Hollow microcapsules are expected to be integral components of drug delivery systems in medical and pharmaceutical applications. Among the methods studied, the bubble template method (Makuta et al. Mater. Lett. 2009, 63, 703-705) should easily fabricate uniform hollow microcapsules covered with biodegradable polymers. In this study, we clarified the two conditions required to fabricate uniform hollow microcapsules using the bubble template method: the stability of uniformly sized microbubbles in a liquid droplet and the release of hollow microcapsules from the droplet. Furthermore, our experiments evaluated the radius distributions of template microbubbles and fabricated hollow poly(lactic acid) microcapsules.
Due to their particular water absorption capacity, hydrogels are the most widely used scaffolds in biomedical studies to regenerate damaged tissue. Hydrogels can be used in tissue engineering to design scaffolds for three-dimensional cell culture, providing a novel alternative to the traditional two-dimensional cell culture as hydrogels have a three-dimensional biomimetic structure. This material property is crucial in regenerative medicine, especially for the nervous system, since it is a highly complex and delicate structure. Hydrogels can move quickly within the human body without physically disturbing the environment and possess essential biocompatible properties, as well as the ability to form a mimetic scaffold in situ. Therefore, hydrogels are perfect candidates for biomedical applications. Hydrogels represent a potential alternative to regenerating tissue lost after removing a brain tumor and/or brain injuries. This reason presents them as an exciting alternative to highly complex human physiological problems, such as injuries to the central nervous system and neurodegenerative disease.
Hollow capsules are gas-filled spherical particles. Hollow biodegradable capsules with a diameter of a few microns are expected to be used as diagnostic ultrasound contrast agents and carriers of drug-delivery systems, while those with a diameter of a few tens of microns have been widely used in various engineering applications and medical and pharmaceutical applications, providing weight reduction of the material and improved thermal and acoustical insulation. In this study, uniformly sized hollow polylactic acid (PLA) microcapsules with diameters of 10-20 mm and 1-2 mm have been fabricated by two different methods, both based on the nature of microbubbles. One method is based on the growth and/or coalescence of microbubbles inside microdroplets of PLA organic solution dispersed in a continuous aqueous phase, and the other one is based on the spontaneous release of independent microbubbles covered with PLA from millidroplets into the continuous phase. Neither of these methods uses microfluidic devices, and they have thus high potential for mass production without compromising the uniformity.
Hollow microcapsules of poly(lactic acid) (PLA) were fabricated using the bubble template method, which involves the nucleation of bubbles inside droplets of a dichloromethane solution of PLA prepared in a continuum medium of an aqueous solution of poly(vinyl alcohol) (PVA). PLA-covered microbubbles are formed by PLA adsorbing onto the microbubble surface and then spontaneously released from the dichloromethane droplets into the surrounding aqueous solution. Thereby, hollow PLA microcapsules are formed. In the present study, we focus on the effects of the initial PLA concentration, addition of PVA to the aqueous medium, and PLA molecular weight on the radius distribution of the hollow PLA microcapsules. Results show that a low initial concentration of PLA, the addition of PVA, and low molecular weight PLA are required to form uniform hollow microcapsules. It is suggested that these factors reduce the energy barrier at the liquid-liquid interface, which allows the PLA-covered microbubbles to pass smoothly through the interface. Furthermore, we observed the release of the microbubbles from the dichloromethane droplets through a microscope and clarified the relationship between the uniformity of the hollow PLA microcapsules and the bubble-release mechanism.
The effect of dissolved
poly(lactic acid) (PLA) on the solubility
of gases (CO2, N2, and He) in dichloromethane
(CH2Cl2) was investigated, between 288 and 303
K, by measuring the equilibrium pressure in a closed vessel containing
a gas and CH2Cl2 solutions of different types
(molecular weights) and concentrations of PLA. The results show that,
in the absence of PLA, the order of the solubility of gases in dichloromethane
was He < N2 < CO2. Furthermore, an increase
in the concentration of PLA did not appreciably change the solubility
of CO2 in the solutions but led to a higher solubility
of N2 and He. The effect of PLA on the increase of gas
solubility in CH2Cl2 was larger for less soluble
gases. Semiempirical correlations of the dependence of the Henry’s
law constant of the gases on the temperature and PLA concentration
were also derived from the measured data.
The effect of commercial Atrazine (ATR) on Rattus Novergicus organs was determined for a concentration of c ATR of 1, 3, 13, 30, and 50 ppb. ATR was dissolved in drinking water. The rats were allowed to drink from it ad libitum for an uninterrupted period of 28 days as established by the Offi ce of Environmental Protection protocol under the number EPA OPPTS 870.3050. In the 28 days of the test, data on the behavior of the medicated animals was recorded before the extraction of sample tissues (heart, liver, spleen, brain, and testicles) for histological analysis. A direct correlation of c ATR and organ damage was found. The study showed that even for the smallest doses (1ppb), commercial ATR produced several lesions in the studied animals. The rats showed hepatic periacinar necrosis with acute coagulation, hepatocyte lipidosis, severe portal lymphocytic infl ammation, coronary periarteritis, and lymphocytic meningoencephalitis for high concentrations. In the male reproductive system, testicular degeneration with mild acute tubular necrosis was observed.
This document describes an investigation undertaken to examine attitudes towards lockdowns through COVID-19 as a psychosocial risk predictor in Panama. We conducted the study through a cross-sectional, prospective, and correlational approach. The study was constructed containing psychometric characteristics in the form of 36 Likert scale items to collect data. The instrument was sent to 233 participants via Google form between April 17 and April 30, 2020. The participants responded fully to the questionnaire. We analyzed the data by mean comparisons, correlation, and regression. There is a significant correlation between each of the studied factors and attitudes. The results indicate that women and people over the age of 51 have a positive attitude towards lockdown. Finally, from the predictive risk model in which 99.9% of the data fit., the affective factor represents 68%, the cognitive factor 22%, and the behavioral factor 10% of predictive importance for lockdown attitudes to COVID-19.
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