Enhanced thrombolysis by endovascular low-frequency ultrasound with bifunctional microbubbles in venous thrombosis: in vitro and in vivo study

Smart Hydrogel Swelling State Detection Based on a Power-Transfer Transduction Principle

Stimulus-responsive (smart) hydrogels are a promising sensing material for biomedical contexts due to their reversible swelling change in response to target analytes. The design of application-specific sensors that utilize this behavior requires the development of suitable transduction concepts. The presented study investigates a power-transfer-based readout approach that is sensitive to small volumetric changes of the smart hydrogel. The concept employs two thin film polyimide substrates with embedded conductive strip lines, which are shielded from each other except at the tip region, where the smart hydrogel is sandwiched in between. The hydrogel's volume change in response to a target analyte alters the distance and orientation of the thin films, affecting the amount of transferred power between the two transducer parts and, consequently, the measured sensor output voltage. With proper calibration, the output signal can be used to determine the swelling change of the hydrogel and, consequently, to quantify the stimulus. In proof-of-principle experiments with glucose- and pH-sensitive smart hydrogels, high sensitivity to small analyte concentration changes was found along with very good reproducibility and stability. The concept was tested with two exemplary hydrogels, but the transduction principle in general is independent of the specific hydrogel material, as long as it exhibits a stimulus-dependent volume change. The application vision of the presented research is to integrate in situ blood analyte monitoring capabilities into standard (micro)catheters. The developed sensor is designed to fit into a catheter without obstructing its normal use and, therefore, offers great potential for providing a universally applicable transducer platform for smart catheter-based sensing.

Ultrasound Combined With Continuous Microbubble Injection to Enhance Catheter-Directed Thrombolysis in Vitro and in Vivo

OBJECTIVES

To investigate the influence of microbubble perfusion mode on catheter-directed thrombolysis (CDT), we evaluated the effect of two different types of microbubble perfusion modes (continuous injection versus bolus injection) on the thrombolytic efficacy of CDT in vitro and further assessed the effect of continuous microbubble injection on CDT in vivo.

METHODS

In an in vitro experimental setup, 50 fresh bovine whole blood clots were randomized into five groups: ultrasound and continuous microbubble injection-enhanced CDT (US + cMB + CDT), ultrasound and bolus microbubble injection-enhanced CDT (US + bMB + CDT), US + CDT, US + cMB, and CDT. In a porcine femoral vein thrombosis model, 16 completely obstructive thrombi were randomly assigned to the CDT group and the US + cMB + CDT group, respectively. Thrombolysis rate, vascular recanalization rate, hematoxylin-eosin, and immunofluorescence staining were used to evaluate the thrombolytic effect in vitro and in vivo.

RESULTS

In vitro, US + cMB + CDT group resulted in a significantly higher thrombolysis rate compared with the other four groups (P < .05). Meanwhile, this group also demonstrated a looser clot structure and more disrupted fibrin structures. In vivo, US + cMB + CDT contributed to a significantly higher vascular recanalization rate compared with CDT (87.50% versus 25.00%, P < .05).

CONCLUSIONS

US + cMB + CDT was more effective than US + bMB + CDT in thrombolysis, and ultrasound combined with continuous microbubble injection could enhance the thrombolytic efficacy of CDT.

A Self-Healing Optoacoustic Patch with High Damage Threshold and Conversion Efficiency for Biomedical Applications

Compared with traditional piezoelectric ultrasonic devices, optoacoustic devices have unique advantages such as a simple preparation process, anti-electromagnetic interference, and wireless long-distance power supply. However, current optoacoustic devices remain limited due to a low damage threshold and energy conversion efficiency, which seriously hinder their widespread applications. In this study, using a self-healing polydimethylsiloxane (PDMS, Fe-Hpdca-PDMS) and carbon nanotube composite, a flexible optoacoustic patch is developed, which possesses the self-healing capability at room temperature, and can even recover from damage induced by cutting or laser irradiation. Moreover, this patch can generate high-intensity ultrasound (> 25 MPa) without the focusing structure. The laser damage threshold is greater than 183.44 mJ cm-2, and the optoacoustic energy conversion efficiency reaches a major achievement at 10.66 × 10-3, compared with other carbon-based nanomaterials and PDMS composites. This patch is also been successfully examined in the application of acoustic flow, thrombolysis, and wireless energy harvesting. All findings in this study provides new insight into designing and fabricating of novel ultrasound devices for biomedical applications.

A Quantitative Method for the Evaluation of Deep Vein Thrombosis in a Murine Model Using Three-Dimensional Ultrasound Imaging

Deep vein thrombosis (DVT) is a life-threatening condition that can lead to its sequelae pulmonary embolism (PE) or post-thrombotic syndrome (PTS). Murine models of DVT are frequently used in early-stage disease research and to assess potential therapies. This creates the need for the reliable and easy quantification of blood clots. In this paper, we present a novel high-frequency 3D ultrasound approach for the quantitative evaluation of the volume of DVT in an in vitro model and an in vivo murine model. The proposed method involves the use of a high-resolution ultrasound acquisition system and semiautomatic segmentation of the clot. The measured 3D volume of blood clots was validated to be correlated with in vitro blood clot weights with an R2 of 0.89. Additionally, the method was confirmed with an R2 of 0.91 in the in vivo mouse model with a cylindrical volume from macroscopic measurement. We anticipate that the proposed method will be useful in pharmacological or therapeutic studies in murine models of DVT.

Sonothrombolysis: State-of-the-Art and Potential Applications in Children

In recent years, advances in ultrasound therapeutics have been implemented into treatment algorithms for the adult population; however, the use of therapeutic ultrasound in the pediatric population still needs to be further elucidated. In order to better characterize the utilization and practicality of sonothrombolysis in the juvenile population, the authors conducted a literature review of current pediatric research in therapeutic ultrasound. The PubMed database was used to search for all clinical and preclinical studies detailing the use and applications of sonothrombolysis, with a focus on the pediatric population. As illustrated by various review articles, case studies, and original research, sonothrombolysis demonstrates efficacy and safety in clot dissolution in vitro and in animal studies, particularly when combined with microbubbles, with potential applications in conditions such as deep venous thrombosis, peripheral vascular disease, ischemic stroke, myocardial infarction, and pulmonary embolism. Although there is limited literature on the use of therapeutic ultrasound in children, mainly due to the lower prevalence of thrombotic events, sonothrombolysis shows potential as a noninvasive thrombolytic treatment. However, more pediatric sonothrombolysis research needs to be conducted to quantify the safety and ethical considerations specific to this vulnerable population.

[Ultrasound-accelerated thrombolysis. Initial experience in patients with contraindications to systemic thrombolysis]

Background

acute pulmonary embolism (APE) is a complex and potentially deadly entity, with a variable clinical course, considered the third cardiovascular cause of death. Its management varies according to the stratified risk from anticoagulation to reperfusion therapy, suggesting systemic thrombolysis as a first-choice strategy; however, in a large group of patients their use will be contraindicated, discouraged or will have failed, thus recommending as options in such cases endovascular therapies or surgical embolectomy. With the presentation of 3 clinical cases and a review of the literature, we seek to communicate our initial experience in the use of ultrasound-accelerated thrombolysis with the EKOS system and to investigate key elements for its understanding and application.

Clinical cases

the cases of 3 patients with APE of high and intermediate risk with contraindications for systemic thrombolysis taken to accelerated thrombolysis therapy by ultrasound are discussed. They presented adequate clinical and hemodynamic evolution in the short term, achieving a rapid decrease in thrombolysis, systolic and mean pulmonary arterial pressure, improvement of right ventricular function and reduction of thrombotic burden.

Conclusion

Ultrasound-accelerated thrombolysis is a novel pharmaco-mechanical therapy that combines the emission of ultrasonic waves with the infusion of a local thrombolytic agent, a strategy that, according to different trials and clinical registries, has a high success rate and a good safety profile.