Nina Lokar

The development and characterization of a microfluidic electrochemical glucose biosensor are presented herein. The transducer part is based on thin-film metal electrodes on a glass substrate. The biological recognition element of the biosensor is the pyrroloquinoline quinone–glucose dehydrogenase (PQQ-GdhB) enzyme, selectively in situ immobilized via microcontact printing of a mixed self-assembling monolayer (SAM) on a gold working electrode, while the microfluidic part of the device comprises microchannel and microfluidic connections formed in a polydimethylsiloxane (PDMS) elastomer. The electrode properties throughout all steps of biosensor construction and the biosensor response to glucose concentration and analyte flow rate were characterized by cyclic voltammetry and chronoamperometry. A measurement range of up to 10 mM in glucose concentration with a linear range up to 200 μM was determined. A detection limit of 30 µM in glucose concentration was obtained. Respective biosensor sensitivities of 0.79 nA/µM/mm² and 0.61 nA/µM/mm² were estimated with and without a flow at 20 µL/min. The developed approach of in situ enzyme immobilization can find a wide number of applications in the development of microfluidic biosensors, offering a path towards continuous and time-independent detection.

Cholinesterase inhibitors are widely used as pesticides, as chemical warfare agents and as drugs to treat symptoms of Alzheimer’s disease. Therefore, it is a high need to develop methods for their detection which are fast, sensitive, and reliable. This paper reports a preliminary work in the development of an electrochemical biosensor based on acetylcholinesterase (AChE) which is constructed by immobilization layers – cysteamine/glutaraldehyde/AChE on thin layer gold electrode for detection of cholinesterase inhibitors. Eserine (physostigmine) was used as a test inhibitor. The enzyme immobilization efficacy was evaluated by measuring activity of immobilized enzyme via Ellman’s method. The enzyme activity of the initial reduction of 33% in five days remained after that stable for at least one week. Chronoamperometric response to substrate acetylthiocholine chloride (ATCl) was assumed to follow Michaelis-Menten kinetics. After exposure biosensor to 25 mM eserine for 10 min, 70% inhibition of enzyme was detected. Reactivation factor of inhibited AChE was determined as 0.016 min-1.