NACL Sensors
Glucose

Legend: Schematic representation of a Pt/GOx/PPD biosensor for targeting ECF brain glucose. The enzyme glucose oxidase (GOx) is immobilised in a polymer/protein (PPD/BSA) composite film electrosynthesised in situ on Pt microcylinders, which may be coated with other modifiers, e.g., lipid (PEA). The Pt surface, held at a high positive relative potential, oxidises electroactive species reaching it. Target analyte (Glucose) reacts at the enzyme site to produce small hydrogen peroxide molecules that easily diffuse through the various coatings to yield the amperometric signal. Interference molecules, such as ascorbic acid (AA), must penetrate with difficulty the permselective membrane to be oxidised on the Pt.

Legend (top): An example of the effect of an intraperitoneal injection of ascorbate (2 g/kg) on the amperometric response of a carbon paste electrode (CPE) at 200 mV and a Pt/PPD/GOx electrode at 700 mV, implanted bilaterally in the striatum of a freely-moving rat 8 days after implantation. These results illustrate the efficient rejection of ascorbate interference by the PPD-based design. 

Legend (bottom): The response of a Pt/PPD/GOx electrode implanted in the striatum of a freely-moving fasting rat over a 10-h period, 12 days after sensor implantation.  Injection of insulin (15 U/kg) intraperitoneally caused a decrease in the level of the glucose signal that was reversed by the ingestion of food. These results illustrate the sensitivity of the Pt/PPD/GOx biosensor to brain glucose.

References:

  • Lowry J.P. and O'Neill R.D. (1994) Partial characterization in vitro of glucose oxidase-modified poly(phenylenediamine)-coated electrodes for neurochemical analysis in vivo. Electroanalysis, 6, 369-379.
  • Lowry J.P., McAteer K., El Atrash S.S., Duff A. and O'Neill R.D. (1994) Characterization of glucose oxidase-modified poly(phenylenediamine)-coated electrodes in vitro and in vivo: homogeneous interference by ascorbic acid in hydrogen peroxide detection. Anal. Chem., 66, 1754-1761.
  • Lowry J.P., O'Neill R.D., Boutelle M.G. and Fillenz M. (1998) Continuous monitoring of extracellular glucose concentrations in the striatum of freely moving rats with an implanted glucose biosensor. J. Neurochem., 70, 391-396.
  • Lowry J.P., Demestre M. and Fillenz M. (1998) Relation between cerebral blood flow and extracellular glucose in rat striatum during mild hypoxia and hyperoxia. Dev. Neurosci., 20, 52-58.
  • Lowry J.P. and Fillenz M. (2001) Real-time monitoring of brain energy metabolism in vivo using microelectrochemical sensors: the effects of anesthesia. Bioelectrochemistry, 54, 39-47.
  • Dixon B.M., Lowry J.P. and O'Neill R.D. (2002) Characterization in vitro and in vivo of the oxygen dependence of an enzyme/polymer biosensor for monitoring brain glucose. J. Neurosci. Methods, 119, 135-142.
  • McMahon C.P., Killoran S.J. and O'Neill R.D. (2005) Design variations of a polymer–enzyme composite biosensor for glucose: Enhanced analyte sensitivity without increased oxygen dependence.  J. Electroanal. Chem., 580, 193-202.