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RESEARCH ARTICLE

Formation of cell spheroids using Standing Surface

Acoustic Wave (SSAW)

*
Yannapol Sriphutkiat, Surasak Kasetsirikul, Yufeng Zhou
Singapore Centre for 3D Printing (SC3DP), School of Mechanical and Aerospace Engineering, Nanyang Technological
University, Singapore

Abstract: 3D bioprinting becomes one of the popular approaches in the tissue engineering. In this emerging application,
bioink is crucial for fabrication and functionality of constructed tissue. The use of cell spheroids as bioink can enhance
the cell-cell interaction and subsequently the growth and differentiation of cells in the 3D printed construct with the
minimum amount of other biomaterials. However, the conventional methods of preparing the cell spheroids have
several limitations, such as long culture time, low-throughput, and medium modification. In this study, the formation of
cell spheroids by SSAW was evaluated both numerically and experimentally in order to overcome the aforementioned
limitations. The effects of excitation frequencies on the cell accumulation time, diameter of the formed cell spheroids,
and subsequently, the growth and viability of cell spheroids in the culture medium over time were studied. Using the
high-frequency (23.8 MHz) excitation, cell accumulation time to the pressure nodes could be reduced in comparison to
that of the low-frequency (10.4 MHz) excitation, but in a smaller spheroid size. SSAW excitation at both frequencies
does not affect the cell viability up to 7 days, > 90% with no statistical difference compared with the control group. In
summary, SSAW can effectively prepare the cell spheroids as bioink for the future 3D bioprinting and various
biotechnology applications (e.g., pharmaceutical drug screening and tissue engineering).
Keywords: standing surface acoustic wave (SSAW); cell spheroid; cell viability; bioink; interdigital transducer (IDT)

*Correspondence to: Yufeng Zhou, Singapore Centre for 3D Printing (SC3DP), School of Mechanical and Aerospace Engineering, Nanyang
Technological University, 50 Nanyang Ave, 639798, Singapore; Email: yfzhou@ntu.edu.sg

Received: November 28, 2017; Accepted: December 14, 2017; Published Online: January 17, 2017
Citation: Sriphutkiat Y, Kasetsirikul S, Zhou Y F, 2018, Formation of cell spheroids using Standing Surface Acoustic Wave
(SSAW). Int J Bioprint, 4(1): 130. http://dx.doi.org/10.18063/IJB.v4i1.130

1. Introduction and excellent bioink include printability, biocompatibility,
and bioactivity [11] . Cells suspension in the gelatin is usually
3D bioprinting has attracted great attention in the field used as the bioink. However, the cells in the monolayer
tissue engineering and regenerative medicine; different condition were found to grow slowly and loss functionality
types of cells and extracellular matrix (ECM) proteins after culture for a long time [12–15] . In contrast, cell viability
can be deposited simultaneously to form complex tissue- and differentiated functions in a cell spheroid, accumulation
[3]
engineered constructs for skin [1,2] perfusable blood vessels ,
[4]
[5]
[7]
[6]
cartilage , bone , neuronal and cardiac tissue . 3D of hundreds of cells in the shape of a sphere, could be
maintained for prolonged periods of time. Retention in
bioprinting has a capability to fabricate complicated
structures in high accuracy and reproducibility in the aspect 3D structure, establishment of cell-cell contacts, and presence
of the shape, size, internal porosity, and interconnectivity [8–10] . of extracellular matrix (ECM) are important reasons for
[16–18]
One of the essential components of 3D bioprinting is the spheroidal aggregation . Currently, cell spheroids are
use of bioink which consists of multiple types of cells and used extensively in the study of tissue anatomy, drug
[19,20]
[21]
various biomaterials. The requirements for appropriate screening , toxicology , and cell proliferation and

Formation of cell spheroids using Standing Surface Acoustic Wave (SSAW). © 2018 Sriphutkiat Y, 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, distribution, and reproduction in any medium, provided the original work is properly cited.
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