Nitric oxide (NO) plays an important role in physiological functions in the body, naturally synthesized by nitric oxide synthase. NO was discovered as the endotheliumderived relaxing factor, allowing for vasodilation to occur in blood vessels, thus preventing platelet aggregation. It is also known as an antimicrobial agent. As it has been shown to enhance wound healing, recent efforts have been made to incorporate NO into thromboresistant polymers for medical devices. In this work, an acrylonitrile-co-1-vinylimidazole (AN/ VIM) copolymer was melt-spun to produce a surgical suture type material with high durability and tensile strength which can store and release NO. The acrylonitrile (AN) comonomers are stabilized in the melt-spinning process, allowing for the formation of the NO molecular donor group, a diazeniumdiolate or NONOate. When AN/VIM is reacted with NO, the NONOate will form on AN segments. Each NONOate releases two molar equivalents of NO upon reaction with a proton source. The fiber mechanical properties were maintained after the polymer is reacted with NO. To control the release of NO, the suture is dipped in polycaprolactone (PCL), creating a porous coating on the fiber. A delayed release is desired in order for NO to be effective in wound healing over long periods of time. The biodegradable coating significantly slows release of the NO compared to the uncoated fiber. Over a course of 3 days, the PCL coated melt-spun AN/VIM copolymer releases a total of 84 μmol NO/g.
Modifications to the chemical nature of polyols, catalysts, and surfactants which give easier foaming conditions are presented. Two new series of activated polyols are described. Their surface-active properties, efficiency as co-solvents for urethane inter mediates, and gelation rates are discussed and means of separating the control of these phenomena outlined. Results are given on the use of a number of new catalyst and surfac tant systems, some of which have shown out standing promise, particularly in the areas where catalyst balance has previously been difficult. Formulations and physical properties of the foams produced are presented and discussed.
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