Biomimetic mesoporous carbon-silica/AAO asymmetric nanochannel array for electrochemical sensing of K⁺ in rat brain microdialysates and serum

Acquirement of chemical expression in practical brain system is vital to understand the molecular mechanism involved in physiological and pathological processes in brain. Though nanochannels have been demonstrated to be promising platform for electrochemical sensor, it is a great challenge for nanochannels to be employed in practical brain biofluid. In this work, we rationally designed and created the biomimetic asymmetric nanochannels for sensing of K⁺ through integrating in situ modification of a two-component mesoporous carbon-silica (MCS) thin film with a pore size of ∼3.6 nm at anodic alumina nanochannel array (AAO) with the ∼40 nm pores (denoted as MCS/AAO). Apparent rectification phenomenon in such functionalized nanochannel array was achieved based on diode-like ion transport. Then, 4′-aminobenzeno-18-crown-6 (SP) was selected to be chemically decorated at MCS/AAO as the specific recognition for K⁺ (SP/MCS/AAO). The developed SP/MCS/AAO exhibited good selectivity towards K⁺ detection against the coexisting interferences in brain, and possessed a good linear response to K⁺ concentration in the range of 0.5–10 mM with a detection limit of 0.1 mM. Combined with microdialysis technique, the variation of K⁺ was successfully determined in rat brain microdialysates and serums. Compared with normal rats, the concentration of K⁺ was found to be greatly decreased in the cerebral microdialysates and serum of rats with hypertensive model (SHR). This work unveiled a powerful platform for K⁺, and promised to be extended to design new strategy for detecting other chemical species, in particular non-electroactive species in biofluid related to physiological and pathological events.