In Vitro Assessment of EmboGel and UltraGel Radiopaque Hydrogels for the Endovascular Treatment of Aneurysms

Endovascular treatment of intracranial aneurysms: Past and present

Intracranial aneurysm is common in stroke and, once rupturing, will cause disaster to patients. Nowadays, endovascular treatment has become a routine to reduce the risk of intracranial aneurysms rupture. Successive endovascular methods, like balloon-assisted coiling, stent-assisted coiling, and flow diversion, have become new choices for doctors. More and more doctors have been entering this field. Understanding the current general situation is crucial for more medical workers to learn the endovascular treatment of intracranial aneurysms. In the past, many devices and ideas about the treatment of intracranial aneurysms appeared. Although developing unceasingly, endovascular treatment still has some deficiencies to overcome. The advantages and drawbacks of current endovascular methods are discussed.

Development of an Injectable, ECM-Derivative Embolic for the Treatment of Cerebral Saccular Aneurysms

Cerebral aneurysms are a source of neurological morbidity and mortality, most often as a result of rupture. The most common approach for treating aneurysms involves endovascular embolization using nonbiodegradable medical devices, such as platinum coils. However, the need for retreatment due to the recanalization of coil-treated aneurysms highlights the importance of exploring alternative solutions. In this study, we propose an injectable extracellular matrix-derived embolic formed in situ by Michael addition of gelatin-thiol (Gel-SH) and hyaluronic acid vinyl sulfone (HA-VS) that may be delivered with a therapeutic agent (here, RADA-SP) to fill and remodel aneurysmal tissue without leaving behind permanent foreign bodies. The injectable embolic material demonstrated rapid gelation under physiological conditions, forming a highly porous structure and allowing for cellular infiltration. The injectable embolic exhibited thrombogenic behavior in vitro that was comparable to that of alginate injectables. Furthermore, in vivo studies in a murine carotid aneurysm model demonstrated the successful embolization of a saccular aneurysm and extensive cellular infiltration both with and without RADA-SP at 3 weeks, with some evidence of increased vascular or fibrosis markers with RADA-SP incorporation. The results indicate that the developed embolic has inherent potential for acutely filling cerebrovascular aneurysms and encouraging the cellular infiltration that would be necessary for stable, chronic remodeling.

Single Component Polymers, Polymer Blends, and Polymer Composites for Interventional Endovascular Embolization of Intracranial Aneurysms

Intracranial aneurysm is the abnormal focal dilation in brain arteries. When untreated, it can enlarge to rupture points and account for subarachnoid hemorrhage cases. Intracranial aneurysms can be treated by blocking the flow of blood to the aneurysm sac with clipping of the aneurysm neck or endovascular embolization with embolics to promote the formation of the thrombus. Coils or an embolic device are inserted endovascularly into the aneurysm via a micro-catheter to fill the aneurysm. Many embolization materials have been developed. An embolization coil made of soft and thin platinum wire called the "Guglielmi detachable coil" (GDC) enables safer treatment for brain aneurysms. However, patients may experience aneurysm recurrence because of incomplete coil filling or compaction over time. Unsatisfactory recanalization rates and incomplete occlusion are the drawbacks of endovascular embolization. So, the fabrication of new medical devices with less invasive surgical techniques is mandatory to enhance the long-term therapeutic performance of existing endovascular procedures. For this aim, the current article reviews polymeric materials including blends and composites employed for embolization of intracranial aneurysms. Polymeric materials used in embolic agents, their advantages and challenges, results of the strategies used to overcome treatment, and results of clinical experiences are summarized and discussed.

Remodelers of the vascular microenvironment: The effect of biopolymeric hydrogels on vascular diseases

Vascular disease is the leading health problem worldwide. Vascular microenvironment encompasses diverse cell types, including those within the vascular wall, blood cells, stromal cells, and immune cells. Initiation of the inflammatory state of the vascular microenvironment and changes in its mechanics can profoundly affect vascular homeostasis. Biomedical materials play a crucial role in modern medicine, hydrogels, characterized by their high-water content, have been increasingly utilized as a three-dimensional interaction network. In recent times, the remarkable progress in utilizing hydrogels and understanding vascular microenvironment have enabled the treatment of vascular diseases. In this review, we give an emphasis on the utilization of hydrogels and their advantages in the various vascular diseases including atherosclerosis, aneurysm, vascular ulcers of the lower limbs and myocardial infarction. Further, we highlight the importance and advantages of hydrogels as artificial microenvironments.

Hydrogels for Cardio and Vascular Tissue Repair and Regeneration

Cardiovascular disease (CVD), the leading cause of death globally, affects the heart and arteries with a variety of clinical manifestations, the most dramatic of which are myocardial infarction (MI), abdominal aortic aneurysm (AAA), and intracranial aneurysm (IA) rupture. In MI, necrosis of the myocardium, scar formation, and loss of cardiomyocytes result from insufficient blood supply due to coronary artery occlusion. Beyond stenosis, the arteries that are structurally and functionally connected to the cardiac tissue can undergo pathological dilation, i.e., aneurysmal dilation, with high risk of rupture. Aneurysms of the intracranial arteries (IAs) are more commonly seen in young adults, whereas those of the abdominal aorta (AAA) are predominantly seen in the elderly. IAs, unpredictably, can undergo rupture and cause life-threatening hemorrhage, while AAAs can result in rupture, internal bleeding and high mortality rate. In this clinical context, hydrogels, three-dimensional networks of water-seizing polymers, have emerged as promising biomaterials for cardiovascular tissue repair or protection due to their biocompatibility, tunable properties, and ability to encapsulate and release bioactive molecules. This review provides an overview of the current state of research on the use of hydrogels as an innovative platform to promote cardiovascular-specific tissue repair in MI and functional recovery or protection in aneurysmal dilation.

Swarming self-adhesive microgels enabled aneurysm on-demand embolization in physiological blood flow

The recent rise of swarming microrobotics offers great promise in the revolution of minimally invasive embolization procedure for treating aneurysm. However, targeted embolization treatment of aneurysm using microrobots has significant challenges in the delivery capability and filling controllability. Here, we develop an interventional catheterization-integrated swarming microrobotic platform for aneurysm on-demand embolization in physiological blood flow. A pH-responsive self-healing hydrogel doped with magnetic and imaging agents is developed as the embolic microgels, which enables long-term self-adhesion under biological condition in a controllable manner. The embolization strategy is initiated by catheter-assisted deployment of swarming microgels, followed by the application of external magnetic field for targeted aggregation of microrobots into aneurysm sac under the real-time guidance of ultrasound and fluoroscopy imaging. Mild acidic stimulus is applied to trigger the welding of microgels with satisfactory bio-/hemocompatibility and physical stability and realize complete embolization. Our work presents a promising connection between the design and control of microrobotic swarms toward practical applications in dynamic environments.

Sodium Phytate-Incorporated Gelatin-Silicate Nanoplatelet Composites for Enhanced Cohesion and Hemostatic Function of Shear-Thinning Biomaterials

Shear-thinning biomaterials (STBs) based on gelatin-silicate nanoplatelets (SNs) are emerging as an alternative to conventional coiling and clipping techniques in the treatment of vascular anomalies. Improvements in the cohesion of STB hydrogels pave the way toward their translational application in minimally invasive therapies such as endovascular embolization repair. In the present study, sodium phytate (Phyt) additives are used to tune the electrostatic network of SNs-gelatin STBs, thereby promoting their mechanical integrity and facilitating injectability through standard catheters. We show that an optimized amount of Phyt enhances storage modulus by approximately one order of magnitude and reduces injection force by ≈58% without compromising biocompatibility and hydrogel wet stability. The Phyt additives are found to decrease the immune responses induced by SNs. In vitro embolization experiments suggest a significantly lower rate of failure in Phyt-incorporated STBs than in control groups. Furthermore, the addition of Phyt leads to accelerated blood coagulation (reduces clotting time by ≈45% compared to controls) due to the contributions of negatively charged phosphate groups, which aid in the prolonged durability of STB in coagulopathic patients. Therefore, the proposed approach is an effective method for the design of robust and injectable STBs for minimally invasive treatment of vascular malformations.

Image-guided intratumoral immunotherapy: Developing a clinically practical technology

Immunotherapy has revolutionized the contemporary oncology landscape, with durable responses possible across a range of cancer types. However, the majority of cancer patients do not respond to immunotherapy due to numerous immunosuppressive barriers. Efforts to overcome these barriers and increase systemic immunotherapy efficacy have sparked interest in the local intratumoral delivery of immune stimulants to activate the local immune response and subsequently drive systemic tumor immunity. While clinical evaluation of many therapeutic candidates is ongoing, development is hindered by a lack of imaging confirmation of local delivery, insufficient intratumoral drug distribution, and a need for repeated injections. The use of polymeric drug delivery systems, which have been widely used as platforms for both image guidance and controlled drug release, holds promise for delivery of intratumoral immunoadjuvants and the development of an in situ cancer vaccine for patients with metastatic cancer. In this review, we explore the current state of the field for intratumoral delivery and methods for optimizing controlled drug release, as well as practical considerations for drug delivery design to be optimized for clinical image guided delivery particularly by CT and ultrasound.

Recent progress in liquid embolic agents

Vascular embolization is a non-surgical procedure used to treat diseases or morbid conditions related to blood vessels, such as bleeding, arteriovenous malformation, aneurysm, and hypervascular tumors, through the intentional occlusion of blood vessels. Among various types of embolic agents that have been applied, liquid embolic agents are gaining an increasing amount of attention owing to their advantages in distal infiltration into regions where solid embolic agents cannot reach, enabling more extensive embolization. Meanwhile, recent advances in biomaterials and technologies have also contributed to the development of novel liquid embolic agents that can resolve the challenges faced while using the existing embolic materials. In this review, we briefly summarize the clinically used embolic agents and their applications, and then present selected research results that overcome the limitations of the embolic agents in use. Through this review, we suggest the required properties of liquid embolic agents that ensure efficacy, which can replace the existing agents, providing directions for the future development in this field.

In situ crosslinking temperature-responsive hydrogels with improved delivery, swelling, and elasticity for endovascular embolization

Endovascular embolization of cerebral aneurysms is a common approach for reducing the risk of often-fatal hemorrhage. However, currently available materials used to occlude these aneurysms provide incomplete filling (coils) or require a complicated, time-consuming delivery procedure (solvent-exchange precipitating polymers). The objective of this work was to develop an easily deliverable in situ forming hydrogel that can occlude the entire volume of an aneurysm. The hydrogel is formed by mixing a solution of a temperature-responsive polymer containing pendent thiol groups (poly(NIPAAm-co-cysteamine) or poly(NIPAAm-co-cysteamine-co-JAAm)) with a solution of poly(ethylene glycol) diacrylate (PEGDA). Incorporation of hydrophilic grafts of polyetheramine acrylamide (JAAm) in the temperature-responsive polymer caused weaker physical crosslinking, facilitated faster and more complete chemical crosslinking, and increased gel swelling. One formulation (30 wt % PNCJ20 + PEGDA) could be delivered for over 220 s after mixing, formed a strong and elastic hydrogel (G' > 6000 Pa) within 30 min and once set, maintained its shape and volume in a model aneurysm under flow. This gel represents a promising candidate water-based material utilizing both physical and chemical crosslinking that warrants further investigation as an embolic agent for saccular aneurysms.

Injectable hydrogels for vascular embolization and cell delivery: The potential for advances in cerebral aneurysm treatment

Cerebral aneurysms are vascular lesions caused by the biomechanical failure of the vessel wall due to hemodynamic stress and inflammation. Aneurysmal rupture results in subarachnoid hemorrhage often leading to death or disability. Current treatment options include open surgery and minimally invasive endovascular options aimed at secluding the aneurysm from the circulation. Cerebral aneurysm embolization with appropriate materials is a therapeutic approach to prevent rupture and the resultant clinical sequelae. Metallic platinum coils are a typical, practical option to embolize cerebral aneurysms. However, the development of an alternative treatment modality is of interest because of poor occlusion permanence, coil migration, and coil compaction. Moreover, minimizing the implanted foreign materials during therapy is of importance not just to patients, but also to clinicians in the event an open surgical approach has to be pursued in the future. Polymeric injectable hydrogels have been investigated for transcatheter embolization and cell therapy with the potential for permanent aneurysm repair. This review focuses on how the combination of injectable embolic biomaterials and cell therapy may achieve minimally invasive remodeling of a degenerated cerebral artery with promise for superior outcomes in treatment of this devastating disease.

Embolization of Vascular Malformations via In Situ Photocrosslinking of Mechanically Reinforced Alginate Microfibers using an Optical-Fiber-Integrated Microfluidic Device

Embolization, which is a minimally invasive endovascular treatment, is a safe and effective procedure for treating vascular malformations (e.g., aneurysms). Hydrogel microfibers obtained via spatiotemporally controllable in situ photocrosslinking exhibit great potential for embolizing aneurysms. However, this process is challenging because of the absence of biocompatible and morphologically stable hydrogels and the difficulty in continuously spinning the microfibers via in situ photocrosslinking in extreme endovascular environments such as those involving a tortuous geometry and high absorbance. A double-crosslinked alginate-based hydrogel with tantalum nanopowder (DAT) that exploits the synergistic effect of covalent crosslinking by visible-light irradiation and ionic crosslinking using Ca2+ , which is present in the blood, is developed in this study. Furthermore, an effective strategy to design and produce an optical-fiber-integrated microfluidic device (OFI-MD) that can continuously spin hydrogel microfibers via in situ photocrosslinking in extreme endovascular environments is proposed. As an embolic material, DAT exhibits promising characteristics such as radiopacity, nondissociation, nonswelling, and constant mechanical strength in blood, in addition to excellent cyto- and hemo-compatibilities. Using OFI-MD to spin DAT microfibers continuously can help fill aneurysms safely, uniformly, and completely within the endovascular simulator without generating microscopic fragments, which demonstrates its potential as an effective embolization strategy.

Pulsatile Flow-Induced Fatigue-Resistant Photopolymerizable Hydrogels for the Treatment of Intracranial Aneurysms

An alternative intracranial aneurysm embolic agent is emerging in the form of hydrogels due to their ability to be injected in liquid phase and solidify in situ. Hydrogels have the ability to fill an aneurysm sac more completely compared to solid implants such as those used in coil embolization. Recently, the feasibility to implement photopolymerizable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels in vitro has been demonstrated for aneurysm application. Nonetheless, the physical and mechanical properties of such hydrogels require further characterization to evaluate their long-term integrity and stability to avoid implant compaction and aneurysm recurrence over time. To that end, molecular weight and polymer content of the hydrogels were tuned to match the elastic modulus and compliance of aneurysmal tissue while minimizing the swelling volume and pressure. The hydrogel precursor was injected and photopolymerized in an in vitro aneurysm model, designed by casting polydimethylsiloxane (PDMS) around 3D printed water-soluble sacrificial molds. The hydrogels were then exposed to a fatigue test under physiological pulsatile flow, inducing a combination of circumferential and shear stresses. The hydrogels withstood 5.5 million cycles and no significant weight loss of the implant was observed nor did the polymerized hydrogel protrude or migrate into the parent artery. Slight surface erosion defects of 2–10 μm in depth were observed after loading compared to 2 μm maximum for non-loaded hydrogels. These results show that our fine-tuned photopolymerized hydrogel is expected to withstand the physiological conditions of an in vivo implant study.

In vitro Implementation of Photopolymerizable Hydrogels as a Potential Treatment of Intracranial Aneurysms

Intracranial aneurysms are increasingly being treated with endovascular therapy, namely coil embolization. Despite being minimally invasive, partial occlusion and recurrence are more frequent compared to open surgical clipping. Therefore, an alternative treatment is needed, ideally combining minimal invasiveness and long-term efficiency. Herein, we propose such an alternative treatment based on an injectable, radiopaque and photopolymerizable polyethylene glycol dimethacrylate hydrogel. The rheological measurements demonstrated a viscosity of 4.86 ± 1.70 mPa.s, which was significantly lower than contrast agent currently used in endovascular treatment (p = 0.42), allowing the hydrogel to be injected through 430 μm inner diameter microcatheters. Photorheology revealed fast hydrogel solidification in 8 min due to the use of a new visible photoinitiator. The addition of an iodinated contrast agent in the precursor contributed to the visibility of the precursor injection under fluoroscopy. Using a customized light-conducting microcatheter and illumination module, the hydrogel was implanted in an in vitro silicone aneurysm model. Specifically, in situ fast and controllable injection and photopolymerization of the developed hydrogel is shown to be feasible in this work. Finally, the precursor and the polymerized hydrogel exhibit no toxicity for the endothelial cells. Photopolymerizable hydrogels are expected to be promising candidates for future intracranial aneurysm treatments.

Advancements in the development on new liquid embolic agents for use in therapeutic embolisation

This review covers the current state-of-the-art in the development of liquid embolics for therapeutic embolisation.

Advances in Biomaterials and Technologies for Vascular Embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology used for the deliberate occlusion of blood vessels for the treatment of diseased or injured vasculature. A wide variety of embolic agents including metallic coils, calibrated microspheres, and liquids are available for clinical practice. Additionally, advances in biomaterials, such as shape-memory foams, biodegradable polymers, and in situ gelling solutions have led to the development of novel preclinical embolic agents. The aim here is to provide a comprehensive overview of current and emerging technologies in endovascular embolization with respect to devices, materials, mechanisms, and design guidelines. Limitations and challenges in embolic materials are also discussed to promote advancement in the field.

Polymeric materials for embolic and chemoembolic applications

Percutaneous transcatheter embolization procedures involve the selective occlusion of blood vessels. Occlusive agents, referred to as embolics, vary in material characteristics including chemical composition, mechanical properties, and the ability to concurrently deliver drugs. Commercially available polymeric embolics range from gelatin foam to synthetic polymers such as poly(vinyl alcohol). Current systems under investigation include tunable, bioresorbable microspheres composed of chitosan or poly(ethylene glycol) derivatives, in situ gelling liquid embolics with improved safety profiles, and radiopaque embolics that are trackable in vivo. This article reviews commercially available materials used for embolization as well as polymeric materials that are under investigation.

pH-Sensitive sulfamethazine-based hydrogels as potential embolic agents for transcatheter vascular embolization

After delivery through a catheter, a three-dimensional hydrogel network was formed upon the change of environmental pH, and thus block the targeted blood vessels, as presented in white color under the fluoroscopic angiogram.

An in situ forming biodegradable hydrogel-based embolic agent for interventional therapies

We present here the characteristics of an in situ forming hydrogel prepared from carboxymethyl chitosan and oxidized carboxymethyl cellulose for interventional therapies. Gelation, owing to the formation of Schiff bases, occurred both with and without the presence of a radiographic contrast agent. The hydrogel exhibited a highly porous internal structure (pore diameter 17±4 μm), no cytotoxicity to human umbilical vein endothelial cells, hemocompatibility with human blood, and degradability in lysozyme solutions. Drug release from hydrogels loaded with a sclerosant, tetracycline, was measured at pH 7.4, 6 and 2 at 37°C. The results showed that tetracycline was more stable under acidic conditions, with a lower release rate observed at pH 6. An anticancer drug, doxorubicin, was loaded into the hydrogel and a cumulative release of 30% was observed over 78 h in phosphate-buffered saline at 37°C. Injection of the hydrogel precursor through a 5-F catheter into a fusiform aneurysm model was feasible, leading to complete filling of the aneurysmal sac, which was visualized by fluoroscopy. The levels of occlusion by hydrogel precursors (1.8% and 2.1%) and calibrated microspheres (100-300 μm) in a rabbit renal model were compared. Embolization with hydrogel precursors was performed without clogging and the hydrogel achieved effective occlusion in more distal arteries than calibrated microspheres. In conclusion, this hydrogel possesses promising characteristics potentially beneficial for a wide range of vascular intervention procedures that involve embolization and drug delivery.

Preliminary investigation of the dissolution behavior, cytocompatibility, effects of fibrinogen conformation and platelet adhesion for radiopaque embolic particles

Experimental embolic particles based on a novel zinc-silicate glass system have been biologically evaluated for potential consideration in transcatheter arterial embolization procedures. In addition to controlling the cytotoxicity and haemocompatibility for such embolic particles, its glass structure may mediate specific responses via dissolution in the physiological environment. In a 120 h in-vitro dissolution study, ion release levels for silicon (Si4+), sodium (Na+), calcium (Ca2+), zinc (Zn2+), titanium (Ti4+), lanthanum (La3+), strontium (Sr2+), and magnesium (Mg2+), were found to range from 0.04 to 5.41 ppm, 0.27-2.28 ppm, 2.32-8.47 ppm, 0.16-0.20 ppm, 0.12-2.15 ppm, 0.16-0.49 ppm and 0.01-0.12 ppm, respectively for the series of glass compositions evaluated. Initial release of Zn2+ (1.93-10.40 ppm) was only evident after 120 h. All compositions showed levels of cell viabilities ranging from 61.31 ± 4.33% to 153.7 ± 1.25% at 25%-100% serial extract dilutions. The conformational state of fibrinogen, known to induce thrombi, indicated that no changes were induced with respect of the materials dissolution by-products. Furthermore, the best-in-class experimental composition showed equivalency to contour PVA in terms of inducing platelet adhesion. The data generated here provides requisite evidence to continue to in-vivo pre-clinical evaluation using the best-in-class experimental composition evaluated.

A new injectable radiopaque chitosan-based sclerosing embolizing hydrogel for endovascular therapies

Endovascular repair of abdominal aortic aneurysms with a stent graft is limited by the persistence or recurrence of endoleaks. These are believed to be related to the recanalization of the aneurismal sac by endothelialized neochannels, which could lead to late type I and II endoleaks. Embolization has been proposed to treat or prevent endoleaks, but presently commercialized embolizing materials have several drawbacks and do not fully prevent endoleak recurrence. A novel chitosan hydrogel that is injectable, radiopaque and contains sodium tetradecyl sulfate (STS), a well-known sclerosing agent, was developed in order to combine blood flow occlusion and endothelium ablation properties. chitosan/STS hydrogels were characterized and optimized using rheometry, scanning electron microscopy, swelling and ex vivo embolization assay. They were shown to exhibit rapid gelation and good mechanical properties, as well as sclerosing properties. Their potential for the embolization of aneurysms was subjected to preliminary in vivo evaluation in a bilateral iliac aneurysm model (three dogs) reproducing persistent endoleaks after endovascular aneurysm repair (EVAR). At 3 months no endoleak was detected in any of the three aneurysms treated with chitosan/STS hydrogels. In contrast, type I endoleaks were detected in two of the three aneurysms treated with chitosan hydrogels. Generally, chitosan/STS hydrogels have great potential as embolizing and sclerosing agents for EVAR and possibly other endovascular therapies.

Influence of aneurysm wall stiffness and the presence of intraluminal thrombus on the wall movement of an aneurysm - an in vitro study

The purpose of this in vitro study was to investigate the influence of aneurysm wall stiffness and of the presence of intraluminal thrombus (ILT) on aneurysm wall movement. Three latex aneurysms were used with different wall stiffness. The aneurysms, equipped with 20 tantalum markers, were attached to an in vitro circulation model. Fluoroscopic roentgenographic stereo photogrammetric analysis was used to measure marker movement during six cardiac cycles at three different systemic pressures. To investigate the influence of ILT on wall movement, we repeated the same experiment with one of the aneurysms. The aneurysm sac was then filled with one of two E-moduli differing thrombus analogues (Novalyse 8 and 20) or with perfusate as a control. It was noted that the amplitude of the wall movement (mm) increased significantly (P < 0.05) as the compliance of the wall increased. The mean amplitude of the wall movement decreased (P < 0.05) as the stiffness (E-modulus) of the ILT increased. In conclusion, ILT has a 'cushioning effect'. Wall movement (and theoretically wall stress) diminishes when the stiffness of the ILT increases. Compliance of the aneurysm wall influences wall movement. When the stiffness of the wall increases, the wall movement diminishes.

Assessment of EmboGel--a selectively dissolvable radiopaque hydrogel for embolic applications

PURPOSE

To evaluate the embolic properties of an alginate-based embolic biomaterial (EmboGel) and its solvent (EmboClear) in treatment of aneurysms.

MATERIALS AND METHODS

EmboGel is a mixture of iohexol and alginate that polymerizes into a hydrocoil when delivered through a coaxial catheter with a distal mixing tip, exposing alginate to a calcium chloride solution. In contrast to previously reported embolic agents, EmboGel can be selectively dissolved by EmboClear, a mixture of the enzyme alginate lyase and ethylenediaminetetraacetic acid (EDTA). The embolic and contrast properties of EmboGel were assessed in in vitro models of saccular aneurysm and an aortic aneurysm endoleak. The dissolvability of EmboGel with EmboClear was assessed further after endovascular delivery in the New Zealand white rabbit in the native aortoiliofemoral territory, a created saccular aneurysm, and the native carotid arteries.

RESULTS

EmboGel effectively filled aneurysm cavities in the case of stent excluded saccular and fusiform aneurysms. EmboGel was readily dissolved by EmboClear in vitro and after in vivo embolization. When the distal abdominal aorta and pelvic arteries were occluded with EmboGel, within 1 minute of EmboClear infusion, patency of the aorta and most of the pelvic circulation was regained as noted by angiography. Embolization in the subclavian artery and numerous distal branches was rapidly dissolved by EmboClear. Finally, the carotid artery occluded with EmboGel regained patency after administration of EmboClear.

CONCLUSIONS

EmboGel is a dissolvable alginate-based biomaterial that can be used for numerous embolic applications. EmboGel can be selectively dissolved with EmboClear, a solution of alginate lyase and EDTA.