Jammed Microgel-Based Inks for 3D Printing of Complex Structures Transformable via pH/Temperature Variations.

Structure changes mediated by anisotropic volume changes of stimuli-responsive hydrogels are useful for many research fields, yet relatively simple structured objects are mostly used due to limitation in fabrication methods. To fabricate complex 3 dimensional (3D) structures that undergo structure changes in response to external stimuli, jammed microgel-based inks containing precursors of stimuli-responsive hydrogels are developed for extrusion-based 3D printing. Specifically, the jammed microgel-based inks are prepared by absorbing precursors of poly(acrylic acid) or poly(N-isopropylacrylamide) in poly(acrylamide) (PAAm) microgels, and jamming them. The inks exhibit shear-thinning and self-healing properties that allow extrusion of the inks through a nozzle and rapid stabilization after printing. Stimuli-mediated volume changes are observed for the extruded structures when they are post-crosslinked by UV light to form interpenetrating networks of PAAm microgels and stimuli-responsive hydrogels. Using this method, a dumbbell-shaped object that can transform to a biconvex shape, and a gripper that can grasp and lift an object in response to stimuli are 3D-printed. The jammed microgel-based 3D printing strategy is a versatile method useful for variety of applications as diverse types of monomers absorbable in the microgels can be used to fabricate complex 3D objects transformable by external stimuli.

Fabrication of 2D and 3D Cell Cluster Arrays Using a Cell-Friendly Photoresist.

Cells in 3D behave differently than cells in 2D. We develop a new method for the fabrication of 2D and 3D cell cluster arrays on an identical substrate using a cell-friendly photoresist, which enables comparative study between cells in 2D and 3D cell clusters. The fabricated cell cluster arrays maintain their structure up to 3 days with good viability. Using this method, 2D and 3D cancer cell clusters with comparable sizes are fabricated, and natural killer (NK) cell cytotoxicity assays are performed to assess how dimensionality of cancer cell clusters influence their susceptibility to immune cell-mediated killing.

A multilayered blood vessel/tumor tissue chip to investigate T cell infiltration into solid tumor tissues.

Cancer immunotherapies based on the ability of T cells to recognize and kill tumor cells (TCs), including immune checkpoint blockade (ICB) therapy and chimeric antigen receptor (CAR) T cell therapy, have been greatly successful recently, but they are applicable for only a fraction of patients. One of the main challenges in cancer immunotherapy is the improvement of T cell infiltration into solid tumor tissues, as T cells can exert cytotoxicity against TCs only when they are in contact with TCs. T cells in the bloodstream infiltrate into solid tumor tissues by following two steps known as extravasation and interstitial migration. Herein, we developed a multilayered blood vessel/tumor tissue chip (MBTC) that allows systematic investigation on T cell tumor infiltration. The MBTC is composed of a top fluidic chamber, a porous membrane covered with an endothelial cell (EC) monolayer, and a collagen gel block encapsulating TCs. The full sequence of T cell tumor infiltration, including extravasation and interstitial migration, required for TC killing is demonstrated in the MBTCs: T cells applied through the top fluidic chamber of the MBTCs exhibited dynamic interactions with ECs for extravasation, including intraluminal crawling and transendothelial migration (TEM). After extravasation, T cells migrate toward TCs located at the bottom of a collagen block to kill them. Key characteristics of T cell dynamics in tumor microenvironments are recapitulated in the MBTCs: the vascular endothelial growth factor (VEGF) produced by TCs suppressed EC activation by inflammatory cytokines, or induced EC anergy, thereby significantly reducing T cell extravasation, whereas chemokines produced by TCs triggered T cell chemotaxis toward TCs. Anti-VEGF treatment in the MBTCs reverts EC anergy and promotes T cell infiltration, similar to the clinical effects of anti-VEGF. The MBTC is a useful model for pre-clinical evaluation of immunotherapeutics and the fundamental study of tumor immunology.