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REVIEW ARTICLE

Smart hydrogels for 3D bioprinting

*
Shuai Wang, Jia Min Lee and Wai Yee Yeong
Singapore Centre for 3D Printing, Nanyang Technological University, Singapore 6397798

Abstract: Hydrogels are 3D networks that have a high water content. They have been widely used as cell carriers and
scaffolds in tissue engineering due to their structural similarities to the natural extracellular matrix. Among these,
“Smart” hydrogels refer to a group of hydrogels that is responsive to various external stimuli such as pH, temperature,
light, electric, and magnetic field. Combining the potential of 3D printing and smart hydrogels is an exciting new para-
digm in the fabrication of a functional 3D tissue. In this article, we provide a state-of-the-art review on smart hydrogels
and bioprinting. We identify the critical material properties needed for the most commonly used bioprinting techniques,
namely extrusion-based, inkjet-based, and laser-based techniques. The latest progress in different smart hydrogel sys-
tems and their applications in bioprinting are presented. The challenges of printing these hydrogel systems are also
highlighted. Lastly, we present the potentials and the future perspectives of smart hydrogels in 3D bioprinting.
Keywords: hydrogel, bioprinting, 3D printing, addictive manufacturing, rapid prototyping, tissue engineering

*Correspondence to: Wai Yee Yeong, Singapore Centre for 3D Printing, Nanyang Technological University, Singapore 6397798;
Email: wyyeong@ntu.edu.sg

Received: May 20, 2015; Accepted: June 19, 2015; Published Online: July 2, 2015
Citation: Wang S, Lee J M and Yeong W Y, 2015, Smart hydrogels for 3D bioprinting. International Journal of Bioprinting, vol.1(1):
3–14. http://dx.doi.org/10.18063/IJB.2015.01.005.

Smart hydrogels are 3D high water content matrix-
1. Introduction es that are able to respond to various environmental
W factors such as pH, ionic strength, temperature, light,
ith the hope of solving the shortage of
transplantable organs, 3D bioprinting has
electric, and magnetic field. Over the years, they have
gained much attention due to its potential
in tissue engineering. This technology represents the become especially appealing for biomedical applica-
[13–17]
. The main advantages of smart hydrogels
tions
bottom up process in which biological materials are: (i) High water content mimics natural tissue en-
and/or cells are patterned and assembled into comput- vironment and promotes more efficient mass trans-
er-designed two-dimensional (2D) or three-dimen- portation. (ii) In comparison to the traditional hydro-
[1]
sional (3D) organizations . 3D bioprinting brings gels, smart hydrogels possess unique characteristics
new approaches in addressing traditional tissue engi- such as controllable sol-gel transition, or shape mem-
neering issues such as the lack of a controlled and [18–21]
functional histoarchitecture [2–5] . For example, pa- ory, or self-healing .
Combining the potential of 3D printing and smart
tient-specific bone grafts with well-defined shapes and hydrogels is an exciting new paradigm in bioprinting
internal structures can be constructed using the 3D of functional 3D tissues. In this review, we provide a
bioprinting and medical imaging techniques [6–8] . Some state-of-the-art review on smart hydrogels and bio-
applications of 3D bioprinting include stem cell re- printing. We identify the critical material properties
[9]
search , cancer model [10] , drug testing [11] , and tissue needed for the most commonly-used bioprinting tech-
model [12] . niques, namely extrusion-based, inkjet-based, and la-

Smart hydrogels for 3D bioprinting. © 2015 Shuai Wang, et al. This is an Open Access article distributed under the terms of the Creative Commons
Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/), permitting all non-commercial use, distribu-
tion, and reproduction in any medium, provided the original work is properly cited.
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