3, Georgia Institute of Technology, Atlanta, Georgia, United States
2, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
6, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
7, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
4, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
5, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
The integration of engineered living cells with3D printed soft scaffolds can enable the fabrication of biological machines for soft robotics and tissue engineering. The realization of these biological machines and their sub-components will require a number of suitable cell sources, biomaterials, and enabling technologies. Here, we review our group’s recent efforts towards understanding the lifetime and degradation mechanisms in these centimeter scale biohybrid devices and also to develop new strategies to enable healing from mechanical damage in these devices. We fabricated locomotive ‘‘bio-bots’’ using a 3D printer with hydrogel powered by a muscle strip composed of differentiated skeletal myofibers in a matrix of natural proteins, including fibrin, that provide physical support and cues to the cells as an engineered basement membrane. Firstly, we examined the life expectancy, breakdown, and device failure of engineered skeletal muscle bio-bots as a result of degradation by three classes of proteases: plasmin, cathepsin L, and matrix metalloproteinases. We demonstrated the use of gelatin zymography to determine the effects of differentiation and inhibitor concentration on protease expression. These results could also prove useful for design the next generation of complex biological machines with controllable function, specific life expectancy and greater consistency in other tissue engineering applications. Secondly, we examined the underlying mechanisms of mechanical damage as a cause of skeletal muscle loss of function in vitro and demonstrated a healing strategy to counteract this damage. We believe that understanding and exploiting the adaptive response behaviors inherent within cellular systems is a crucial step forward in designing bio-hybrid machines that are broadly applicable to grand engineering challenges.