Abstract

“Primary” poly(vinyl alcohol) (PVA) cryogels have been obtained by cryogenic processing (freezing at –21.6°C for 12 h followed by defrosting via heating to 20°C at a rate of 0.03°C/min) of a 100 g/L solution of PVA in dimethyl sulfoxide (DMSO) in the absence and presence of urea (2 or 4 mol/L), which exhibits kosmotropic properties in such a medium. Subsequent hydration of the cryogels by replacing DMSO with water causes a decrease in the volume and weight of the samples, as well as leads to a significant increase in the elasticity modulus of resulting “secondary” cryogels. The absolute magnitude of such effects depends both on the concentration of urea in an initial PVA solution and on the volume ratio between gel samples and an aqueous extractant during their hydration. Using optical microscopy, it has been found that the presence of urea in the initial DMSO polymer solution in a concentration close to the limit of its solubility in such a medium induces the formation of a gel matrix with a wide-pore morphology. Since high-modulus secondary PVA cryogels are of great interest as materials for biomedical applications, the possibility of their functioning as carriers of drug delivery systems has been assessed in the work. Ibuprofen sodium salt has been used as a model drug. The analysis of the release kinetics of this substance within the framework of the Weibull function has been employed to show that the dynamic hydrogen bonding of its carboxylate groups with the hydroxyl groups of PVA decelerates the release of the drug from the polymer carrier, i.e., prolongs the release process. At the same time, the rate of the process depends on the urea content in the initial polymer solution most likely due to microstructural differences between the polymer phases of the macropore walls in the cryogel matrix.

中文翻译：

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聚合物体系的冷冻结构研究。66. 冷冻二甲亚砜中添加尿素并用水代替有机介质水合的聚(乙烯醇)冷冻凝胶的性能和微观结构

摘要

“初级”聚乙烯醇 (PVA) 冷冻凝胶通过低温加工（在 –21.6°C 冷冻 12 小时，然后以 0.03°C/min 的速率加热至 20°C 除霜）获得 100 g/L PVA 的二甲基亚砜 (DMSO) 溶液，在不存在和存在尿素（2 或 4 mol/L）的情况下，在这种介质中表现出亲液特性。随后用水代替 DMSO 进行冷冻凝胶的水合，导致样品的体积和重量减少，并导致所得“二次”冷冻凝胶的弹性模量显着增加。这种影响的绝对大小取决于初始 PVA 溶液中尿素的浓度以及凝胶样品和水合过程中水提取剂之间的体积比。使用光学显微镜，已经发现初始DMSO聚合物溶液中尿素的存在（其浓度接近其在这种介质中的溶解度极限）诱导了具有大孔形态的凝胶基质的形成。由于高模量二次 PVA 冷冻凝胶作为生物医学应用材料引起了人们的极大兴趣，因此在工作中评估了它们作为药物输送系统载体的可能性。布洛芬钠盐已被用作模型药物。在威布尔函数框架内对该物质的释放动力学进行分析表明，其羧酸根基团与PVA的羟基之间的动态氢键作用减缓了药物从聚合物载体中的释放，即延长了药物的释放时间。发布过程。同时，该过程的速率取决于初始聚合物溶液中的尿素含量，这很可能是由于冷冻凝胶基质中大孔壁的聚合物相之间的微观结构差异所致。