Further In-vitro Characterization of an Implantable Biosensor for Ethanol Monitoring in the Brain

Abstract

Ethyl alcohol may be considered one of the most widespread central nervous system (CNS) depressants in Western countries. Because of its toxicological and neurobiological implications, the detection of ethanol in brain extracellular fluid (ECF) is of great importance. In a previous study, we described the development and characterization of an implantable biosensor successfully used for the real-time detection of ethanol in the brain of freely-moving rats. The implanted biosensor, integrated in a low-cost telemetry system, was demonstrated to be a reliable device for the short-time monitoring of exogenous ethanol in brain ECF. In this paper we describe a further in-vitro characterization of the above-mentioned biosensor in terms of oxygen, pH and temperature dependence in order to complete its validation. With the aim of enhancing ethanol biosensor performance, different enzyme loadings were investigated in terms of apparent ethanol Michaelis-Menten kinetic parameters, viz. IMAX, KM and linear region slope, as well as ascorbic acid interference shielding. The responses of biosensors were studied over a period of 28 days. The overall findings of the present study confirm the original biosensor configuration to be the best of those investigated for in-vivo applications up to one week after implantation.

Characterization of Biosensors Based on Recombinant Glutamate Oxidase: Comparison of Crosslinking Agents in Terms of Enzyme Loading and Efficiency Parameters

“…At these potentials, however, endogenous reducing agents, such as ascorbic acid (AA), which is present in high concentrations in most biological tissues and fluids, can give rise to false positive biosensor responses in vivo . A permselective barrier is therefore essential in the design of implantable biosensors, and a range of electro-deposited poly-phenylenediamines [30,31,32,33,34,35] and polyphenols [36,37,38,39] have been developed to improve biosensor selectivity for brain monitoring where ECF ascorbate levels are particularly high (up to 1 mM) [40,41]. …”

A New Perspective on Using Glycols in Glutamate Biosensor Design: From Stabilizing Agents to a New Containment Net

“…Hydrogen peroxide (H 2 O 2 ), which is generated during the enzymatic reaction, is measured on a platinum (Pt) surface when an anodic potential of +0.7 V vs. Ag/AgCl is applied [29][30][31][32]. The current generated from H 2 O 2 oxidation is proportional to the glutamate concentration in the matrix.…”

Direct monitoring of ethanol in the brain

“…Indeed, the time course of brain ethanol concentrations is affected by several aspects, including both the ethanol dose and path of administration 9 . amperometrically detectable by a transducer 11,12 .…”

“…The selected biosensor design has been developed to obtain the best working conditions, especially in terms of working pH, temperature 12 , sensitivity and shielding against the main interfering electroactive Figure 2: Schematic functioning of an implantable biosensor loading the AOx enzyme. Ethanol is selectively converted into H 2 O 2 , which is directly oxidized through the application of an anodic potential of +700 mV vs. Ag/AgCl.…”

“…Magnetic resonance spectroscopy MRS is a non-invasive analytical technique that has been used to study metabolic changes in several Recently, an amperometric biosensor for direct ethanol monitoring in the brain has been developed 11,12 .…”