Microchannel conductivity measurements in microchip for on line monitoring of dephosphorylation rates of organic phosphates using paramagnetic-beads linked alkaline phosphatase

This paper presents the use of polymer coated microelectrodes for the realtime conductivity monitoring in a microchannel photoablated through the polymer without contact. Based on this strategy, a small conductometry sensor has been developed to record in time conductivity variation when an enzymatic reaction occurs through the channel. The rate constant determination, k2, for the dephosphorylation of organic phosphate–alkaline phosphatase–superparamagnetic beads complex using chemically different substrates such as adenosine monoesterphosphate, adenosine diphosphate and adenosine triphosphate was taken as an example to demonstrate selectivity and sensivity of the detection scheme. The k2 value measured for each adenosine phosphate decreases from 39 to 30s−1 in proportion with the number (3, 2 and 1) of attached phosphate moiety, thus emphasizing the steric hindrance effect on kinetics. Electrical admittance spectroscopy is used for the online monitoring of the kinetics of dephosphorylation rate of biomolecules in organic phosphate-paramagnetic beads linked to alkaline phosphatase (ALP) in a flow microchannel. The key step of this study is to avoid the degradation of biological complexes from which the microelectrodes are coated with polyethylene terephthalate (5µm-PET layer) which acts as dielectric interface. Thus, the conductivity of a microchannel can be probed with indirect electrical contact through the microchannel. [Display omitted] •Microband electrodes were coated with dielectric polymer for non-contact admittance spectroscopy.•Microchannel conductivity were monitored with indirect electrical contact.•Dephosphorylation rate determination of organic phosphates illustrates selectivity and sensivity of the detection scheme.