Polydopamine (PDA) has been found to be as functional materials in a wide range of applications. However, the degradation behavior and mechanism of PDA are still in debate. For well understanding the degradation, PDA nanoparticles (PDA NPs) were prepared by oxidation and self-polymerization of dopamine and employed to study the degradation properties. We systematically studied the degradation of PDA NPs by adjusting the pH value, temperature and alkali strength of the system. PDA NPs were more prone to degrade under alkaline conditions above pH 11.0, and the stronger the alkalinity (pH 13.0) induced the faster the degradation rate. The analysis results for the entire degradation process showed that the size of the PDA NPs firstly decreased and then the morphology of PDA NPs changed from spheres to nanosheets with degradation time. After 120 h of degradation, PDA was completely degraded into monomers and oligomers with three or four repeat units that can be soluble in water. Moreover, PDA showed good biocompatibility. This study would give a strong evidence to confirm the degradation of PDA and help for designing the new PDA materials in biomedical and environmental fields.

中文翻译：

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碱度引发聚多巴胺纳米粒子的降解

聚多巴胺 (PDA) 已被发现在广泛的应用中作为功能材料。然而，PDA的降解行为和机制仍存在争议。为了更好地理解降解，通过多巴胺的氧化和自聚合制备了 PDA 纳米颗粒（PDA NPs）并用于研究降解特性。我们通过调节体系的pH值、温度和碱强度，系统地研究了PDA NPs的降解。PDA NPs 在高于 pH 11.0 的碱性条件下更容易降解，并且碱性越强（pH 13.0）诱导降解速度越快。整个降解过程的分析结果表明，随着降解时间的推移，PDA NPs 的尺寸先减小，然后PDA NPs 的形貌从球形变为纳米片。降解 120 h 后，PDA 完全降解为具有三或四个可溶于水的重复单元的单体和低聚物。此外，PDA显示出良好的生物相容性。该研究将为证实PDA的降解提供强有力的证据，并有助于设计生物医学和环境领域的新型PDA材料。