Composite Capsules Research Articles

Dual-Responsive Nanotubes Assembled by Amphiphilic Dendrimers: Controlled Release and Crosslinking.

Although stimuli-responsive release systems have attracted great attention in medical applications, there has been no attempt at “precise” deep profile control based on such systems, which is greatly need to improve oil recovery. With this in mind, we provided a facile and simple strategy to prepare stimuli-responsive composite capsules of amphiphilic dendrimers–poly(styrene sulfonic acid) sodium/halloysite nanotubes (HNTs) via layer-by-layer (LbL) self-assembly technique, controlling the release crosslinking agent methenamine under different pH or salinity conditions. The release time of methenamine encapsulated in multilayer shells is about 40 h, which can be prolonged with the introduction of salt or shortened via the addition of acid, which accordingly induces the gelation of polyacrylamide (PAM) solutions, taking from a few hours to a dozen days. This study provided a novel approach for controllable release of chemical agents and controllable crosslinking of deep profiles in many application fields.

PREPARATION AND APPLICATION OF GLUTARALDEHYDE CROSS-LINKED CHITOSAN COATED BENTONITE CLAY CAPSULES: CHROMIUM(VI) REMOVAL FROM AQUEOUS SOLUTION

New sources in literature have explained that more efficient biosorbents can be developed from natural adsorbents. One of the methods to make these natural adsorbents more efficient is preparation of composites. Hydroxyl (-OH) and amino (-NH2) groups within the structure of chitosan leads adsorbents to have a binding potential with heavy metals. In this study, a composite adsorbent made of chitosan and bentonite clay was prepared. Bentonite clay and chitosan-coated Bentonite clay composite capsules (BC) were characterized in terms of FTIR and SEM analysis. (BC) composite adsorbent was used for the adsorption of Cr(VI) ions from aqueous solution. The effects of some parameters such as pH, adsorbent dosage, adsorbate concentration, temperature and contact time on the adsorption of Cr(VI) on BC were investigated. In order to evaluate the experimental data, Langmuir, Freundlich, Scatchard and Dubinin-Radushkevich (D-R) adsorption isotherm models were used for the analysis of adsorption equilibrium. The adsorption process was well fitted to Scatchard adsorption isotherm. While bentonite clay had 11,076 mg/g maximum adsorption capacity, BC composite had 106.444 mg/g maximum adsorption capacity for the removal of Cr(VI) ions (25 °C, pH 2, contact time 60 minutes). It was concluded that chitosan-bentonite composite adsorbent can be effectively used for the removal of Cr(VI).

An Alternative Hard Capsule Prepared with the High Molecular Weight Pullulan and Gellan: Processing, Characterization, and In Vitro Drug Release

Albeit gelatin hard capsules were predominantly applied, their disadvantages call for endeavours on non-gelatin capsules in healthcare aspects. Herein, high molecular weight (Mw = 1 × 106) pullulan was purified from yeast fermentation broth. This high Mw pullulan and commercial low Mw pullulan were respectively co-blended with gellan to prepare the optimal solutions for capsule production. Further investigations, including loss-on-drying, brittleness and tightness, showed that the obtained pullulan-gellan capsules were of low water content, brittleness, leakage, and of high tightness. These capsules exhibited an extended release of amoxicillin over 60 min in simulated gastric fluid. Although the use of high and low Mw pullulan produced composite capsules with similar properties, the required concentration of high Mw pullulan was nearly half of that for low Mw pullulan, suggesting a cost-saving characteristic of using high Mw pullulan. This work proposes a potential substitution of gelatin with pullulan-gellan composites for preparing hard capsules.

Evaluation of jelly fig polysaccharide as a shell composite ingredient of colon-specific drug delivery

The polysaccharide extracted from the achenes of jelly fig (Ficus pumila var. awkeotsang) was characterized as low methoxyl pectin and was blended with commercial high methoxyl pectin in film casting to evaluate the suitability of the combinations for developing a composite encapsulant for colon target drug delivery. The physiochemical properties of the casted films were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, color measurement, thickness test, water content analysis, and mechanical strength measurement. Among all tested blending ratios, the film prepared from pure jelly fig polysaccharide has higher tensile strength and better performance of anti-erosion in simulated gastrointestinal fluids. Hence, for evaluation of applicability, the composite hard capsules were prepared by using jelly fig polysaccharide as the main component blending with xanthan gum and resistant starch. The results of the in vitro release study showed that jelly fig polysaccharide composite capsules were stable without significant deformation and releasing of encapsulated substance in the simulated gastrointestinal fluids during the test period. Then, the capsules were degraded in simulated colonic fluid in 2 h and the release rate was increased from 15% to 90%. Therefore, pectinous polysaccharide extracted from jelly fig could be a useful material for the preparation of a colon-targeted capsule.

Dielectric Analysis of Microcapsule-Immobilized Composite Capsules Suspension: Substances Release.

Dielectric spectroscopy has unique advantages in monitoring drug release. In this work, a dielectric measurement was carried out on the release of the substances of microcapsule-immobilized composite capsules, which were fabricated by encapsulating the Perinereis aibuhitensis extract-loaded gum Arabic/gelatin microcapsules (PaE: GA/GE-MCs) in calcium alginate hydrogel (PaE: CA/GA/GE-CCs). We established the dielectric model of PaE: CA/GA/GE-CCs and got in-depth information on the systems. There are two relaxations in the dielectric spectroscopy, both of which are caused by interfacial polarization. The relaxation mechanisms correspond to the interfacial polarization of the PaE-loading core/calcium alginate shell interface and the calcium alginate shell/solution interface, respectively. Besides, the swelling of composite capsules and substance migration in the composite capsules were observed by analyzing phase parameters. Finally, the characteristic release of calcium alginate composite capsules was confirmed, and the substance release mechanism of composite capsules, namely, the swelling-diffusion mechanism, was obtained.

Method and device with catalyst storage and delivery capsule for converting biomass into solid and gaseous components

We have designed microcapsules-immobilized composite capsules and evaluated the oral delivery efficacy. The composite capsules were developed by encapsulating Perinereis aibuhitensis extract (PaE), a model substance possessing antioxidant activity, loaded gum Arabic/gelatin microcapsules in calcium alginate (CA) hydrogel (PaE:CA/GA/GE-CCs). In vitro antioxidant assay showed the obtained composite capsules were able to protect PaE from gastric acid, since O2− scavenging rate of encapsulated PaE was about 1.8 folds as that of free PaE after 5 h incubation in simulated gastrointestinal fluid. Moreover, in vivo study showed that after the treatment of oral administration for 30 days, the mice of PaE:CA/GA/GE-CCs group suffered significantly lower oxidative stress level than those of other groups, illustrated as higher SOD and catalase activity, as well as lower malondialdehyde content in liver cells. The results demonstrated the composite capsules could concentrate PaE in small intestine, and enhance the absorption efficiency and in vivo efficacy.

Preparation and Physicochemical Characterization of Softgels Cross-Linked with Cactus Mucilage Extracted from Cladodes of Opuntia Ficus-Indica.

A new crosslinking formulation using gelatin (G) and cactus mucilage (CM) biopolymers was developed, physicochemically characterized and proposed as an alternative wall material to traditional gelatin capsules (softgels). The effect of G concentration at different G/CM ratios (3:1, 1:1 and 1:3) was analyzed. Transparency, moisture content (MC), solubility in water (SW), morphology (scanning electron microscopy, SEM), vibrational characterization (Fourier transform infrared, FTIR), color parameters (CIELab) and thermal (differential scanning calorimetry/thermogravimetric analysis, DSC/TGA) properties of the prepared composite (CMC) capsules were estimated and compared with control (CC) capsules containing only G and glycerol. In addition, the dietary fiber (DF) content was also evaluated. Our results showed that the transparency of composite samples decreased gradually with the presence of CM, the G/CM ratio of 3:1 being suitable to form the softgels. The addition of CM decreased the MC, the SW and the lightness of the capsules. Furthermore, the presence of polysaccharide had significant effects on the morphology and thermal behavior of CMC in contrast to CC. FTIR spectra confirmed the CMC formation by crosslinking between CM and G biopolymers. The addition of CM to the softgels formulation influenced the DF content. Our findings support the feasibility of developing softgels using a formulation of CM and G as wall material with nutritional properties.

Encapsulation of Lactobacillus plantarum in cellulose based microgel with controlled release behavior and increased long-term storage stability

Probiotics are believed to provide benefits to human health; however, a good storage stability is the prerequisite for the probiotic products making function. Herein, we reported a pathway to fabricate the Ca-alginate/cryoprotectants/cellulose composite (ACFP) capsules to protect L. plantarum cells, which showed the minimal loss of viability during the vacuum freeze-drying process. The trehalose and whey protein isolate (WPI) ingredients in the cryoprotectants prolonged the dissolution time of Ca-alginate shell, which contributed to controlling the release of cells in the desired region. The dry ACFP capsules exhibited gradual release of L. plantarum cells in simulated intestinal fluid (SIF), 2.6 × 106 cfu/mL at 210 min. In addition, 0.1 g of the dry ACFP capsules showed the viable release amount of 3.3 × 106 cfu/mL after the storage of 160 days at 4 °C. The promising results provided a strategy of encapsulating probiotic cells to achieve long-term storage stability and enhanced controlled release behavior in simulated intestinal fluid in the meantime.

Transitioning from batch to flow hypersaline microbial fuel cells

Application of electro-active halotolerant bacteria in bioelectrochemical systems opens for the sustainable on line monitoring of saline wastewater treatment; however, this approach has been investigated only in lab-scale devices, mostly in batch configuration. The field application of the technology introduces several parameters that can influence bioelectrochemical and degradation performance. Herein, we report the detailed study of how continuous flow operation (3 ± 1 mL min−1) affects the bioelectrochemical performance of a flow hypersaline microbial fuel cell. Flow operation resulted in a 70% decrease of power density (passing from 2.1 ± 0.1 to 0.67 ± 0.01 mW m−2), where the washout of endogenous redox mediator played a critical role. Engineering of bacteria entrapment techniques mitigated the inhibitory effects of continuous flow, ensuring successful extracellular electron transfer. Specifically, bacteria entrapment in composite alginate capsules with activated carbon to enhance their conductivity was investigated, and the effects of different activated carbon loads are presented. A maximum power density comparable to batch operation was achieved for composite capsules with 0.15 gL-1 activated carbon (1.8 ± 0.9 mW m−2), as well as the possible correlation of electrochemical and COD removal performance, enabling future development of self-powered hypersaline flow microbial biosensor for contaminants monitoring.

Development of alginate hydrogel/gum Arabic/gelatin based composite capsules and their application as oral delivery carriers for antioxidant.

We have designed microcapsules-immobilized composite capsules and evaluated the oral delivery efficacy. The composite capsules were developed by encapsulating Perinereis aibuhitensis extract (PaE), a model substance possessing antioxidant activity, loaded gum Arabic/gelatin microcapsules in calcium alginate (CA) hydrogel (PaE:CA/GA/GE-CCs). In vitro antioxidant assay showed the obtained composite capsules were able to protect PaE from gastric acid, since O2- scavenging rate of encapsulated PaE was about 1.8 folds as that of free PaE after 5 h incubation in simulated gastrointestinal fluid. Moreover, in vivo study showed that after the treatment of oral administration for 30 days, the mice of PaE:CA/GA/GE-CCs group suffered significantly lower oxidative stress level than those of other groups, illustrated as higher SOD and catalase activity, as well as lower malondialdehyde content in liver cells. The results demonstrated the composite capsules could concentrate PaE in small intestine, and enhance the absorption efficiency and in vivo efficacy.

Thermal and Structural Characterization of Geopolymer-Coated Polyurethane Foam-Phase Change Material Capsules/Geopolymer Concrete Composites.

The thermal and structural performance of geopolymer-coated polyurethane foam–phase change material capsules/geopolymer concrete composites was investigated. Three groups of concrete composites were prepared. The first was pure geopolymer (GP, control sample), the second was a GP/polyurethane foam (F) concrete composite, and the third was GP-coated polyurethane foam-phase change material capsules (GP-F-PCM)/GP concrete composites. Three different percentages of foam and GP-F-PCM capsules (25%, 50%, and 75%) were used in the composites. Thermal and U-value tests were conducted for all composites to characterize their peak temperature damping and insulation performances. The addition of 75% foam has been noticed to increase the back-surface temperature by 5.9 °C compared to the control sample. This may be attributed to the degradation of foam into low molecular constituents in the presence of a strong alkali. However, a temperature drop of 12.5 °C was achieved by incorporating 75% of GP-F-PCM capsules. The addition of 50% foam as a sandwich layer between two halves of a geopolymer concrete cube is also investigated. It was found that inserting a foam layer reduced the back-surface temperature by 3.3 °C, which is still less than the reduction in the case of GP-F-PCM capsules. The compressive strength was tested to check the integrity of the prepared concrete. At 28 days of aging, the compressive strength dropped from 65.2 MPa to 9.9 MPa with the addition of 75% GP-F-PCM capsules, which is still acceptable for certain building elements (e.g., nonloadbearing exterior walls). Generally, the best results were for the GP-F-PCM composite capsules as a heat insulator.

Mixed matrix membranes containing well-designed composite microcapsules for CO2 separation

Hollow fillers with tailored nanostructures and functionalities have become promising candidates for advanced mixed matrix membranes (MMMs). Herein, polydopamine/poly (ethylene glycol) (PEG) composite microcapsules are synthesized by hard template method and embedded into the Pebax matrix to fabricate MMMs for CO2 capture. As a well-known biomimetic adhesive, polydopamine in the capsule wall renders adequate polymer-filler interfacial adhesion. The template removal process produces through-wall mesopores, which allow rapid gas diffusion into the lumen, further significantly reducing the trans-membrane mass transfer resistance. The remaining PEG in the capsule wall not only increases CO2 affinity, but also avoids excessive chain rigidification at polymer-filler interface. In this way, the composite capsules, compared with those without PEG, confer significantly enhanced separation performance on membranes. The optimal gas transport property of the resultant membranes is obtained with a CO2 permeability of 510 Barrer and an ideal selectivity of 84.6 for CO2/N2 at humidified state, i.e., 108%, 98% higher than those of neat Pebax membrane, respectively. In addition, owing to dopamine-enabled strong adhesion, the MMMs exhibit better stability than Pebax membrane in the long-term test at 85 °C.

Synthesis and Characterization of Graphene Oxide–Polystyrene Composite Capsules with Aqueous Cargo via a Water–Oil–Water Multiple Emulsion Templating Route

Graphene oxide/polystyrene (GO/PS) nanocomposite capsules containing a two-compartment cargo have been successfully fabricated using a Pickering emulsion strategy. Highly purified GO sheets with typically micrometer-scale lateral dimensions and amphiphilic characteristics were prepared from the oxidation reaction of graphite with concomitant exfoliation of the graphite structure. These GO sheets were employed as a stabilizer for oil-in-water emulsions where the oil phase comprised toluene or olive oil. The stability and morphology of the emulsions were extensively studied as a function of different parameters including GO concentration, aqueous phase pH, ultrasonication time, effects of added electrolytes and stability to dilution. In selected conditions, the olive oil emulsions showed spontaneous formation of multiple w/o/w emulsions with high stability, whereas toluene formed simple o/w emulsions of lower overall stability. Olive oil emulsions were therefore used to prepare capsules templated from emulsion droplets by surrounding the oil phase with a GO/PS shell. The GO sheets, emulsions and composite capsules were characterized using a variety of physical and spectroscopic techniques in order to unravel the interactions responsible for capsule formation. The ability of the capsules to control the release of a model active agent in the form of a hydrophilic dye was explored, and release kinetics were monitored using UV-visible spectroscopy to obtain rate parameters. The composite capsules showed promising sustained release properties, with release rates 11× lower than the precursor GO-stabilized multiple emulsion droplets.

Sustained Dye Release Using Poly(urea-urethane)/Cellulose Nanocrystal Composite Microcapsules.

The aim of this study is to develop methods to reinforce polymeric microspheres with cellulose nanocrystals (CNCs) to make eco-friendly microcapsules for a variety of applications such as medicines, perfumes, nutrients, pesticides, and phase change materials. Surface hydrophobization treatments for CNCs were performed by grafting poly(lactic acid) oligomers and fatty acids (FAs) to enhance the dispersion of nanoparticles in the polymeric shell. Then, a straightforward process is demonstrated to design sustained release microcapsules by the incorporation of the modified CNCs (mCNCs) in the shell structure. The combination of the mCNC dispersion with subsequent interfacial polyurea (PU) to form composite capsules as well as their morphology, composition, mechanical properties, and release rates were examined in this study. The PU microcapsules embedded with the mCNC were characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The morphologies of the microcapsules were characterized by optical microscopy (OM) and scanning electron microscope (SEM). The rupture stress and failure behavior of the microcapsules were determined through single-capsule compression tests. Oil-soluble Sudan II dye solution in mineral oil was utilized as a model hydrophobic fill, representing other latent fills with low partition coefficients, and their encapsulation efficiency was measured spectroscopically. The release rates of the encapsulated dye from the microcapsules were examined spectroscopically by both ethanol and 2-ethyl-1-hexanol medium at room temperature. The concentration of released dye was determined by using UV-vis absorption spectrometry (UV-vis). The mCNC embedded poly(urea-urethane) capsules have strong and dense walls, which function as excellent barriers against leakage due to their extended diffusion path length and ensure enough mechanical strength from rupture for handling or postprocessing.

Intracellularly Biodegradable Polyelectrolyte/Silica Composite Microcapsules as Carriers for Small Molecules.

Microcapsules that can be efficiently loaded with small molecules and effectively released at the target area through the degradation of the capsule shells hold great potential for treating diseases. Traditional biodegradable polyelectrolyte (PE) capsules can be degraded by cells and eliminated from the body but fail to encapsulate drugs with small molecular weight. Here, we report a poly-l-arginine hydrochloride (PARG)/dextran sulfate sodium salt (DEXS)/silica (SiO2) composite capsule that can be destructed in cells and of which the in situ formed inorganic SiO2 enables loading of small model molecules, Rhodamine B (Rh-B). The composite capsules were fabricated based on the layer-by-layer (LbL) technique and the hydrolysis of tetraethoxysilane (TEOS). Capsules composed of nondegradable PEs and SiO2, polyllamine hydrochloride (PAH)/poly(sodium 4-styrenesulfonate) (PSS)/silica (the control sample), were prepared and briefly compared with the degradable composite capsules. An intracellular degradation study of both types of composite capsules revealed that PARG/DEXS/silica capsules were degraded into fragments and lead to the release of model molecules in a relatively short time (2 h), while the structure of PAH/PSS/silica capsules remained intact even after 3 days incubation with B50 cells. Such results indicated that the polymer components played a significant role in the degradability of the SiO2. Specifically, PAH/PSS scaffolds blocked the degradation of SiO2. For PARG/DEXS/silica capsules, we proposed the effects of both hydrolytic degradation of amorphous silica and enzymatic degradation of PARG/DEXS polymers as a cell degradation mechanism. All the results demonstrated a new type of functional composite microcapsule with low permeability, good biocompatibility, and biodegradability for potential medical applications.

Physico-chemical properties of alginate/shellac aqueous-core capsules: Influence of membrane architecture on riboflavin release

To enhance physico-chemical properties of alginate liquid-core capsules, shellac was incorporated into the membrane (composite capsules) or as an additional external layer (coated capsules). The influence of pH, coating time, shellac concentration and preparation mechanism (acid or calcium precipitation) were investigated. Results showed that shellac significantly influenced the capsules properties. The feasibility of shellac incorporation was closely related to the preparation conditions as confirmed by Infrared spectroscopy. Optical, fluorescence and scanning electron microscopy, highlighted different capsules and membranes architectures. In contrast to simple and composite capsules, coated capsules showed a pH-dependent release of the entrapped vitamin especially after shellac crosslinking with calcium. Heating of coated capsules above the glass transition temperature investigated by Differential Scanning Calorimetry, led to irreversible structural change due to thermoplastic behavior of shellac and enhanced riboflavin retention under acidic conditions. This global approach is useful to control release mechanism of low molecular weight molecules from macro and micro-capsules.

Preparation and characterization of novel polysulfone-red mud composite capsules for the removal of fluoride from aqueous solutions

This study is the first investigation on the encapsulation of red mud by a polysulfone matrix through a phase inversion process to obtain composite capsules for the removal of fluoride from aqueous solutions.

Characterization and Biodegradation Evaluation of Biocapsules Composed of Polyester/Natural Product Composites

ABSTRACTThe feasibility of using acrylic acid-grafted poly(hydroxyalkanoate) and a treated (cross-linked) natural product (treated marine algae powder) as a bacteria-encapsulated film capsule material was evaluated for the controlled release of an encapsulated bacterium. For the purposes of comparison and accurate characterization, a poly(hydroxyalkanoate) or acrylic acid-grafted poly(hydroxyalkanoate) and its composite film capsules were also assessed. The water resistance of acrylic acid-grafted poly(hydroxyalkanoate)/treated marine algae powder was greater than that of poly(hydroxyalkanoate)/marine algae powder, although the weight loss of composites buried in Azospirillum brasilense compost indicated that both were biodegradable, especially at high levels of marine algae powder or treated marine algae powder substitution. After 120 days, the weight loss of the acrylic acid-grafted poly(hydroxyalkanoate)/treated marine algae powder (20 wt%) composite was greater than 50%. Poly(hydroxyalkanoate)/marine algae powder exhibited a weight loss of approximately 3–12 wt% more than acrylic acid-grafted poly(hydroxyalkanoate)/treated marine algae powder. The bacterium completely degraded both the poly(hydroxyalkanoate) and acrylic acid-grafted poly(hydroxyalkanoate) and their composite film capsules, resulting in cell release. Based on the results of this work, the controlled release of bacteria-encapsulated film capsules for fertilizer utilization promotion appears achievable.

Controlled Delivery of Human Cells by Temperature Responsive Microcapsules.

Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line—human umbilical vein endothelial cells (HUVECs). While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation.

Composite silica nanoparticle/polyelectrolyte microcapsules with reduced permeability and enhanced ultrasound sensitivity.

Many chemical and biomedical systems require delivery and controlled release of small molecules, which cannot be achieved by conventional polyelectrolyte-based layer-by-layer capsules. This work proposes an innovative hybrid microcapsule by incorporating in situ formed silica nanoparticles within or on the shell. The influence of various experimental conditions on the stability, mechanical strength and morphology of capsules was investigated and characterised by SEM, TEM, XRD, EDX and FTIR. The multifunctional capabilities of the formed capsules were examined by encapsulating a small molecule rhodamine B (Rh-B) which could be further released by an ultrasonic trigger. The results show that in situ formed SiO2 nanoparticles through hydrolysis greatly reduced the permeability of the shell yet showed increased mechanical strength and ultrasound response. SiO2 nanoparticles were shown to be distributed on the surface or inside the polyelectrolyte shell, acting as supports for free-standing capsules in both liquid and dry environments. Rapid Rh-B molecule release and the fragmentation of the capsule shells were observed under 50 W ultrasound irradiation for a few seconds. Such innovative capsules with the capability of small molecule encapsulation and high ultrasound sensitivity could be promising for many applications where pulse release of small molecules is required.