Biomedical subjects

Yvonne Moussy

Publications and source records attributed to Yvonne Moussy.

6 recordsLinked to original sources

PubMed2005

A long-term flexible minimally-invasive implantable glucose biosensor based on an epoxy-enhanced polyurethane membrane.

This paper describes the preparation method as well as the in vitro and in vivo evaluation of a novel flexible glucose biosensor designed for long-term subcutaneous implantation. An epoxy-enhanced polyurethane membrane, which includes ca. 30-40% epoxy resin adhesive and 50-70% polyurethane, has been developed and used for the first time as the outer protective membrane of the sensor. This new membrane was developed to increase the in vivo durability and lifetime of implantable biosensors. This epoxy-polyurethane membrane was shown to be porous and is of excellent durability. A sensor with such a membrane shows excellent long-term stability and can last for 4-8 months in solutions at room temperature. To verify the in vivo performance of the sensor, nine sensors were implanted in three rats and tested regularly. Eight sensors kept functioning well in the rats for 10-56 days. The ninth sensor was damaged during implantation. All original sensitivity data as well as four response curves obtained at days 7, 17, 52 and 56, respectively are presented.

Animals↗

PubMed2005

Coil-type implantable glucose biosensor with excess enzyme loading.

As part of our overall long-term objective of designing a glucose sensor for long-term subcutaneous implantation, a coil-type implantable glucose sensor loaded with excess glucose oxidase (GOD) inside the coils of a 0.125mm diameter coiled platinum-iridium wire has been developed. The excess GOD was immobilized in a glutaraldehyde/bovine serum albumin (BSA) gel reinforced with cotton and located inside the coils chamber of the sensor. The excess GOD increased the lifetime of the sensor. Based on this coil-type design, various coil-type glucose sensors with cellulose acetate (CA), poly(vinyl chloride)(PVC), polyurethane (PU), poly(bisphenol A carbonate) (PC) and Nafion outer membranes were investigated and compared. Comparatively, Nafion based biosensors provided the best long-term response stability. However, Nafion can still not meet the lifetime requirement of the coil-type sensor with high enzyme loading because the observed function failure of these sensors was indeed caused by outer membrane damage rather than loss of enzyme activity. Additional experiments also revealed that hydrogen peroxide accumulation occurred in the GOD impregnated cotton when the sensors were not polarized which could cause a small false positive measurement. However, this artifact can be easily avoided by using an appropriate measurement technique.

Animals↗

PubMed2005

Strategies for testing long-term transcutaneous amperometric glucose sensors.

OBJECTIVES: Transcutaneous and embedded devices were developed for use in characterizing the in vivo performance of subcutaneously implanted glucose sensors. The devices were used as a portal for accessing electrochemical glucose sensors from the exterior. They were designed to prevent the sensors from being pulled out of the animals and the sensor leads from breaking. Development of the devices took into consideration rodent mobility, infection control, and animal welfare balanced with sensor durability, accessibility, and functionality. METHODS: Our approach was developed over five animal protocols spanning a period of 6 months. A total of 68 sensors were implanted with 60 associated devices in 22 Sprague-Dawley outbred rats. RESULTS: The average sensor lifetime was 11.2 +/- 3.1 days with a maximum of 56 days. All-cause sensor failure averaged one sensor per day. As implantation devices were modified, failure attributable to the device was decreased by 40%. The resulting devices showed good durability and allowed for easy sensor access and testing. CONCLUSIONS: These data represent baseline sensor function against which future sensor improvements may be measured. The new devices and techniques described should be a valuable tool in the development of continuous glucose sensors.

Animals↗

PubMed2003

Convective flow through a hollow fiber bioartificial liver.

A study of open shell flow through a hollow fiber bioartificial liver with a cell packed shell region (the extracapillary space between the fibers) was performed. Previous analyses of flow through a hollow fiber bioartificial liver have ignored the porous nature of the shell region. Existing analytic expressions were used to describe the flow through the porous hollow fibers, and the flow through the shell region was described using Darcy's law. The operational parameters were taken from clinical trials of the Hepatix extracorporeal liver assist device (ELAD). From the experimental parameters, the permeability value of the cell packed shell region of the ELAD was determined. The results suggest the possible formation of preferential flow channels and hypoperfusion of many cells leading to an inadequately functioning bioreactor. Some simple design changes may improve the performance of the ELAD.

Bioreactors↗

PubMedDate not supplied

Distribution of [3H]dexamethasone in rat subcutaneous tissue after delivery from osmotic pumps.

Inflammation surrounding implantable glucose sensors may be controlled through local release of dexamethasone at the site of implantation. In the present study, we evaluated the distribution of dexamethasone in rat subcutaneous tissue during the first 2.5 days after local release. Osmotic pumps containing [3H]dexamethasone were implanted into the subcutaneous tissue of rats. Digital autoradiography was used to measure the distribution of the [3H]dexamethasone within the subcutaneous tissue at 6, 24, and 60 h after implantation. Measured concentration profiles, near the catheter tip through which the agent was released, were compared to mathematical models of drug diffusion and elimination. The results demonstrate that the majority of the [3H]dexamethasone delivered into the subcutaneous tissue was found within a 3 mm region surrounding the catheter tip. There was good agreement between the experimental data and the mathematical model. The diffusion coefficient for dexamethasone in subcutaneous tissue was found to be D = 4.11 +/- 1.77 x 10(-10) m2/s, and the elimination rate constant was found to be k = 3.65 +/- 2.24 x 10(-5) s(-1). The diffusion coefficient and elimination rate constants for dexamethasone in subcutaneous tissue have not been previously reported. The use of a mathematical model may be useful in predicting the effectiveness of local delivery of dexamethasone around implantable glucose sensors.

Animals↗

PubMedDate not supplied

Diffusion of [3H]dexamethasone in rat subcutaneous slices after injection measured by digital autoradiography.

A relatively simple method for the determination of the diffusion coefficient of a substance that has been injected into tissue is described. We illustrate this method using [3]dexamethasone injected into the subcutaneous tissue of rats. Digital autoradiography was used to measure the distribution of the [3H] dexamethasone within the subcutaneous tissue at 2.5 and 20 min after injection. Measured concentration profiles of the injection were compared to a mathematical model of drug diffusion from an injection. There was good agreement between the experimental data and the mathematical model. The diffusion coefficient found using this simple injection method was (4.01 +/- 2.01) x 10(-10) m2/s. This D value was very close to the value of D = (4.11 +/- 1.77) x 10(-10) m2/s found previously using different mathematical and experimental techniques with osmotic pumps implanted for 6, 24, and 60 h in rats (1). The simple method given here for the determination of the diffusion coefficient is general enough to be applied to other substances and tissues as well.

Algorithms↗