified based on differences in dielectric properties using impedance spectroscopy techniques which are non-invasive and label-free. The microcapsule characterization system permits will be a powerful tool for evaluating the microencapsulation process as well as calculating the number of produced microcapsules. Besides, there is a potential to calculate the number of single cells in each capsule if the method is optimized.Monodisperse droplet generation in microfluidic devices has wide biomedical applications such as drug encapsulation. Due to the fine control of individual droplets using the developed device, we hope this study attracts significant interest in food and pharmaceutical studies. Reference Zhu, Pingan, and Liqiu Wang. "Passive and active droplet generation with microfluidics: a review." Lab on a Chip1 (2017): 34-75.Chong, Zhuang Zhi, et al. "Active droplet generation in microfluidics." Lab on a Chip1 (2016): 35-58.Shang, Luoran, Yao Cheng, and Yuanjin Zhao. "Emerging droplet microfluidics." Chemical reviews12 (2017): 7964-8040Shi, Zhi, et al. "Step emulsification in microfluidic droplet generation: mechanisms and structures." Chemical Communications64 (2020): 9056-9066. Figure 1

Temperature controlled transformations of giant unilamellar vesicles of amphiphilic triblock copolymers synthesized via microfluidic mixing

We report on a simple approach for synthesis of temperature-responsive giant unilamellar vesicles (GUVs) from poly(N-vinylcaprolactam)15-block-poly(dimethylsiloxane)65-block-poly(N-vinylcaprolactam)15 (PVCL15-PDMS65-PVCL15) triblock copolymer and non-temperature responsive small and giant vesicles from novel poly(N-vinylpyrrolidone)-block-poly(dimethylsiloxane)-block-poly(N-vinylpyrrolidone) (PVPON15-PDMS65-PVPON15 and PVPON6-PDMS30-PVPON6) triblock copolymers using microfluidic mixing at 25 °C. We show that temperature-responsive PVCL15-PDMS65-PVCL15 GUVs with the average diameter of 1.4 ± 0.2 µm while being stable at room temperature for at least 14 days, transformed irreversibly into small vesicles of 168 ± 40 nm after incubation of their aqueous solution at 42 °C for 24 h. We hypothesized that this transformation is induced by local compressive stresses of the vesicle membrane due to the collapse of PVCL blocks above the copolymer lower critical solution temperature (LCST) leading to the decrease of the vesicle membrane thickness. Consequently, we found that the temperature-induced size transformation of the PVCL-based GUVs at 42°C can be suppressed by substituting PVCL with its hydrophilic homologue PVPON, or by suppressing the PVCL's LCST behavior through hydrogen-bonding with tannic acid molecules. In the former case, novel PVPONn-PDMSm-PVPONn triblock copolymers (n = 15, m = 65 and n = 6, m = 30) assemble into vesicles stable from 25 °C to 55 °C as confirmed by optical and electron microscopy, dynamic light scattering (DLS) and small-angle neutron scattering (SANS). In the latter, hydrogen bonding interactions of PVCL with the polyphenol tannic acid (TA) at room temperature resulted in stable PVCL-based GUVs at 42°C as confirmed by optical, electron, and atomic force microscopies. We also found that physical crosslinking of the PVCL corona through hydrogen bonding with TA in PVCL15-PDMS65-PVCL15 GUVs will delay their low pH-induced degradation at 37°C by 48 h compared to non-modified GUVs. Our findings open opportunities for the development of temperature-regulated stable micro-vehicles that would change their structural characteristics in the physiologically relevant temperature range from 25 to 42°C and can be utilized for cell mimicking studies. The developed GUVs also have potential in theranostic drug delivery as substitutes for polymer microcapsules and lipid microbubbles as well as for stimuli-triggered sensing, protection, and rapid response in an aqueous environment.

A one-step in vitro continuous flow assessment of protein release from core-shell polymer microcapsules designed for therapeutic protein delivery

Developing accurate methods for the assessment of therapeutic protein release from polymer drug delivery systems (microcapsules, microspheres, nanoparticles, 3D-printed systems) is of paramount importance for new formulation development. The most straightforward method for protein release assessment is spectrophotometric analysis of the release medium surrounding the formulation. However, direct spectrophotometric analysis is inapplicable to formulations releasing interfering compounds (co-encapsulated drugs, additives) absorbing light in the same spectrum as proteins. Conventional protein release assays also require frequent release medium sampling and replacement, which reduces their accuracy. We propose a one-step method to assess protein release from core/shell microcapsules eliminating the need for sampling and allowing selective real-time protein quantitation in the release medium. To prevent spectral interferences, released protein is differentiated from interfering compounds by employing a colorimetric protein assay reagent, forming a colour complex selectively with the protein, as the release medium. To eliminate sampling, we employed a continuous flow closed loop set-up, where the release medium is constantly circulating between microcapsule-containing tank and spectrophotometer. A series of colorimetric protein assay reagents (bromocresol green, tetrabromophenol blue, eosin B, eosin Y, biuret) were evaluated in terms of their applicability as the release medium in described system. Only biuret reagent was found compatible with proposed method due to formation of color complex stable over extended period of time and low adsorption to microcapsules. Presented method allowed effective evaluation of albumin release from alginate-polyethersulfone microcapsules with accuracy equal to conventional ‘sample and separate’ technique. Albumin release followed first-order kinetics with plateau reached after 19 h.

Evaluation of the synthesis variables’ effect on the properties of PUF/ENB microcapsules using experimental design

Polymers and polymeric composites are constantly susceptible to damage due to the emergence of microcracks which may compromise the structure as well as the useful life of the material during use. Thus, self-healing systems have been increasingly studied and the use of polymeric microcapsules is one of the effective solutions for repairing damage during application. In this work, poly (urea–formaldehyde) microcapsules (PUF) containing 5 ethylidene 2 norbornene (ENB) as core material were prepared by in situ polymerization. To do so, a experimental design Plackett–Burman (PB) was used to evaluate the effect of seven entrance variables of the process on the properties of the obtained microcapsules. The evaluated responses were average diameter, the encapsulated content, synthesis yield, thermal stability temperature and degradation temperature. It was observed that the stirring speed and the emulsifier amount presented the most significant effects for all analyzed parameters on the analyzed response variables. The high curvature significance observed in the Pareto charts for some of the variables indicated that microcapsules with satisfactory properties can be obtained in the central points. None of the analyzed parameters were statistically significant for the synthesis yield and encapsulated content at a confidence level of 90%.

Encapsulation of fluazinam to extend efficacy duration in controlling Botrytis cinerea on cucumber.

Fluazinam is an effective fungicide in controlling gray mold, but has short duration of efficacy. Increasing application dosage may cause phytotoxicity. To overcome this shortage, a controlled-release technology was studied by encapsulating fluazinam. Ethyl cellulose polymer microcapsules were loaded with fluazinam to formulate a fluazinam capsule suspension (FCS). The efficacy for inhibition of B. cinerea and persistency of the FCS were examined by comparing with fluazinam technical concentrate (FTC) and aqueous fluazinam suspension concentrate (FSC) using microscopic observation and high-performance liquid chromatography analysis. FCS formed capsules, with median size of 3.17 μm in diameter, had 82.3% encapsulation efficiency. It had a stronger inhibitory activity against B. cinerea than FTC and FSC measured 7 days after the treatments. The half-life of FCS on cucumber leaves was 3.4 days, longer than the 2.3 days of FSC. FCS formulation significantly improved the inhibition of B. cinerea and resulted in prolonged and sustained release. Moreover, microencapsulation increased the duration of the efficacy of fluazinam on target crops. This formulation could help to sustain pesticides and protect the environment. © 2021 Society of Chemical Industry.

Wear Behavior and Surface Quality of Dental Bioactive Ions-Releasing Resins Under Simulated Chewing Conditions.

Bioactive materials can reduce caries lesions on the marginal sealed teeth by providing the release of ions, such as calcium, phosphate, fluoride, zinc, magnesium, and strontium. The presence of such ions affects the dissolution balance of hydroxyapatite, nucleation, and epitaxial growth of its crystals. Previous studies mostly focused on the ion-releasing behavior of bioactive materials. Little is known about their wear behavior sealed tooth under mastication. This study aimed to evaluate the wear behavior and surface quality of dental bioactive resins under a simulated chewing model and compare them with a resin without bioactive agents. Three bioactive resins (Activa, BioCoat, and Beautifil Flow-Plus) were investigated. A resin composite without bioactive agents was used as a control group. Each resin was applied to the occlusal surface of extracted molars and subjected to in vitro chewing simulation model. We have assessed the average surface roughness (Ra), maximum high of the profile (Rt), and maximum valley depth (Rv) before and after the chewing simulation model. Vickers hardness and scanning electron microscopy (SEM) also analyzed the final material surface quality). Overall, all groups had increased surface roughness after chewing simulation. SEM analysis revealed a similar pattern among the materials. However, the resin with polymeric microcapsules doped with bioactive agents (BioCoat) showed increased surface roughness parameters. The material with Surface Pre-reacted Glass Ionomer (Beautifil Flow-Plus) showed no differences compared to the control group and improved microhardness. The addition of bioactive agents may influence surface properties, impairing resin composites' functional and biological properties. Future studies are encouraged to analyze bioactive resin composites under high chemical and biological challenges in vitro with pH cycles or in situ models.

Ordered Mesoporous Microcapsules from Double Emulsion Confined Block Copolymer Self-Assembly.

Polymeric microcapsules with shells containing homogeneous pores with uniform diameter on the nanometer scale are reported. The mesoporous microcapsules are obtained from confined self-assembly of amphiphilic block copolymers with a selective porogen in the shell of water-in-oil-in-water double emulsion drops. The use of double emulsion drops as a liquid template enables the formation of homogeneous capsules of 100s of microns in diameter, with aqueous cores encapsulated in a shell membrane with a tunable thickness of 100s of nanometers to 10s of microns. Microcapsules with shells that exhibit an ordered gyroidal morphology and three-dimensionally connected mesopores are obtained from the triblock terpolymer poly(isoprene)-block-poly(styrene)-block-poly(4-vinylpyridine) coassembled with pentadecylphenol as a porogen. The bicontinuous shell morphology yields nanoporous paths connecting the inside to the outside of the microcapsule after porogen removal; by contrast, one-dimensional hexagonally packed cylindrical pores, obtained from a traditional diblock copolymer system with parallel alignment to the surface, would block transport through the shell. To enable the mesoporous microcapsules to withstand harsh conditions, such as exposure to organic solvents, without rupture of the shell, we develop a cross-linking method of the nanostructured triblock terpolymer shell after its self-assembly. The microcapsules exhibit pH-responsive permeability to polymeric solutes, demonstrating their potential as a filtration medium for actively tunable macromolecular separation and purification. Furthermore, we report a tunable dual-phase separation method to fabricate microcapsules with hierarchically porous shells that exhibit ordered mesoporous membrane walls within sponge-like micron-sized macropores to further control shell permeability.

Surface Permeability of Membrane and Catalytic Performance Based on Redox-Responsive of Hybrid Hollow Polymeric Microcapsules.

“Smart” polymeric microcapsules with excellent permeability of membranes have drawn considerable attention in scientific and industrial research such as drug delivery carriers, microreactors, and artificial organelles. In this work, hybrid hollow polymeric microcapsules (HPs) containing redox-active gold-sulfide bond were prepared with bovine serum albumin, inorganic metal cluster (AuNCs), and poly(N-isopropylacrylamide) conjugates by using Pickering emulsion method. HPs were transferred from water-in-oil to water-in-water by adding PEGbis(N-succinimidylsuccinate). To achieve redox-responsive membrane, the Au-S bond units incorporated into the microcapsules’ membranes, allowed us to explore the effects of a new stimuli, that is, the redox Au-S bond breaking on the microcapsules’ membranes. The permeability of these hybrid hollow polymeric microcapsules could be sensitively tuned via adding environment-friendly hydrogen peroxide (H2O2), resulting from a fast fracture of Au-S bond. Meanwhile, AuNCs and conjugates could depart from the microcapsules, and enhance the permeability of the membrane. Based on the excellent permeability of the membrane, phosphatase was encapsuled into HPs and p-nitrophenyl phosphate as a substrate. After adding 1 × 10−2 and 1 × 10−4 M H2O2, the catalytic efficiency was nearly 4.06 and 2.22 times higher than that of HPs in the absence of H2O2, respectively. Hence, the unique redox-responsive HPs have potential applications in biocatalytic reaction, drug delivery, and materials as well as in bioscience.

Biodegradable Defined Shaped Printed Polymer Microcapsules for Drug Delivery.

This work describes the preparation and characterization of printed biodegradable polymer (polylactic acid) capsules made in two different shapes: pyramid and rectangular capsules about 1 and 11 μm in size. Obtained core-shell capsules are described in terms of their morphology, loading efficiency, cargo release profile, cell cytotoxicity, and cell uptake. Both types of capsules showed monodisperse size and shape distribution and were found to provide sufficient stability to encapsulate small water-soluble molecules and to retain them for several days and ability for intracellular delivery. Capsules of 1 μm size can be internalized by HeLa cells without causing any toxicity effect. Printed capsules show unique characteristics compared with other drug delivery systems such as a wide range of possible cargoes, triggered release mechanism, and highly controllable shape and size.

Monodispersed sodium hyaluronate microcapsules for transdermal drug delivery systems

Here, we present an alternative to cross-linking for the preparation of monodispersed polymer microcapsules made from water-soluble and biocompatible sodium hyaluronate.

Enhanced cytotoxicity caused by AC magnetic field for polymer microcapsules containing packed magnetic nanoparticles

Magnetic hyperthermia (MH) is a perspective tool to treat the tumor while the magnetic material is delivered. The key problems in MH development is to ensure an effective local heating within cancer cell without overheating other cells. In order to do that one has to reach substantial local accumulation of magnetic nanoparticles (MNPs) and/or magnetically sensitive objects with advanced heat properties. Absorbing heat energy for destroying tumor cells can be generated only if there is sufficient amount of locally placed MNPs. In this work, we propose polyelectrolyte microcapsules modified with iron oxide nanoparticles as an approach to tie magnetic materials in high concentration locally. These microcapsules (about 3 microns in diameter) can be readily internalized by various cells. The human fibroblasts uptake of the microcapsules and cytotoxic effect upon the influence of alternating magnetic field (AMF) while magnetic capsules are inside the cells is under study in this work. The cytotoxicity of the magnetic microcapsules was compared with the cytotoxicity of the MNPs while free in the solution to evaluate the effect of bounding MNPs. A cytotoxic effect on cells was found in the case of preliminary incubation of fibroblasts with capsules while the AMF is applied. In the case of MNPs in an equivalent dose per mass of magnetic material, there was no cytotoxic effect noticed after the treatment with the field. It is noteworthy that during the treatment of cells with the AMF, the increase in temperature of the incubation medium was not registered. The morphological changes on fibroblasts were consistent with the data of the viability assessment. Thus, the synthesized capsules are shown as a means for local enhancement of magnetic hyperthermia in the treatment of tumor diseases.

Novel reusablepH‐responsive photocatalyst polymeric microcapsules for dye treatment

Novel reusable<scp>pH</scp>‐responsive photocatalyst polymeric microcapsules for dye treatment

Global Sensitivity Analysis for the Polymeric Microcapsules in Self-Healing Cementitious Composites.

Cementitious composites with microencapsulated healing agents are appealing due to the advantages of self-healing. The polymeric shell and polymeric healing agents in microcapsules have been proven effective in self-healing, while these microcapsules decrease the effective elastic properties of cementitious composites before self-healing happens. The reduction of effective elastic properties can be evaluated by micromechanics. The substantial complicacy included in micromechanical models leads to the need of specifying a large number of parameters and inputs. Meanwhile, there are nonlinearities in input–output relationships. Hence, it is a prerequisite to know the sensitivity of the models. A micromechanical model which can evaluate the effective properties of the microcapsule-contained cementitious material is proposed. Subsequently, a quantitative global sensitivity analysis technique, the Extended Fourier Amplitude Sensitivity Test (EFAST), is applied to identify which parameters are required for knowledge improvement to achieve the desired level of confidence in the results. Sensitivity indices for first-order effects are computed. Results show the volume fraction of microcapsules is the most important factor which influences the effective properties of self-healing cementitious composites before self-healing. The influence of interfacial properties cannot be neglected. The research sheds new light on the influence of parameters on microcapsule-contained self-healing composites.