Surface Of Microcapsules Research Articles

Fabrication of dual network self-healing alginate/guar gum hydrogels based on polydopamine-type microcapsules from mesoporous silica nanoparticles.

In this manuscript, dual network self-healing alginate/guar gum hydrogels with polydopamine-type microcapsules from mesoporous silica nanoparticles were facilely prepared through one-pot method. Glutaraldehyde (GA) was used as a crosslinking agent to crosslink guar gum and sodium alginate, respectively. Metal-ligand interactions as reversible non-covalent bonds make the dual network hydrogels have a high degree of self-healing ability, which FeCl3·6H2O was coordinated with sodium alginate and polydopamine on the surface of microcapsules, respectively. The dual network structure significantly enhances the strength of the hydrogels (up to 7.3 MPa). It has also proved that these hydrogels exhibit excellent self-healing performance at ambient temperatures, which self-healing efficiency can reach to 95.5%. The obtained self-healing hydrogels have a promising application prospect for the design and synthesis of functional self-healing materials.

Ultralow Tribological Properties of Polymer Composites Containing [BMIm]PF6‐Loaded Multilayer Wall Microcapsule

AbstractMultilayer wall microcapsules efficiently loaded with a lubricant (ionic liquid [BMIm]PF6) are successfully synthesized via a combination of interfacial and in situ polymerization reactions based on lignin nanoparticle–stabilized Pickering emulsion templates. The resulting microcapsules are spherical in shape, with an ideal structure of a rough outer surface and a smooth inner surface. The mean diameter and wall thickness of the resultant microcapsules are 52 ± 18 µm and 3–6 µm. The core fraction is ≈71.29 wt%. Compared with the pure epoxy resin, the friction coefficient of self‐lubricating composites decreases by 83.6% (from 0.55 to 0.09) and the wear rate decreases by 218 times (from 76.8 × 10−14 to 0.352 × 10−14 m3 N−1 m−1) by incorporating 20 wt% of the resultant microcapsules into the epoxy resin. It is demonstrated that [BMIm]PF6, a more efficient lubricant, release from the microcapsules during the friction process produced a boundary lubricating film. The bipolar property of [BMIm]PF6 makes the lubricating film firmer, which can efficiently prevent direct contact between the resin matrix and counterface. Furthermore, the rough poly(urea‐formaldehyde) outer surface of multilayer microcapsules brings in an improved interface property between the microcapsules and resin matrix.

Taking a microfluidic approach to the production of self-healing construction materials

Taking a microfluidic approach to the production of self-healing construction materials

Characterization of Polyethylene Glycol-Reinforced Alginate Microcapsules for Mechanically Stable Cell Immunoisolation.

Islet transplantation within mechanically stable microcapsules offers the promise of long-term diabetes reversal without chronic immunosuppression. Reinforcing the ionically gelled network of alginate (ALG) hydrogels with covalently linked polyethylene glycol (PEG) may create hybrid structures with desirable mechanical properties. This report describes the fabrication of hybrid PEG-ALG interpenetrating polymer networks and the investigation of microcapsule swelling, surface modulus, rheology, compression, and permeability. It is demonstrated that hybrid networks are more resistant to bulk swelling and compressive deformation and display improved shape recovery and long-term resilience. Interestingly, it is shown that PEG-ALG networks behave like ALG during microscale surface deformation and small amplitude shear while exhibiting similar permeability properties. The results from this report's in vitro characterization are interpreted according to viscoelastic polymer theory and provide new insight into hybrid hydrogel mechanical behavior. This new understanding of PEG-ALG mechanical performance is then linked to previous work that demonstrated the success of hybrid polymer immunoisolation devices in vivo.

Cancer Cell Targeting With Functionalized Quantum Dot-Encoded Polyelectrolyte Microcapsules.

Imaging agents and drug carriers are commonly targeted toward cancer cell through functionalization with specific recognition molecules. Quantum dots (QDs) are fluorescent semiconductor nanocrystals whose extraordinary brightness and photostability make them attractive for direct fluorescent labeling of biomolecules or optical encoding of the membranes and cells. Here, we analyse the cytotoxicity of QD-encoded microcapsules, validate an approach to the activation of the microcapsule's surface for further functionalization with monoclonal antibody Trastuzumab, a humanized monoclonal antibody targeting the extracellular domain of the human epidermal growth factor receptor 2 (HER2) and already in clinical use for the treatment of HER2 positive breast cancer. In addition, we characterize the cell-specific targeting activity of the resultant bio-conjugate by immunofluorescence assay (IFA) and real-time analysis of interaction of the conjugates with live HER2 overexpressing human breast cancer cells. We demonstrate, that encapsulation of QDs into the polymer shell using the layer-by-layer deposition method yields highly fluorescent polyelectrolyte microcapsules with a homogeneous size distribution and biocompatibility upon in vitro treatment of cancer cells. Carbodiimide surface activation ensures optimal disperse and optical characteristics of the QD-encoded microcapsules before antibody conjugation. The prepared conjugates of the microcapsules with cancer-specific monoclonal antibody targeting HER2 provide sufficiently sensitive and specific antibody-mediated binding of the microcapsules with live cancer cells, which demonstrated their potential as prospective cancer cell–targeting agents.

Development of smart alginate/chitosan grafted microcapsules for colon site-specific drug delivery

In this study, a smart delivery system for colon site-specific release of diclofenac sodium (DS) was developed based on alginate grafted chitosan (Alg-g-CS) microcapsules. The developed microcapsules were characterized using FTIR and SEM characterization tools, while the present amine content on the alginate microcapsules surface was estimated by ion exchange capacity (IEC) measurements. Besides, both swelling and in vitro drug release profiles were studied at colon pH medium (pH7.4). The results showed an increase in IEC values from 1.1 to 3.6meq/g with increasing CS concentration from 0.1 to 0.5%. Moreover, grafting of alginate microcapsules with chitosan prevented the drug burst release as well as protected alginate microcapsules from the fast disintegration at colon conditions. The gained results clearly suggested that the developed smart Alg-g-CS (0.5%CS) microcapsules could be used effectively for the delivery of diclofenac sodium (DS) to colon tract.

Astaxanthin from Haematococcus pluvialis Microencapsulated by Spray Drying: Characterization and Antioxidant Activity

AbstractAstaxanthin (AX) is an unstable functional food ingredient. A stable AX powder was developed and its characteristics (such as moisture content, bulk density, solubility, repose angle, and morphology) and antioxidant activity were evaluated. The microencapsulated AX powder was produced by spray drying using maltodextrin (MD)–gelatin and the parameters were optimized by response surface methodology. The results revealed that an optimal microencapsulation process has a ratio of MD to gelatin of 2.1:1, a ratio of wall to core materials of 5.9:1, and a ratio of glycerol monostearate to sucrose fatty‐acid ester of 1.1:1. The AX encapsulation yield and encapsulation efficiency were 38.02% and 71.76%, respectively. AX microcapsules had a lower moisture content and bulk density, greater solubility, and good flowability. AX microcapsules showed antioxidant activities greater than Vitamin C, which indicated that the antioxidant activity of AX was not lost. AX microcapsule micrographs showed almost no cracks or fissures on the surface of microcapsules produced by spray drying under the optimal conditions.

Ortho-substituted azobenzene: shedding light on new benefits

Abstract Novel functional polymeric microcapsules, based on modified azobenzene moieties, are exhaustively investigated, both from a theoretical and experimental points of view. Theoretical calculations and several measurements demonstrate that visible light can act as a trigger for release of encapsulated material, as a consequence of trans-cis isomerization which modifies microcapsule surface topography and can induce a “squeezing” release mechanism. Interfacial polymerization of an oil-in-water emulsion is performed and leads to core-shell microcapsules which are characterized by means of atomic force microscopy (AFM), optical microscopy (OM), scanning electron microscopy (SEM) and light scattering. These analyses put into evidence that microcapsules’ size and surface morphology are strongly affected by irradiation under visible light: moreover, these changes can be reverted by sample exposure to temperatures around 50°C. This last evidence is also confirmed by NMR kinetic analyses on modified azobenzene moiety. Finally, it is shown that these smart microcapsules can be successfully used to get a controlled release of actives such as fragrancies, as a consequence of visible light irradiation, as confirmed by an olfactive panel.

Characteristics and release of monosodium glutamate microcapsules obtained by spray drying

The present study aimed at investigating the characteristics of monosodium glutamate (MSG) microcapsules. Spray-drying was used to prepare the microcapsules, in which the core material (MSG) was coated with gum Arabic (GA) and maltodextrin (MD), and the weight ratio of MD with GA was 1:2. The characteristics of microcapsules were evaluated by scanning electron microscopy (SEM), moisture content, particle size, Fourier-transform infrared (FTIR), differential scanning calorimeter (DSC), thermogravimetry analysis (TGA), release behavior, the flavor, and taste in hot-pot. Few concave wrinkles were observed on the quasispheres surface of microcapsules coated with GA and MD. The particle size of the microcapsules ranged from 14.00 to 30.00 µm in the mean diameter, and moisture content was 2.08%. An FTIR study indicated a successful packet of MSG by wall materials and the formation of MSG microcapsules during spray drying. Results of DSC and TGA showed that hybrid encapsulation was conducive to the improvement of thermal stability of MSG. In the release of hot-pot study, tests of slow-release, electronic nose, and electronic tongue demonstrated that MSG microcapsules were available in hot water conditions to release. The MSG microcapsules coated with GA and MD exhibited long time for slow-release. Therefore, spraying drying is a suitable approach to manufacture slow-released powdered microcapsules.

High Performance Poly(methyl methacrylate-acrylic acid-divinylbenzene) Microcapsule Encapsulated Heat Storage Material for Thermoregulating Textiles

The preparation of high performance poly(methyl methacrylate-acrylic acid-divinylbenzene) (P(MMA-AADVB)) microcapsule encapsulating octadecane (OD) having carboxyl groups on the surface for textile application was studied. The P(MMA-methyl acrylate (MA)-DVB) microcapsule was previously prepared by microsuspension iodine transfer polymerization prior to hydrolysis of MA segment to obtain AA in the P(MMA-AA-DVB) shell. Using 30 wt% of MA and 20 wt% of DVB, the latent heats of melting and crystallization of the encapsulated OD were close to those of original OD (245 and 251 J/g-OD, respectively). After hydrolysis, the zeta potential value of the obtained P(MMA-AADVB) microcapsule surface was -33 mV representing the formation of carboxyl groups of PAA derived from PMA. The influences of nucleating agent amount and type on the reduction of supercooling were then investigated. Using 1-octadecanol at 10 wt% of OD provided the best result. Tc of the encapsulated OD increased and reached to that of original OD while the latent heats were maintained. The hydrolyzed P(MMA-AA-DVB) presented higher efficiency than P(MMA-MA-DVB) microcapsules for fabric coating without external binder which may due to the interaction of microcapsule surface functional group with fabric.

Improving particle characteristic and encapsulated indicators of urea–formaldehyde/epoxy self-healing microcapsule by incorporating resorcinol

ABSTRACTMicromorphology, surface property, chemical structure and size distribution of self-healing microcapsules were characterized by ESEM, surface plasmon resonance analyzer, FTIR and standard sieve shaker. The yield and core content of self-healing microcapsules were determinated. The results showed that chemical reaction between resorcinol and UF resin shell materials could promote the polymerization of UF resin shell particles and enhance the degree of cross-linking of the UF resin shell materials. Particle size and microcapsule surface roughness increase with increasing degrees of cross-linking in the UF resin. The yield and core content of the microcapsules initially rose and then decreased with continued increases in the ratio of resorcinol to urea. When the ratio of resorcinol to urea was 12%, the microcapsules achieved the maximum particle size and had favorable micromorphology. Moreover, the yield and core content of the microcapsules were at their highest, at 75.49% and 69.8%.

Thermochromic ink–paper interactions and their role in biodegradation of UV curable prints

In this study, biodegradability aspects of UV thermochromic leuco dye print on three different paper materials (synthetic, recycled, and bulky) were studied using the soil burial test under anaerobic conditions. Biodegradation of UV curable thermochromic prints were evaluated for changes by visual examination, microbial growth assay, weight loss measurements, Fourier transform infrared spectroscopy, scanning electron microscopy and colorimetric measurements. Results showed a better absorption of ink into the bulky paper structure, followed by recycled paper. Synthetic paper is not absorbent. The ink binder altogether with classic pigment and microcapsules penetrates into the structure of bulky paper. Recycled paper absorbs ink binder mostly with classic pigment. Better adsorption of binder into the bulky paper structure results in thinner layer of ink binder on the paper surface. On non-absorbent synthetic paper, microcapsules are covered with thicker layer of ink binder. In the case of bulky paper, the highest rate of biodegradation was observed, resulting in a higher number of bacteria, higher weight loss, higher changes in colour (destruction of almost all microcapsules) and almost complete reduction in thermochromic effect of the prints. Results show that microcapsules, which penetrate into the structure of bulky paper, are promoting the rate of bulky paper biodegradation. The opposite behaviour was noticed for the penetration of classic pigment into the structure of recycled paper, which resulted in remarkable reduction of recycled paper biodegradation rate. The thicker layer of ink binder (containing classic pigment) on the surface of microcapsules on recycled paper resulted in slower rate of microcapsules degradation and smaller colour change of the print. The thickest layer of ink binder and classic pigment on synthetic paper surface causes the slowest rate of biodegradation of print.

Morphological study of surface-modified urea–formaldehyde microcapsules using 3-aminopropyltriethoxy silane

In the current study, urea–formaldehyde (UF) microcapsules containing drying oils were prepared by in situ polymerization method. The surface of the prepared UF microcapsules was functionalized by using a silane-coupling agent. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), as well as atomic force microscopy observations showed that the surface roughness of the microcapsules has been promoted by the silane treating. Fourier transform infrared spectra and field-emission scanning electron microscopy coupled with energy-dispersive X-ray (EDX) analyses showed that the silane-coupling agent molecular binds strongly to the UF microcapsules surface. The particle size analyzer results show that agglomeration of the treated microcapsules was highly reduced. Thermogravimetric analysis indicated that this modification has improved thermal properties of the microcapsules. The SEM and TEM results indicated the surface roughness is increased after the functionalization treatment, and the silane molecules were attached to the surface of the UF microcapsules. According to EDXA, the weight percent of silicon was increased from 0.95 to 1.25 in the case of increasing the weight percent of the silane-coupling agent from 2 to 5 wt%. In fact, it was concluded that two major factors had influenced the UF microcapsules adhesion into the matrix, which were included as the interfacial bonds between the components and the surface roughness. The heat resistance of the microcapsules had been improved by silane-coupling agent functionalization.

PH-Dependent intestine-targeted delivery potency of the O-carboxymethyl chitosan – gum Arabic coacervates

Bovine serum albumin (BSA)-loaded microcapsules were prepared at pH 3.0, 4.5, and 6.0 through O-carboxymethyl (O-CMC) – gum Arabic (GA) coacervation followed by genipin crosslinking to explore the effects of coacervation acidity on the intestine-targeted delivery potency of resultant microcapsules. Confocal laser scanning microscope observation revealed that microcapsules with the multilayer structure were successfully prepared. As the coacervation pH rose from 3.0 to 6.0, the amount of O-CMC deposited on the microcapsule surface and the particle size increased accordingly. Swelling and BSA release results indicated that coacervation at higher pH conferred greater stability against simulated gastric fluid and better intestine-targeted delivery potency to the microcapsules. Circular dichroism analysis demonstrated that the structural integrity of entrapped BSA was well maintained during microencapsulation and incubation in simulated gastrointestinal fluids. Hence, genipin-crosslinked O-CMC – GA coacervates could be used to deliver nutraceuticals to the intestine and its delivery performance could be tailored by varying the coacervation pH.

Synthesis of novel multilayer composite microcapsules and their application in self-lubricating polymer composites

Novel lubricant oil-loaded multilayer composite microcapsules with poly(urea-formaldehyde) (PUF) shells assembled with polydopamine-functionalized oxidized carbon nanotubes (CNTs-o-PDA) are fabricated. Results indicate that the PUF microcapsules show spherical shape structure with a mean diameter of 110 μm and an encapsulation capacity of 83.5%. CNTs are successfully assembled on the surface of lubricant oil-containing PUF microcapsules (LPMs). Thermal stability tests reveal the initial decomposition temperature of microcapsules elevated by 75 °C. Furthermore, the microcapsules are embedded into epoxy to prepare self-lubricating composites. The coefficient friction and wear rate of self-lubricating composites incorporating 20 wt% CNTs-o-PDA assembled LPMs are 33.79% and 74.28% lower than that of composites incorporating LPMs, and which are 64.07% and 99.54% lower than that of the pure epoxy resin, respectively. Further studies confirm that the interface bonding strength between epoxy and microcapsules is effectively improved by the introduction of CNTs-o-PDA on the surface of PUF microcapsules. The synergistic effect between microcapsules containing lubricant oil and CNT layer played an important role in improving the tribological properties of polymer composites.

Structural, morphological and thermal properties of novel hybrid-microencapsulated phase change materials based on Fe2O3, ZnO and TiO2 nanoparticles for latent heat thermal energy storage applications

In this investigation, some kinds of novel organic-inorganic hybrid-microencapsulated phase change materials (hybrid-MEPCMs) were synthesized using paraffin as core and urea-formaldehyde (UF) polymer containing metal oxide nanoparticles as shell. 0.3, 1 and 3% wt/wt of metal oxide nanoparticles were used separately to prepare these composites. The use of hybrid materials composed of organic and inorganic materials constitutes a promising way to improve chemical and thermal properties of microencapsulated phase change materials. The prepared composites were characterized using Fourier Transform Infrared spectroscopy, X-Ray Diffraction, Scanning Electron Microscopy, Differential Scanning Calorimetry and Thermogravimetric analyses. The obtained results show that the synthesized hybrid-MEPCMs are in spherical and irregular forms, and present a rougher surface due to the presence of metal oxide nanoparticles which are scattered onto the surface of microcapsules or wrapped by UF shell material. They also indicate a probable improvement of hybrid-MEPCMs’ thermal stability. In this work, the effects of the nature and the amount of metal oxide nanoparticles on structural, morphological and thermal properties of hybrid-MEPCMs were also discussed.

Porous epoxy phenolic novolac resin polymer microcapsules: Tunable release and bioactivity controlled by epoxy value.

Microcapsules (MCs) prepared with diverse wall material structures may exhibit different properties. In this study, MCs were fabricated with three kinds of epoxy phenolic novolac resins (EPNs), which possessed unique epoxy values as wall-forming materials by interfacial polymerization. The effects of the EPN types on the surface morphology, particle size distribution, encapsulation efficiency, thermal stability as well as release behavior and bioactivity of the MCs were investigated. In all three samples, the MCs had nearly spherical shapes with fine monodispersities and sizes in the range of 7-30 μm. Scanning electron microscopy (SEM) images showed that some small pores (ranging from 50 nm to 400 nm) appeared on the microcapsule surfaces and that the porosity decreased with an increasing of epoxy value. The X-ray diffractometer (XRD) analysis indicated that the cured EPN shells had larger degrees of crosslinking with higher epoxy values, leading to better thermal stabilities. Moreover, the release rate of the core material (pendimethalin) decreased with an increasing of epoxy value and thus resulted in a lower herbicidal control efficacy. The results of our research will enhance the potential application of EPNs as smart wall-forming materials to prepare porous MCs for controlled release.

Effect of a new shell material—Jackfruit seed starch on novel flavor microcapsules containing vanilla oil

Vanilla essential oil was microencapsulated by different shell materials including jackfruit seed starch (JM), chitosan (CM), and β-cyclodextrin (βM) based on the ultrasonic method. The effects were compared among the different shell materials when the yield, encapsulation efficiency, storage stability and slow-releasing potential were used as evaluation indexes. The results showed that the yield of βM and CM were 87.99% and 86.35%, on the other hand, the encapsulation efficiency (EE) of these two microcapsules were 77.92% and 76.64%, respectively. While the yield and EE of JM was 84.82% and 79.33%, respectively. The microcapsule surface formed smooth membrane structure. At the same time, the results of peroxide value and the aroma intensity also demonstrated that JM had good storage stability and slow-releasing potential so that its shelf life could reach 250days. By contrast, the shelf life of βM and CM only reached to 160days. The EE, storage stability and slow-releasing potential of JM were more excellent than those of βM and CM, although the yield of JM was not outstanding. All these results indicated that the jackfruit seed starch showed its tremendous potential to be a good shell material of microcapsule and be well used in the food industrial.

Kinetics and Mechanisms of Chemical and Biological Agents Release from Biopolymeric Microcapsules

Kinetics and mechanisms of copper cations and Trichoderma viride spores release from uncoated and chitosan coated alginate microcapsules were investigated. The gelation of a fixed amount of sodium alginate at different concentrations of copper ion solutions resulted in distinct kinetics and release mechanisms. The increase in copper cation concentration promoted, but the presence of the chitosan layer on the microcapsule surface and the increase in microcapsule size reduced the rate of active agent release. Fitting to simple Korsmeyer-Peppas empirical model revealed that the underlying release mechanism (Fickian diffusion or a combination of the diffusion and erosion mechanisms) depends on the copper cation concentration and presence of T. viride spores. The investigation pointed out that the proper selection of formulation variables helps in designing microcapsules with the desirable release of copper ions and T. viride for plant protection and nutrition.

THE INFLUENCE OF COATING MATERIAL DIFFERENCE AGAINST ENCAPSULATION EFFICIENCY OF RED GINGER OLEORESIN

The purpose of this study was to determine the effect of different coating materials on the efficiency of red ginger oleoresin encapsulation and characterization of microcapsule surface. The encapsulation process begins by dissolving chitosan with 1 % (v/v) acetic acid and dissolving sodium alginate using aquadest to be used as a coating material. Red ginger oleoresin alginate included in the solution was stirred. The mixture entered into the chitosan solution and added tween 80 was stirred using a homogenizer to emulsify. The emulsion that forms included in the <em>spray dryer</em> to be converted into a powder of microcapsules, and then analyzes the encapsulation efficiency and surface morphology of microcapsules using scanning electron microscopy (SEM). Differences in the coating material used were chitosan, mixture of chitosan-alginate and mixture of chitosan-alginate-sodium tripolyphosphate (STPP). Weight ratio of red ginger oleoresin and the coating material were 1: 1, 1: 2 and 1: 3. The research results obtained were the highest encapsulation efficiency obtained from the coating material of the chitosan-alginate-sodium tripolyphosphate (STPP) at a ratio of 1: 3, namely by 85 %.