Microcapsules Research Articles

Concurrent Superhydrophobicity and Thermal Energy Storage of Microcapsule with Superior Thermal Stability and Durability

Despite considerable success in design and preparation of superhydrophobic particles, a facile and low-cost approach to develop multifunctional particles, especially microcapsules with the integrated performances of intrinsically long-lasting and highly stable superhydrophobicity and other passive/active functionalities, remains extremely challenging and is still in its infancy. Herein, we report a microcapsule (MC) with a micro/nano-hierarchical shell and a phase change material (PCM) core by a low-cost one-pot method. The resulting microcapsules (MCs) possess concurrent features of superhydrophobicity and thermal energy storage. Against thermal attack up to approximately 240 °C, the microstructure of MCs is nearly intact to avoid an obvious leakage of encapsulated PCM at high temperature, and meanwhile superhydrophobicity of MCs is enhanced unexpectedly to a static contact angle (CA) of 167.4 ± 0.3° and slide angle (SA) of 5 ± 0.5°. After conventional storage of 80 days, MCs still show a good superhydro...

Optimization of de-esterified tragacanth microcapsules by computational fluid dynamic and the Taguchi design with purpose of the cell encapsulation

This work presents the development of the new De-Esterified Tragacanth (DET) microcapsules (MCs). Co-flow extrusion method was applied for producing the MCs; the processing parameters were optimized by the Taguchi design to obtain the smallest and the most spherical MCs. Computational Fluid Dynamic (CFD) modeling was accomplished to show the formation of droplets at different airflows, and finally, βTC3 pancreatic cells were encapsulated in the MCs. The optimum MCs had 214.58μm size and 60.75% sphericality. The air pressure and the cross-linking reaction of DET were the most influential parameter in size and the sphericality of MCs, respectively. CFD showed two velocity vortices with rotational flow formed in the chamber, which caused changing the droplet moving direction. The encapsulated cells were proliferated, and cell viability was not reduced during six days. These phenomena make DET MCs a potential candidate for the cell encapsulation.

Preparation and characterization of PHMB-based multifunctional microcapsules

Insects and microbes can cause disease and corrode materiel deployed in humid environments. Materials with multifunctional properties are highly desirable to the Army to create textile products that would inherently mitigate these issues and decrease Soldier load. Microcapsules (MCs) that encapsulate active compounds such as insect repellents are a potential platform to accomplish this. MCs that exhibit antibacterial and antifungal properties were prepared using an antimicrobial polymer, PHMB, as the shell, and the encapsulation of an insect repellent, picaridin, is reported. MCs are spherical, uniform, and demonstrate a positive zeta potential. FTIR analysis confirms the presence of both active components. MCs were studied for storage stability and their ability to impart functionality to a military relevant textile. Microscopy images demonstrate that MCs remain stable when stored in diH2O for at least six months. Antibacterial activity is observed for MC concentrations across two orders of magnitude in solution. MCs were adsorbed onto a 50:50 nylon:cotton blend (NyCo) as a model for functionalized materiel. GC data indicates that picaridin loading levels are more than ten times the required dose for deterring mosquitoes and both antibacterial and antifungal properties are exhibited. Treated fabric is resistant to fungal growth throughout a four week culture period. A four week storage study demonstrates no discernible loss in picaridin content, and NyCo swatches sustain at least a three log reduction in bacteria growth for all time points. The findings detailed in the following report suggest that these PHMB-based MCs could be used to functionalize materials against microbial organisms and mosquitoes, and are robust enough to endure storage in their crude form and as a coating.

Polysiloxane microcapsules, microspheres and their derivatives

Polysiloxane microcapsules, microspheres and their derivatives

Using Coordination Assembly as the Microencapsulation Strategy to Promote the Efficacy and Environmental Safety of Pyraclostrobin

The broad‐spectrum and widely used fungicide pyraclostrobin is encapsulated using a coordination assembly between Fe3+and tannic acid to promote its efficacy and environmental safety. The deposition is confirmed by the surface zeta potential and energy dispersive spectroscopy. Optical microscopy, scanning electron microscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM) observations are integrated to characterize the pyraclostrobin‐loaded microcapsules (MCs). These MCs retain a spherical shape when suspended in water but quickly deform or rupture after the water evaporates when deposited for 1 cycle. After sequential deposition of the membrane, the membrane thickness increases linearly according to TEM and AFM height analyses. These MCs show satisfactory efficacy on rice blast, resulting in significantly higher yields at doses of 120 and 180 g ha−1. Moreover, these MCs display significantly lower toxicity toBrachydanio rerio,Daphnia magna,Xenopus laevis, andRana nigromaculata. Overall, this novel microencapsulation strategy is capable of promoting the efficacy and environmental safety of pyraclostrobin.

Microencapsulation of β-Carotene Based on Casein/Guar Gum Blend Using Zeta Potential-Yield Stress Phenomenon: an Approach to Enhance Photo-stability and Retention of Functionality.

β-Carotene, abundant majorly in carrot, pink guava yams, spinach, kale, sweet potato, and palm oil, is an important nutrient for human health due to its scavenging action upon reactive free radicals wherever produced in the body. Inclusion of liposoluble β-carotene in foods and food ingredients is a challenging aspect due to its labile nature and low absorption from natural sources. This fact has led to the application of encapsulation of β-carotene to improve stability and bioavailability. The present work was aimed to fabricate microcapsules (MCs) of β-carotene oily dispersion using the complex coacervation technique with casein (CA) and guar gum (GG) blend. The ratio of CA:GG was found to be 1:0.5 (w/v) when optimized on the basis of zeta potential-yield stress phenomenon. These possessed a higher percentage yield (71.34±0.55%), lower particle size (176.47±4.65μm), higher encapsulation efficiency (65.95±5.33%), and in general, a uniform surface morphology was observed with particles showing optimized release behavior. Prepared MCs manifested effective and controlled release (up to 98%) following zero-order kinetics which was adequately explained by the Korseymer-Peppas model. The stability of the freeze-dried MCs was established in simulated gastrointestinal fluids (SGF, SIF) for 8h. Antioxidant activity of the MCs was studied and revealed the retention of the functional architecture of β-carotene in freeze-dried MCs. Minimal photolytic degradation upon encapsulation of β-carotene addressed the challenge regarding photo-stability of β-carotene as confirmed via mass spectroscopy.

Thermotolerance Study of Bagasse-alginate Encapsulant Using Effective Thermal Conductivity Model for Sustainable Probiotic Feed

A great potential in the synthesis of heat resistant microcapsules for probiotic was developed via the synthesis of heterogeneous material. In the study of heterogeneous material, effective thermal conductivity is widely used in measuring the thermal behaviour of the material and is regarded as a key thermophysical property. Production of heterogeneous material could be created via filler incorporation. Incorporation of filler in the microcapsule matrix could enhance the thermotolerance characteristic of the microcapsule. The encapsulation wall concentration also could contribute to the value of effective thermal conductivity of the heterogeneous material. This research is aimed to model fitting the series model of effective thermal conductivity using data collected from immobilised Lactobacillus rhamnosus NRRL 442 in alginate microcapsule (NaA) with incorporated sugarcane bagasse (SB). Different alginate concentration of 1 %, 2 % and 3 % and NaA : SB ratio of 1 : 0, 1 : 1 and 1 : 1.5 were used in synthesising the microcapsules. The microcapsules were produced using the extrusion method. The lowest effective thermal conductivity was obtained from the same microcapsule preparation using 3 % of alginate concentration and at a NaA : SB concentration ratio of 1 : 1.5. The microcapsules prepared using 1 % of alginate concentration and a NaA : SB concentration ratio of 1:0 showed the highest effective thermal conductivity. The regression values (R2) for all alginate concentrations (1 %, 2 % and 3 %) were found to be 0.9997, 1.0000, and 0.9973. The regression models of the effective thermal conductivity in all alginate concentrations versus filler (SB) concentration were plotted. High coefficient of determination was obtained and showed strong correlation between effective thermal conductivity and SB concentration for different alginate concentration. This study could be beneficial in the production of products that necessitate heat treatment thermo tolerance especially in pelleted probiotic feed.

Drying and Preservation of Phytochemicals from Elateriospermum Tapos Seed Oil Using Combination of Freeze Drying and Microwave Technique

Elateriospermum Tapos seed oil (ETSO) or known as perah seed oil contain high concentration of omega 3 fatty acid and exposed to lipid oxidation in the form of free oil. In this work, microencapsulation process of ETSO was formulated by using combination of freeze drying and microwave technique assisted freeze drying using maltodextrin (MD) and sodium caseinate (SC) as wall materials in order to protect the oil from oxidation. This kind of drying technique is a new technology of oil microencapsulation with faster drying time than conventional freeze drying. The main goal of this study was to evaluate the microencapsulation process on the physical and chemical characteristic of oil microcapsule. The microencapsulation effectiveness was determined in base of process yield and the microencapsulation efficiency. The white dry microcapsules were subjected to Field Emission Scanning Electron Microscope (FESEM) to study the powder morphology, Fourier Transform Infrared Spectroscopy (FTIR) to study chemical bonding and thermogravimetric (TGA) for thermal profile. Highest encapsulation yields of 82 % and microencapsulation efficiency of 42 % were achieved when the compositions of wall material used as encapsulation agents were 75 % maltodextrin and 25 % sodium caseinate, freeze drying time was 7 h and the ratio of oil-wall material was 1 : 4.

Production and Characterization of Biodegradable Films Incorporated with Clove Essential Oil/ß-cyclodextrin Microcapsules

Biodegradable films can be designed to contain natural antioxidants, vitamins and antimicrobials in order to extend shelf life of the product keeping the natural sensorial properties. The objective of this study was production and characterization of biodegradables films incorporated with clove essential oil (CEO) microcapsules. The CEO was encapsulated in s-cyclodextrin (s-CD) by freeze drying and spray drying methods. The encapsulation efficiencies were 277.17 and 575.49 mg CEO/ g of sample, for spray drying and freeze drying methods, respectively. Alginate films incorporated with CEO/s-CD inclusion complexes were prepared by casting method, and investigated for mechanical and barrier properties. Generally, the films prepared with CEO encapsulated, compared with the control films, were less transparent, and less flexible. The CEO/s-CD inclusion complex increased water vapor permeability (WVP) of films and decreased their elasticity, contributing to greater hardness. The films were evaluated by moisture sorption isotherms and it was observed that the encapsulation decreased the hydrophilicity of cyclodextrin, and consequently, the films. The films developed could be a possible future application for shelf life extension of fresh food.

Amino surface functionalized microcapsules as curing agents for polyurethane foams

ABSTRACTThis work regards the manufacturing process and assessment of amino surface functionalized microcapsules (MCs) containing glycerol in their core, for application in one-component polyurethane (PU) foams to act as a sustainable curing catalyst. Microemulsion techniques combined with sol–gel processing, involving the development of specific steps during the synthesis, were found to enable this type of functional active microparticles. The MCs should only burst and release their content at the spraying stage, in order to assist and promote an accelerated curing of the foam. It has been found that the surface treatment employed in the last step of inorganic silica MCs synthesis procedure, using an amino silane, led to the best curing performance for PU foams. In fact, the amino functionalized MCs exhibited a more perfect spherical format and less aggregation than the inorganic MCs, did not exhibit significant leaching, and led to a significant increase in the curing rate of the PU foam. The study involved characterization techniques, such as scanning electron microscopy, Fourier transformed infrared spectroscopy, thermal gravimetric analyses, leaching, and curing speed evaluation.

Amino-silica microcapsules as effective curing agents for polyurethane foams

The present paper regards the development of functional microcapsules (MCs), containing encapsulated glycerol, to act as sustainable solid curing agents for one-component polyurethane (PU) foams. They consist of silica-based MCs with an aminosilane surface treatment, obtained through sol–gel processing technique. These MCs are intended to burst and release their content only at the spraying process, in order to promote an accelerated curing of the PU foam. The superficial amino groups react with the isocyanate groups present in the PU pre-polymer, producing polyurea moieties on the MCs’ surface, which prevents the leaching of encapsulated glycerol inside the PU aerosol can. This enables the long shelf life of the product, required for commercial application. The amino-silica MCs exhibit a perfect spherical shape, without significant leaching, in opposition to silica-based MCs and led to a significant increase in the curing rate of the PU foam. The study involved various characterization techniques, such as scanning electron microscopy, Fourier transformed infrared spectroscopy, thermogravimetric analyses, leaching and curing speed evaluation.

Microcapsule Structure with a Tunable Textured Surface via the Assembly of Polyoxomolybdate Clusters: A Bioinspired Strategy and Enhanced Activities in Alkene Oxidation.

A polyamine-mediated bioinspired strategy to assemble Keggin-type phosphomolybdic acid (PMA) clusters is demonstrated for the fabrication of microcapsule (MC) structures with unique surface textures. It involves supramolecular aggregation of polyamines with multivalent anions, which then allows the assembly of negatively charged PMA into MCs in an aqueous medium under ambient conditions. Resembling the role of polyamines in biosilicification of diatoms, the polyamine-anion interaction is shown to be the key for the assembly process. It not only provides structural stability but also facilitates an interesting transition from a smooth to a wrinkled surface alongside a change in the Keggin form to its lacunary form depending on the pH of the medium. Moreover, the presence of isolated PMA units in the hybrid structure enables them to be active in catalyzing the aerobic oxidation of alkenes under solvent-free conditions with better selectivity and reusability. Hence, the assembly approach represents an effective way for heterogenization of PMA-based materials and is expected to find considerable application in the wider hybrid-cluster field.

Development of Polymer Microcapsules Functionalized with Fucoidan to Target P-Selectin Overexpressed in Cardiovascular Diseases.

New tools for molecular imaging and targeted therapy for cardiovascular diseases are still required. Herein, biodegradable microcapsules (MCs) made of polycyanoacrylate and polysaccharide and functionalized with fucoidan (Fuco-MCs) are designed as new carriers to target arterial thrombi overexpressing P-selectin. Physicochemical characterizations demonstrated that microcapsules have a core-shell structure and that fucoidan is present onto the surface of Fuco-MCs. Furthermore, their sizes range from 2 to 6 µm and they are stable on storage over 30 d at 4 °C. Flow cytometry experiments evidenced the binding of Fuco-MCs for human activated platelets as compared to MCs (mean fluorescence intensity: 12 008 vs. 9, p < 0.001) and its absence for nonactivated platelets (432). An in vitro flow adhesion assay showed high specific binding efficiency of Fuco-MCs to P-selectin and to activated platelet aggregates under arterial shear stress conditions. Moreover, both types of microcapsules reveal excellent compatibility with 3T3 cells in cytotoxicity assay. One hour after intravenous injection of microcapsules, histological analysis revealed that Fuco-MCs are localized in the rat abdominal aortic aneurysm thrombotic wall and that the binding in the healthy aorta is low. In conclusion, these microcapsules appear as promising carriers for targeting of tissues characterized by P-selectin overexpression and for their molecular imaging or treatment.

Imaging and Analysis of Encapsulated Objects through Self-Assembled Electron and Optically Transparent Graphene Oxide Membranes.

We demonstrate a technique for facile encapsulation and adhesion of micro- and nano objects on arbitrary substrates, stencils, and micro structured surfaces by ultrathin graphene oxide membranes via a simple drop casting of graphene oxide solution. A self-assembled encapsulating membrane forms during the drying process at the liquid-air and liquid-solid interfaces and consists of a water-permeable quasi-2D network of overlapping graphene oxide flakes. Upon drying and interlocking between the flakes, the encapsulating coating around the object becomes mechanically robust, chemically protective, and yet highly transparent to electrons and photons in a wide energy range, enabling microscopic and spectroscopic access to encapsulated objects. The characteristic encapsulation scenarios were demonstrated on a set of representative inorganic and organic micro and nano-objects and microstructured surfaces. Different coating regimes can be achieved by controlling the pH of the supporting solution, and the hydrophobicity and morphology of interfaces. Several specific phenomena such as compression of encased objects by contracting membranes as well as hierarchical encapsulations were observed. Finally, electron as well as optical microscopy and analysis of encapsulated objects along with the membrane effect on the image contrast formation, and signal attenuation are discussed.

Dually reinforced all-polyamide laminate composites via microencapsulation strategy

A new two-stage strategy is disclosed for the preparation of all-polyamide laminate composites based on polyamide 6 (PA6) matrices reinforced by high volume fractions of polyamide 66 (PA66) textile structures and three different types of nanoclays. In the first stage, PA6 microcapsules (MC) loaded with montmorillonite nanoclays (MMT) are synthesized by activated anionic ring-opening polymerization of e-caprolactam in solution in the presence of three different organically treated MMT brands. In the second stage, the MMT-loaded MC obtained with controlled molecular weight, composition and granulometry are compression molded in the presence of PA66 textile structures to produce the final dually reinforced laminate composites. Mechanical tests in tension, flexion, and impact for selected composites in this study showed up to 73% increase of the Young's modulus, up to 142% increase of the stress at break, and more than a fivefold increase of the notched impact resistance. The mechanical behavior of the dually reinforced composites was discussed in conjunction with the morphology of the samples studied by optical and electron microscopy, and the matrix crystalline structure as revealed by DSC and microfocus synchrotron X-ray diffraction. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

차선의 시인성 향상을 위한 SrAl2O4 : Eu2+,Dy3+ 축광 마이크로 캡슐화에 관한 연구

차선의 시인성 향상을 위한 SrAl₂O₄ : Eu²⁺,Dy³⁺ 축광 마이크로 캡슐화에 관한 연구

Cure kinetics of cyanate ester resin using microencapsulated dibutyltin dilaurate as catalyst

Dibutyltin dilaurate (DBTDL) catalyst-filled microcapsules (MCs) were used to catalyze the reaction of thermosetting cyanate ester (CE) resins. Dynamic differential scanning calorimetry (DSC) experiments were performed at multiple heating rates (β) to investigate the effects of the MC content (0.125, 0.25, and 0.5 %) on the cure kinetics of CE resins. The kinetic parameters of CE/MC systems, including activation energy (E a), preexponential factor (A), and reaction order (n), were analyzed using the Flynn–Wall–Ozawa method, Kissinger method, Crane method, Ozawa isoconversional method, and Coats–Redfern method. The results indicate that, as the MC content increases, the reaction temperature of CE/MC system gradually shifts to low temperature owing to the increase of the DBTDL catalyst released from MCs under heating conditions. Compared to the unencapsulated DBTDL, the encapsulated DBTDL can decrease the E a, A, and the reaction rate constant of CE resins due to the gradual release of DBTDL from MCs and the homogeneous dispersion of the released DBTDL in CE resins. The E a, A, and the reaction rate constant of CE/MC systems are effectively adjusted by the MC content and heating process. The reaction orders for all CE/MC systems are close to 1. The reaction model of CE/MCs is considered as a two-dimensional nucleation (A 2).

Microencapsulated Garcinia kola and Hunteria umbellata Seeds Aqueous Extracts - Part 2: Influence of Some Selected Pharmaceutical Excipients

Objective: This study investigates the effect of selected excipients on microcapsules properties of seeds extracts of Garcinia kola (GK) and Hunteria umbellata (HU). Method: Extracts from macerated dried powdered seeds were microencapsulated with chitosan-alginate including either talc, HPMCAS, Eudragit ® RLPO or Eudragit ® L100 up to 25% in the core. Microcapsules were characterized using differential scanning calorimertry (DSC), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and In vitro release. Results: DSC, XRD and FTIR showed no change in crystalline properties and functional groups of microcapsules and excipients in the formulations. In vitro extract release showed retardation of extract release in acid medium after 2 h and between 80 to 100% at pH 6.8. Generally, the microcapsules fitted more closely to first order model than the other models. Conclusion: Inclusion of these excipients did not impart negatively in interaction and release profile on microcapsules containing GK and HU aqueous extracts and can therefore be added to facilitate microcapsule production and enhance dosage form performance.

Synthesis and characterization of novel epoxy resins-filled microcapsules with organic/inorganic hybrid shell for the self-healing of high performance resins

Novel microcapsules (MCs) with organic/inorganic hybrid shell were successfully fabricated using epoxy resin as core material and nano boron nitride (BN) and mesoporous silica (SBA-15) as inorganic shell materials in aqueous solution containing a water-compatible epoxy resin curing agent. The morphologies, thermal properties and Young's moduli of MCs were investigated. The results indicated that epoxy resins were encapsulated by BN/SBA-15/epoxy polymer hybrid layer, the resulting MCs were spherical in shape and the introduction of inorganic particles made MCs had rough surface morphology. The mean modulus value of MCs was from 2.8 to 3.1 GPa. The initial decomposition temperature (Tdi) of MCs at 5 wt% weight loss was from 309 to 312°C. MCs showed excellent thermal stability below 260°C. The structures and properties of MCs could be tailored by controlling the weight ratio of inorganic particle. When the weight ratio of BN to SBA-15 was 0.15:0.10, MCs had the highest Tdi and modulus. The resulting MCs were applied to high performance 4,4′-bismaleimidodiphenylmethane/O,O′-diallylbisphenol A (BMI/DBA) system to design high performance BMI/DBA/MC systems. Appropriate content of MCs could improve the fracture toughness and maintain the glass transition temperature (Tg) of BMI/DBA system. The core materials released from fractured MCs could bond the fracture surfaces of the BMI/DBA matrix through the polymerization of epoxy resins. When the healing temperature schedule of 100°C/2h+150°C/1h was applied, 15 wt% MCs recovered 98% of the virgin fracture toughness of BMI/DBA. Copyright © 2016 John Wiley & Sons, Ltd.

Experimental research about the copolymers of DR-PLGA microcapsule and CPC on the treatment of rabbit femoral defect model

Objective To study the effects about rhizoma drynariae poly(lactic-co-glycolic acid) (DR-PLGA) /Calcium phosphate cement (CPC) composite scaffold on treating rabbit femoral bone defect. Methods Eight Newzealand rabbits were randomly divided into experiment group(n=4) and control group (n=4). The preparation of rabbit femoral bone defect model, separately implanted DR-PLGA/CPC scaffold and PLGA/CPC scaffold. After 4, 8 weeks, we took out the materials, observed with X-ray, gross anatomy, histology observation to evaluate the osteogenetic activity, the effect of accelerating the healing of bone defect. Resuits At the 4th week and 8th week after implantation, the effect of promoting fracture healing and osteogenic activity of the experiment group were greater than those in the control group. Conclusions DR-PLGA combined with CPC could induce new bone formation, promote the healing of rabbit femoral defect. Key words: Polypodiacease; Rhizoma-drynariae/poly, lactic-co-glycolide facid; Calcium phosphate cement; Rabbits; Treatment outcome