Biodegradable, Shape Morphing Structure to Program the Stepwise Control of Cerebral Blood Flow for Vascular Regeneration

Cerebral hyperperfusion syndrome (CHS) is a rare but devastating complication that can occur after a revascularization procedure, which is one of the most common treatments for ischemic stroke. CHS is difficult to diagnose and, if not addressed promptly, can lead to a fatal intracerebral hemorrhage. There is an unmet need to manage changes in cerebral blood flow (CBF) following ischemic stroke treatment, specifically in preventing hyperperfusion after revascularization surgery and facilitating the gradual recovery of CBF as cerebral autoregulation improves. Therefore, as a potential solution, implantable autonomous materials, devices, and structures that prevent hyperperfusion immediately after surgery and allow gradual CBF adaptation following the tissue recovery rate are promising CHS preventive measures.
Here, we have developed a vascular clip that regulates blood flow at the desired intensity and duration while ensuring biocompatibility. The vascular clip is made of shape memory polymer (SMP) that autonomously compresses the cerebrovascular vessel in response to body temperature and a biodegradable polymer that gradually releases the compressed cerebrovascular vessel. This clip aims to address the underlying cause of CHS by reducing excessive CBF following revascularization surgery and gradually restoring normal CBF over time. A computational fluid dynamics (CFD) simulation was conducted to predict and analyze the reduction in blood flow and recovery rates based on the clip's design and the properties of materials to optimize its design. The clip's ability to regulate blood flow was validated using a custom-made artificial blood flow model and an in-vivo rat model. We analyzed whether biocompatible blood flow intervention was achieved through the clip via CFD simulation and rat model, assessing the mechanical properties of biodegradable polymer and the shape recovery rate of SMP and identifying the optimal material characteristics. In vivo studies illustrate blood flow control capabilities in live-animal models, promising effective prevention of CHS. The autonomous compression feature of the vascular clip using SMP offers ease of use and consistent effects for physicians and patients. Customized vascular clips, produced by additive manufacturing, can accommodate various sizes of blood vessels for different indications, showing the potential for versatile applications.