Preparation Of Microcapsules Research Articles

Zein coacervate as a new coating material for temperature-triggered microcapsule and fruit preservation

Due to the opposite effect of hydrophilicity and hydrophobicity, the formation of a hydrophobic shell on the surface of hydrophilic cores in aqueous environments is a challenge. Zein coacervate originating from plant protein liquidliquid phase separation has low interfacial energy, which creates conditions to achieve the above goals. This work proposed zein coacervate as a new coating material for the preparation of hydrophilic-hydrophobic core-shell microcapsules or the coating of fruit. Different from particles simply stacking at the interface, this zein coacervate coated on the surface could form a denser shell. For the prepared microcapsules, this dense zein coacervate shell could prevent the release of ascorbic acid at a low temperature, while the dense shell could be destroyed to have a quick release at approximately 37 ℃, creating a kind of hydrophilic-hydrophobic core-shell microcapsule with temperature-dependent triggered performance. This dense shell could also endow microcapsules with anti-ultraviolet and antioxidant capacities, features that microcapsules without this dense shell are lacking. For the coating of fruits, this dense shell derived from plants could come in contact with food products and be beneficial for the preservation of fruits. Therefore, this zein coacervate could have the potential to be a healthy and green coating material for a broad range of applications, such as cosmetics, food, drug delivery and the preservation of fruits and vegetables.

Preparation and application of cinnamon-Litsea cubeba compound essential oil microcapsules for peanut kernel postharvest storage

This research developed a novel, efficient and safe antimildew for peanut kernel postharvest storage. The antimildew, cinnamon-Litsea cubeba compound essential oil (CLCEO) microcapsule (CLCEOM), was synthesized with CLCEO as core materials and β-cyclodextrin as wall materials. Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry analyses indicated that major antifungal compounds of CLCEO were encapsulated in the cavity of β-cyclodextrin. The inhibition zone experiment showed that CLCEOM retained antifungal effect on Aspergillus spp. strains even after storage for 2 months at 4 ℃. Besides, CLCEOM reduced total number of fungal colonies, relative abundance of Aspergillus spp., and aflatoxin B1 content of peanut kernels, and had positive effect on slowing down the increase in acid value of peanut oil without causing any adverse effect on the viability and sensory properties during storage process. Overall, CLCEOM presented good preservative effects on peanut kernels, providing evidence for its potential use as antimildew for peanut storage.

Preparation and properties of n-hexane microcapsules by complex coacervation

In order to improve the encapsulation efficiency of low density core material microcapsules, the complex condensation method was used to prepare microcapsules with n-hexane as the core material and gelatin and Arabic gum as the wall material.For n-hexane with low density, the influence of wall material concentration on microcapsule morphology, the influence of core wall ratio on microcapsule wall thickness, the influence of emulsifying speed on emulsifying effect, the influence of crosslinking curing reaction pH on thermal stability, and the influence of complex coacervation pH on turbidity were studied by turbidimetric titration. The experimental results show that: For the low-density core microcapsules, the spherical multi-core microcapsules prepared are regular in capsule shape, but the encapsulation efficiency is lower than 30%, and the waste of wall material is serious. The wall material concentration is 2%, the core-to-wall ratio is 3:1, the emulsification speed is 10000 r/min, the pH of complex oacervation is 4.0, and the pH of crosslinking curing reaction is 10.0. The microcapsules prepared on this basis are monocytic and irregular. Although the shape and phase of the capsules are irregular, they have good encapsulation effect, with the yield up to 71.86% and encapsulation efficiency up to 70%. Meanwhile, they have good thermal stability.

Preparation of probiotic microcapsules using gelatin-xylooligosaccharides conjugates by spray drying: Physicochemical properties, survival, digestion resistance and colonization

Limosilactobacillus fermentum NCU001464 is a probiotic bacterium with anti-hyperuricemia potential, however, its viability decreases during food processing, storage and in the gastrointestinal tract. This study aims to microencapsulate Limosilactobacillus fermentum NCU001464 by spray-drying with Maillard reaction products of gelatin and xylooligosaccharides, heated for various times. Properties of powders and bacterial vitality change during producing, storage and simulated digestion were evaluated. The microcapsules had a low moisture content and the encapsulation appeared effective, however, under scanning electron microscope, cracks were visible on the surface of microcapsules with longer-time heat-treated Maillard reaction products. Heat treatment for 60 min resulted in the highest bacterial viability and adhesion capacity to intestinal epithelial cells after gastrointestinal digestion. After 10 weeks storage at 4 °C and 25 °C, the viable count of MRP-microencapsulated cells was 9.00–6.80 Log CFU/g, more than the recommended dose of 6 Log CFU/mL.

Correction: Xu et al. Preparation of Long-Term Antibacterial SiO2-Cinnamaldehyde Microcapsule via Sol–Gel Approach as a Functional Additive for PBAT Film. Processes 2020, 8, 897

In the original publication [...]

Soy lecithin increases the stability and lipolysis of encapsulated algal oil and probiotics complex coacervates.

Co-encapsulation of probiotics and omega-3 oil using complex coacervation is an effective method for enhancing the tolerance of probiotics under adverse conditions, whereas complex coacervation of omega-3 oil was found to have low lipid digestibility. In the present study, gelatin (GE, 30 g kg-1 ) and gum arabic (GA, 30 g kg-1 ) were used to encapsulate Lactobacillus plantarum WCFS1 and algal oil by complex coacervation to produce microcapsules containing probiotics (GE-P-GA) and co-microcapsules containing probiotics and algal oil (GE-P-O-GA), and soy lecithin (SL) was added to probiotics-algal oil complex coacervates [GE-P-O(SL)-GA] to enhance its stability and lipolysis. Then, we evaluated the viability of different microencapsulated probiotics exposed to freeze-drying and long-term storage, as well as the survival rate and release performance of encapsulated probiotics and algal oil during in vitro digestion. GE-P-O(SL)-GA had a smaller particle size (51.20 μm), as well as higher freeze-drying survival (90.06%) of probiotics and encapsulation efficiency of algal oil (75.74%). Moreover, GE-P-O(SL)-GA showed a higher algal oil release rate (79.54%), lipolysis degree (74.63%) and docosahexaenoic acid lipolysis efficiency (64.8%) in the in vitro digestion model. The viability of microencapsulated probiotics after simulated digestion and long-term storage at -18,4 and 25 °C was in the order: GE-P-O(SL)-GA > GE-P-O-GA > GE-P-GA. As a result of its amphiphilic properties, SL strongly affected the physicochemical properties of probiotics and algal oil complex coacervates, resulting in higher stability and more effective lipolysis. Thus, the GE-P-O(SL)-GA can more effectively deliver probiotics and docosahexaenoic acid to the intestine, which provides a reference for the preparation of high-viability and high-lipolysis probiotics-algal oil microcapsules. © 2022 Society of Chemical Industry.

Preparation of photothermal conversion and energy storage microcapsules based on Pickering emulsions with poly (p-phenylenediamine) as stabilizer and photothermal materials

Passive energy recycling for thermal management is one of the best energy-saving paths. However, phase change energy storage driven by temperature fluctuation is difficult to realize in some application scenarios such as winter or alpine regions. Here, novel photothermal conversion and energy storage composite was designed and fabricated to solve the problem. Firstly, nanoscale poly (p-phenylenediamine) (PPPD) as stabilizer and photothermal conversion material was synthesized and used in the encapsulation of lauryl myristate as phase change material (PCM) with phase change temperature of 34.6 °C based on Pickering emulsion, following photoinduced energy storage microcapsules were successfully prepared using melamine formaldehyde resin as shell. The obtained microencapsulated phase change materials (MPCMs) can absorb and release heat energy within a temperature range of 25–45 °C with a latent heat of 185.7 J/g. Owing to the excellent photothermal conversion efficiency of the MPCMs (82.4 %), their temperature-regulating function can be triggered in those low temperature environments by photothermal conversion. The microcapsules were then treated on fabric by printing and showed good thermal management effect under light irradiation.

One-pot preparation of inorganic-organic double-shell microcapsule with good barrier and mechanical property via photopolymerization

Microcapsule has been widely used for fabricating functional coatings. For practical application in coatings, an ideal microcapsule should possess outstanding barrier, thermal and mechanical properties simultaneously. In this paper, a series of double-shell hybrid microcapsule loaded with self-healing agent (linseed oil, LO) with outer inorganic SiO2 shell and inner UV-cured polymeric shell were successfully synthesized via photopolymerization. The obtained double-shell hybrid microcapsule was characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The barrier properties, thermal stability and mechanical property of the microcapsules were investigated in detail. Via the adjustment of chemical structure of photo-curable resin and the crosslinking density, the core release of the microcapsule could be reduced to only 2.5 wt% after immersing in organic solvent for 48 h, suggesting the outstanding barrier properties of the double-shell microsphere. The double-shell hybrid microcapsules also possessed outstanding thermal stability, and its initial decomposition temperature increased by about 32 ℃ and 14 ℃ compared with that of mono-shell organic and inorganic microcapsules. Moreover, the Young's modulus and hardness of the double-shell hybrid microcapsules were thirty-fold and forty-fold that of mono-shell organic microcapsules, which proved their excellent mechanical property. And the prepared double-shell hybrid microcapsule could encapsulate LO stably for a long time to avoid its failure, which was successfully employed to the construction of self-healing coatings.

Preparation and characterization of sorafenib-loading microcapsules by complex coacervation of gum Arabic with chitosan or modified chitosan

Sorafenib is an oral multi-target kinase inhibitor that has been used to treat unresectable hepatocellular carcinoma and advanced renal cell carcinoma. The aim of the study was to prepare gum Arabic-chitosan (GA-CS) and gum Arabic-modified chitosan (GA-MCS) microcapsules containing sorafenib as the core phase by complex coacervation. The fluorescence microscopy, dynamic light scattering (DLS), drug loading, and encapsulation efficiency of the microcapsules were clarified. The GA-MCS microcapsule was successfully performed at approximate pH of 4 with a 1% modified chitosan -to- 5% gum Arabic ratio of 5:1 (v/v), while the GA-CS microcapsule was successfully prepared at pH 3.5 with a volume ratio of 1% chitosan -to- 5% gum Arabic 1:1 (v/v). Sorafenib was encapsulated in the microcapsules as shown through the fluorescence microscopy images. The formation of GA-CS and GA-MCS microcapsules with hydrodynamic sizes of 6.31 μm and 6.56 μm, respectively, was successfully achieved. The drug loading and encapsulation efficiency of the GA-MCS microcapsule was greater than that of the GA-CS microcapsule. The findings indicated that the GA-MCS microcapsule could be an appropriate formation to load sorafenib with a high encapsulation yield.

Exploring the Teaching Model of Research-Oriented Comprehensive Experimental Analysis in Analytical Chemistry: A Case Study of “Preparation of Alginate Microcapsules, Drug Encapsulation, and Sustained Controlled Release Analysis Experiment”

Exploring the Teaching Model of Research-Oriented Comprehensive Experimental Analysis in Analytical Chemistry: A Case Study of “Preparation of Alginate Microcapsules, Drug Encapsulation, and Sustained Controlled Release Analysis Experiment”

Preparation of STF-loaded micron scale polyurethane polyurea double layer microcapsules and study on the mechanical properties of composites.

In this study, we report on a novel and effective approach for the encapsulation of the shear thickening fluid in polyurethane polyurea double layer microcapsules. Under the action of dibutyltin disilicate as a catalyst, CD-MDI reacted with polyethylene glycol to form polyurethane inner shell and reacted with diethylenetriamine to form a polyurea outer shell. The results show that the shear thickening liquid was emulsified using liquid paraffin as a solvent and Span80 as a surfactant to form a lotion similar to water-in-oil. The shear thickened droplets can be stably and uniformly dispersed to a diameter of 100 μm at a rotation speed of 800 rpm min-1. The bilayer shell material achieves a good coating effect on STF, which provides support for strength and stress conduction and improves the compatibility between STF and polyurea matrix. The toughness and impact resistance of the composites were analyzed by a universal testing machine and drop hammer impact tester. Finally, compared with the pure polyurea material, the elongation at break of 2% added amount is increased by 22.70%, and the impact resistance of 1% added amount is the best, which is 76.81 N more than that of the pure specimen.

Advances in the preparation and application of microencapsulation to protect food functional ingredients.

Functional ingredients have multiple health benefits for humans, but are sensitive to oxidative degradation during manufacture and storage, and have poor chemical stability and reduced bioaccessibility. Therefore, microcapsules are prepared by encapsulating the active ingredient in a matrix to enhance the stability of the active ingredient. Their use as microcapsule carriers in the food industry is now an effective and promising technology. This paper reviews the preparation of microcapsules based on different principles. It summarizes the protein and polysaccharide bioactive substances commonly used for encapsulation. It also discusses the practice of modifying the wall material by chemical reactions (Maillard reaction) to obtain excellent properties. Finally, the applications of microcapsules in the production of beverages, baked goods, meat, dairy products, probiotic delivery and food preservation are discussed as well as their feasibility as effective protective bioactive substance delivery systems. The microencapsulation process can improve the storability of food products, make bioactive compounds stable over time and apply co-microencapsulation in the formulation of co-effective functional foods, which is a direction for future research.

Preparation and characterization of glucoamylase microcapsules prepared by W/O/W type complex coacervation freeze drying.

Glucoamylase was often used in the brewing industry but was unstable to several environmental factors and reacted quickly to produce fermentable sugar, which limited its applications. Microencapsulation could effectively overcome the drawbacks. This study evaluated the feasibility of the preparation of glucoamylase microcapsules (GM) using W/O/W complex coacervation-freeze-drying method. The parameters of the microcapsules were optimized by the response surface optimization design: core-wall ratio at 1:1, wall-material concentration at 8%, and coagulation time for 20min. Under current condition, the final microencapsulation efficiency reached 85.64±1.60%. Glucoamylase could be slowly released for more than 96h in the liquid state, and could react slowly for more than 336h in the solid state. The optimized GM were incubated for 1h, and the relative enzyme activity was better than that of free glucoamylase under high temperature conditions. The water capacity, solubility, morphology, differential scanning calorimetry, and Fourier transform infrared spectroscopy were conducted. Glucoamylase exhibited good sustained release characteristics. The microcapsules were more resistant to environmental stimuli and showed stronger robustness after optimization. PRACTICAL APPLICATION: Saccharification enzymes are often used in the winemaking industry, and direct addition will cause the fermentation process to heat up too quickly, resulting in the inactivation of microorganisms and saccharification enzymes, affecting the efficiency of saccharification enzymes. Therefore, microcapsules are used to encapsulate the saccharification enzyme, and its efficacy is slowly released for a long time during the fermentation process.

Understanding the microfluidic generation of double emulsion droplets with alginate shell

The monodisperse double emulsions obtained by microfluidic method can serve as ideal templates for preparing core-shell alginate microcapsules, which have attracted much attention in biological applications, such as drug delivery systems and cell encapsulation, tissue engineering. However, the formation behavior and dynamic analysis of double emulsion with an alginate shell is still unclear due to the complex rheological behavior of alginate solutions. Herein, we employ a dual-coaxial microfluidic device to generate the high-quality double emulsion droplets with alginate shell, focusing on the effects of the fluid properties of alginate solution in the middle phase (viscosity, μm) and the fluid flow rate on the droplet formation mechanism. As the viscosity of the middle fluid (μm) increased, the size of compound droplets (D2) increased and the size of inner droplets (D1) decreased, and the break-up regimes occurred a dripping-to-jetting transition when μm = 160 mPa s. The number of encapsulated inner droplets can be predicted and precisely controlled by regulating the generation frequency of inner (f1) and outer droplets (f2). The breakup dynamics of the alginate thread are also analyzed by using the volume-of-fluid/continuum-surface-force (VOF/CSF) method. The results show that the pressure and velocity in the neck of pinch-off is lower in the jetting than that in the dripping regime. This study will provide useful guidance for the rational design and controllable preparation of core-shell alginate microcapsules.

Preparation and performance of reversible thermochromic phase change microcapsules based on negative photochromic spiropyran

Thermochromic phase change materials have been widely studied for their importance in energy-efficient buildings, thermal control clothing, and low-temperature energy storage. Herein, we successfully designed and synthesized a spiropyran compound with negative photochromic properties in a solid matrix, 3-(3′,3′-dimethyl-6,8-dinitrospiro[chromene-2,2′-indolin]−1′-yl) propyl methacrylate (SPMA), as a thermochromic dye. The synthesized spiropyran was copolymerized with methyl methacrylate (MMA) using photoinitiation, and then n-octadecane was encapsulated by the copolymer to prepare reversible thermochromic phase change microcapsules (TC-microPCMs) through the solvent evaporation technique. The encapsulation efficiency of n-octadecane by copolymers prepared with different photoinitiator concentrations was also investigated. According to the results of SEM, particle size analysis (DLS), and DSC, the copolymer prepared at 3% concentration possessed the best encapsulation effect on n-octadecane, and the melting enthalpy of the microcapsules reached 168.7 J/g and the encapsulation ratio was 89.5%, which was not significantly different from that of microcapsules without the addition of thermochromic dyes. This di-functionalization process effectively avoids the "impurity effect" of dye addition. In addition, the homogeneous spherical structure and stable chemical composition of the microcapsules are the key factors to achieve a fully reversible thermochromic behavior. What's more, the functionalized film based on TC-microPCMs, TC-microPCMs@PVA, was used to explore the potential for applications in thermal storage and temperature sensing. The results demonstrated that the composite film has excellent reversible thermochromic performance, high latent heat storage performance, and good cycling durability, which make the bifunctional microcapsules highly promising candidates for thermal sensors, solar energy storage, and smart textiles.

Preparation and application of low-temperature binary eutectic lauric acid-stearic acidSiO2 phase change microcapsules

Most phase change materials developed in current research have high phase change temperatures, making them challenging to use in buildings. To solve this problem, the microencapsulated phase change materials (MPCMs) with low eutectic temperature were prepared by interfacial polymerization using binary eutectic of lauric acid (LA) and stearic acid (SA) as the core material and silica as the shell material. And the phosphogypsum-based phase change microcapsules (PG-MPCM) were prepared. Morphology, structure and thermal properties of microcapsules have been investigated. The differential scanning calorimetry (DSC) results indicate that the melting and freezing temperatures of MPCMs prepared under optimal conditions are 27.9 °C and 28.3 °C, and the latent heats of melting and freezing are 170.3 J/g and 155.7 J/g. The thermogravimetry (TG) analysis results confirm that the microcapsules have good thermal stability. There is no significant change in the latent heat of the microcapsules phase change after 300 melting/freezing cycling. The heat storage performance shows that PG-MPCMs have good heat energy storage capacity and temperature regulation ability. In general, the LA-SA/SiO2 microcapsule is suitable as the energy storage material for buildings.

Aerosol OT Quantity Impacts on Calcium Nitrate Self-Healing Microcapsule Properties Used for Sustainable Construction Applications

This paper is a continuation of a previously published paper on this issue that studied the microencapsulation of calcium nitrate in urea-formaldehyde shell using Aerosol OT (AOT) in hexane solution. The aim of this paper is to determine the quantity of AOT that optimizes microcapsule distribution, diameter, and shell thickness. Different quantities of AOT, namely 0.25 g, 0.50 g, 1.5 g, and 2.5 g were dissolved in 180 g of hexane solution to prepare the continuous phase. A Scanning Electron Microscopy (SEM) was used to characterize the distribution and the diameters of the prepared microcapsules. A Transmission Electron Microscopy (TEM) was used to investigate the microcapsule shell thicknesses. The SEM images have shown that using 0.25 g of AOT may be insufficient to totally polymerize the whole quantity of the core materials into fully independent capsules. On the other hand, using 0.50 g of AOT has shown a uniform distribution and almost complete polymerization of the core material components into distinct microcapsules. Higher quantities of AOT (i.e., 1.50 g and 2.5 g) have resulted in agglomerated microcapsules and nonuniform distributions. The results have also demonstrated that the quantity of AOT does not have a significant impact on the microcapsule diameter. Microcapsule average shell thicknesses were found to decrease by increasing AOT amount up to 0.50 g and to increase again due to the agglomeration witnessed for increased AOT quantity. Accordingly, 0.50 g of AOT was recommended for the preparation of calcium nitrate microcapsules in future research work.

Fabrication of highly durable functional textile through microencapsulation of organic citronella oil

The use of organic and eco-friendly plant-based materials has shown an increasing interest for researchers over recent years. This study describes the preparation of microcapsules from a natural citronella oil and its treatment on polyester-cotton blended (PC) fabric. The citronella oil is an essential oil obtained from the leaves and stems of various species of Cymbopogon. Microcapsules containing citronella oil as core material were produced by a complex coacervation technology and applied to fabric using the pad-dry-cure method. The morphology of the solution of microcapsules was investigated by optical microscope and the dried microcapsules were examined by scanning electron microscope (SEM). Furthermore, the microcapsules were also characterized for particle size distribution and zeta potential. SEM was also used to investigate the surface morphology of fabric surfaces after the treatment of microcapsules. A conventional test technique (cage test) was used to evaluate the medicated fabric's ability to keep mosquitoes away and comfort properties of fabric like air permeability and water absorbency were also studied. The fabric sample finished with 15% (solid in water) citronella oil microcapsules at zero wash exhibited 90% mosquito repellency, and after 30 washes the fabric possessed 80% mosquito repellency committing the durability of as prepared finished fabric. The medicated PC fabric revealed good air permeabilities and water absorbencies. Hence, this report presented an eco-friendly approach for the development of highly durable functional mosquito repellent textiles. • The successful synthesis of microcapsules using organic oils as core material. • Application of microcapsules on a polyester cotton blended fabric using the pad-dry-cure method. • Characterization of the prepared microcapsules by optical microscope, SEM, DLS, and zeta potential. • Establishing the mosquito repellent property of the prepared textile fabric in cage test. • Investigation of the durability under rigorous washing cycles.

Preparation of magnetic microcapsules of α-amylase and α-glucosidase for dual-target affinity screening of active components from Toona sinensis

Natural products are an important source of drug development and have good prospects in the treatment of many diseases. However, the efficacy of many natural drugs is achieved through multi-targets, which poses a huge obstacle to their development. In this study, a bienzyme microcapsule system based on α-amylase and α-glucosidase was constructed for the ligand fishing of natural compounds. The microcapsules were formed on the surface of calcium carbonate particles by self-polymerization of dopamine, which physically encapsulated iron oxide and α-glucosidase. Then, α-amylase was immobilized on the surface of magnetic material with glutaraldehyde as crosslinking agent, and calcium carbonate template was removed by EDTA to form a bienzyme system for affinity screening of active components from Toona sinensis. The results showed that two compounds, 1,2,3,4,6-penta-O-galloyl-β-D-glucose and quercitrin were affinity screened from the extracts of Toona sinensis. In vitro activity experiment proved that they were α-amylase and α-glucosidase inhibitors, respectively. Moreover, both of them were mixed type inhibitors that can interact with active centers of corresponding enzymes through multiple hydrogen bonds, van der Waals forces, etc. This study not only proved the effectiveness of the bienzyme system, but also provided a successful example for multi-target screening of natural products.

Preparation of pH-stabilized microcapsules for controlled release of DEET via novel CS deposition and complex coacervation

In order to slow down the volatilization rate of N, N-Diethyl-m-toluidine (DEET) and enhance its safe application, an improved complex coacervation method was developed to encapsulated it to prepare microcapsules with the function of mosquito repellent. Tannic acid as a cross-linking agent for gelatin and Arabic gum enhanced the structural stability of the capsule through hydrogen bonding. Chitosan was selected to further deposited on the surface of G/AG MC for the improvement of pH stability and formed CS-G/AG MC. Scanning electron microscopy and optical microscope confirmed the chitosan was successful deposited on the G/AG MC, which ameliorated the agglomeration of microcapsules and promoted their monodispersity. Fourier transform infrared spectroscopy confirmed that electrostatic attraction accounted predominantly for the forces between the shell materials. The deposition of chitosan imparted controlled release to the microcapsules, resulting in a high retention efficacy of DEET in the pH range of 2–10. The CS-G/AG MC showed good storage stability and biocompatibility, and the static leakage of DEET within 40 days was negligible. The microcapsules prepared by this method showed green ecological properties, derived from the natural origin and biocompatibility of the shell material. And the tight structure of the microcapsule shell effectively barriered the volatile of DEET, while greatly extending its release time. This study can effectively protect the biological activity of core materials of microcapsules, and has long-lasting release performance, which has potential economic benefits in personal care products market directly contacted by humans.