Rheology of hydrogels using ultrasound and rheometer

Tissue engineering applications necessitate biocompatible hydrogel scaffolds that helps in cell growth and differentiation. There is a growing interest in characterizing the mechanical properties of such hydrogel scaffolds geared toward a variety of tissue engineering applications such as native tissue enhancement, tissue replacement, and drug delivery. This study examines chemically cross-linked gelatin methacrylate (GelMA) and poly(ethylene glycol) diacrylate (PEGDA) hydrogels, two popular biomaterials used in tissue engineering. We characterized an array of scaffolds, fabricated by varying both GELMA and PEGDA concentrations and ultraviolet (UV) light exposure time. Pulse-echo ultrasound techniques were used to non-invasively determine the sound speed and attenuation of the scaffolds, revealing significant dependence on GelMA and PEGDA concentrations. Steady shear and frequency-controlled oscillatory shear tests were performed using a rotational rheometer (Model: DHR-2, TA Instruments) varying strain rates, oscillation frequencies, and amplitudes. By probing hydrogels using acoustic and rotational rheometer techniques, we establish a relationship between the two methods additionally offering an understanding of the effect of chemical crosslinking on the dynamic response of hydrogels. They can inform the selection of scaffold materials in tissue engineering applications. [Partially supported by the National Science Foundation].