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Cybersensors Implantable Continuous Glucose Sensor Device

Introduction

The supply of therapeutic and diagnostic products to diabetics is one of the largest business areas in medicine. In particular, for many diabetics frequent measurement of blood glucose concentration is required. This is unpleasant involving frequent puncturing of the skin and it is expensive. This is an expanding market as the number of diabetics increases and health education leads to remote testing. An implantable sensor if perfected would be preferable for use with severe forms of diabetes and could form an essential element of a feedback system for drug delivery systems.

Much effort has been expended on attempting to develop such an in vivo glucose sensor for monitoring glucose levels in diabetic patients. These efforts have been focused primarily on adapting known biosensor technology for such use. Although progress has been made, there are still many technical hurdles to overcome. In particular there remain problems of biocompatibility, drift, instability, fouling, infection and the means of connection to external electronic components.

There remains considerable doubt about the commercial feasibility of such systems for anything other than intensive care. The two main problems are the inherent instability of any enzyme-based system which limits the potential life of such a sensor device and designing a reliable interface between the indwelling sensor and its associated electronics.

The Cybersensors solution

Cybersensors have established and patented a dramatically new approach, which does not employ conventional sensors with their inherent deterioration problems. The concept arises from combining existing technologies from quite diverse fields and is comprised of a few stable components that can be assembled in a biocompatible format. In practice a device of the type would be capable of many years of reliable in-body operation. The overall format of the sensor is a small, self contained, biocompatible, malleable implant of dimensions of less than 0.5 cubic centimetre.

There are only three components - a robust, semi-permeable biocompatible outer membrane enclosing a non-toxic glucose sensitive polymeric mixture, in which resides a miniature radio microchip device incorporating a minute physical sensor. The underlying principle of this revolutionary approach is that the rheological properties of the glucose sensitive polymeric mixture change in specific response to the concentration of glucose. Large physical changes occur within the relevant physiological range with the greatest sensitivity at lower concentrations (1 - 10mM). These physical changes are detected by the integral microsensor and can be monitored from outside the body non-invasively by low-energy radio-frequency communication techniques.

This totally novel product concept is made possible by proprietary passive microchip and sensing technology. These minute devices (3.5mm x 3.5mm x 0.5mm) contain a complete radio communication system including antenna and do not require a battery to operate - power is supplied from an external reader by wireless means.

Preliminary specification:

Glucose Sensor: The sensor is a small, safe, robust, self contained, biocompatible, malleable implant whose key features include:
- Typical Size: 10mm x 10mm x 2.75mm
- Interrogation range : 2.5cm
- Long implant life: >2 years.
- Response time: <10 seconds
- Continuous reading.
- Non Toxic, Biocompatible.
- Ease of calibration and recalibration non-invasively
- Minor surgical procedure*

* Typically the sensor implant would be inserted just under the surface of the skin, by a simple surgical procedure involving a local anaesthetic.

Glucose Sensor Reader: The reader unit utilises low power radio (wireless) to interface with the glucose sensor and is designed to provide patient mobility by being highly portable, safe, robust, accurate, easy to use and extremely compact. Can be produced in a 'wrist watch' or 'pager' type formats. Key features include:

- Extremely Compact q Integral transmit/receive antenna
- Visual LCD display
- Pre-settable Acoustic, tactile alarms
- Continuous monitoring capability
- Data logging feature
- Different form factors
- Battery powered.

Typical applications for an implantable glucose sensor include:

Brittle Diabetics: Continuous monitoring, sleep time monitoring.

Paediatric Diabetes: Intensive care, continuous monitoring.

Severe Diabetes: "On the move" monitoring for patients with an active lifestyle.

Drug Delivery Systems: Continuous glucose monitor/sensor

General: Sensor reader can offer data logging and supervisory control for patients. Diet/insulin administration/management.