Helical Microfilament-Electrode-Based Semi-Implantable Biosensors for In Vivo Electrochemical Detection

Semi- implantable devices have shown potential for real-time sensing of physiological information in vivo. For glucose detection in diabetes, semi-implantable electrodes have the ability to measure glucose concentration directly from interstitial fluid (ISF) with high accuracy and continuous monitoring performance. However, electrochemical detection by the amperometric method is limited by the electrode size, which can restrict signal magnitude and sensitivity of the implantable microfilament electrode. To address this limitation, a semi-implantable helical microfilament- based glucose electrode (HMGE) is developed. The helical structure of the HMGE enhances the electrochemical sensing area, while the coating with carbon nanotube and poly(3,4-ethylene-dioxythiophene): polystyrene sulfonate provides an electron-transfer interface for electrochemical sensing. The HMGE exhibits high selectivity and sensitivity for glucose detection. Through in vitro experiments, the sensitivity of HMGE is improved by about 7 times compared with that of the non-helical structure. In in vivo studies in rats, it is demonstrated that HMGE system can continuously monitor glucose concentration changes in ISF with reasonable accuracy after signal calibrations. Furthermore, a circuit-sensing system and smartphone application are developed to support the operation of HMGE system as a phenotype. The HMGE presents a promising semi-implantable device for monitoring various electrolytes, metabolites, and biochemical signals in vivo.