Development of Optimal Gelatin Methacryloyl Bioink for 3D Inkjet Bioprinting

Abstract

Gelatin methacryloyl (GelMA) is receiving significant attention in the field of biofabrication due to its biocompatibility, mechanical tunability, and printability. However, it is difficult to print the hydrogel with high-resolution inkjet bioprinting because of the high viscoelasticity involved during the printing process. In this study, we suggest a simple ultrasound sonication method to control the viscoelasticity of the bioink without sacrificing its biocompatibility and mechanical properties. After the 20 hours of sonication, the viscosity of 10%(w/v) GelMA ink decreased from 81 mPa·s to 21 mPa·s at the 10,000 s-1, making unprintable GelMA bioink be printed possible. Multi-Angle Light Scattering measurement showed that the molecular weight of GelMA was reduced, which led to a decrease in viscoelasticity. In addition, Nuclear Magnetic Resonance spectroscopy confirmed that the sonication did not destroy the methacryloyl group that determines the degree of crosslinking. We compared the physical hydrogel properties of the 3% (w/v) pristine GelMA ink, 10 hours sonicated 6% GelMA ink, and 20 hours sonicated 10% GelMA ink which were all printable in inkjet printer. SEM image analysis was conducted to observe the microstructure of each lyophilized hydrogel. Higher wall thickness was observed with the high concentration of GelMA hydrogel. Due to dense microstructure, 10% GelMA hydrogel with 20 hours sonication showed about 7 times higher compressive modulus than pristine 3% GelMA hydrogel. Also, the higher concentration of GelMA hydrogel showed a slower enzyme degradation rate. Finally, we fabricated the three-dimensional cylindrical hydrogel constructs with different physical properties by using inkjet printing. Since the characteristics of ink can be easily controlled through the ultrasound sonication, this method will be widely used for biofabrication by expanding the range of inkjet bioinks.