Robert John Morff

In vivo evaluation of an electroenzymatic glucose sensor implanted in subcutaneous tissue

Cleanroom processing techniques have been used to mass-produce flexible, electroenzymatic glucose sensors designed for implantation in subcutaneous tissue. In vitro characterization studies have shown the sensors performance to be acceptable. Initial in vivo studies were conducted with the sensor implanted in the subcutaneous tissue of rabbits. Sensors implanted in the subcutaneous tissue of normal human subjects showed an excellent correlation between glucose concentrations measured by the sensor and capillary finger sticks measured with a commercial analyzer.

Small Intestinal Submucosa as a Vascular Graft: A Review

Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventitia. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.

An electroenzymatic glucose sensor fabricated on a flexible substrate

Abstract A glucose-oxidase-based electroenzymatic glucose sensor has been developed using thin-/thick-film processing techniques. We believe that this processing scheme will overcome a major impediment to the successful movement of the devices from the research laboratory to the marketplace by removing the difficulty of fabricating large numbers of reproducible and economical sensors. Several hundred sensors have been fabricated and tested in vitro. The sensors respond linearly to glucose, are stable for 72 h, are oxygen independent and have a 90 s response time. The sensors have also responded appropriately during preliminary glucose tolerance tests performed in rabbits.

Microfabrication Of Reproducible, Economical, Electroenzymatic Glucose Sensors

We present a method for fabricating electroenzymatic glucose sensors. The general approach i s to utilize thin- and thick-film deposition techniques similar to those used in the semiconductor processing industry. The sensors are fabricated in lots of 130, with the goal of a cheiving r eproducible s ensor performance and economical fabrication costs, using processes that can be readily up-scaled for manufacturing large numbers of sensors. The sensors are formed on a flexible substrate to provide less irritation and longer, more reliable operation when placed in vivo. Sensor operation has been characterized in vitro, and sensor performance has been found to meet

Multilaminate resorbable biomedical device under biaxial loading

The design and test of a multilaminate sheet developed for a hernia repair application is presented. As biomaterial applications become more complex, characterization of uniaxial properties becomes insufficient and biaxial testing becomes necessary. A measure of the in-plane biaxial strength of the device is inferred from a ball burst test. The results of this test for different thicknesses of the device are correlated with the uniaxial strength of the material. A biaxial test such as the ball burst test is more indicative of the properties of a planar material than would be a uniaxial test. The interactions in the biaxial mode of failure are of value and can be related back to a classical uniaxial tensile test from the ball burst test. The material used in this study to fabricate the device was a resorbable biomaterial called small intestinal submucosa (SIS). The effects of rehydration on the stiffness and associated ball burst properties of the SIS device were also measured. It is shown that at a rehydration time of 5 min from a reference dry state, steady-state mechanical properties are reached.

Preliminary clinical results from an electroenzymatic glucose sensor implanted in subcutaneous tissue

A glucose-oxidase based electroenzymatic glucose sensor has been developed using thin/thick film processing techniques. This processing scheme has provided the ability to mass-produce the sensors in a cost effective and reproducible manner. The small, flexible sensors are designed for implantation in the subcutaneous tissue. Previous in vitro characterization studies and in vivo rabbit studies have shown the sensors performance to be acceptable. Glucose measurements obtained with sensors implanted in the subcutaneous tissue of normal human subjects showed an excellent correlation with glucose measurements obtained from capillary, finger-stick blood and intravenous blood.