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Nano and Micro Technologies

Nano and Micro Technologies - Poster Session D

Poster Y16 - A MICROFLUIDIC METHOD FOR CELL TRAPPING AND PAIRING TOWARDS MECHANOBIOLOGY STUDIES

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Microfluidics enables precise manipulation of fluids at the microscale to study how single cells respond to mechanical cues. These devices facilitate cell trapping, pairing, and manipulation, providing a platform for high-throughput analysis of cellular biomechanics. Here, we present a novel method for trapping single cells and forming cell pairs for mechanobiological studies. Our method is based on a modified version of the bypass-channel trapping method [1,2]. This method relies on a trapping site with a lower flow resistance channel to capture a single particle and a bypass channel with greater flow resistance to divert flow away once the trap site is occupied. Initially, colloidal particles flow through the trap site due to its low resistance, resulting in particle confinement aided by fluid flow and physical constriction. The constriction point, located in the middle of the main channel, temporarily retains cells or particles through hydrodynamic forces. Once occupied, additional particles preferentially flow through the bypass channel

Materials and

Methods:  We modified the bypass-channel trapping method to trap and pair particles/cells (Fig. 1a-b). Trap sites with a capture cup and constriction are positioned between two channels. Particles first follow the low-resistance middle channel into the capture cup; subsequent particles are directed into the capture cup by the flow into the bypass channels until both channels are blocked, diverting flow away. In contrast to previous bypass channel designs, we incorporated the bypass channel within the capture cup [1,3-6], facilitating sequential capture and pairing of particles.
We fabricated trap sites to capture of a pair of cells and particles. The width and depth of the capture cup were 16 and 32 µm, respectively, while the middle channel and bypass channels were 4 and 5 µm wide. We also used valves to direct the flow direction and facilitate trapping. This flow direction is illustrated in Figure 1a-b. The green arrows indicate the flow direction, and the red lines indicate the closed outlets. Initially, the device is primed by opening Inlet 1 and Outlet 1, allowing fluid without particles to flow through. For complete priming, all outlets (Outlet 1, Outlet 2, and Outlet 3) can be opened to fill the channels with fluid. Following priming, particles are introduced by closing Outlet 1 and Outlet 3, forcing them through the trapping site one by one (Fig 1a-b). 15 µm polystyrene beads were sequentially confined at the capture cup (Fig. 2).

Results, Conclusions, and Discussions: The first bead was captured at the bottom of the capture cup, followed by the recruitment of an additional bead facilitated by the bypass channels (Fig 2b). The beads were suspended in an aqueous solution with a viscosity of 1.76 cP, and at a concentration of 1000 beads/mL. The bead solution was introduced at 10 µL/hr. Using smaller beads increased the number of captured particles (Fig 2d), suggesting that capture cup design should consider particle size for efficient particle trapping and pairing. We further captured pairs of U87 cells (12-15 µm) at the capture cups (Fig. 3). Figure 3a and 3b demonstrates sequential capture of the first and the second cell respectively. As cells deform and squeeze into the trap channels, capture of the second cell pushes the first into the channel (Fig 3b). In addition, we designed and fabricated a microfluidic device with an array of capture cups capable of generating an array of particle/cell pairs (Fig. 4). The device allows for the controlled capture and release of particles or cells in a predetermined order, enabling sequential capture of particles.
Our work differs from previous studies by positioning particles to face the flow within the channel, unlike U-shaped traps, and allowing force application using fluid flow. Unlike previously reported methods [7], our approach facilitates cell pairing while isolating one cell from the main flow, exposing only one cell pair to the main flow. This method allows one cell to be exposed to the outer channel while the other is shielded, facilitating the study of intercellular force transduction. It enables researchers to investigate cellular responses to various forces, such as shear stress and compression and provides insights into cellular biomechanics and communication.

Acknowledgements (Optional):