Radio Frequency-Based Implantable Glucose Biosensor

Abstract

Current implantable sensors are invasive, form fibrotic capsules, and are susceptible to a disconnection between the sensor and the controller. Here, we have developed an implantable wireless glucose monitoring system. This device is composed of an external controller to serve as a human-system interface and an implantable sensor to electrochemically measure glucose levels. Communication between the controller and the sensor is through a pair of an antenna (or coils) using peer-to-peer radio frequency (RF) technology. In addition, the implant’s power is supplied by the controller through RF coupling. Wireless RF technology allows the controller to issue commands to the implant while receiving signals from the sensor. For implantation into rats, the entire implant unit was sealed with polydimethylsiloxane. The working electrodes were modified with various thermoplastic polyurethane (TPU) concentrations for glucose oxidase (GOx) immobilization and evaluated for protein adsorption in a simulated interstitial fluid environment by AUTOLAB. Results indicated that 30 mg/mL of TPU reduced protein adsorption most effectively. To evaluate the signal detection resolution, the device measured hydrogen peroxide levels and compared the data with AUTOLAB. Results indicate that the resolutions of our developed system and AUTOLAB were 114 and < 9.7 nA, respectively. The glucose biosensor with the TPU membrane was subsequently implanted in normoglycemic and hyperglycemic rats. The signal responses obtained from the study rats’ ISF exhibited a significant difference when the blood glucose level changed. A comparison of intravenous and ISF glucose levels revealed a 30 to 170 minutes delay