Current cardiac drug screening and testing methods lack the power to eliminate ineffective and harmful drug candidates to treat heart failure, a growing epidemic in Canada. Miniaturized three-dimensional heart models show great promise to better mimic human biology, disease, and drug responses, but their full potential requires innovative analytical tools to assess disease- and drug-induced alterations in tissue microstructure and mechanical properties. Current techniques to measure the microstructure and stiffness of miniature heart models are invasive, low-throughput, and incapable of long-term monitoring. In this thesis, an ultrasound imaging method is developed to evaluate the acoustic and mechanical properties of engineered tissues and biomaterials to address these analytical tool gaps. This high-frequency ultrasound technique is non-destructive, non-invasive, and capable of real-time monitoring.

We show that high-frequency ultrasound can accurately measure the intrinsic acoustic properties of biomaterials and engineered tissues by accounting for attenuation effects in coupling media, hydrogel thickness, and interfacial transmission/reflection coefficients. This approach enabled independent assessment of hydrogel cellularity despite significant contraction, providing valuable insights into tissue structure. We also developed a novel high-frequency ultrasound elastography (USE) system with a highly focused acoustic radiation force (ARF) excitation transducer, achieving non-invasive and high-resolution measurements of biomaterial mechanical properties, with strong agreement to shear rheometry. Through in silico modelling, we demonstrated that shear wave frequency exhibits non-linear dependencies on ARF excitation duration and tissue properties, enhancing the accuracy of mechanical characterization. Finally, we applied this USE system to cardiac cell-laden fibrin domes with validation to previous studies. Our work advances high-frequency ultrasound as a powerful tool for assessing biomaterial mechanics and engineered tissue properties, with future work focused on system improvements and future applications in dynamic tissue systems and organ-on-a-chip platforms to better understand bioengineered tissue behaviour in healthy, diseased, and treated states.