RESUMEN
Abdominal aortic aneurysms (AAAs) are a local dilation of the aorta and are associated with significant mortality due to rupture and treatment complications. There is a need for less invasive treatments to prevent aneurysm growth and rupture. In this study, we used two experimental murine models to evaluate the potential of pentagalloyl glucose (PGG), which is a polyphenolic tannin that binds to and crosslinks elastin and collagen, to preserve aortic compliance. Animals underwent surgical aortic injury and received 0.3% PGG or saline treatment on the adventitial surface of the infrarenal aorta. Seventeen mice underwent topical elastase injury, and 14 mice underwent topical calcium chloride injury. We collected high-frequency ultrasound images before surgery and at 3-4 timepoints after. There was no difference in the in vivo effective maximum diameter due to PGG treatment for either model. However, the CaCl2 model had significantly higher Green-Lagrange circumferential cyclic strain in PGG-treated animals (p < 0.05). While ex vivo pressure-inflation testing showed no difference between groups in either model, histology revealed reduced calcium deposits in the PGG treatment group with the CaCl2 model. These findings highlight the continued need for improved understanding of PGG's effects on the extracellular matrix and suggest that PGG may reduce arterial calcium accumulation.
RESUMEN
A microrobot system comprising an untethered tumbling magnetic microrobot, a two-degree-of-freedom rotating permanent magnet, and an ultrasound imaging system has been developed for in vitro and in vivo biomedical applications. The microrobot tumbles end-over-end in a net forward motion due to applied magnetic torque from the rotating magnet. By turning the rotational axis of the magnet, two-dimensional directional control is possible and the microrobot was steered along various trajectories, including a circular path and P-shaped path. The microrobot is capable of moving over the unstructured terrain within a murine colon in in vitro, in situ, and in vivo conditions, as well as a porcine colon in ex vivo conditions. High-frequency ultrasound imaging allows for real-time determination of the microrobot's position while it is optically occluded by animal tissue. When coated with a fluorescein payload, the microrobot was shown to release the majority of the payload over a 1-h time period in phosphate-buffered saline. Cytotoxicity tests demonstrated that the microrobot's constituent materials, SU-8 and polydimethylsiloxane (PDMS), did not show a statistically significant difference in toxicity to murine fibroblasts from the negative control, even when the materials were doped with magnetic neodymium microparticles. The microrobot system's capabilities make it promising for targeted drug delivery and other in vivo biomedical applications.
RESUMEN
Arterial aneurysms are pathological dilations of blood vessels, which can be of clinical concern due to thrombosis, dissection, or rupture. Aneurysms can form throughout the arterial system, including intracranial, thoracic, abdominal, visceral, peripheral, or coronary arteries. Currently, aneurysm diameter and expansion rates are the most commonly used metrics to assess rupture risk. Surgical or endovascular interventions are clinical treatment options, but are invasive and associated with risk for the patient. For aneurysms in locations where thrombosis is the primary concern, diameter is also used to determine the level of therapeutic anticoagulation, a treatment that increases the possibility of internal bleeding. Since simple diameter is often insufficient to reliably determine rupture and thrombosis risk, computational hemodynamic simulations are being developed to help assess when an intervention is warranted. Created from subject-specific data, computational models have the potential to be used to predict growth, dissection, rupture, and thrombus-formation risk based on hemodynamic parameters, including wall shear stress, oscillatory shear index, residence time, and anomalous blood flow patterns. Generally, endothelial damage and flow stagnation within aneurysms can lead to coagulation, inflammation, and the release of proteases, which alter extracellular matrix composition, increasing risk of rupture. In this review, we highlight recent work that investigates aneurysm geometry, model parameter assumptions, and other specific considerations that influence computational aneurysm simulations. By highlighting modeling validation and verification approaches, we hope to inspire future computational efforts aimed at improving our understanding of aneurysm pathology and treatment risk stratification.
RESUMEN
We are introducing a wireless and passive strain sensing scheme that utilizes ultrasound imaging of a highly stretchable hydrogel embedded with zinc oxide (ZnO) nanoparticles, named "ZnO-gel". The incorporation of ZnO nanoparticles into a polymer network of the hydrogel improves both its elasticity and strength. It also serves as an ideal biocompatible ultrasound contrast agent that allows remote interrogation of the changes in volume or dimensions of the hydrogel in response to mechanical strains through simple ultrasound imaging. A systematic study of various ratios of ZnO nanoparticle fillers (ranging from 0 to 40% w/w), cross-linked within the poly (DMA-co-MAA) hydrogel, was performed to identify the appropriate ZnO-to-gel ratio that provided the optimal mechanical and ultrasound imaging properties. The results of these investigations showed that 10% w/w of ZnO nanoparticles provided the highest stretchability of 260% with the effective amount of contrast agents to achieve clear visibility of the hydrogel dimension during ultrasound imaging. In general, the applied strain deforms the ZnO-gel specimens by reducing the cross-sectional area at a linear rate of 0.24% area change per % of applied strain for strain levels of up to 250%. Biocompatibility tests with stromal cells (fibroblasts) did not show any acute toxicity of the hydrogel and the ZnO nanoparticles used in this technology. It is anticipated that this technology can be applied to a broad range of wireless and passive monitoring of physiological functions for which microenvironmental strain matters throughout the body, simply by tuning both the mechanical properties of the hydrogel and ZnO nanoparticle concentration.
