Biomedical Engineering Reference
In-Depth Information
12.1.6.3 Delivery
The present state-of-the-art includes a variety of delivery systems. At a minimum, these delivery meth-
ods need to be optimized to deal with the conflicting requirements of spatial resolution, viscosity of
bioink, efficiency of printing, and cell density. Maintaining cell suspensions in the print-reservoir to
avoid cell clumping during printing, or worse, clogging of the print nozzles, is important. Multiple
nozzles may be required for chemical cross-linking of the bioink, for delivery of different cell types,
or different ingredients in the bioink (multi-ink printing). Finally, a robust platform is needed that can
accurately control the spatial location and orientation of the print head, coordinate the delivery of the
ink, and maintain the biological integrity of the bioink.
12.2
FUTURE DIRECTIONS
It is important to demonstrate that 3D printing can recapitulate the crucial architectural features of
articular cartilage. Even more important is generating evidence that printed artificial tissue with these
appropriate features can resolve the major obstacles facing cartilage tissue engineering: integration
with host tissue and long-term function.
Discoveries in cellular biology especially in the identification and characterization of the various
stages between stem cells and progenitor status are likely to be of great significance in advancing the
field of bioprinting. Factors influencing cell differentiation including biochemical, biomechanical, and
other biophysical cues are critical in determining the fate of printed tissue.
Research in biomaterials is required to enhance printing efficiency and material properties. Other
areas worthy of attention are responsive biomaterials that release growth factors or agents that modu-
late proliferation and other cellular functions such as differentiation and matrix production.
Finally, the ultimate goal is not merely to engineer biomimetic features, but to generate tissue that
survives physiologic loading, remodels to adapt to changing conditions, and self-heals when exposed
to injury.
ACKNOWLEDGMENTS
We thank Dr. Shantanu Patil for providing knee images, and Judy Blake for manuscript formatting and copyediting.
We are grateful for the continued funding support by Donald and Darlene Shiley, and the Shaffer Family Foundation.
REFERENCES
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