A Multi-Parametric Islet Perifusion System within a Microfluidic Perifusion Device

Summary

A microfluidic islet perifusion device was developed for the assessment of dynamic insulin secretion of multiple islets and simultaneous fluorescence imaging of calcium influx and mitochondrial potential changes.

Abstract

A microfluidic islet perifusion device was developed for the assessment of dynamic insulin secretion of multiple islets and simultaneous fluorescence imaging of calcium influx and mitochondrial potential changes. The device consists of three layers: first layer contains an array of microscale wells (500 μm diameter and 150 μm depth) that help to immobilize the islets while exposed to flow and maximize the exposed surface area of the islets; the second layer contains a circular perifusion chamber (3 mm deep, 7 mm diameter); and the third layer contains an inlet-mixing channel that fans out before injection into the perifusion chamber (2 mm in width, 19 mm in length, and 500 μm in height) for optimizing the mixing efficiency prior to entering the perifusion chamber. The creation of various glucose gradients including a linear, bell shape, and square shapes also can be created in the microfluidic perifusion network and is demonstrated.

Protocol

A. Microfabrication of 3-layer microfluidic perifusion device

Bottom Well Master Protocol (150 μm deep wells)

1. Clean the wafer using a razor blade if needed. Clean with Acetone, Methanol, and IPA. Perform plasma treatment at 50 Watts for 30 s.
2. Spin SU8-100 @ 2000 rpm. [Step 1: 500 rpm, 10 s, 100 rpm/s, Step 2: 2000 rpm, 30 s, 300 rpm/s].
   [NOTE: do not hold the wafer with tweezers after spinning SU8]
3. Soft bake the wafer at 65 °C for 20 min and at 95 °C for 50 min.
4. The wafer is exposed to UV light through a desired mask. Dose for 150 μm height is 650 mJ/cm².
5. Post expo....

Discussion

Traditional islet perifusion systems (macroscale and microscale) have some limitations including complex of setup and design, high technical requirements, and difficulty to create user-prescribed chemical gradients in the system. The microfluidic perifusion system described here overcomes these limitations with simple geometry of design and fabrication. More important, this system can be integrated with fluorescence imaging approach that provide as a unique tool to study islet physiology. The system demonstrated with hig.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
60ml Syringes	BD Biosciences
Fura-2 fluorescence dye	Molecular Probes, Life Technologies
Rhodamine123 Fluorescence dye	Molecular Probes, Life Technologies
Glucose	Sigma-Aldrich
Bovine Serum Albumin	Sigma-Aldrich
30" Silicone tubings	Cole-Parmer		1/16 x 1/8in
1.5ml Eppendorf tubes	Fisher Scientific
Y-connectors	Cole-Parmer		1/16” & 4mm
Syringe connectors	Cole-Parmer		female luer plug 1/16”
Straight connectors	Cole-Parmer		1/16”
Elbow connector	Cole-Parmer		1/16”
Havard syringe pump	Harvard Apparatus
Perifusion device
Hot plate	PMC
Thermometer	Omega Engineering, Inc.
Fraction collector	Gibson
Pippettor	Fisher Scientific
Inverted epiflorescence microscope	Olympus Corporation	IX71
Charge-coupled device	QImaging		Retiga-SRV, Fast 1394