Semi-implantable device based on multiplexed microfilament electrode cluster for continuous monitoring of physiological ions

Modern medicine is increasingly interested in advanced sensors to detect and analyze biochemical indicators. Ion sensors based on potentiometric methods are a promising platform for monitoring physiological ions in biological subjects. Current semi-implantable devices are mainly based on single-parameter detection. Miniaturized semi-implantable electrodes for multiparameter sensing have more restrictions on the electrode size due to biocompatibility considerations, but reducing the electrode surface area could potentially limit electrode sensitivity. This study developed a semi-implantable device system comprising a multiplexed microfilament electrode cluster (MMEC) and a printed circuit board for real-time monitoring of intra-tissue K⁺, Ca²⁺, and Na⁺ concentrations. The electrode surface area was less important for the potentiometric sensing mechanism, suggesting the feasibility of using a tiny fiber-like electrode for potentiometric sensing. The MMEC device exhibited a broad linear response (K⁺: 2–32 mmol/L; Ca²⁺: 0.5–4 mmol/L; Na⁺: 10–160 mmol/L), high sensitivity (about 20–45 mV/decade), temporal stability (>2 weeks), and good selectivity (>80%) for the above ions. In vitro detection and in vivo subcutaneous and brain experiment results showed that the MMEC system exhibits good multi-ion monitoring performance in several complex environments. This work provides a platform for the continuous real-time monitoring of ion fluctuations in different situations and has implications for developing smart sensors to monitor human health.

Graphic abstract