Hydrogel nanoparticles (also known as nanogels) have been utilized for a wide range of applications including analytics, sensors, drug delivery, immune engineering, and biotechnology. While these types of nanoparticles can be characterized using standard colloidal characterization techniques, degradation profiles typically must be inferred from those of bulk gels with the same formulation, typically by applying swelling ratios and rheological measurements that tend to severely underestimate nanoparticle degradation rates. Herein, we present an analysis of the degradation via ester hydrolysis of poly(ethylene glycol)diacrylate (PEGDA)-based hydrogel nanoparticles in water, varied pH conditions, and reducing environments. We perform this characterization using thermogravimetric analysis and mass spectrometry to analyze rates of degradation and products released, respectively, and compare results to those for equivalent bulk gel formulations. Our findings show that PEGDA-based nanoparticles display significant mass loss over time accompanied by negligible changes in hydrodynamic diameter, indicating a bulk mode of degradation. Nanoparticle mass loss occurs at a much higher rate than for bulk gels under comparable incubation conditions, confirming that bulk gel degradation serves as a poor surrogate for nanoparticle degradation. We further demonstrate that the incorporation of other diacrylate-based co-monomers drastically accelerates nanoparticle degradation rates. Through formulation considerations of co-monomer content and weight percent of PEGDA, we demonstrate the ability to tune the degradation rates of PEGDA-based nanoparticles on a range of hours to weeks. These findings highlight critical design considerations for enhancing the tunability and utility of PEGDA hydrogel nanoparticles and introduce a rigorous framework for the characterization of nanogel degradation.

中文翻译：

---

聚乙二醇二丙烯酸酯（PEGDA）基水凝胶纳米颗粒的降解曲线†

水凝胶纳米颗粒（也称为纳米凝胶）已被广泛用于包括分析，传感器，药物输送，免疫工程和生物技术在内的各种应用。尽管可以使用标准的胶体表征技术对这些类型的纳米颗粒进行表征，但是通常必须从具有相同配方的块状凝胶的降解曲线中推断出降解曲线，通常是通过应用倾向于严重低估纳米颗粒降解速率的溶胀比和流变学方法来进行的。在这里，我们通过聚乙二醇二丙烯酸酯（PEGDA）基水凝胶纳米粒子在水中，不同的pH条件和还原环境中进行酯水解。我们使用热重分析和质谱法分别对降解速率和产物释放进行了表征，并将结果与​​等效的本体凝胶制剂进行了比较。我们的发现表明，基于PEGDA的纳米颗粒随着时间的流逝显示出明显的质量损失，同时流体动力学直径的变化可忽略不计，表明整体降解方式。在可比的温育条件下，纳米颗粒的质量损失发生率远高于本体凝胶，这证明本体凝胶的降解是纳米颗粒降解的不良替代物。我们进一步证明，掺入其他基于二丙烯酸酯的共聚单体可大大加快纳米颗粒的降解速度。通过共聚单体含量和PEGDA重量百分比的配方考虑，我们证明了在数小时至数周的范围内调整PEGDA基纳米粒子降解速率的能力。这些发现突出了用于增强PEGDA水凝胶纳米颗粒的可调性和实用性的关键设计考虑因素，并为表征纳米凝胶降解引入了严格的框架。