Implantable enzyme-based monitoring systems adapted for long term use

Abstract

Improved implantable monitoring systems suitable for long-term in vivo use to measure the concentration of one or more prescribed substances, such as glucose are described herein. In particular, an implantable enzyme-based glucose monitoring system is described that includes at least one of the following: means for replenishing the enzyme solution as it is consumed by the enzymatic reaction; means for replenishing the electrolyte solution bathing the electrode assembly; and microprocessing means proximal the electrode assembly. In preferred embodiments a microprocessor assembly is hermetically associated with the substrate to which the electrode assembly is affixed. Further, the monitoring systems employ one or more reservoir systems in fluid communication with enzyme and electrolyte chambers wherein the enzyme and electrolyte solutions are used. In a further embodiment, the monitoring systems use enzyme and electrolyte reservoir bulbs in fluid communication with the enzyme and electrolyte reservoirs, respectively, and positioned near the skin surface, thereby providing ready access to the enzyme and electrolyte solutions without the need for explantation of the device. Further provided herein is an enzyme solution including microspheres in association with the enzyme; whereby the enzyme is immobilized by the microspheres and the microspheres are in a fluid, flowable solution. Also provided herein is a method of extending the useful life of an implantable enzyme-based monitoring system, which method includes providing means, within the system, to replenish the enzyme and/or electrolyte solution.