Abstract
The feasibility of light-addressed detection and manipulation of pH gradients inside an electrochemical microfluidic cell was studied. Local pH changes, induced by a light-addressable electrode (LAE), were detected using a light-addressable potentiometric sensor (LAPS) with different measurement modes representing an actuator-sensor system. Biosensor functionality was examined depending on locally induced pH gradients with the help of the model enzyme penicillinase, which had been immobilized in the microfluidic channel. The surface morphology of the LAE and enzyme-functionalized LAPS was studied by scanning electron microscopy. Furthermore, the penicillin sensitivity of the LAPS inside the microfluidic channel was determined with regard to the analyte’s pH influence on the enzymatic reaction rate. In a final experiment, the LAE-controlled pH inhibition of the enzyme activity was monitored by the LAPS.
Highlights
Lab-on-a-chip systems, microfluidic bioreactors and organ-on-chip platforms with integrated sensors and actuators for the monitoring of crucial parameters are of great interest to maintain micro-environmental conditions [1,2,3]
To characterize the surface morphology of the fabricated TiO2 and the enzymemodified Si3N4, scanning electron microscopy (SEM) images were taken with a Schottky field-emission microscope (JSM-7800F, JEOL GmbH, Freising, Germany)
A light-addressable electrode (LAE)/microfluidic foil/light-addressable potentiometric sensor (LAPS) sandwich structure was utilized for the detection and manipulation of pH gradients inside a microfluidic system
Summary
Lab-on-a-chip systems, microfluidic bioreactors and organ-on-chip platforms with integrated sensors and actuators for the monitoring of crucial parameters (e.g., flow rate, temperature and pH) are of great interest to maintain micro-environmental conditions [1,2,3]. On the other hand, inducing perturbations of these parameters leads to new perceptions of such systems, e.g., by changing the extracellular pH during cell culturing [4,5,6,7]. Due to geometrical restrictions inside microfluidic channels, the flexible integration of “conventional” sensing devices is not easy to accomplish [1]. Actuation functionalities should be flexible as well, enabling manipulation of e.g., local pH changes without affecting neighboring elements. A precise addressability of both the actuator (here, a light-addressable electrode, LAE) and the sensor (here, a light-addressable potentiometric sensor, LAPS) is required
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