Title

Fully implantable miniaturized telemetry based glucose biosensor and real-time video camera implant for tissue biocompatibility studies

Date of Completion

January 2000

Keywords

Engineering, Biomedical|Biophysics, General

Degree

Ph.D.

Abstract

Diabetics typically monitor glycemia levels by repeatedly obtaining capillary blood samples by painful finger pricking, sometimes six times a day. Non-compliance can lead to complications like blindness, poor circulation, coma, or death. Continuous glucose monitoring and long-term implanted sensor operation are our ultimate goals. ^ A subminiature implantable potentiostat and telemetry electronics package was developed for remote monitoring of implantable amperometric glucose sensors. Included are a potentiostat for sensor biasing, transimpedance amplifier to produce the sensor-current proportional voltage, and optically coupled interface to the commercially available telemetry unit which transmits data to a receiver and computer. Potentiostat components were individually tested in vitro, then as a system utilizing telemetry for end-to-end remote data monitoring. In vitro sensor calibrations with our subminiature potentiostat/telemetry unit and traditional potentiostat correlated well (R2 = 0.9994). ^ An implantable real-time video telemetry system was developed for remote monitoring and evaluation of tissue reactions to an implant such as a biosensor. Experimental biosensor coatings and treatments can be evaluated in situ for improved blood vessel growth, reduced inflammation, and fibrous encapsulation reduction. Continuous non-surgical site testing will save animal lives. The implantable system comprises a fiber optic lens CCD camera, a TV Video transmitter, a 4-LED illumination module, and a 9 VDC battery. The video signal was telemetried to TV sets and video tape recorders having tuners. The 512 by 492 image pixels represent a 1.6 by 1.2 mm field of view. Magnification approaches 200, depending on image size, with 2 μm resolution (4 μm Nyquist). Modulation transfer functions showed resolvability at 90 lp/mm (5.5 μm line), for telemetried and direct images. In vivo and ex vivo images showed blood vessels as small as 5–10 μm in diameter. Various tissue types such as muscle and connective tissue were also distinguishable. Finally, experimental drug delivery microspheres of 10–20 μm diameter were easily distinguishable. ^ Therefore, we conclude we have developed both an implantable real-time glucose monitoring system, and an innovative video monitoring system to study in vivo tissue reactions and biocompatibility issues. ^