In Situ Measurement of Intra-tumoral Tissue Rigidity.

Local tissue scale mechanical properties are essential for understanding cell fate and function; however, few methods to measure stiffness at this length scale exist, and applications in 3D tissues can present further challenges. To address this need, microgel-based sensors fabricated out of the thermally responsive hydrogel poly(N-isopropylacrylamide) were developed allowing internal architectures of tissues to be mapped by optically measuring microgel response when actuated in a matrix. These robust probes are widely applicable for in vitro and in vivo studies of tissue mechanics providing tissues can be fluorescently imaged. Here we describe the fabrication of these thermally responsive hydrogel sensors, calibration of the microgels using phantom tissues, and image processing techniques used to make the measurements.