Three Dimensional Biomimetic Platforms for Cell Interactions

Abstract

Traditional investigation of natural killer (NK) cells' immune response on target cells is based on bulk culture and group interaction, leaving the process of single cell interaction not well understood. We developed a three dimensional platform with various innovative patterns, including micro-wells that confine single cells inside and micro-channels that guide NK cells to migrate for interaction. The resolution of 3D printing was too limited to fabricate micro-platforms and its material’s fluorescent emission would interfere with cell observation. Polydimethylsiloxane (PDMS) platform was made based on inductively coupled plasma (ICP) etched Si molds or SU8 molds. Double replication of PDMS was needed for SU8 molds due to the polarization change with SU8 being a negative resist. 7.5 μm undercut on each side of the 35 μm deep ICP etched Si wells was achieved by tuning the etch conditions. Target cell (U2OS cell line) seeding tests on 50 μm x 50 μm x 35 μm wells and 100 μm x 100 μm x 35 μm wells were completed. More cells resided in the larger wells. Small wells restrained the cell growth as U2OS cells typically are 70-80 μm long. Bright-field images of cells on the platforms were clear but fluorescent images were smeared due to fluorescence scattering through PDMS. Thin (~100 μm) PDMS platforms with deep (>50 μm) structures are expected to provide better image quality and cell confinement.