Continuous Monitoring of Extracellular Glucose Concentrations in the Striatum of Freely Moving Rats with an Implanted Glucose Biosensor

Abstract

Abstract:We have used a glucose oxidase-based sensor implanted in the striatum of freely moving rats to determine the concentration of extracellular glucose in two distinct ways. With a modification of the zero net flux method, in which different concentrations of glucose are infused through a dialysis probe glued to the biosensor, we calculated the concentration at which there was no change in glucose current by regression analysis; this gave a concentration of 0.351 ±0.016 mM. Calculating the concentration from the basal current and the in vitro calibration of the biosensor was not significantly different from this. The basal extracellular glucose concentration determined by either method remained constant over a period of several days. Infusion of 50 1aM veratridine through the adjacent dialysis probe caused a steep decrease in glucose current as soon as the drug reached the brain in contrast to the delayed fall (7.5 mm) seen with microdialysis in previous experiments from this laboratory. These results demonstrate that this biosensor provides a direct, real-time measure of the extracellular concentration of glucose. Key Words: Glucose biosensorBrain glucose concentration-Veratridine-Rat striatum.

Simultaneous recording of hippocampal oxygen and glucose in real time using constant potential amperometry in the freely-moving rat

“…The second day was chosen to allow time for sensors to settle and so that baseline levels were determined prior to any experimental interventions. The baseline current values were matched to the post-implantation calibration data for the CPE (average sensitivity to oxygen = −1.07 nA/M) and the pre-implantation calibration data for Pt/PPD/GOx (average sensitivity to glucose = 1.56 nA/mM) as post-implantation calibration data is not available for Pt/PPD/GOx as the GOx component is lost during the explant procedure (Lowry et al, 1998c). It was determined that the basal oxygen concentration in the hippocampus is 100.26 ± 5.76 M during the day and 99.37 ± 5.51 M during the night.…”

Oxygen tolerance of an implantable polymer/enzyme composite glutamate biosensor displaying polycation-enhanced substrate sensitivity

“…The task of detecting brain ECF Glu, however, is significantly more challenging than glucose monitoring, mainly because the baseline ECF concentration of Glu appears to be ≤5 M (Miele et al, 1996;Lada and Kennedy, 1996;Baker et al, 2002;Chen, 2005;Fillenz, 2005), although values as high as 15 M have been suggested (Kulagina et al, 1999), and compares to ∼500 M for ECF glucose (Boutelle et al, 1992;Lowry et al, 1998a). Thus, optimization of Glu sensitivity is critical for physiological applications, and we reported recently a significant enhancement of the linear region slope (LRS) for Glu, by incorporating the polycation polyethyleneimine (PEI) in these PPD-based biosensors (Pt/PEI/GluOx/PPD) (McMahon et al, 2006b The protein immobilizing agent (Tang et al, 1998) and stabilizer (Bryjak, 1995;Andersson and Hatti-Kaul, 1999), PEI, has been used previously in biosensors for a number of analytes, including Glu (Belay et al, 1999;Rahman et al, 2005;Varma et al, 2006).…”

Design and construction of a low cost single-supply embedded telemetry system for amperometric biosensor applications

“…This biosensor design has been successfully used to quantify ECF striatal brain glucose (∼400 M) in freely moving rats [13]. In brief 40 mm length Teflon © -coated platinum/iridium (90%/10%) wire (5T-125 m diameter, Advent Research Materials, Suffolk, UK) was soldered to a gold pin (RS Components) after carefully cutting 2 mm of the Teflon © insulation.…”