Electrodeposition of Gold Nanostructures at the Interface of a Pickering Emulsion.
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ABSTRACT:
SUBMITTER: Booth SG
PROVIDER: S-EPMC6099388 | biostudies-literature | 2018 Aug
REPOSITORIES: biostudies-literature
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Project description:Janus particles, which have two surfaces exhibiting different properties, are promising candidates for various applications. For example, magneto-optic Janus particles could be used for in-vivo cancer imaging, drug delivery, and photothermal therapy. The preparation of such materials on a relatively large scale is challenging, especially if the Janus structure consists of a hard magnetic material like barium hexaferrite nanoplatelets. The focus of this study was to adopt the known Pickering emulsion, i.e., Granick's method, for the preparation of barium-hexaferrite/gold Janus nanoplatelets. The wax-in-water Pickering emulsions were stabilized with a combination of cetyltrimethyl ammonium bromide and barium hexaferrite nanoplatelets at 80 °C. Colloidosomes of solidified wax covered with the barium hexaferrite nanoplatelets formed after cooling the Pickering emulsions to room temperature. The formation and microstructure of the colloidosomes were thoroughly studied by optical and scanning electron microscopy. The process was optimized by various processing parameters, such as the composition of the emulsion system and the speed and time of emulsification. The colloidosomes with the highest surface coverage were used to prepare the Janus nanoplatelets by decorating the exposed surfaces of the barium hexaferrite nanoplatelets with gold nanospheres using mercaptan chemistry. Transmission electron microscopy was used to inspect the barium-hexaferrite/gold Janus nanoplatelets that were prepared for the first time.
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Project description:In the present study, a novel catalytic route for the Knoevenagel condensation reaction has been developed by Pickering interfacial catalysis using magnesium oxide (MgO) as both an emulsion stabilizer and a base catalyst. MgO was prepared by the precipitation method using sodium hydroxide or ammonium hydroxide as the precipitating agent and calcined at different temperatures. The calcined samples were characterized by XRD, SEM, TEM, AFM, BET, and DLS techniques. The catalytic application of the emulsions stabilized by MgO was investigated for the Knoevenagel condensation reaction of benzaldehyde and its derivatives with malononitrile. All of the reactions were carried out at an ambient temperature (30 °C) under static conditions without stirring. Both the emulsion-stabilizing ability and the catalytic activity of MgO were found to be affected by the method of preparation, calcination temperature, and the nature of the oil phase. It was observed that the method of preparation varied the texture and morphology of MgO and thus the stability and droplet size of the emulsion formed. This was further reflected in the catalytic activity. The highest yield (87%) of the condensation product was obtained with MgO prepared by precipitation using a strong base (NaOH) and further calcined at 400 °C. The developed catalytic system offers several green chemistry advantages such as reusable solid-base catalyst and use of a single material as both emulsion stabilizer and catalyst. Room-temperature reaction under static conditions is an additional advantage of the developed catalytic system.
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Project description:The biodegradable cellular capsule, being prepared from simple vaporization of liquid marbles, is an ideal vehicle for the potential application of drug encapsulation and release. This paper reports the fabrication of cellular capsules via facile vaporization of Pickering emulsion marbles in an ambient atmosphere. Stable Pickering emulsion (water in oil) was prepared while utilizing dichloromethane (containing poly(l-lactic acid)) and partially hydrophobic silica particles as oil phase and stabilizing agents respectively. Then, the Pickering emulsion marbles were formed by dropping emulsion into a petri dish containing silica particles with a syringe followed by rolling. The cellular capsules were finally obtained after the complete vaporization of both oil and water phases. The technique of scanning electron microscope (SEM) was employed to research the microstructure and surface morphology of the prepared capsules and the results showed the cellular structure as expected. An in vitro drug release test was implemented which showed a sustained release property of the prepared cellular capsules. In addition, the use of biodegradable poly(l-lactic acid) and the biocompatible silica particles also made the fabricated cellular capsules of great potential in the application of sustained drug release.
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Project description:Malaria is a life-threatening global epidemic disease and has caused more than 400,000 deaths in 2019. To control and prevent malaria, the development of a vaccine is a potential method. An effective malaria vaccine should either combine antigens from all stages of the malaria parasite's life cycle, or epitopes of multiple key antigens due to the complexity of the Plasmodium parasite. Malaria's random constructed antigen-1 (M.RCAg-1) is one of the recombinant vaccines, which was selected from a DNA library containing thousands of diverse multi-epitope chimeric antigen genes. Moreover, besides selecting an antigen, using an adjuvant is another important procedure for most vaccine development procedures. Freund's adjuvant is considered an effective vaccine adjuvant for malaria vaccine, but it cannot be used in clinical settings because of its serious side effects. Traditional adjuvants, such as alum adjuvant, are limited by their unsatisfactory immune effects in malaria vaccines, hence there is an urgent need to develop a novel, safe and efficient adjuvant. In recent years, Pickering emulsions have attracted increasing attention as novel adjuvant. In contrast to classical emulsions, Pickering emulsions are stabilized by solid particles instead of surfactant, having pliability and lateral mobility. In this study, we selected aluminum hydroxide gel (termed as "alum") as a stabilizer to prepare alum-stabilized Pickering emulsions (ALPE) as a malaria vaccine adjuvant. In addition, monophosphoryl lipid A (MPLA) as an immunostimulant was incorporated into the Pickering emulsion (ALMPE) to further enhance the immune response. In vitro tests showed that, compared with alum, ALPE and ALMPE showed higher antigen load rates and could be effectively endocytosed by J774a.1 cells. In vivo studies indicated that ALMPE could induce as high antibody titers as Freund's adjuvant. The biocompatibility study also proved ALMPE with excellent biocompatibility. These results suggest that ALMPE is a potential adjuvant for a malaria vaccine.
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Project description:A massive amount of chalaza with nearly 400 metric tons is produced annually as waste in the liquid-egg industry. The present study aimed to look for ways to utilize chalaza as a natural emulsifier for high internal phase emulsions (HIPEs) at the optimal production conditions to expand the utilization of such abundant material. To the author's knowledge, for the first time, we report the usage of hen egg chalaza particles as particulate emulsifiers for Pickering (HIPEs) development. The chalaza particles with partial wettability were fabricated at different pH or ionic strengths by freeze-drying. The surface electricity of the chalaza particles was neutralized when the pH was adjusted to 4, where the chalaza contained a particle size around 1500 nm and held the best capability to stabilize the emulsions. Similarly, the chalaza reaches proper electrical charging (-6 mv) and size (700 nm) after the ionic strength was modified to 0.6 M. Following the characterization of chalaza particles, we successfully generated stable Pickering HIPEs with up to 86% internal phase at proper particle concentrations (0.5-2%). The emulsion contained significant stability against coalescence and flocculation during long term storage due to the electrical hindrance raised by the chalaza particles which absorbed on the oil-water interfaces. Different rheological models were tested on the formed HIPEs, indicating the outstanding stability of such emulsions. Concomitantly, a percolating 3D-network was formed in the Pickering HIPES stabilized by chalaza which provided the emulsions with viscoelastic and self-standing features. Moreover, the current study provides an attractive strategy to convert liquid oils to viscoelastic soft solids without artificial trans fats.
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Project description:BackgroundNanoparticles assembled from food-grade calcium carbonate have attracted attention because of their biocompatibility, digestibility, particle and surface features (such as size, surface area, and partial wettability), and stimuli-responsiveness offered by their acid-labile nature.ResultsHerein, a type of edible oil-in-water Pickering emulsion was structured by calcium carbonate nanoparticles (CaCO3 NPs; mean particle size: 80 nm) and medium-chain triglyceride (MCT) for delivery of lipophilic drugs and simultaneous oral supplementation of calcium. The microstructure of the as-made CaCO3 NPs stabilized Pickering emulsion can be controlled by varying the particle concentration (c) and oil volume fraction (φ). The emulsification stabilizing capability of the CaCO3 NPs also favored the formation of high internal phase emulsion at a high φ of 0.7-0.8 with excellent emulsion stability at room temperature and at 4 °C, thus protecting the encapsulated lipophilic bioactive, vitamin D3 (VD3), against degradation. Interestingly, the structured CaCO3 NP-based Pickering emulsion displayed acid-trigged demulsification because of the disintegration of the CaCO3 NPs into Ca2+ in a simulated gastric environment, followed by efficient lipolysis of the lipid in simulated intestinal fluid. With the encapsulation and delivery of the emulsion, VD3 exhibited satisfying bioavailability after simulated gastrointestinal digestion.ConclusionsTaken together, the rationally designed CaCO3 NP emulsion system holds potential as a calcium-fortified formulation for food, pharmaceutical and biomedical applications.
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