(602e) Bioresorbable Shape-Adaptive Structures for Ultrasonic Monitoring of Deep-Tissue Homeostasis

Monitoring homeostasis at relevant anatomical sites is an essential aspect in obtaining pathophysiological insights for the early diagnosis of diseases. Attenuation in biological tissues limits the use of sensing modalities including optical, thermal, and radiofrequency to shallow depths, insufficient for detection in deep tissues. Accurate assessment of homeostatic dysregulation in deep anatomical locations typically require invasive biopsies or expensive imaging techniques. This work introduces an engineered platform of bioresorbable, shape-adaptive materials and structures, that enables real-time monitoring of deep-tissue homeostasis using ultrasound instruments. Specifically, the thin and flexible implants incorporate symmetrically distributed metal discs that generate strong contrast in ultrasound images embedded within a soft, pH-responsive hydrogel matrix, to allow ultrasound-based measurements of spatio-temporal changes in local pH. The hydrogel undergoes well-defined dimensional changes upon pH perturbations in the surrounding environment, transforming changes in the spacings between metal discs to enable quantitative determination by ultrasound imaging. The envisioned clinical use case is in early assessments of anastomotic leaks that can occur following gastrointestinal surgeries to address an unmet clinical need in patient monitoring, where bioresorption after a recovery period bypassing the need for surgical extraction. Experimental and computational studies of the materials structures, the mechanisms for contrast generation in ultrasound imaging, and the process for bioresorption establish the scientific foundations for this technology. Demonstrations in small and large animal models illustrate capabilities in monitoring leaks from the stomach, the small intestine, and the pancreas. Similar concepts have the potential to measure other forms of chemical or physical specificity by ultrasound imaging.