Composite Microcapsules Research Articles

Development and Optimization of Attapulgite Clay Based Microencapsulation for Lactic Acid Bacteria by Response Surface Methodology

Abstract Lactic acid bacteria (LAB), screened and purified from the fermented yogurt, were microencapsulated in sodium alginate (SA) and attapulgite composite microcapsules by external gelation to increase their viability and stability. Surface characterization by scanning electron microscope clearly evidenced a high number of the LAB embedded in SA/attapulgite composite microcapsules than SA counterparts due to a more cohesive structure, and biocompatible microenvironment. SA/attapulgite and CaCl2/attapulgite composites analysis revealed a better embedding effect of attapulgite blend with SA solvent compared with attapulgite mixed with CaCl2. Influence of three major factors including SA, calcium chloride, and attapulgite concentration on LAB embedding rate were optimized by “single factor strategy” as well as response surface methodology (RSM). Optimal conditions of these factors obtained by RSM were SA (1.03 %), Attapulgite (0.28 %), and CaCl2 concentration (1.17 %). The related embedding rate was predicted as 87.1369 %, and the actual measured value was 91.24 % by experiments using the optimal conditions. In conclusion, the results revealed that LAB microencapsulation in the SA and attapulgite composite might display noteworthy protection against the gastrointestinal environment.

Drug delivery from microcapsules: How can we estimate the release time?

Predicting the release performance of a drug delivery device is an important challenge in pharmaceutics and biomedical science. In this paper, we consider a multi-layer diffusion model of drug release from a composite spherical microcapsule into an external surrounding medium. Based on this model, we present two approaches for estimating the release time, i.e. the time required for the drug-filled capsule to be depleted. Both approaches make use of temporal moments of the drug concentration at the centre of the capsule, which provide useful insight into the timescale of the process and can be computed exactly without explicit calculation of the full transient solution of the multi-layer diffusion model. The first approach, which uses the zeroth and first temporal moments only, provides a crude approximation of the release time taking the form of a simple algebraic expression involving the various parameters in the model (e.g. layer diffusivities, mass transfer coefficients, partition coefficients) while the second approach yields an asymptotic estimate of the release time that depends on consecutive higher moments. Through several test cases, we show that both approaches provide a computationally-cheap and useful tool to quantify the release time of composite microcapsule configurations.

Focused ultrasound-mediated fluorescence of composite microcapsules loaded with magnetite nanoparticles: In vitro and in vivo study

High intensity focused ultrasound (HIFU) is widely used in medical practice, including cancer therapy. Also this approach is promising for remote release of encapsulated drugs in various other biomedical applications where local treatment is needed. Our approach underpins the minimization of HIFU impact on possible degradation of biological tissues and expand the use of HIFU in the controlled release of encapsulated drugs. We demonstrated the efficient ultrasound-induced release of labeled protein (Cy7-BSA) from elaborated nanocomposite microcapsules in vitro an in vivo. The capsule fabrication was done using combination of recently developed freezing-induced loading (FIL) technique and Layer-by-Layer assembly (LbL) used for the preparation of complex multilayer BSA/tannic acid nanocomposite capsules sensitive to HIFU. These capsules contain NIR fluorescent Cy7-labeled BSA in the shell for tracking in vivo and the high concentration of labels inside the capsules resulted in self-quenching provides the real-time detection of the protein once it is released from the capsule. Ultrasound-induced release in vivo of Cy7-labeled BSA initially quenched by magnetite nanoparticles was confirmed by fluorescent tomography. The significant decrease of Cy7 fluorescence under HIFU treatment in vitro was found to be due to a generation of reactive oxygen species and fast dye oxidation. Our results demonstrate that adapted HIFU setup can be used for the directed release of encapsulated substances in vivo under tissue compatible NIR monitoring by fluorescent tomography.

Sulfonic acid functionalized PVA/PVDF composite hollow microcapsules: Highly phenomenal & recyclable catalysts for sustainable hydrogen production

Abstract Hydrolysis of NaBH4 is a promising solution for on-site hydrogen energy generation. In the present paper, we report the preparation of hollow composite microcapsules made from sulfonic acid functionalized polyvinyl alcohol (SPVA) using simple chemical reaction followed by the addition of PVDF and applied for the hydrogen generation by means of hydrolysis of NaBH4. To develop series of microcapsules different ratios of water and isopropanol solvent systems such as 90: 10, 80:20, 70:30, 60:40 and 50:50 were used and five types of composite microcapsules were prepared. The structure, morphology and properties of the prepared microcapsules were characterized with the assistance of various spectroscopic and analytical techniques. By employing prepared SPVA/PVDF hollow composite microcapsules as catalyst, hydrogen generation was studied by hydrolysis of NaBH4. Interestingly, SPVA/PVDF-Mcs-3 hollow composite microcapsules prepared using 70:30 ratio of water and isopropanol generated the highest amount of 570 mL hydrogen in 180 min at room temperature which can be attributed to the high porosity and less wall thickness. Additionally, various microcapsules and effect of different reaction parameters were also studied and discussed. The synthesized composite microcapsules have an imperative advantage of easy recovery and consecutive reusability for 10 cycles without destruction of activity and morphology. The fast kinetics, hydrogen generation efficiency and comparatively low activation energy (10.91 kJ mol−1) makes SPVA/PVDF composite microcapsules a promising candidate as catalyst for hydrogen generation by hydrolysis of NaBH4.

PH-responsive composite micro-capsule as an efficient intestinal-specific oral delivery system for lactoferrin

To improve the bioavailability of lactoferrin (Lf) and achieve its controlled release in the intestinal tract, a pH-responsive composite system for the oral delivery of Lf was successfully developed for the first time. The negatively charged poly(lactide-co-glycolide) (PLGA)/poly(styrene-co-4-styrene-sulfonate) (PSS) nanoparticles (NPs) were firstly prepared by solvent displacement, and the resulting NPs were spherical in shape with diameter of around 120 nm and zeta potential of −50.7 mV. Then, the positively charged Lf was incubated with PLGA/PSS NPs followed by coating with pectin to improve the Lf adsorption efficiency. The Lf adsorption efficiency decreased with the increase of Lf concentration, but it was even as high as 80.5% when Lf concentration was 8.0 mg/mL. The pectin coated Lf-PLGA/PSS NPs were further incorporated into Eudragit S-100 (ES-100) micro-capsule by the self-assembly method and the obtained composite ES-100 micro-capsule was found to be spherical with an average diameter of 2.22 μm. The in vitro release experiment showed that only a little Lf (<1%) was released from micro-capsule in simulated gastric fluid comparing with that of pectin coated Lf-PLGA/PSS NPs (30%), and around 82% Lf was released into the simulated intestinal tract in the following 8 h. The results of cytotoxicity test suggested that there was negligible toxicity of the composite micro-capsule against Caco-2 cells. The SDS-PAGE and CD spectrum analysis indicated that the micro-encapsulated Lf retained the integrity of its primary and secondary structure during the heating treatment process. Hence, the obtained Lf-loaded composite micro-capsule is promising in the oral delivery of Lf.

Production and Application of Highly Efficient and Reusable Palladium Nanocatalyst Decorated on the Magnetically Retrievable Chitosan/Activated Carbon Composite Microcapsules

This study reports (i) the production of magnetically retrievable microcapsules as immobilizing agents, which are composed of chitosan/activated carbon composite (CS-AC/Fe3O4), (ii) the green synthesis of highly stable palladium nanoparticles on CS-AC/Fe3O4 without using any toxic reducing agents (Pd NPs@CS-AC/Fe3O4), (iii) the investigation of catalytic behavior of Pd NPs@CS-AC/Fe3O4 in Suzuki–Miyaura reactions of different aryl iodides, bromides, and chlorides, and (iv) the examination of recoverability and reusability of Pd NPs@CS-AC/Fe3O4. The characterization of Pd NPs@CS-AC/Fe3O4 was performed by FT-IR, TG/DTG, XRD, SEM, and EDS analyses. It was found that the average sizes of palladium nanoparticles were changed in the range of 31–48 nm. The catalytic tests revealed that Pd NPs@CS-AC/Fe3O4 was a very effective catalyst against synthesis of various biaryl compounds via Suzuki–Miyaura reactions, by giving high reaction yields under mild reaction conditions. Furthermore, it was found that Pd NPs@CS-AC/Fe3O4 was a highly retrievable and practical nanocatalyst due to its reusable nature. Pd NPs@CS-AC/Fe3O4 gave 95% of yield after ten successive cycles. These results show that Pd NPs@CS-AC/Fe3O4 is a superb catalyst and it can be applied in different catalytic systems or industrial applications due to the fact that it offers notable advantages such as high catalytic performance, reusability, stability, excellent functional group tolerance, wide substrate scope, and simple separation.

Cell laden alginate-keratin based composite microcapsules containing bioactive glass for tissue engineering applications.

Microcapsules based on alginate-keratin, alginate dialdehyde (ADA)-keratin and ADA-keratin-45S5 bioactive glass (BG) were successfully prepared. The samples were characterized by light microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results showed that ADA-based materials possess higher degradation rate compared to alginate-based materials. The incorporation of BG particles (mean particle size: 2.0 µm) improved the bioactivity of the materials. Moreover, the biological properties of the samples were evaluated by encapsulating MG-63 osteosarcoma cells into the microcapsules. The cell viability in all samples increased during 21 days of cultivation. However, the presence of 0.5% BG particle seemed to have initial negative effect on cell growth compared to other samples without BG. On the other hand, the positive effect of CaP formation was visible after 3 weeks in the BG containing samples. The results are relevant to consider the development of cell laden bioinks incorporating inorganic bioactive particles for biofabrication approaches.

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.

Disruption of Polymer and Composite Microcapsule Shells under High-Intensity Focused Ultrasound

A process has been described for obtaining polymer (polyelectrolyte) microcapsules and polyelectrolyte/magnetite composite microcapsules, as well as silica-based hybrid capsules via silane-type precursor hydrolysis, which gives rise to the formation of silica nanoparticles in the structures of shells containing different numbers of polymer layers. The polymer and nanocomposite microcapsules have been formed by successive adsorption of oppositely charged polyelectrolytes and/or nanoparticles on the surface of microparticles of vaterite, which is a polymorphous modification of calcium carbonate. The obtained shells of microcapsules of all types have been studied by atomic force microscopy, confocal fluorescence microscopy, and scanning electron microscopy before and after sonication. The effect of high-intensity focused ultrasound on the obtained samples of microcapsules has been investigated and the sonication parameters that ensure efficient disruption of their shells in an aqueous medium have been determined. It has been found that composite microcapsules containing magnetite nanoparticles in their shells are most sensitive to sonication. The obtained composite microcapsules are promising for developing new systems for delivery of biologically active substances and multifunctional coatings.

Systemic Administration of Polyelectrolyte Microcapsules: Where Do They Accumulate and When? In Vivo and Ex Vivo Study.

Multilayer capsules of 4 microns in size made of biodegradable polymers and iron oxide magnetite nanoparticles have been injected intravenously into rats. The time-dependent microcapsule distribution in organs was investigated in vivo by magnetic resonance imaging (MRI) and ex vivo by histological examination (HE), atomic absorption spectroscopy (AAS) and electron spin resonance (ESR), as these methods provide information at different stages of microcapsule degradation. The following organs were collected: Kidney, liver, lung, and spleen through 15 min, 1 h, 4 h, 24 h, 14 days, and 30 days after intravenous injections (IVIs) of microcapsules in a saline buffer at a dosage of 2.5 × 109 capsule per kg. The IVI of microcapsules resulted in reversible morphological changes in most of the examined inner organs (kidney, heart, liver, and spleen). The capsules lost their integrity due to degradation over 24 h, and some traces of iron oxide nanoparticles were seen at 7 days in spleen and liver structure. The morphological structure of the tissues was completely restored one month after IVI of microcapsules. Comprehensive analysis of the biodistribution and degradation of entire capsules and magnetite nanoparticles as their components gave us grounds to recommend these composite microcapsules as useful and safe tools for drug delivery applications.

Characterization of Bovine Serum Albumin and (-)-Epigallocatechin Gallate/3,4- O-Dicaffeoylquinic Acid/Tannic Acid Layer by Layer Assembled Microcapsule for Protecting Immunoglobulin G in Stomach Digestion and Release in Small Intestinal Tract.

The protein-polyphenol layer by layer (LbL) assembled polymer composite microcapsule is a considerable delivery system that can be used to improve the bioactive stability and effectiveness of natural compounds in various applications. In the present study, three kinds of polyphenols were loaded in the sequence of (-)-epigallocatechin gallate (EGCG), 3,4- O-dicaffeoylquinic acid (3,4-diCQA), and tannin acid (TA) to prepare a BSA-polyphenol LbL membrane. The composition of IgG-(BSA-EGCG/3,4-diCQA/TA) n microcapsules and their stability and releasing ability in the gastrointestinal tract were evaluated. In addition, by binding of these three kinds of polyphenols to BSA, the thermal denaturation temperature and ordered secondary structure of the BSA-polyphenol microcapsules were increased, and the time of scavenging activity on 2,2'-azinobis(3-ethylbenzothiazolin-6-sulfonic acid) free radicals was significantly prolonged. These findings suggest that (BSA-EGCG/3,4-diCQA/TA) n microcapsules can not only protect IgG in food processing and stomach digestion but also release it in the small intestinal tract for bioactive delivery.

Multifunctional Scaffolds with Improved Antimicrobial Properties and Osteogenicity Based on Piezoelectric Electrospun Fibers Decorated with Bioactive Composite Microcapsules.

The incorporation of bioactive compounds onto polymer fibrous scaffolds with further control of drug release kinetics is essential to improve the functionality of scaffolds for personalized drug therapy and regenerative medicine. In this study, polymer and hybrid microcapsules were prepared and used as drug carriers, which are further deposited onto polymer microfiber scaffolds [polycaprolactone (PCL), poly(3-hydroxybutyrate) (PHB), and PHB doping with the conductive polyaniline (PANi) of 2 wt % (PHB-PANi)]. The number of immobilized microcapsules decreased with increase in their ζ-potential due to electrostatic repulsion with the negatively charged fiber surface, depending on the polymer used for the scaffold's fabrication. Additionally, the immobilization of the capsules in dynamic mechanical conditions at a frequency of 10 Hz resulted in an increase in the number of the capsules on the fibers with increase in the scaffold piezoelectric response in the order PCL < PHB < PHB-PANi, depending on the chemical composition of the capsules. The immobilization of microcapsules loaded with different bioactive molecules onto the scaffold surface enabled multimodal triggering by physical (ultrasound, laser radiation) and biological (enzymatic treatment) stimuli, providing controllable release of the cargo from scaffolds. Importantly, the microcapsules immobilized onto the surface of the scaffolds did not influence the cell growth, viability, and cell proliferation on the scaffolds. Moreover, the attachment of human mesenchymal stem cells (hMSCs) on the scaffolds revealed that the PHB and PHB-PANi scaffolds promoted adhesion of hMSCs compared to that of the PCL scaffolds. Two bioactive compounds, antibiotic ceftriaxone sodium (CS) and osteogenic factor dexamethasone (DEXA), were chosen to load the microcapsules and demonstrate the antimicrobial properties and osteogenesis of the scaffolds. The modified scaffolds had prolonged release of CS or DEXA, which provided an improved antimicrobial effect, as well as enhanced osteogenic differentiation and mineralization of the scaffolds modified with capsules compared to that of individual scaffolds soaked in CS solution or incubated in an osteogenic medium. Thus, the immobilization of microcapsules provides a simple, convenient way to incorporate bioactive compounds onto polymer scaffolds, which makes these multimodal materials suitable for personalized drug therapy and bone tissue engineering.

Solar-driven phase change microencapsulation with efficient Ti4O7 nanoconverter for latent heat storage

A sort of novel microencapsulated phase change materials (PCMs) has attracted much attention for energy storage. However, the solar energy utilization efficiency of traditional microcapsulated PCMs is still not very high up to date. In this work, new core@shell structured paraffin@SiO2/Ti4O7 composite microcapsules were developed to harvest environmental full-spectrum sunlight by smart and rational design using a sol-gel method. The SiO2 shell not only prevented the leakage of paraffine, but also improves its thermal conductivity. The black 300 nm Ti4O7 particles, which were successfully embedded into the SiO2 shell, can achieve the efficient absorption of sunlight and simultaneously high conversion from light to thermal. The resultant paraffin@SiO2/Ti4O7 microcapsules retained most enthalpy of paraffin, increased its stability, and exhibited an excellent thermal energy storage performance. The thermal conductivity of paraffin@SiO2/Ti4O7 microcapsules was significantly enhanced by 334.87% (1.322 W m−1 K−1) compared with 0.304 W m−1 K−1 of one for paraffin. When the mass fraction of Ti4O7 nanoparticles is 3 wt% of paraffin, these paraffin@SiO2/Ti4O7 microcapsules exhibited remarkable 85.36% of photo-thermal storage efficiency compared with 24.14% of one for paraffin. Due to their huge superiority of high efficient use of abundant solar energy in natural resources, these new photo-driven PCMs are very promising materials for solar-to-thermal conversion and energy storage.

Encapsulation efficiency and release of citral using methylcellulose as emulsifier and interior wall material in composite polysaccharide microcapsules

AbstractTo better explore the encapsulation efficiency of citral microcapsules through spray‐drying, amphiphilic methylcellulose (MC) was used as the emulsifier and the interior wall material, with chitosan (CTS) and alginate (ALG) as the composite external wall materials. The sequence and proportion of wall materials were compared and optimized based on the stability of the emulsions and citral content in the microcapsules. MC/CTS/ALG was the best wall material for citral microencapsulation. Formulation comprising 1.5 ml citral, 0.8 g MC, 1.0 g CTS, and 6.0 g ALG had the best entrapment of citral, resulting in citral unit content of 46.4 mg/g and the encapsulation efficiency of 82.2%. Scanning electron microscope and transmission electron microscopy images expressed distinct spherical core–shell structure of the microcapsules. Citral microcapsules absorbed water during storage, which resulted in particle size increase and cracks in the microcapsules surface. Water absorption properties in common used environments (open in air, sealed plastic bag, glass bottle) were investigated. CoCl2 microcapsules were used to intuitively express the water absorption through the color change. The results are referential for industry to select proper wall materials and storage conditions for spice microcapsules to increase the shelf life of relevant foods.

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.

Ceria Nanoparticles-Decorated Microcapsules as a Smart Drug Delivery/Protective System: Protection of Encapsulated P. pyralis Luciferase.

The design of novel, effective drug delivery systems is one of the most promising ways to improve the treatment of socially important diseases. This article reports on an innovative approach to the production of composite microcontainers (microcapsules) bearing advanced protective functions. Cerium oxide (CeO2) nanoparticles were incorporated into layer-by-layer polyelectrolyte microcapsules as a protective shell for an encapsulated enzyme (luciferase of Photinus pyralis), preventing its oxidation by hydrogen peroxide, the most abundant type of reactive oxygen species (ROS). The protective effect depends on CeO2 loading in the shell: at a low concentration, CeO2 nanoparticles only scavenge ROS, whereas a higher content leads to a decrease in access for both ROS and the substrate to the enzyme in the core. By varying the nanoparticle concentration in the microcapsule, it is possible to control the level of core shielding, from ROS filtering to complete blocking. A comprehensive analysis of microcapsules by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, confocal laser scanning microscopy, and energy-dispersive X-ray spectroscopy techniques was carried out. Composite microcapsules decorated with CeO2 nanoparticles and encapsulated luciferase were shown to be easily taken up by rat B-50 neuronal cells; they are nontoxic and are able to protect cells from the oxidative stress induced by hydrogen peroxide. The approach demonstrated that the active protection of microencapsulated substances by CeO2 nanoparticles can be used in the development of new drug delivery and diagnostic systems.

Fabrication of sustained‐release and antibacterial citronella oil‐loaded composite microcapsules based on Pickering emulsion templates

ABSTRACTIn this work, the citronella oil (CTO)‐loaded composite microcapsules with hydroxyapatite (HAp)/quaternary ammonium salt of chitosan (HACC)/sodium alginate (SA) shells are facilely and effectively fabricated by templating citronella oil‐in‐water Pickering emulsions, which are stabilized with HAp nanoparticles. The microcapsule composite shells are prepared by the electrostatic adsorption of HACC and SA, and then chelation interaction of alginate and Ca2+ ions released from HAp nanoparticles. Scanning electronic microscope observation shows that the microcapsules have a spherical shape. Thereafter, Fourier transform infrared spectroscopy and thermal gravimetric analysis results indicate that CTO is successfully loaded into the microcapsules, and the related CTO‐loaded microcapsules possess the thermal stability. Moreover, the in vitro release study of CTO shows that the microcapsules have sustained release activity, and the related CTO release profiles can be well described by Rigter–Peppas model. The antimicrobial assays of microcapsules display the antibacterial effect of CTO‐loaded microcapsules against Staphylococcus aureus and Escherichia coli. Overall, this study opens up new potentiality for unstable active ingredient as an environmental friendly and ingenious microencapsulation in food and agriculture applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46386.

ВОЗДЕЙСТВИЕ ВЫСОКОИНТЕНСИВНОГО СФОКУСИРОВАННОГО УЛЬТРАЗВУКА НА МОДЕЛЬНЫЕ ФАНТОМЫ БИОТКАНЕЙ И КОМПОЗИТНЫЕ МИКРОКАПСУЛЫ С НАНОРАЗМЕРНЫМИ ОБОЛОЧКАМИ

ВОЗДЕЙСТВИЕ ВЫСОКОИНТЕНСИВНОГО СФОКУСИРОВАННОГО УЛЬТРАЗВУКА НА МОДЕЛЬНЫЕ ФАНТОМЫ БИОТКАНЕЙ И КОМПОЗИТНЫЕ МИКРОКАПСУЛЫ С НАНОРАЗМЕРНЫМИ ОБОЛОЧКАМИ

Fabrication and characterization of DDAB/PLA-alginate composite microcapsules as single-shot vaccine.

The most effective method to reduce chronic hepatitis B virus infection is the universal implementation of vaccination. The commercial aluminum-based vaccines need multiple-injection protocols for complete protection resulting in poor compliance in developing countries. It is necessary to develop single-shot vaccine formulations. In this study, novel antigen-loaded DDAB/PLA (didodecyldimethylammonium bromide/poly(lactic acid)) nanoparticles (NPs)-alginate composite microcapsules were developed as a single-shot vaccine. The hepatitis B surface antigen (HBsAg)-loaded DDAB/PLA NPs were successfully encapsulated into alginate microcapsules by a modified spray-solidification technique. The response surface method was applied to optimize the preparation parameters employing encapsulation efficiency of HBsAg and particle size of microcapsules as response variables. The antigen-loaded DDAB/PLA NPs-alginate composite microcapsules were prepared under these optimal conditions: the size of composite microcapsules was 24.25 μm, the Span value was 1.627, and the encapsulation efficiency of HBsAg was 68.4%. The obtained microcapsules were spherical gel microparticles with excellent dispersity and narrow size distributions. In vitro release profile indicated a slow release rate of encapsulated HBsAg especially in phosphate buffered saline solution. The microcapsules showed little toxicity in vivo. This vaccine delivery system could induce stronger immune responses by a single shot, which exhibited much higher cytokine secretion levels closely related to cellular immunity and comparable IgG titers to the traditional aluminum-adjuvanted vaccine with three shots.

Robust Microencapsulated Silicone Oil with a Hybrid Shell for Reducing Propellant Erosion

AbstractA morphologically stable silicon oil microcapsule base polystyrene as shell modified with TiO2 and Si3N4 nanoparticles was synthesized, characterized and applied as an inhibitor for high energy propellant to reduce erosion of gun barrel. The composite microcapsules were obtained by an eco‐friendly method. Embedding heat‐resistant TiO2 and Si3N4 nanoparticles in polystyrene shell enhances the reliability of polymeric shell. The anti‐erosion effect of composite microcapsules for high energy propellant was investigated by using an erosion tester. Results showed that the erosion property of high energy propellant with composite microcapsule was significantly decreased when compared to control sample (without microcapsules). It showed a decrease of 20.6 % in erosion mass when 7 wt.% of composite microcapsules were added to the high energy propellant. Moreover, the anti‐erosion efficiency of composite additives exhibited an increasing trend with the increase of their contents. The pressure and time history confirmed that the composite microcapsules also have ability to adjust the combustion performance of high energy propellants. The developed silicon oil microcapsule shows a potential application for propellant erosion additive.