ORGAN PRINTING - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 324

CHAPTER

15

ORGAN PRINTING

Robert C. Chang and Filippos Tourlomousis
Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, USA

15.1 INTRODUCTION
Our enhanced understanding of the fundamental biological sciences, primarily the interplay between
biological cells and integrative biological, chemical, and structural cues within the in vivo milieu or
natural three-dimensional (3D) microenvironment, demands a defined role for engineering design and
manufacturing to meet the challenges presented by increasingly complex biological problems. Organ
printing in tissue engineering is the application of additive, computer-aided manufacturing process
technologies toward the layered, patterned deposition of complex 3D cell-bearing biological struc-
tures with biomolecular and biopolymer material integration. Organ printing therefore encapsulates an
ever-expanding range of enabling bioadditive manufacturing processes and strategies that show great
promise in regenerative medicine applications where novel fabrication, in conjunction with rapidly
evolving stem cell technologies, is envisioned to address the challenge of limited donor grafts for
functional organ repair and replacement.
The term organ printing has previously been more narrowly defined as “a biomedical variant of
rapid prototyping technology or computer-aided robotic layer-by-layer additive biofabrication of
3D human tissues and organs using self-assembling tissue spheroids as building blocks ( Mironov
et al., 2003 ; Mironov et al., 2008 ; Mironov et al., 2009 ; Mironov et al., 2011 ).” Such a definition is
rooted in developmental biology principles in which the self-assembly process refers to “one in which
humans are not actively involved, in which atoms, molecules, aggregates of molecules, and compo-
nents arrange themselves into ordered functioning entities without human intervention ( Whitesides
and Grzybowski, 2002 ).” Accordingly, the raw material or tissue spheroid “bioink” for bioprinting is
initially preprocessed by achieving high-density cell aggregates via traditional hanging drop meth-
ods, high-throughput digital microfluidics, and other scalable fabrication methods of tissue spheroids
with self-organizing properties ( Rezendea et al., 2013 ). More broadly defined in the context of tissue
engineering, the autonomous organization of biological entities along the continuum of biological
scales can be described conceptually as man kick-starting nature's mechanism of constructing an in-
nately coordinated system whereby “people may design the process, and they may launch it, but once
underway, it proceeds according to its own internal plan, either toward an energetically stable form or
toward some system whose form and function are encoded in its individual parts ( Whitesides, 1995 ).”
Therefore, given the significant insight we've gained in systematically engineering cell-instructive