Composite Microcapsules Research Articles

A composite capsule strategy to support longevity of microencapsulated pancreatic β cells

Pancreatic islet microencapsulation allows transplantation of insulin producing cells in absence of systemic immunosuppression, but graft survival is still limited. In vivo studies have demonstrated that many islet-cells die in the immediate period after transplantation. Here we test whether intracapsular inclusion of ECM components (collagen IV and RGD) with necrostatin-1 (Nec-1), as well as amino acids (AA) have protective effects on islet survival. Also, the inclusion of pectin was tested as it enhances the mitochondrial health of β-cells. To enhance the longevity of encapsulated islets, we studied the impact of the incorporation of the mentioned components into the alginate-based microcapsules in vitro. The efficacy of the different composite microcapsules on MIN6 β-cell or human islet-cell survival and function, as well as suppression of DAMP-induced immune activation, were determined. Finally, we examined the mitochondrial dynamic genes. This was done in the absence and presence of a cytokine cocktail. Here, we found that composite microcapsules of APENAA improved insulin secretion and enhanced the mitochondrial activity of β-cells. Under cytokine exposure, they prevented the cytokine-induced decrease of mitochondrial activity as well as viability till day 5. The rescuing effects of the composite capsules were accompanied by alleviated mitochondrial dynamic gene expression. The composite capsule strategy of APENAA might support the longevity of microencapsulated β-cells by lowering susceptibility to inflammatory stress. Our data demonstrate that combining strategies to support β-cells by changing the intracapsular microenvironment might be an effective way to preserve islet graft longevity in the immediate period after transplantation.

An approach to mass produce peppermint oil-sodium alginate composite microcapsules by drop-on-demand system loaded with stabilized nanoemulsion

ABSTRACT Microencapsulation technology has found widespread applications in current fields of food industries. In this study, by combining water-in-oil emulsion with drop-on-demand (DOD) technique, we successfully produced sodium alginate (SA) shell microcapsules containing peppermint oil (PO). Response surface methodology (RSM) was employed to optimize the surfactant used for nanoemulsification. A comprehensive investigation into the morphology, structure, and encapsulation efficiency of resulting microcapsules was conducted. The study revealed that various parameters, especially of Hydrophilic-Lipophilic Balance (HLB) values, can affect the physical properties of PO/SA nanoemulsion. The optimized formulation achieved emulsions with a mean droplet size of 46.60 nm. Microcapsules with different shell/core ratios (2, 1, and 0.5) were prepared by pulse duration of 20 ms, exhibiting varying antibacterial activities against Escherichia coli in subsequent tests. This work confirms the feasibility of nanoemulsion-DOD system, highlighting the potential of PO/SA microcapsules as a more environmentally friendly alternative to conventional antimicrobials.

A new way to achieve infrared stealth by composite phase change microcapsules

With the development of infrared detection technology, there is a demand for more simple and convenient infrared shielding technology in some specific aspects, such as military applications. Here a new way to infrared stealth was presented, that is, a composite phase change microcapsules which were prepared by in situ polymerization, and have a core-shell structure, exhibited a good infrared stealth property. A series of tests were provided by scanning electron microscope, Fourier transform infrared absorption spectrometer, differential thermal scanning calorimeter, thermogravimetric analyses, infrared thermal imager, etc. The maximum enthalpy of the samples in the melting process is about 119 J/g, which enhanced sample infrared stealth performance. A good shape stability was proved by many thermal cycles. The samples are effective in reducing the infrared radiation intensity of target surfaces as well as in prolonging the appearance of infrared signatures.

Investigation of encapsulation of pancreatic beta cells and curcumin within alginate microcapsules

AbstractCell encapsulation is an ideal approach for the replacement of pancreatic function in Type 1 diabetes. Poor biocompatibility of microcapsules generates an inflammatory response in the implantation site and induces fibrosis infiltration, which causes microencapsulated cell death and graft failure. To prevent inflammation after implantation, composite microcapsules that exhibit anti‐inflammatory properties were designed. This study is about encapsulating beta cells and curcumin within 1.5% alginate by the jet‐breaking regime of the syringe pump. The microcapsules’ size distribution and rate of the alginate solution were characterized to find uniform particles. Micro‐size particles were attained at a rate of 25 mL/min. Uniform spherical microcapsules (200–300 μm) were created in large amounts in a short period. Microcapsule breakage was less than 3% during 7 days, which demonstrated the stability of the encapsulation method. Insulin secretion and cell viability assays were performed 1, 3, and 7 days after microencapsulation by glucose‐stimulated insulin secretion (GSIS) and 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5 diphenyl tetrazolium bromide (MTT) assays. No significant differences in the amount of insulin secretion and beta cell viability were observed among free cells, alginate microcapsules, and curcumin‐alginate microcapsules during 7 days (p > 0.05). Therefore, the curcumin and alginate membrane did not show any harmful impacts on the function and survival of the beta cells.

Full-spectrum photo-thermal conversion enabled by plasmonic titanium carbide modified phase change microcapsules

Phase change materials (PCMs) have been considered one of the promising strategies to harvest the clean solar energy and convert to latent heat for storage (LHS). However, solar-thermal conversion efficiencies of most PCMs are poor ascribed to their low thermal conductivity, leakage issue, and poor solar radiation absorbability. This work presents a facile method for the fabrication of n-Eicosane@TiC/TiO2 composite microcapsules for the first time that exhibit outstanding full-spectrum solar energy absorption and enables excellent energy-storage capability of 99.31 % and 73.45 % photo-thermal conversion efficiency owing to localized surface plasmon resonance effect of the TiC. The composite microcapsules will offer a new paradigm for LHS technologies in direct solar collectors.

Fabrication of multiple protective fabric based on ZnO/chitosan composite microcapsules via thiol-ene click modification

Fabrication of multiple protective fabric based on ZnO/chitosan composite microcapsules via thiol-ene click modification

Preparation of polyaniline encapsulated acrylic resin microcapsules and its active corrosion protection of coating for magnesium alloy

Herein, novel microcapsules were designed and synthesized by emulsion polymerization and used for self-healing coating for magnesium alloy. Polyaniline (PANI) was used directly as a capsule shell, and thermoplastic acrylic resin was used as the core material. Polymerization processes of microcapsules were observed by optical microscopy, and some key polymerization parameters were discussed. Composite microcapsules were analyzed by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. The corrosion protection performance of microcapsule and epoxy varnish coatings with defect was tested by electrochemical impedance spectroscopy. Results showed that the microcapsule coating had a higher corrosion protection than epoxy varnish coating because capsule core acrylic resin could significantly improve the shield performance of the defect coating and capsule shell PANI could inhibit the corrosion reaction of magnesium alloy.

Preparation of pH sensitive bacteriostatic W/O/W emulsion microcapsules

This experiment was done to study the zeolite molecular sieve as a drug-binding effector, the non-antibiotic drug potassium diformate uniformly disperse in the internal aqueous phase of the 'egg box' structure formed by pectin-calcium ions. With oil phase as the intermediate phase and Xanthan gum Chitosan as the external water phase, the W/O/W type sustained release bacteriostatic microcapsules with pH response were prepared and characterized by Fourier transform infrared, thermogravimetric, SEM, and TEM. It can be obtained through characterization experiments that the inner water phase, oil phase, and outer water phase were formed by observation, and W/O/W emulsion microcapsules were obtained and the bacteriostasis effect of microcapsules was verified by bacteriostasis experiment. The permeance experiment showed that the molecular sieve was successfully coated in the microsphere. Studying on drug release mechanism and sustaining release performance of composite emulsion microcapsules. In vitro drug release study showed that the encapsulation efficiency and drug loading rate of microcapsules were improved by adding molecular sieve, reaching 12.31% and 61.55%, respectively. At the same time, we observed that the drug release rate slowed down during the simulated intestinal release process, and the drug release kinetics were in line with the first-order kinetic model and Ritger-Peppas model equation. Experiments had proven that the drug-loaded microcapsules exerted a significant bacteriostatic effect on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, with the highest antibacterial rates of 97.25%, 94.05%, and 95.93%, respectively. Therefore, the composite emulsion microcapsules can be used as a new controlled-release drug delivery system in vivo.

Enhanced thermal conductivity and photothermal effect of microencapsulated n-octadecane phase change material with calcium carbonate-polydopamine hierarchical shell for solar energy storage

The development of microencapsulated phase change materials with excellent photothermal conversion and storage performances is significant for solar energy utilization. Herein, a kind of the novel n-octadecane microcapsules with calcium carbonate-polydopamine (CaCO3-PDA) hierarchical shell was fabricated through a simple one-pot synthetic strategy. The n-octadecane droplets were firstly encapsulated into inorganic CaCO3 shell in the SDBS-templating emulsion, and subsequently the formed n-octadecane microcapsules were further modified by adhesive PDA. The resultant composite microcapsules displayed a regular and compact spherical morphology with a well-defined core-shell microstructure, and the light-absorption PDA coating uniformly deposited onto the CaCO3 shell surface. The phase change microcapsules possessed a satisfactory latent heat storage capability of more than 140 J g−1 and a favorable energy storage efficiency of about 60%. Owing to the existence of CaCO3 shell, the as-prepared n-octadecane microcapsules achieved a remarkable enhancement in the thermal conductivity compared to pristine n-octadecane. With the surface modification of PDA, the composite microcapsules demonstrated not only superior thermal stability and phase change reliability but also improved photothermal effect. Moreover, the microcapsules exhibited stable photothermal conversion and storage performances under the cycling sunlight irradiation. Therefore, the developed composite n-octadecane microcapsules in this work present a promising prospect in the field of solar-to-thermal energy utilization and storage.

Preparation of enzymolysis porous corn starch composite microcapsules embedding organic sunscreen agents and its UV protection performance and stability

In this paper, a natural composite wall material sunscreen microcapsule was prepared, which significantly improved the SPF value and photostability of the embedded sunscreen agents. Using modified porous corn starch and whey protein as wall materials, the sunscreen agents 2-[4-(diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl ester and ethylhexyl methoxycinnamate were embedded by adsorption, emulsion, encapsulation and solidification. The embedding rate of the obtained sunscreen microcapsules was 32.71 % and the average size was 7.98 μm; the enzymatic hydrolyzed starch formed a porous structure, its X-ray diffraction pattern did not change significantly, and the specific volume and oil absorption rate increased by 39.89 % and 68.32 %, respectively, compared with those before enzymatic hydrolyzed; The porous surface of the starch after embedding the sunscreen was covered and sealed with whey protein. 120 h sunscreen penetration rate was lower than 12.48 %; Compared with the lotion containing the same amount of sunscreen but not encapsulated, the SPF value of the lotion containing sunscreen microcapsules increased by 62.24 %, and the photostability of sunscreen microcapsules increased by 66.28 % within 8 h under the irradiation intensity of 25 w/m2. The wall material and the preparation method are natural and environmentally friendly, and have a good application prospect in low-leakage drug delivery system.

Phase Change Composite Microcapsules with Low-Dimensional Thermally Conductive Nanofillers: Preparation, Performance, and Applications

Phase change materials (PCMs) have been extensively utilized in latent thermal energy storage (TES) and thermal management systems to bridge the gap between thermal energy supply and demand in time and space, which have received unprecedented attention in the past few years. To effectively address the undesirable inherent defects of pristine PCMs such as leakage, low thermal conductivity, supercooling, and corrosion, enormous efforts have been dedicated to developing various advanced microencapsulated PCMs (MEPCMs). In particular, the low-dimensional thermally conductive nanofillers with tailorable properties promise numerous opportunities for the preparation of high-performance MEPCMs. In this review, recent advances in this field are systematically summarized to deliver the readers a comprehensive understanding of the significant influence of low-dimensional nanofillers on the properties of various MEPCMs and thus provide meaningful enlightenment for the rational design and multifunction of advanced MEPCMs. The composition and preparation strategies of MEPCMs as well as their thermal management applications are also discussed. Finally, the future perspectives and challenges of low-dimensional thermally conductive nanofillers for constructing high performance MEPCMs are outlined.

Development of composite-phase change microcapsule coating and numerical investigation on its effect in ballastless track slabs

To solve the problems of interlayer cracking, up-arching and warping of ballastless track slab of high-speed railway under temperature load, a composite phase-change microcapsule (MPCM) was developed, and a series of physical and chemical experiments was conducted. The practicality and functional advantages of composite phase-change microcapsules were investigated by SEM, FTIR, DSC and other material tests. The cooling effects of the coating were evaluated and simulated by indoor tests and numerical simulations. The results show that the developed MPCM exhibits both strong reflectivity of TiO2 and the phase change energy storage property of paraffin, which can reflect 59%-63% of the near-infrared radiation in solar radiation. Moreover, 1 g MPCM can absorb and store 98.3–112.5 J of heat when the ambient temperature exceeds 40 °C. The MPCM coating can reduce the rate of temperature rise of the test specimen, and also decrease its overall temperature difference to 12–15 °C. Furthermore, it can reduce the longitudinal temperature gradient of the test specimen at least by 50%, and its surface temperature by 18%-28%. The temperature regulation ability of coating is positively correlated with the content of MPCM, and its cooling effect reaches the best when the content of MPCM is 20%. The coating reduces the vertical deformation of track slab by 25%-59.6% and the temperature difference inside the track slab by 12.2 °C under high-temperature condition.

Novel Silicone-Grafted Alginate as a Drug Delivery Scaffold: Pharmaceutical Characterization of Gliclazide-Loaded Silicone-Based Composite Microcapsules

A novel gliclazide-loaded elastomeric carbohydrate pharmaceutical vehicle was successfully developed. This new siliconized alginate platform showed pseudoplastic rheology with a zeta potential ranging from (-43.8 mV to -75.5 mV). A Buchi-B390 encapsulator was employed to formulate different types of silicone-grafted alginate microcapsules loaded with gliclazide relying on the vibrational ionic gelation technology. The use of tetraethyl orthosilicate (TEOS) to crosslink the silicone elastomer (hydroxy terminated polydimethylsiloxane) of this new platform had improved the gliclazide encapsulation (>92.13% ± 0.76) of the free-flowing composite microcapsules, which showed good mechanical durability (up to 12 h in PBS pH 6.8) and promising results to sustain the drug release.

Marine polymers-alginate/chitosan composited microcapsules for wound healing

Skin damage is a serious problem that has attracted remarkable attention. Novel wound dressings with optimized compositional and structural design that could adapt to the wound area are highly expected. In this study, we prepare marine polymer composite microcapsules via microfluidic electrospray for promoting wound healing. An alginate (ALG) core and a chitosan (CS) shell formed microcapsules through polyelectrolyte complexation and glutaraldehyde cross-linking. Such composition ensures the great biocompatibility and antibacterial capacity of the microcapsules. Besides, vascular endothelial growth factor (VEGF) can be loaded into the microcapsules as well as released in a sustainable way. Based on these advantages, the microcapsules are casted on the wound site and their roles in inhibiting bacterial growth and promoting angiogenesis during wound closure are demonstrated. These results confirm the values of the microcapsules in wound healing, and we believe that would find potential clinical applications.

Improving the bioaccessibility of lipophilic ingredient in its oral intestinal delivery by ultrasound and biological cross-linker.

Great efforts have been made to improve the oral bioaccessibility of lipophilic ingredients with multi-functionalities. Achieving intestinal delivery of lipophilic ingredients and their encapsulation in micelles composed of bile salts and lipid hydrolysates (i.e. fatty acids) is critical for improving oral bioaccessibility. Therefore, oil-core microcapsules are considered ideal carriers of lipophilic ingredients. Previous studies have reported oil-core/zein-shell microcapsules constructed by a one-step anti-solvent process. Still, its efficacy as an intestinal delivery system was limited because if the porous shell structure. Zein solution was pretreated with ultrasound and tannic acid (TA) cross-linking. Composite oil-core microcapsule (COM) with a compact shell structure was successfully prepared by using modified zein solution in the anti-solvent process. Fourier-transform infrared spectroscopy and circular dichroism analyses indicated that ultrasound and TA synergistically promote the conformational transition of zein from α-helix to β-sheet and enhance the hydrophobic interactions among protein chains. The above changes contribute to the strengthen of shell zein network. Correspondingly, COM presents superior encapsulation efficiency and environmental stability over the simple oil-core microcapsule (SOM) prepared without the use of ultrasound and TA. Furthermore, antioxidant activity of β-carotene was well retained during the encapsulation process. In vitro studies indicated that COM was more resistant to digestibility and acid-induced swelling. More than 87% of β-carotene could be released in the intestine in a sustainable way. The controllable release behavior thus promoted a significant increase in bioaccessibility of β-carotene encapsulated in COM compared to SOM (85.9% versus 48.5%). The COM generated here shows potential for bioaccessibility improvement of lipophilic ingredients. © 2022 Society of Chemical Industry.

Preparation and characterization of Perilla essential oil composite microcapsule based on the complex coacervation and interface polymerization.

In this paper, we prepared a novel double-layer Perilla essential oil composite membrane microcapsule (PEOCM) by the composite methods of complex coacervation and interface polymerization. The particle size distribution, morphology, pressure resistance, thermal stability, and elemental proportions of the microcapsule shell of the obtained microcapsules were characterized by laser particle size analyzer, scanning electron microscopy (SEM), dynamic rheometer, thermogravimetric analysis (TGA), and energy spectrometer. In order to further examine the application effect of the PEOCM, we carried out a fresh-keeping experiment on nectarines. The results showed that the average volume diameter of the microcapsules was 226.9µm, with a completely spherical shape and a slight depression on the surface and had good pressure resistance and thermal stability. The results also demonstrated that microencapsulation does not change the composition of Perilla essential oil, and the polyurea membrane with amide structure (-NH-CO-NH-) was formed successfully. Furthermore, the total soluble solids content and peroxidase activity of nectarines indicated that the PEOCM can be a preservative of food. PRACTICAL APPLICATION: We prepared a double-layer Perilla essential oil composite membrane microcapsule by the composite methods of complex coacervation and interface polymerization. The encapsulation conditions of the microcapsules were optimized, the structure of the microcapsule was characterized, and the fresh-keeping effects of the microcapsule on nectarine were studied. The results showed that microcapsules had a completely spherical shape and a slight depression on the surface and had good pressure resistance, good thermal stability, and good fresh-keeping ability. The above characteristics indicated that the double-layer microcapsules have good application prospect and plays an important role in food fresh-keeping and the preservation of essential oils.

Formation of cinnamon essential oil/xanthan gum/chitosan composite microcapsules basing on Pickering emulsions.

Cinnamon essential oil (CNO) is a natural and renewable antibacterial agent. However, CNO is highly volatile and unstable, which limits its practical application as a long-term and wide antibacterial agent. In order to improve the CNO stability, we have microencapsulated CNO into composite microcapsules basing on Pickering emulsion stabilized by silica (SiO2) nanoparticles. The CNO-loaded composite microcapsules possess the hybrid microcapsule shell including SiO2, xanthan gum and chitosan. Moreover, the results show that the microcapsules have spherical appearance. Microencapsulation technique effectively promotes the CNO stability, and the loaded CNO is slowly released from microcapsules. The antibacterial test indicates that the minimal inhibitory concentration of microcapsules was 2 mg mL−1 against Escherichia coli and Staphylococcus aureus, and the microcapsules can play an effective long-term antibacterial effect. Thus, Pickering emulsion templates is a convenient and effective technique to construct antibacterial essential oil-contained microcapsules, which can be used as long-term antibacterial agents.

Fabrication and Biocompatibility of Layer-by-layer Assembled Composite Graphene Oxide-polysaccharide Microcapsules

The present study is focused on the construction and characterization of the morphology and biocompatibility of polysaccharide multilayered microcapsules (PMC) composed of natural polyelectrolytes (chitosan/alginate/hyaluronic acid), and on the effect of graphene oxide (GO) incorporation in the polymer matrix. The insertion of GO in the polymer matrix is an innovative and still evolving strategy used to modify the properties of the polyelectrolyte microcapsules. We have fabricated a number of hybrid GO-polysaccharide multilayered capsules by layer-by-layer assembling technique onto a CaCO3 core, followed by core decomposition in mild conditions. Hybrid microcapsules with different composition were constructed by varying the number or localization of the incorporated GO-layers. It was found that the thickness of the hybrid microcapsules, evaluated by atomic force microscopy, decreases after incorporation of GO nanosheets in the polymer matrix. Analysis of the viability and proliferation of fibroblasts after incubation with hybrid PMC revealed pronounced concentration-dependent cytotoxic and antiproliferative effect. Based on the results, we can conclude that the hybrid multilayered microcapsules made of natural polysaccharides and graphene oxide could be used for biomedical applications.

Effect of Coating Process of Photochromic and Thermochromic Composite Microcapsules on Coating Properties for Basswood

In this paper, photochromic and thermochromic microcapsules were selected. There are three different coating processes: “the primer with the photochromic microcapsules, the topcoat with the thermochromic microcapsules”, “the primer with the thermochromic microcapsules, the topcoat with the photochromic microcapsules”, and “the photochromic and thermochromic microcapsules added into the primer and topcoats” to explore the color-changing effect of the coating on the surface of basswood (Tilia) and the comprehensive properties of the paint film. The optical properties, mechanical properties, cold liquid resistance, and aging resistance of the coating were mainly analyzed. It was concluded that the comprehensive performance of the coating was the best when thermochromic and photochromic microcapsules were mixed on the surface of basswood (Tilia). At a temperature of 80 °C, the color difference reached a maximum of 20.2, and the coating was completely discolored. The color difference of the coating after discoloration under visible light illumination was 56.9. The gloss under the angle of incidence at 60° was 37.4, hardness was 3H, adhesion grade was 1, impact resistance was 10.0 kg·cm, and cold liquid resistance grade was 1. The method of mixing the two microcapsules had better aging resistance. In this paper, the photochromic and thermochromic properties of the coating were studied, and the optimal discoloration of the surface coating of the basswood substrate was solved by different coating processes. This study provided a method for a coating to achieve both photochromic and thermochromic discoloration, broadening the application of discoloration coatings.

Thermal behavior and phase transition of the aminostaldehyde as the wall and bromohexadecane as a phase change material enriched via gold nanoparticles: Molecular dynamics study

This paper is examined the thermal conductivity (TC) of phase change material (PCM) composite microcapsules with gold nanoparticles (NPs) using molecular dynamics simulation (MDS). These microcapsules are made with aminostaldehyde (C2H5NO) as the wall and bromohexadecane (BrC16) as the PCM. First, the physical equilibrium in simulated samples is examined by the change in the temperature and potential energy of atomic samples. Then, the TC of samples in the presence of external heat flux (HF) and a magnetic field (MF) is examined. The parameters of HF, TC, and viscosity of the simulated samples are investigated to study the thermal behavior. The results show that increasing the external HF from 0.1 to 0.5 W/m2 increases the simulated sample's HF and TC. Also, the viscosity of the simulated sample decreases with increasing HF from 0.0092 to 0.0085 Pa.s. On the other hand, the HF and TC values are increased by increasing the amplitude of the external MF from 0.1 to 0.5 T. Also, the viscosity increases with the MF amplitude to 0.00098 Pa.s. Finally, by enhancing the frequency of the external MF from 0.01 to 0.05 fs−1, the values of HF and TC decrease. Also, increasing the MF frequency reduces the viscosity in the simulated samples up to 0.00088 Pa.s.