Encapsulating Ionophores in Zeolite Imidazolate Framework-8 for Long-Term Monitoring of Ion Fluctuations in Living...

Various ions in the brain (e.g., H⁺, K⁺, and Ca²⁺) play essential roles in neural information transmission and physiopathological processes. Real-time monitoring of these ions will provide critical information for understanding neural functions and diagnosing diseases. However, long-term monitoring the dynamics of ions with microelectrodes remains a challenge due to the limited availability of sensing strategies capable of in vivo measurements with high stability in the mechanically soft and chemically complex brain of freely moving rats. Here, we develop a flexible and stable ion-selective microsensor for long-term monitoring of ions in rat brain, in which zeolite imidazolate framework-8 (ZIF-8) nanoparticles incorporated with ionophores are used for selective ion recognition and flexible polyvinyl alcohol (PVA) fibers sputtered with gold nanoparticles (AuNP) is used as the soft electrode substrate. The flexible microsensors allow long-term in vivo ion sensing with good stability in the brain of behaving rat, avoiding progressively deteriorating response of traditional polymer-based rigid ion selective microsensor caused by its instability interface and mechanical mismatch to soft brain tissue.