The influence of printing parameters on cell survival rate and printability in microextrusion-based 3D cell printing technology

Significance Statement

High cell survival rate and good printability, commonly conflicts with each other, has always been the pursuit in the practice of cell 3D printing technology. Since both can be influenced by many process parameters, Yao and her coworkers from Tsinghua University, China and Drexel University, USA focused on the establishment of an applicable protocol for microextrusion-based 3D cell printing technology to achieve both high cell survival rate and good printability. Their studies demonstrated that even though the bioink composition and concentration, holding temperature and holding time would all influence bioink rheological property in the printing period, bioink storage modulus was the decisive factor for both cell survival rate and printability. Different process parameter combinations would result in the similar storage modulus and thus showed similar cell survival rate after 3D bioprinting process. When the bioink storage modulus was in the range of 154 Pa to 382 Pa, 3D printing of A549 cell-laden gelatin/alginate construct with both high cell survival rate (>90%) and good printability could be achieved. Researchers in the bioprinting field may find this protocol useful for adjusting the printing process quickly. And the methodology and the protocol in this study may also be useful for the design and development of new temperature-sensitive bioinks for 3D cell printing. Future work will be focused on revealing the detailed mechanism and mathematical modelling of cell survival and printability in microextrusion-based 3D cell printing technology and optimizing the parameter ranges for bioprinting other types of cells, e.g. pluripotent stem cells.

About the author

Dr. Rui Yao is Assistant Professor of Biomanufacturing Research Center, Department of Mechanical Engineering, Tsinghua University, Beijing, China. She has interdisciplinary background of tissue engineering, biomaterials, biofabrication and stem cells from Tsinghua University, MIT and Peking Union Medical University. Her main focus is Stem Cell-based Biofabrication and applications in Tissue Engineering, 3D Physiology/Pathological Model and Drug Testing Model. She has published over 40 journal papers and conference abstracts, filed over 10 patents and conducted over 10 oral presentations in international conferences in the field of her research.

Journal Reference

Biofabrication. 2015 Nov 2;7(4):045002.

Zhao Y, Li Y, Mao S, Sun W, Yao R.

Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing, People’s Republic of China. Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing, People’s Republic of China.

Abstract

Three-dimensional (3D) cell printing technology has provided a versatile methodology to fabricate cell-laden tissue-like constructs and in vitro tissue/pathological models for tissue engineering, drug testing and screening applications. However, it still remains a challenge to print bioinks with high viscoelasticity to achieve long-term stable structure and maintain high cell survival rate after printing at the same time. In this study, we systematically investigated the influence of 3D cell printing parameters, i.e. composition and concentration of bioink, holding temperature and holding time, on the printability and cell survival rate in microextrusion-based 3D cell printing technology. Rheological measurements were utilized to characterize the viscoelasticity of gelatin-based bioinks. Results demonstrated that the bioink viscoelasticity was increased when increasing the bioink concentration, increasing holding time and decreasing holding temperature below gelation temperature. The decline of cell survival rate after 3D cell printing process was observed when increasing the viscoelasticity of the gelatin-based bioinks. However, different process parameter combinations would result in the similar rheological characteristics and thus showed similar cell survival rate after 3D bioprinting process. On the other hand, bioink viscoelasticity should also reach a certain point to ensure good printability and shape fidelity. At last, we proposed a protocol for3D bioprinting of temperature-sensitive gelatin-based hydrogel bioinks with both high cell survival rate and good printability. This research would be useful for biofabrication researchers to adjust the 3D bioprinting process parameters quickly and as a referable template for designing new bioinks.

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