Distribution Of Microcapsules Research Articles

Behavior of microcapsules in FML under different pressure of manufacturing in autoclave

Magnesium alloys are the lightest available structural metals. The low density and high strength-to-weight ratio make magnesium and its alloys an excellent option for use in the automotive and transport vehicles. In the case of magnesium and its alloys, the corrosion phenomenon is a serious problem especially when it is connected with epoxy-carbon composite (CFRP). Poor adhesion can easily cause delamination at the interface. So in this the work was analyzing the influence of pressure in laminate manufacturing in the autoclave process of a magnesium alloy/CFRP on the stability and distribution of microcapsules and observation about delamination. It was concluded that the PEO layer with sol–gel improves the adhesion between CFRP and the MCs. Different pressures in the autoclave process promote porosity if a pressure lower than 0.4 MPa is used.

Preparation and characterization of Sparassis latifolia β-glucan microcapsules

Abstract In order to effectively protect the biological activity of Sparassis latifolia β-glucan, improve its stability, and realize its high-value utilization, single-factor test and orthogonal test were carried out to optimize the microencapsulation conditions of S. latifolia β-glucan prepared using spray drying method. The β-glucan microcapsules were characterized by scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and laser particle size analyzer. The results showed that the optimal microencapsulation conditions were as follows: maltodextrin and whey protein with a mass ratio of 1:2, core and wall material with a mass ratio of 1:2, and monoglyceride and core material with a mass percentage of 0.3. Under these conditions, the powder yield and embedding rate of β-glucan microcapsules were 47.32 ± 0.58% and 86.76 ± 1.19%, respectively. The preparation technique was proved to be stable. The β-glucan microcapsules were spherical particles, with the characteristics of a smooth surface, no cracks. The particle size of microcapsules was smaller, and its Dv (50) was 8.43 µm. The distribution of microcapsules was more uniform, and its uniformity was 0.503. The good embedding performance and high thermal stability can effectively protect the biological activity of the core material.

Examination of the Coating Method in Transferring Phase-Changing Materials

This study intends to identify the characteristics of heat regulation in heat storage microencapsulated fabrics and to examine the effect of the microcapsules application method. For this purpose, phase-changing material (PCM) microcapsules were applied by impregnation and coating methods on cotton fabrics. The presence and distribution of microcapsules on the fabric surface were investigated by scanning electron microscopy (SEM). The temperature regulation of the fabrics was examined using a temperature measurement sensor and data recorder system (thermal camera). According to the differential scanning calorimetry (DSC) analysis, melting in fabrics coated with microcapsules occurred between 25.83°C–31.04°C and the amount of heat energy stored by the cotton fabric during the melting period was measured as 2.70 J g−1. Changes in fabric surface temperature due to the presence of microcapsules in the fabric structure were determined. When comparing the PCM capsules transfer methods, the contact angle of impregnated and coated fabric was obtained as 42° and 73°, respectively. Analysis of the microcapsules transferred to the fabric by impregnation and coating methods shows that the PCM transferred fabric prepared by the impregnation method performs more efficient temperature regulation. However, the analysis shows that PCM transferred fabrics prepared by coating also perform heat absorption, although not as much as the impregnation method. Performance evaluation according to the target properties of the textile will give the most accurate results for fabrics treated by coating and impregnation methods.

Octaphenyl polyoxyethylene regulates the flexibility of pyraclostrobin-loaded soft microcapsules by interfacial polymerization for better foliar adhesion and pesticide utilization

In the preparation of microcapsules (MCs) by interfacial polymerization, octaphenyl polyoxyethylene (OP) is utilized as an emulsifier to control the particle size distribution of MCs. In the preparation system with polyisocyanate as the oil phase monomer, OP has a single hydroxyl (–OH) group that can react with the isocyanic group (–CNO) to prevent polymerization, and the aggregation of OP at the oil–water interface affects the polymer configuration. By the “steric hindrance” and “polymer chain end sealing” of OP, the compactness of the shells was reduced significantly to produce soft MCs. As OP-10 was added and used to increase in pyraclostrobin-loaded MCs preparation, the deformation, adhesion and release of pyraclostrobin-loaded MCs were improved. Therefore, the water scouring resistance of MCs on peanut leaves increased significantly as the MCs became soft. Unfortunately, the safety of zebrafish (Danio rerio) declined at the same time. By foliar spraying to control peanut leaf spot in the rainy season, MCs-2% OP-10, with the strongest resistance to rainfall, had the best effect on disease control. In conclusion, an effective strategy is to balance the foliar application efficiency and ecotoxicity of pesticide-loaded MCs by regulating the compactness and components of shells to control their deformation, adhesion and pesticide release.

Design and evaluation of microencapsulated systems containing extract of whole green coffee fruit rich in phenolic acids

The optimal conditions to microencapsulate green coffee (Coffea canephora) fruit extract (GCFE) by spray drying using a maltodextrin (MD)-gum Arabic (GA) mixture as carrier material were selected. For this purpose, a Central Composite Rotational Design was applied to investigate the combined effects of the MD percentage in the mixture and the extract-to-carrier agent mass ratio (mE/mC) as the independent variables. These effects were modelled by second-order polynomial models on several responses, namely process yield, encapsulation efficiency, water activity, losses of reducing capacity, caffeic acid, caffeine, trigonelline, 5-O-caffeoilquinic acid (5-CQA) from microcapsules (MCs) and 5-CQA retention after 180-days storage. The statistically significant effects were then submitted to more in-depth analysis by Response Surface Methodology. The highest process yield was obtained using a MD percentage of 80% and a mE/mC ratio of 1:1.5 (w/w). Both microencapsulated and non-encapsulated GCFE showed good stability during the accelerated stability study performed at 40 °C for 180 days. Surface morphology and particle size distribution of GCFE-loaded MCs were shown to be suitable for use in the food industry.

Essential Oil Microcapsules Immobilized on Textiles and Certain Induced Effects.

In order to obtain textile materials with potential utility in the development of cosmetic textiles, this study examined the deposition by padding of rose and sage microcapsules on woven textile structures, with different fiber compositions (100% cotton and 50% cotton/50% polyester). Cationization of the textile materials was performed to enhance the degree of uptake the pf the microcapsules on the fabrics’ surface. A commercially acrylate-based binder was used to fix the microcapsules to the textile substrate and to improve the durability against external factors. The finished textile materials were characterized in terms of their physical-mechanical characteristics. The distribution of microcapsules on the fabrics surface before and after five washing cycles and 1000 abrasion cycles was investigated by scanning electron microscopy. The biocompatibility in terms of cell viability, cell membrane integrity and inflammation status of the functionalized fabrics was evaluated on CCD-1070Sk normal human dermal fibroblasts. The cell morphology was evaluated by F-actin staining using fluorescence microscopy and no significant changes were noticed after the incubation in the presence of fabrics compared with control. The in vitro biocompatibility evaluation on human skin cells confirmed the absence of cytotoxicity after the short-term exposure, supporting further in vivo use of these innovative textiles with improved properties.

Preparation and stability of microcapsule wood preservative from neem extract

Neem (Melia azedarach) extract has good antibacterial properties, but its bioactivities are easily decomposed. In order to protect the bioactivities of neem extract, melamine urea formaldehyde (MUF) was used as wall material to prepare a wood microcapsule preservative. The size and distribution of microcapsules after treatments at different temperatures were determined by microscopy. These observations showed that increases in temperature caused the microcapsule particles to become smaller and more evenly distributed. The stability of this preservative was studied by use of an environmental factors experiment (ultraviolet light, condensation, and water spray) and a decay test. The results indicated that the microcapsule preservative from neem extract was more stable than the neem extract preservative. The results indicated that the microcapsule preservative from neem extract showed acceptable environmental stability. The water spray resistance of microcapsule preservative from neem extract was the best.

Synthesis and Characterization of Melamine-Formaldehyde Microcapsules Containing Pyraclostrobin by In situ Polymerization

In this study, melamine-formaldehyde microcapsules were prepared via in situ polymerization using pyraclostrobin as the core material, melamine-formaldehyde as the wall material, Tween 80 as the emulsifier and selected a good auxiliaries. The two-stage synthesis comprised the emulsification of the oil and the formation of the wall, respectively. The prepared melamine-formaldehyde microcapsules were characterized by different techniques to estimate the structure, thermal properties, particle size distribution and morphology of microcapsule. The distribution of microcapsules was uniform and the particle size distribution was narrow. The thermal gravimetry analysis proved that the prepared microcapsules contained approximately 30% pyraclostrobin. The pyraclostrobin was microencapsulated successfully by melamine-formaldehyde resin, and an environment friendly pyraclostrobin capsule suspension was proposed in this paper.

Preparation and Antifungal Activities of Microcapsules of Neem Extract Used in Populus tomentosa Deteriorated by Three Mold Fungi

Microcapsules of neem extract (MNE) were observed using an optical microscope (OM) and scanning electron microscope (SEM). The antifungal activity of the extract was evaluated by an agar diffusion assay. The MNE were induced into the wood material by a full-cell process. The diameters of the microcapsules were measured by OM, and the distribution of microcapsules in wood was observed by SEM. Wood blocks of Populus tomentosa were treated with the MNE, neem extract (NE), and an acid mixture of melamine formaldehyde resin (MF) and sodium dodecyl sulfate (AMS); their antifungal properties against Penicillium citrinum, Trichoderma virens, and Aspergillus niger were visually assessed. The microcapsules prepared by MF, 1% sodium dodecyl sulfate (SDS), and 10% NH4Cl showed regular shape and good dispersion. The agar diffusion assay showed that the neem extract had significant inhibition against all tested fungi, and the optimum concentration of NE was 10%. The diameters of the microcapsules were normally distributed in a range of 0.4 μm to 4 μm, and the microcapsules were unevenly distributed in the vessels and surface of Populus tomentosa. Wood specimens treated with MNE observed complete inhibition to all studied fungi, and the mark grades of specimens treated with MNE against three fungi all reached 5 (no growth of fungi).

Two-stage controlled release system possesses excellent initial and long-term efficacy.

In this work, a series of polyurea-based lambda-cyhalothrin-loaded microcapsules (MCs) with three different size distributions (average diameters of 1.35 μm, MC-S; 5.13 μm, MC-M; and 21.48 μm, MC-L) were prepared and characterized. The results indicated that MCs with a smaller particle size distribution had a faster release rate and excellent initial efficacy against pests. MC-L had a remarkably slow incipient release rate, outstanding photostability and better later-stage efficacy than that of the other tested MCs. The results clarified that the diameter distribution of MCs is the key factor in determining the release property and bioactivity of the MC formulations. Subsequently, the binary mixture MC formulations of MC(+M), MC(S+L) and MC(M+L) were obtained by mixing MC-S, MC-M or MC-L at 1:1 to establish a two-stage release system utilized for foliar application situations. Greenhouse and field experiments showed that MC(S+L) provided an optimal efficacy, and its effective duration was much longer than that of the emulsifiable concentrate (EC) group. Therefore, the release system established in this study was simple and workable for regulating the initial and long-term efficacy by adjusting the particle size distribution; in addition, this system has potential applications in other fields such as drug delivery devices.

Impact of varying hydrocolloid proportions on encapsulation of ascorbic acid by spray drying

SummaryThere has been considerable research into ascorbic acid (AA) as a food component in the human diet and disease prevention. Microencapsulation technology has a promising strategy for enhancing the stability of AA towards the carrier food. The effects of varying hydrocolloid proportions on encapsulation of AA by spray drying have been evaluated. Spray drying pilot plant scale was used to produce the microcapsules, and capillary electrophoresis has been applied to analyse the retention of AA during bread making process. To investigate the characteristics of microstructure of encapsulated AA after processing, the environmental scanning electron microscope was used to investigate the structure of microcapsules. In addition to that to measure the particle size and distribution of microcapsules, the laser beam scattering was used. The impact of varying hydrocolloids proportion on encapsulation of AA by spray drying was studied.

Influence of dual-component microcapsules on self-healing efficiency and performance of metal-epoxy composite-lap joints

ABSTRACTDual-component microcapsules were synthesized by solvent evaporation technique using epoxy resin and hardener as core materials and polymethyl methacrylate (PMMA) as shell wall materials. Morphology, core content, and size distribution of microcapsules were monitored by controlling the various processing parameters such as agitation speed, core–shell weight ratio, and concentration of emulsifiers. The molecular structure, morphologies, and thermal characteristics of the microcapsules were examined under Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA), respectively. Synthesized dual-component microcapsules were entrenched into the epoxy polymer to introduce the healing features in single lap shear epoxy adhesive joints. Healing efficiency as high as 89% was achieved when 10 wt% dual-component microcapsules were introduced in adhesives. Investigation of the fractured surfaces of the healing enabled adhesives reveals the presence of crack pinning and crack blunting sites represented by characteristic tails at the wake of microcapsules in cohesive zone. Such failure mechanisms responsibly influence the healing efficiency.

Alginate Microencapsulation for Oral Immunisation of Finfish: Release Characteristics, Ex Vivo Intestinal Uptake and In Vivo Administration in Atlantic Salmon, Salmo salar L.

This study examined the feasibility of alginate microcapsules manufactured using a low-impact technology and reagents to protect orally delivered immunogens for use as immunoprophylactics for fish. Physical characteristics and protein release kinetics of the microcapsules were examined at different pH and temperature levels using a microencapsulated model protein, bovine serum albumin (BSA). Impact of the microencapsulation process on contents was determined by analysing change in bioactivity of microencapsulated lysozyme. Feasibility of the method for oral immunoprophylaxis of finfish was assessed using FITC-labelled microcapsules. These were applied to distal intestinal explants of Atlantic salmon (Salmo salar) to investigate uptake ex vivo. Systemic distribution of microcapsules was investigated by oral administration of FITC-labelled microcapsules to Atlantic salmon fry by incorporating into feed. The microcapsules produced were structurally robust and retained surface integrity, with a modal size distribution of 250-750 nm and a tendency to aggregate. Entrapment efficiency of microencapsulation was 51.2 % for BSA and 43.2 % in the case of lysozyme. Microcapsules demonstrated controlled release of protein, which increased with increasing pH or temperature, and the process had no significant negative effect on bioactivity of lysozyme. Uptake of fluorescent-labelled microcapsules was clearly demonstrated by intestinal explants over a 24-h period. Evidence of microcapsules was found in the intestine, spleen, kidney and liver of fry following oral administration. Amenability of the microcapsules to intestinal uptake and distribution reinforced the strong potential for use of this microencapsulation method in oral immunoprophylaxis of finfish using sensitive immunogenic substances.

Non-destructive 3-dimensional mapping of microcapsules in polymeric coatings by confocal Raman spectroscopy

Abstract Nowadays, the properties of polymeric coatings are enhanced by various additives mixed into the resin. Recently, embedding of polymeric microcapsules into the coating matrix has been investigated to provide special on-demand features to the coating. The detection and characterization of such microcapsules in a polymeric coating are of major importance but difficult, because both are built up by similar molecules with similar densities. Current analysis methods require complex sample preparation to allow reliable measurements. In contrast, confocal Raman spectroscopy allows fast and non-destructive differentiation between characteristic molecular bonds at a spatial resolution below one micrometer. Hence, the objective of this research was to apply this technique on microcapsules embedded in a coating and provide answers to the following questions: Can one detect microcapsules embedded in a coating and clearly identify them? Can one differentiate between full and empty microcapsules and the coating matrix? Can one determine the exact location of the capsules and their distribution in the coating? Therefore, several two-dimensional confocal Raman spectroscopy mappings recorded at different depths allowed a three-dimensional reconstruction of the polymeric coating with the polymeric microcapsules in it. Thereby, the distribution of the capsules within the coating could be determined with micrometer resolution. As a result Raman tomography provides a more detailed insight into the distribution of microcapsules through the possibility of three-dimensional reconstruction.

Microencapsulation of probiotic bacteria using thermo-sensitive sol-gel polymers for powdered infant formula

In this study the application of thermo-sensitive sol-gel polymers in microencapsulation formulation of probiotic bacteria, Bifidobacterium animalis spp lactis, for powdered infant formula (PIF), which is reconstituted at 70 °C, has been assessed. A double-layered microcapsule containing hydroxypropyl methyl cellulose (HPMC) as an inner layer and an outer layer, as the smart coating layer, based on a combination of hydroxypropyl cellulose (HPC) and poloxamer was designed. Generally, this specific microencapsulation provided superior protection against the reconstitution temperature. A high molecular weight of HPC and a greater thickness of the smart coating layer resulted in a delayed release of the bacteria from the microcapsules especially in the PIF composition. However, this was compensated by a high stability of the bacteria at 70 °C. Both the surface texture and particle size distribution of microcapsules have been respectively characterised by scanning electron microscopy and particle size analysis.

Intraperitoneal distribution of alginate microcapsules in mice

Introduction: Improved drug delivery mechanisms for the treatment of residual peritoneal cancer cells following cytoreduction surgery are needed. Alginate microcapsules are a potentially useful mechanism for delivery of bioengineered cells, but when injected into the peritoneum, their distribution and properties are not well described. Methods: Aliquots of 300, 600 or 1200 microcapsules were injected into the peritoneum of 81 mice. Mice were sacrificed at 6, 12, 18, and 48 days and laparotomy was performed to quantify the distribution of microspheres. Results: The injections were well tolerated for up to 48 days. No peritoneal adherence or inflammatory reaction was noted to the microcapsules. Injection of 1200 microcapsules resulted in a better overall persistence and widespread peritoneal distribution at up to 48 days. The volume of fluid used for injection of the microcapsules did not affect their distribution or persistence. Conclusion: The intraperitoneal injection of alginate microspheres allows wide and persistent distribution throughout the abdominal cavity. The next step is to test the distribution of microcapsules when delivered following surgery in a rodent model.

Study of SMA as Protective Colloid on the MF-Resin Micro-Encapsulation

The paper studied the effects of SMA as protective colloid on emulsification and micro-encapsulation process in the preparation of MF-resin microcapsules. The results indicated that pH value and the dosage of the SMA had important effects on zeta value and micro-encapsulation. The SMA dosage, emulsifying time and stirring rate influenced the capsule preparation, mean particle size and particle size distribution of microcapsules. The diameter became smaller with the increase of the amount of protective colloid. The applying amount of the SMA had an optimum value. The zeta potential just after emulsification was much larger than after reaction of MF in the preparation of microcapsules.

Preparation and Characterization of Self-healing Polymeric Materials with Microencapsulated Epoxy and Imidazoline Derivatives Curing Agent

Binary self-healing system consisting of epoxy-containing microcapsules and latent curing agent based on anionic polymerization was investigated. When cracks propagated in the composites, the embedded microcapsules would be damaged and the epoxy healing agent would be released. The latent curing agent used in this study can be well dispersed in epoxy matrix during composites manufacturing, and hence activate the released epoxy wherever it is. As a result, self-healing of the cracked sites is successfully achieved through curing of the released epoxy healing agent. This paper also investigated the preparation and performance of microcapsules synthesized by situ polymerization. The mechanism of anionic chain polymerization between epoxy and curing agent was investigated. On the basis of this work, self-healing ability of the epoxy filled with the healing system was evaluated. It was found that the distribution of microcapsules and latent curing agent greatly influences the healing efficiency but not the stoichiometric composition, and the optimal weight ratio of microcapsules and curing agent 2MZ-AZINE are 15 wt.% and 2 wt.%, offering a ~83% healing efficiency.

Effects of Protective Colloid on the MF-UF Double Wall Micro-Encapsulation Containing Essence Oil

Essence oil is difficult to microencapsulate and difficult to envelop into wall to prepare pressure sensitive microcapsules. With styrene maleic anhydride copolymer (SMA) as the protective colloid, the paper studied the effects of protective colloid and micro-encapsulation of pressure sensitive perfume microcapsules with melamine formaldehyde resin (MF) and urea formaldehyde resin (UF) as double wall first time by using the re-in situ polymerization method. The microcapsules and emusion process were characterized on morphologies, mean particle size and size distribution, zeta potebtial, wall thickness of microcapsules. It was found that the SMA seemed to be suitable for the emulsification and preparation of microcapsule with MF-UF resin as double wall containing essence oil. The results indicated the S/M mole ratio in MSA molecules affected the preparation and quality of microcapsules, pH value and the dosage of SMA had important impact on zeta value and encapsulation in the process of polymerization. The stirring time and stirring rate in emulsification process with MSA as protective colloid influenced the mean particle size and particle size distribution of microcapsules, SMA was one of the components of microcapsules, SMA amount used affected the mean particle size, size distribution and thickness of microcapsules.

A Recommended Laparoscopic Procedure for Implantation of Microcapsules in the Peritoneal Cavity of Non-Human Primates

The anatomical spatial distribution of microencapsulated islets transplanted into the peritoneal cavity of large animals remains a relatively unexplored area of study. In this study, we developed a new implantation approach using laparoscopy in order to avoid microcapsule amalgamation. This approach constitutes a clinically relevant method, which can be used to evaluate the distribution and in vivo biocompatibility of various types of transplanted microcapsules in the future. Two healthy baboons were implanted intraperitoneally with microencapsulated islets through mini-laparotomy and observed at 76 d after implantation. Nine baboons underwent laparoscopic implantation of approximately 80,000 empty microcapsules. Microcapsule distribution was observed by laparoscopic camera during and after implantation at 1, 2, and 4 wk. At each time point, microcapsules were retrieved and evaluated with brightfield microscopy and histologic analysis. Mini-laparotomic implantation resulted in microcapusle aggregation in both baboons. In contrast, laparoscopic implantation resulted in even distribution of microcapsules throughout the peritoneum without sedimentation to the Douglas space in all animals. In eight out of nine animals, retrieved microcapsules were evenly distributed in the peritoneal cavity and presented with no pericapsular overgrowth and easily washed out during laparoscopic procedure. The one exception was attributed to microcapsule contamination with blood from the abdominal wall following trocar insertion. Laparoscopic implantation of microcapsules in non-human primates can be successfully performed and prevents microcapsule aggregation. Given the current widespread clinical application of laparoscopy, we propose that this presented laparoscopy technique could be applied in future clinical trials of microencapsulated islet transplantation.