Continuous amperometric monitoring of subcutaneous oxygen in rabbit by telemetry

Abstract

The primary objective was to develop a telemetric oxygen sensor designed for implantation in subcutaneous tissue. In the sensor, the platinum indicating electrode was covered with polythene to retard oxygen entry and avoid interference. Given the potential for large indicating electrodes to deplete oxygen in vivo, some sensors were made with very small indicating electrodes. Sensors were tested in the anesthetized rabbit at various oxygen concentrations. Animals were studied 1 and 5 days after implementation. The sensor could detect changes in oxygen in vivo. Measurements were similar at 1 and 5 days and sensors with different sized electrodes yielded similar results. This telemetric implantable amperometric sensor can detect variations in tissue oxygenation and may have applications in cardiopulmonary physiology, continuous glucose monitoring and other related fields.

A method for measuring brain partial pressure of oxygen in unanesthetized unrestrained subjects: The effect of acute and chronic hypoxia on brain tissue PO2

“…A carbon paste electrode was used with differential pulse amperometry to measure changes in current as a correlate of changes in brain PtO 2 in a range of conditions (Lowry et al, 1996; Lowry et al, 1997; Lowry and Fillenz, 2001). An amperometric electrode with a self contained power source has been implanted subcutaneously in rabbits and PO 2 monitored up to 5 days post implant (Ward et al, 2002). Constant potential amperometry has been used with an implanted silver electrode connected to a carbon microsensor and a telemetry circuit (Bazzu et al, 2009).…”

“…Clark suggested that 1-3 weeks was required before current stabilized in electrodes implanted in brain (Clark et al, 1958). Some have shown that 24 hrs is sufficient time post implantation of an oxygen sensor to reach a stable, reproducible value for PtO 2 (Liu et al, 1995; Lowry et al, 1997; Ward et al, 2002). A study measuring PtO 2 in brain over 8 days found no significant difference between days, but did not report the error of the measurements (Bazzu et al, 2009) or the time of first measurement.…”

A novel macroencapsulating immunoisolatory device: the preparation and properties of nanomat-reinforced amphiphilic co-networks deposited on perforated metal scaffold

“…Pancreatic islets, particularly porcine islets, are very dependent on oxygen (Ohta et al 1980;Dionne 1989;Hyder et al 1998;Guyton 1991;Soini and Takala 1991;Ward et al 2002;Klossner et al 1974) with an oxygen consumption rate in vitro of 2.5-3 nmol/min per 100 islets and increasing in response to elevated glucose levels (Dionne 1989;Hyder et al 1998;Guyton 1991). Insulin secretion decreases significantly when pO 2 falls below 60 mmHg (Soini and Takala 1991;Ward et al 2002;Klossner et al 1974). The process of islet isolation, culture, and subsequent transplantation results in hypoxia and an immediate loss of islet tissue (Ohta et al 1980;Davalli et al 1996).…”

“…The amount of oxygen would depend upon passive diffusion within the implantation site with the partial pressure of oxygen (pO 2 )~95 mmHg in arterial blood,~40 mmHg in venous blood, and ranges from 35 to 60 mmHg in the peritoneum and subcutaneous tissues (Carlsson et al 1998;Zacharovova et al 2005;Sweet and Gilbert 2006;Hellerstrom 1967). Pancreatic islets, particularly porcine islets, are very dependent on oxygen (Ohta et al 1980;Dionne 1989;Hyder et al 1998;Guyton 1991;Soini and Takala 1991;Ward et al 2002;Klossner et al 1974) with an oxygen consumption rate in vitro of 2.5-3 nmol/min per 100 islets and increasing in response to elevated glucose levels (Dionne 1989;Hyder et al 1998;Guyton 1991). Insulin secretion decreases significantly when pO 2 falls below 60 mmHg (Soini and Takala 1991;Ward et al 2002;Klossner et al 1974).…”

Real-time electrochemical monitoring of brain tissue oxygen: A surrogate for functional magnetic resonance imaging in rodents

“…A wide variety of sensors have been used for direct monitoring of O 2 with the majority of measurements obtained using constant potential amperometry (CPA) at noble metal microelectrodes such gold (Cooper, 1963;El-Deab and Ohsaka, 2003;Holmström et al, 1998) or platinum (Clark et al, 1958;Hitchman, 1978;Travis and Clark, 1965;Ward et al, 2002). The use of carbon-based electrodes has been reported by several groups (Bazzu et al, 2009;Bolger and Lowry, 2005;Lowry and O'Neill, 1996;Venton et al, 2003) and they are often the electrode of choice because of their in-vivo stability and minimal surface poisoning (Bolger and Lowry, 2005).…”