An Aptamer-Based Microelectrode with Tunable Linear Range for Monitoring of K⁺ in the Living Mouse Brain

Potassium ion (K⁺) is widely involved in several physiopathological processes, and its abnormal changes are closely related to the occurrence of brain diseases of cerebral ischemia. In vivo acquirement of K⁺ variation is significant to understand the roles of K⁺ playing in brain functions. A microelectrode based on single-stranded DNA aptamers was developed for highly selective detection of K⁺ in brain, in which the aptamer probes were designed to contain an aptamer part for specific recognition of K⁺, an alkynyl group used for stable confinement of aptamer probe on the gold surface, and an electrochemical redox active ferrocene group to generate current response signal. The response range of the microelectrodes could be rationally tuned by varying the chain length of the aptamer probe. The optimized electrode, LAC, displayed high selectivity for in vivo detection of K⁺, and suitable linear range from 10 μmol·L^–1–10 mmol·L^–1, which could fulfill the requirement of K⁺ detection in brain. Eventually, the microelectrodes were successfully applied for the detection of K⁺ in the living mouse brains followed by hypoxic.