Stretchable 3D cell laden hydrogel microarray platforms for combinatorial screening of cell mechanoresponses

Cells in vivo are constantly subjected to multiple microenvironmental mechanical stimuli that regulate cell function. Although two-dimensional (2D) cell responses to the mechanical stimulation have been established; these methods lack relevance as physiological cell microenvironments are in three dimensions (3D). Moreover, the existing platforms developed for studying the cell responses to mechanical cues in 3D either offer low throughput, involve complex fabrication, or do not allow the combinatorial analysis of multiple cues. Considering this, a stretchable high-throughput (HT) 3D gelatin methacryloyl (GelMA) microarray platform is presented that can apply dynamic mechanical strain to cells encapsulated in arrayed 3D microgels. The platform uses bioprinting methods such as inkjet and stereolithography (SLA) techniques for printing cell-laden GelMA microgel array on an elastic composite substrate that isperiodically stretched. The developed platform is highly biocompatible and transfers the applied strain fromthe stretched substrate to the cells. The HT analysis is conducted to analyze cell mechano-responsesthroughout the printed microgel array. Also, different GelMA microenvironmental stiffnesses is providedin addition to the dynamic stretch by inkjet bioprinting different GelMA hydrogel concentrations on thesame substrate for the combinatorial analysis of distinct cell behaviors. The composite substrate of thedeveloped platform is also improved to make its surface cell adhesive hence allowing the platform suitablefor either 2D, 3D, 2D/3D co-culture cell stretching studies or stretchable microfluidics. The improvedsubstrate is combined with the SLA bioprinting process to print cell-laden GelMA hydrogels with various shapes/geometries for the combinatorial screening of the cell mechanoresponses to both 3D geometry anddynamic stretch. Considering its throughput and flexibility, the developed platform can readily be scaledup to introduce a wide range of microenvironmental cues and to screen the cell responses in a HT way.

A flat-ended cylindrical probe affixed to avertical axis micromechanical testing machine (Mach-1 v500c, Biomomentum Inc., Montreal, QC, Canada)was used to record the force-displacement plots for the hydrogels (diameter = 5 mm). The contacting endof the probe was submerged in DPBS and applied a 10-20% strain on the hydrogel.