Microfluidic organ-on-chip device from glass for the multiparametric measurement of islet function

Background and aims:

To increase the gain of information from perifusion experiments, a custom-made microfluidic glass chip was used as organ-on-chip device (OOC) for dynamic multi-parametric monitoring of collagenase-isolated pancreatic islets.

Methods:

Simulation of flow dynamics and measurements of quinine fluorescence were used to characterize the system. Insulin secretion of islets contained in the chip was measured by ELISA of the fractionated efflux. Oxygen consumption rate (OCR) was measured by sensors at the inlet and outlet. NAD(P)H autofluorescence and Fura-2 fluorescence ratio (cytosolic Ca2+ concentration) were measured by live cell imaging.

Results:

The OOC device had the size of a microscope slide and was made of borosilicate glass by laser ablation and thermal bonding of two layers. The inlet channel branched into 8 parallel channels, each containing 7 wells with increasing depth (50 to 500 µm). A well depth of 300 µm was sufficient to retain beads and islets. In accordance with flow simulations, this well depth permitted a sufficiently fast medium exchange. Insulin secretion in response to 30 mM glucose showed a biphasic pattern while OCR increased from 2 to 6 pmol min-1 x islet-1. Imaging of representative islets showed a concurrent increase of the NAD(P)H fluorescence. When islets were stimulated by 500µM tolbutamide the increase of the Fura ratio preceded the OCR increase.

Conclusion:

The present OOC device demonstrates that a laser fabricated well design provides adequate positioning of islets under constant supply of medium and permits simultaneous measurement of multiple cellular parameters with adequate temporal resolution.