Significance: Personalized medicine requires the tracking of an individual’s metabolite levels over time to detect anomalies and evaluate the body’s response to medications. Implanted sensors offer effective means to continuously monitor specific metabolite levels, provided they are accurate, stable over long time periods, and do no harm. Aim: Four types of hydrogel embedded with pH-sensitive sensors were evaluated for their accuracy, sensitivity, reversibility, longevity, dynamic response, and consistency in static versus dynamic conditions and long-term storage. Approach: Raman spectroscopy was first used to calibrate the intensity of pH-sensitive peaks of the Raman-active hydrogel sensors in a static pH environment. The dynamic response was then assessed for hydrogels exposed to changing pH conditions within a flow cell. Finally, the static pH response after 5 months of storage was determined. Results: All four types of hydrogels allowed the surface-enhanced Raman spectroscopy (SERS) sensors to respond to the pH level of the local environment without introducing interfering signals, resulting in consistent calibration curves. When the pH level changed, the probes in the gels were slow to reach steady-state, requiring several hours, and response times were found to vary among hydrogels. Only one type, poly(2-hydroxyethyl methacrylate) (pHEMA), lasted five months without significant degradation of dynamic range. Conclusions: While all hydrogels appear to be viable candidates as biocompatible hosts for the SERS sensing chemistry, pHEMA was found to be most functionally stable over the long interval tested. Poly(ethylene glycol) hydrogels exhibit the most rapid response to changing pH. Since these two gel types are covalently cross-linked and do not generally degrade, they both offer advantages over sodium alginate for use as implants.

中文翻译：

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水凝胶基质微胶囊化后 SERS pH 探针响应的比较

意义：个性化医疗需要随着时间的推移跟踪个人的代谢水平，以检测异常并评估身体对药物的反应。植入传感器提供了持续监测特定代谢物水平的有效方法，前提是它们准确、长时间稳定且无害。目的：评估嵌入 pH 敏感传感器的四种类型的水凝胶的准确性、灵敏度、可逆性、寿命、动态响应以及静态与动态条件和长期储存的一致性。方法：首先使用拉曼光谱来校准静态 pH 环境中拉曼活性水凝胶传感器的 pH 敏感峰的强度。然后评估水凝胶暴露于流动池内不断变化的 pH 条件下的动态响应。最后，确定储存 5 个月后的静态 pH 响应。结果：所有四种类型的水凝胶都允许表面增强拉曼光谱 (SERS) 传感器响应当地环境的 pH 水平，而不引入干扰信号，从而产生一致的校准曲线。当 pH 值发生变化时，凝胶中的探针很慢才能达到稳定状态，需要几个小时，而且不同水凝胶的响应时间也有所不同。只有一种聚（甲基丙烯酸 2-羟乙酯）(pHEMA) 能够持续五个月，动态范围没有明显下降。结论：虽然所有水凝胶似乎都是作为 SERS 传感化学生物相容性宿主的可行候选者，但 pHEMA 在长期测试期间被发现功能最稳定。聚乙二醇水凝胶对 pH 值变化的响应速度最快。由于这两种凝胶类型是共价交联的并且通常不会降解，因此它们在用作植入物时都比海藻酸钠具有优势。