Abstract

Contracting 3D Printed Microtissues: Solid and Fluid Instabilities

Thomas Angelini, Associate Professor, Department of Mechanical and Aerospace Engineering, University of Florida

Living cells are often dispersed in extracellular matrix (ECM) gels like collagen and Matrigel as minimal tissue models. Generally, large-scale contraction of these constructs is observed, in which the degree of contraction and compaction of the entire system correlates with cell density and ECM concentration. The freedom to perform diverse mechanical experiments on these contracting constructs is limited by the challenges of handling and supporting these delicate samples. Here, we present a method to create simple cell-ECM constructs that can be manipulated with significantly reduced experimental limitations. We 3D print mixtures of cells and ECM (collagen-I) into a 3D growth medium made from jammed microgels. With this approach, we design microtissues with controlled dimensions, composition, and material properties. We also control the elastic modulus and yield stress of the jammed microgel medium that envelops these microtissues. Similar to well-established bulk contraction assays, our 3D printed tissues contract. By contrast, the ability to create high aspect ratio objects with controlled composition and boundary conditions allows us to drive these microtissues into different regimes of physical instability. For example, a contracting tissue can be made to buckle as a whole or break up into droplets, depending on composition, size, and shape. These new instabilities may be employed in tissue engineering applications to anticipate the physical evolution of tissue constructs under the forces generated by the cells within.