An Amperometric Glucose Sensor Integrated into an Insulin Delivery Cannula: In Vitro and In Vivo Evaluation

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Endocrinology

Background:

• Continuous glucose monitoring (CGM) is crucial for type 1 diabetes management.
• Current CGM systems face limitations with integrated insulin delivery due to sensor interference.
• A single device integrating sensing and delivery could improve CGM adoption.

Purpose of the Study:

• To investigate the interference of insulin delivery on glucose sensor readings.
• To compare different sensor chemistries for their susceptibility to insulin-induced artifacts.
• To identify strategies to mitigate interference for combined CGM and insulin delivery systems.

Main Methods:

• Glucose sensors were tested in vivo in swine at the site of bolus insulin delivery.
• Two sensor types were compared: H2O2-measuring sensors (600 mV bias) and redox mediator-type sensors (175 mV bias).
• Sensor signals were analyzed during insulin, saline, and no-liquid delivery conditions.

Main Results:

• H2O2-measuring sensors exhibited a spurious current rise and electrode poisoning after insulin boluses.
• Redox mediator sensors showed signal patterns similar to saline and no-liquid delivery, indicating no significant interference.
• Electrode poisoning in H2O2 sensors was attributed to the oxidation of phenolic preservatives in insulin.

Conclusions:

• Phenolic preservatives in insulin formulations interfere with H2O2-measuring glucose sensors at high bias potentials.
• Redox mediator chemistry with low bias potential effectively avoids insulin-induced interference.
• This finding supports the development of integrated CGM and insulin delivery devices.