Acoustic and viscoelastic characterization of hydrogel scaffolds to optimize preparation parameters for tissue engineering applications

Cell growth and differentiation rely upon both biochemical and mechanical cues. Though the focus has historically been biochemical, there is an increasing interest on the mechanical properties of scaffold materials within the field of tissue engineering. When the mechanical properties of a scaffold material more closely match with those of the intended native tissue, the functionality of the tissue scaffold is significantly enhanced. This study explores how an acoustic and viscoelastic characterization of a popular hydrogel, gelatin methacrylate (GelMA), can be used to inform the synthesis and fabrication parameters for a variety of tissue engineering applications. GelMA scaffolds exhibiting a range of mechanical properties were produced by varying the concentration of GelMA and by varying the curing time of the scaffolds. Pulse-echo ultrasound techniques were used to determine the sound speed and attenuation, revealing a significant dependence on the GelMA concentration. Compression tests were also performed, showing an increased stiffness with certain preparation parameters. Finally, atomic force microscopy experiments were used to obtain the storage and loss moduli of the hydrogels, revealing an increase in hydrogel stiffness at short time scales for both the GelMA concentration and curing time.