Evaluation of Hydrogel-Coated Glutamate Microsensors

Abstract

Glutamate microsensors form a promising analytical tool for monitoring neuronally derived glutamate directly in the brain. However, when a microsensor is implanted in brain tissue, many factors can diminish its performance. Consequently, a thorough characterization and evaluation of a microsensor is required concerning all factors that may possibly be encountered in vivo. The present report deals with the validation of a hydrogel-coated glutamate microsensor. This microsensor is constructed by coating a carbon fiber electrode (10-microm diameter; 300-500 microm long) with a five-component redox hydrogel, in which L-glutamate oxidase, horseradish peroxidase, and ascorbate oxidase are wired via poly(ethylene glycol) diglycidyl ether to an osmium-containing redox polymer. A thin Nafion coating completes the construction. Although this microsensor was previously used in vivo, information concerning its validation is limited. In the present study, attention was given to its selectivity, specificity, calibration, oxygen dependency, biofouling, operating potential dependency, and linear range. In addition, successful microsensor experiments in microdialysate, in vitro (in organotypic hippocampal slice cultures), and in vivo (in anesthesized rats) are shown.

Development and characterization in vitro of a catalase-based biosensor for hydrogen peroxide monitoring

“…The sensitivity of design 6 was slightly less in the presence of 400 M AA (∼20%) than in PBS alone, but the difference was not significant (p > 0.8, paired t-test, n = 6). This modest decrease in the H 2 O 2 signal caused by large excesses of AA is similar to that reported for redox hydrogel-based biosensors (Mitala and Michael, 2006;Oldenziel et al, 2006). Since it is not possible at present to determine absolute ECF levels of an analyte using in situ electrochemical techniques, these sensors are designed to monitor continuous changes in H 2 O 2 concentrations.…”

“…Designs 4-9 all included Nafion ® , a perfluorinated polymer that has been used previously in sensors to block AA interference (Brown and Lowry, 2003;Gerhardt and Hoffman, 2001;Oldenziel et al, 2006). A layer of Nafion ® alone over CAT yielded a high sensitivity H 2 O 2 biosensor (design 4, 0.31 ± 0.04 nA/M, n = 4), while a layer of Nafion ® and PPD-BSA over CAT (design 5) yielded a biosensor with no significant H 2 O 2 response (p = 0.4, n = 3 unpaired t-test).…”

Enzyme-Based Electrochemical Glutamate Biosensors

“…By incorporating a redox mediator, it is possible to lower the potential required for the H 2 O 2 oxidation, thereby further limiting interference in complex biological samples by other species present, such as ascorbic acid or uric acid, which may also be redox active at the higher detection potential. Commonly used redox mediators in enzymatic biosensors include ferrocyanide [12], ferrocene and ferrocene derivatives [52][53][54], osmium complexes [55], quinine derivatives, and hexacyanoferrates, such as Prussian blue [45,56,57] and Ruthenium purple [58]. Prussian blue is the oldest coordination compound and was serendipitously discovered by Diesbach, an artist in 1704.…”

Using electropolymerization based doping for electro-addressable functionalization of a multielectrode array probe for nucleic acid detection

“…Carbon fiber based microelectrodes are commonly used for local and highly sensitive detection of neurotransmitters such as dopamine or recording of neuronal action potentials known as spikes, enabling electrochemical monitoring of neurochemical activity of brain [10][11][12][13] . In addition to being used in such measurements, CFEs have also been used for detection of biologically important molecules with great sensitivity and selectivity by simply modifying the surface of the electrode with a bio-recognition molecule [14][15][16][17] . To the best our knowledge this is the first study to use a probe-type microelectrode array for nucleic acid detection.…”