Poly(2-isopropenyl-2-oxazoline) (PiPOx) is emerging as a promising, versatile polymer platform to design functional materials and particularly biomaterials that rely on the hydrophilic character of the 2-oxazoline side units. To be able to assess the applicability of PiPOx in a biomedical context, it is essential to understand its stability and degradation behavior in physiological conditions. In the present work, the hydrolytic stability of PiPOx was systematically investigated as a function of pH during incubation in various buffers. PiPOx was found to be stable in deionized water (pH 6.9), to have good stability in basic conditions (pH 8 and 9), to be satisfactorily stable in neutral conditions (pH 7.4), and to have moderate to low stability in acidic conditions (decreases drastically from pH 6 to pH 1.2). At pH 4, PiPOx formed a crosslinked network in a timeframe of hours, while at pH 1.2, PiPOx was transformed to a water-soluble poly(N-(2-hydroxyethyl)methacrylamide) type of structure over the course of 2 weeks. In vitro stability assays were performed in phosphate-buffered saline (pH 7.4), simulated body fluid (SBF) (pH 7.4), simulated saliva (pH 6.4), simulated intestinal fluid (pH 6.8), and plasma (pH 7.4) revealing that PiPOx is stable in these SBFs up to 1 week of incubation. When incubated in simulated gastric fluid (pH 1.2), PiPOx exhibited a similar degradation behavior to that observed in the buffer at pH 1.2, rendering a water-soluble structure. The presented results on the stability of PiPOx will be important for future use of PiPOx for the development of drug-delivery systems and biomedical applications, such as hydrogels.

中文翻译：

---

聚（2-异丙烯基-2-恶唑啉）水解稳定性的体外评估

聚 (2-异丙烯基-2-恶唑啉) (PiPOx) 正在成为一种有前途的多功能聚合物平台，用于设计功能材料，特别是依赖 2-恶唑啉侧单元的亲水特性的生物材料。为了能够评估 PiPOx 在生物医学环境中的适用性，必须了解其在生理条件下的稳定性和降解行为。在目前的工作中，系统地研究了 PiPOx 在各种缓冲液中孵育期间作为 pH 值的函数的水解稳定性。发现 PiPOx 在去离子水 (pH 6.9) 中稳定，在碱性条件 (pH 8 和 9) 中具有良好的稳定性，在中性条件 (pH 7.4) 中具有令人满意的稳定性，在酸性条件下具有中等到低的稳定性（从 pH 6 急剧下降到 pH 1.2）。在 pH 值为 4 时，N -（2-羟乙基）甲基丙烯酰胺）类型的结构在 2 周的过程中。在磷酸盐缓冲盐水 (pH 7.4)、模拟体液 (SBF) (pH 7.4)、模拟唾液 (pH 6.4)、模拟肠液 (pH 6.8) 和血浆 (pH 7.4) 中进行体外稳定性测定，结果表明： PiPOx 在这些 SBF 中稳定长达 1 周的孵化期。当在模拟胃液 (pH 1.2) 中孵育时，PiPOx 表现出与在 pH 1.2 的缓冲液中观察到的相似的降解行为，呈现出水溶性结构。所呈现的关于 PiPOx 稳定性的结果对于未来将 PiPOx 用于开发药物递送系统和生物医学应用（如水凝胶）具有重要意义。