Body Interface

Glycaemic control requires two body interfaces: a glucose monitoring interface and an insulin infusion interface, which both link the closed loop device to the patient. Our goal was to develop a glucose monitoring body interface (BI), which is directly connected to online glucose sensors.

In contrast to other commercially available systems relying on glucose determination based on body interfaces providing access to subcutaneous adipose tissue, the CLINICIP team has designed, developed and tested two different systems that allow glucose determination in whole blood. The advantage of using a monitoring BI is that sensors can be located outside the body, which enables greater flexibility in the choice of sensor materials since the issue of biocompatibility is transferred from the sensor to the body interface.

Continuous operation
In a first approach, a monitoring BI has been designed for continuous operation: small amounts of whole blood are continuously withdrawn via a double lumen catheter using heparin to avoid blood coagulation. The withdrawn blood is dialysed using a specially designed membrane to filter out big proteins. This procedure prevents bio-fouling in continuously operated online sensors and increases longevity and stability of online glucose sensors.

On-demand operation
In a second approach a monitoring BI has been designed for on-demand operation: a computer driven system mimics the conventional manual way of blood sampling for routine laboratory analysis. It automatically withdraws small amounts (e.g. 200µl) of undiluted whole blood and delivers it to a sensing unit (e.g. a POC – point of care – device) using a sterile barrier between the patient and the POC device.

Both systems have been successfully tested in vivo in healthy and type 1 diabetic subjects. The results indicate highly stable and precise operation for both systems, which can therefore be regarded as promising approaches to a commercial system for tight glycaemic control.