A novel facile approach to creating many localized giant polymersomes (GPs) (vesicles) is developed. This method allows for the easy capture and testing of the bulk properties of the GPs. Inkjet printing is shown to produce vesicles of a non‐ionic block copolymer, poly(ethylene oxide)16‐poly(butylene oxide)22 (E16B22). The printer deposits a polymer solution (i.e., water/glucose/polymer) on a hydrophobic glass slide. Upon drying, glucose is left between polymer lamellar. Subsequent hydration of the sample dissolves glucose, and as a result, a concentration gradient is generated, which provides the energy necessary for separating the neutral polymer layers. After about 2 h in water, GPs are observed and are free of organic solvents. This novel methodology provides for the efficient formation of localized GPs. The distribution of the solution allows for a metered approach to releasing the GPs. This combination facilitates the collection of vesicles for micropipette aspiration experiments.
The solvent-free polymerization of epsilon-caprolactam on 1,8-diaminooctane-functionalized multi-walled carbon nanotubes (DA-MWNTs) is proposed as a simple and ecologically friendly approach to the preparation of carbon nanotubes/nylon 6 hybrid materials. The main goal of the present study was to find a minimum temperature resulting in an efficient epsilon-caprolactam polymerization, along with the optimization of the weight ratio of DA-MWNTs to epsilon-caprolactam and reaction time. The effect of temperature was studied in the range of 170 degrees C to 210 degrees C. After the reaction at 170 degrees C, the nanotubes functionalized contained a large amount of unreacted monomer along with ca. 14% of polyamide. Increasing the reaction temperature dramatically reduced the content of epsilon-caprolactam impurity and increased the nylon 6 content to ca. 20%. The reaction time tested was 1, 2, 4, 6 and 8 h. Exposures at less than 4 h were insufficient, where the infrared spectral bands of nylon 6 were barely seen. The reaction time of 6 h was found to be optimal since a more prolonged heating for 8 h did not provide an evident further increase in polyamide content. The effect of stoichiometry was studied by varying the weight ratio of DA-MWNTs to epsilon-caprolactam from 1:0.1 to 1:1. The ratios 1:0.1 and 1:0.2 were too high, since they did not provide the amount of epsilon-caprolactam necessary to form the composites with at least 20% content of nylon 6. Starting with the ratio of 1:0.3, the infrared band intensities qualitatively stabilized and did not show dramatic variations. The use of reagent ratios of 1:0.3 to 1:0.7 might be especially appropriate for preparing the composites targeted to biomedical applications, whereas higher weight ratios are expected to increase the content of undesirable monomer impurities.
A methodology which provides a high efficiency of giant vesicle formation was established using the gentle hydration method and a microplotter equipment. The method consists of preparing a mixture of zwitterionic egg yolk phosphatidylcholine/additive in solution and printing a number of droplets onto a glass substrate, which immediately dry after deposition. Then, gentle hydration of these micro-sized thin-films provides a high amount of giant liposomes, per microsized film. Several cases were studied by varying different compounds as additives (i.e., non-electrolytes and electrolytes) at different molar ratios, lipid to additive, in order to find the optimal conditions. Optical and confocal microscopies were employed to characterize vesicle formation. Studies indicate that the kosmotropic salt KH2PO4 at 1:10 molar concentration, EggPC to salt, is the most effective in vesicle production. Abundant liposome formation can be observed in a short time, about 5 min upon hydration. The osmotic pressure is the driven force to produce giant liposomes in our experiments, which is generated by dissolving the additive among two lipid lamellar phases in water. In salt experiments, the osmotic pressure strength is manly determined from the ion-specificity effect (i.e., the Hofmeister effect) rather than the concentration of the salt. The use of a salt as additive provides giant unilamellar vesicles (GUVs). The microplotter protocol provides benefits such as a facile, efficient and rapid way to prepare GUVs in mild conditions (i.e., free of solvents).
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