401 Development of a microfluidic-based array for large-scale ordering, high-throughput screen and high resolution imaging of islets
Tuesday November 17, 2015 from 07:00 to 08:00
Room 110

Yong Wang MD, United States

Assistant Professor

Department of Surgery

Unviersity of Illinois at Chicago


Development of a microfluidic-based array for large-scale ordering, high throughput screen and high resolution imaging of islets

Yong Wang1, Mohammad Nourmohammadzadeh1, Yuan Xing1, Joshua Elias1, Jose Oberholzer1.

1Department of Surgery, University of Illinois at Chicago, Chicago, IL, United States

Introduction: Dynamic investigation of individual islet is crucial for diabetes investigation. Many microarray have been developed for cells, but limited in throughput, implementation, and operator-dependence. Dielectric forces damage cells due to heat and passive capturing allows only 60% capturing efficiency [1,2]. To address this for islets, we designed a microarray for high-density capturing, stimulation, and high resolution imaging of islet.

Theory and Design: This microarray has two stages of design (Figure 1). Since islets have varying sizes(50-350 μm), first stage was designed to use inertial focusing to laterally align islets in non-symmetric serpentine channel before trapper (Figure 1).Second stage is islet-trapping array based on hydrodynamic principle [1]: square-wave loop channels superimposed into 5 straight channels/loop channel (Figure 1). An array of U-cup (300 μm/diameter and 300 μm/depth) along straight channel is for trapping islets.  There is an exit aperture (50 μm/width), referring as  straight channel, at apex of U-cup . When flow carries islet to junction between U-cup and loop channel, flow encounters less resistance in straight channel through unoccupied cup. As islet trapped, resistance is increased in straight channel and flow is redirected into loop channel and flow then carries islets toward next trap.

Results and Discussion: Flow Dynamics: With flow rate of 100 μL/min at inlet and pressure of 0 Pa at outlet, COMSOL simulation showed that the highest flow velocity was located in immobilization site with a decrease flow velocity from trapping site to loop channel. Close-up view (Figure 1A) showed a partially diverted liquid into immobilization site generated allowing particle to flow toward trapper. When a particle occupies U-cup, it increases flow resistance allowing flow to bypass U-cup and directing flow into loop channels.

Trapping Efficiency: Arraying through hydrodynamic fluidic resistance is highly reliable and efficient [2]. Our design was based on the same principle. As shown Figure 1, trapping efficiency of glass beads was dependent on geometry dimension based on flow rate and resistance (Qstraight/Qtrap). With Qstraight/Qtrap: 2.8, there is 99% trapping efficiency. As shown in Figure 1B, islets were precisely positioned without deformation, suggesting minimum shear stress on islets.
Islet Responses to Secretagogues: To verify large scale ordering and high throughput screening capabilities of islets array we tested the device with 100 islets. Islets were loaded into device in 60 seconds using gravity with applying minimum shear stress.  Islets showed heterogeneous [Ca2+]i with average change of 105.82% ± 1.51 in response to 25 mM glucose and a mean change of 110.09% ± 2.44 in response to 30 mM KCL (Figure 1C).

Conclusion: This microarray is capable of trapping hundreds of islets on a 4 cm2 footprint in 60 s, with of 99% capturing efficiency. The optimized focusing and geometry allow for easy and robust islet manipulation and stimulation, and could provide detailed spatiotemporal information of individual islets response to secretagogues. It can serve as a screening tool for therapeutics. 


[1] Tan WH1, Takeuchi S. A trap-and-release integrated microfluidic system for dynamic microarray applications. Proc Natl Acad Sci U S A. 2007 Jan 23;104(4):1146-51. Epub 2007 Jan 16.
[2] Nourmohammadzadeh M, Lo JF, Bochenek M, Mendoza-Elias JE, Wang Q, Li Z, Zeng L, Qi M, Eddington DT, Oberholzer J, Wang Y. Microfluidic array with integrated oxygenation control for real-time live-cell imaging: effect of hypoxia on physiology of microencapsulated pancreatic islets. Anal Chem. 2013 Dec 3;85(23):11240-9. doi: 10.1021/ac401297v. Epub 2013 Nov 15.

© 2018 Melbourne2015