PubMed · 8824069
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K A Nieforth. 1996. Chilling can cause problems.. https://pubmed.ncbi.nlm.nih.gov/8824069/
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All-trans-retinoic acid (atRA) has been proved to be effective against several malignancies in human clinical trials. However, in many patients who were treated with atRA, the cancer relapsed after a brief remission. One reason for such relapse is that atRA is metabolized by specific P450s that are induced in the liver during prolonged atRA treatments. In order to overcome such a drawback of atRA, we prepared biodegradable microspheres to provide continuous release of atRA for a long period of time. These biodegradable microspheres were prepared by poly(L-lactide) (PLLA) and polyethylene glycol (PEG)-PLLA diblock copolymers (PLE) in various blending ratios to control the release rate of atRA. As the PLE content in microsphere was increased, the density of the hydrophilic PEG block of PLE on microsphere surfaces increased and the microspheres were dispersed well in PBS without any surfactants. Various release patterns of atRA were obtained according to PLE and atRA contents in the microspheres. Especially, the pseudo-zero-order release profiles were observed for 5 weeks when the contents of PLE and atRA in the microspheres were above 4 wt.%.
Hot-melt coating allows encapsulation of water-labile, drug-laden substrates to form a barrier that resists moisture ingress. To understand the interaction of water with excipients that can form moisture-protective coatings, sorption behavior of films of lipidic (glyceryl behenate) and polymeric (polyvinyl alcohol) coating excipients was investigated. A simple and rapid method using a new, fully automated instrumental technique to investigate the sorption/desorption behavior of excipient films is reported. Further, the influence of temperature and film thickness on the sorption behavior of films is examined. Both excipient films displayed sorption isotherms that were classified as type III and demonstrated hysteresis during desorption. The sorption data for both films did not follow the Langmuir model, and the BET model could only be used restrictively. The GAB model fitted the sorption data at all conditions and over the entire range of water activity studied. The ability of the Young and Nelson model to explain the hysteresis behavior, from analytical and mechanistic perspectives, is evaluated. Temperature and film thickness were found to profoundly influence the nature of moisture interaction and distribution of moisture in the excipient films. An Arrhenius-type relationship was observed between equilibrium moisture content of excipient films and temperature at constant water activity.
Several ingredients used in skin products have been criticized as being excessively harsh, allergenic, or otherwise unsuitable for use, especially in the elderly population. Preservatives, in particular, have been condemned, leading to a proliferation of "preservative-free" products. Other descriptive/promotional phrases with negative connotations are "fragrance-free" and "emulsifier-free." Inferences regarding these designations might suggest that preservatives, fragrances, emulsifiers, and a number of other ingredients serve no important function, are superfluous in terms of product quality, and, therefore, should be left out of all skin products. While this is obviously not the case, neither is the obverse. Ingredients used in skin care products should be carefully chosen to support or maintain the overall effectiveness and utility of the product, and the concentration of such ingredients should be given careful consideration. After briefly reviewing skin structure and changes that occur during aging, this article examines the concept of product quality. Major nondrug ingredient categories will be addressed, including the reasons for using such ingredients in skin care products, the products in which they are required, the limitations and choices available within each category, and guidelines for product selection.