A Water-Based Liquid Embolic: Evaluation of its Safety and Efficacy in a Rabbit Kidney Model

Vascular embolic nanobiomaterials for efficient tumor treatment

Embolization is a minimally invasive cancer treatment method. Embolization involves artificially blocking blood flow using an embolic agent to block abnormal blood vessels that supply nutrients or oxygen to a specific lesion, thereby killing the lesion, inhibiting its growth, and stopping bleeding. Currently, polyvinyl alcohol (PVA) and gelatin are the most popular embolic agents. These substances are available in various sizes and shapes that physically obstruct blood flow to cause vascular embolization. They are commonly used due to their ease of use and low cost. However, they can cause side-effect such as bleeding and potential complications related to catheter- and insertion-related complications. Recently, nanobiomaterials have been explored as embolization agents with high biocompatibility, such as liquid metals, and can be used with autologous blood. In this review, we cover the types of embolic agents currently used in cancer treatment and focus on those with fewer adverse effects and minimal vascular damage, followed by discussions on new embolic agents under development. Additionally, we explore potential future research directions for developing better embolic agents.

An analysis of the clinical efficacy and safety of a temperature-sensitive liquid embolic agent loaded with lobaplatin for the treatment of unresectable primary hepatocellular carcinoma through chemoembolization

OBJECTIVE

To explore the clinical value of transcatheter arterial chemoembolization (TACE) using a temperature-sensitive liquid embolic agent for the interventional treatment of primary hepatocellular carcinoma.

METHODS

The clinical data and follow-up results sourced from the First Affiliated Hospital of Fujian Medical University were retrospectively analyzed from February 2023 to May 2023. Clinical efficacy was assessed through follow-up imaging using the modified Response Evaluation Criteria in Solid Tumors (mRECIST) version 1.1. In addition, adverse reactions and adverse events were observed and classified using the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTC) version 3.0.

RESULTS

Among the 11 patients analyzed in this study, a total of 41 lesions were identified. The average maximum diameter of the lesions was 3.55 ± 1.88 cm (range: 1.70 cm-6.60 cm). One month postoperatively, the efficacy assessment revealed complete response (CR) in 1 case, partial response (PR) in 9 cases, stable disease (SD) in 1 case, and progression in 0 case. The objective response rate (CR + PR) was 90.91%, and the disease control rate (CR + PR + SD) was 100%. Postoperative adverse reactions were mostly of grade 1-2, including abdominal pain, bloating, fever, nausea, and vomiting.

CONCLUSION

The use of temperature-sensitive liquid embolic agents loaded with lobaplatin for chemoembolization in the treatment of unresectable primary liver cancer is a safe and effective therapeutic modality.

Comparison of Liquid with Particle Embolics in a Translational Rat Model of Hepatocellular Carcinoma: Histologic and Radiographic Responses

PURPOSE

To compare the effectiveness of transarterial embolization (TAE) using a liquid embolic (LE) with that of TAE using a particle embolic (PE) based on radiographic and histologic responses in a translational rat model of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

HCC was induced in Wistar rats using diethylnitrosamine. Tumor response was determined through Response Evaluation Criteria in Solid Tumors applied to T2-weighted magnetic resonance (MR) imaging scans. Tumor necrosis and hypoxia were assessed through hematoxylin and eosin and pimonidazole staining, respectively. Statistical analyses were performed using chi-square tests, Kaplan-Meier estimates, logistic regression, and 1-way analysis of variance, with significance set at P < .05.

RESULTS

Twenty-nine rats were randomized to TAE with LE (n = 13), PE (n = 13), or sham (n = 3). LE TAE demonstrated a significantly higher objective response rate (83%) compared with PE TAE (28%; χ2 = 11.25; P = .0008). Complete responses were observed in 50% of the LE-treated tumors versus 10% in the PE-treated group. LE TAE prolonged local progression-free survival (hazard ratio, 0.31; P = .032). Histologic analysis of an additional 16 rats randomized to TAE with LE (n = 7), PE (n = 6), or sham (n = 3) showed greater necrosis in LE-treated tumors compared to PE-treated tumors. LE induced a significantly greater reduction in viable tumor tissue (P = .009) and proportionally larger necrotic and necrotic + hypoxic tissue areas compared with PE (P = .003).

CONCLUSIONS

LE significantly enhanced the therapeutic effectiveness of TAE in a rat model of HCC compared with PE. These results highlight the potential of LEs to improve ischemia and necrosis, thereby offering a promising option for improving the effectiveness of embolization for HCC treatment.

Angiographic and Histopathological Characteristics of a Novel Polyacrylate Liquid Embolic Agent Compared with Ethylene-Vinyl Alcohol Copolymer in a Large Animal Model

PURPOSE

To study the in vivo safety and effectiveness of a novel radiopaque nonadhesive polyacrylate (PA) peripheral liquid embolic system (AMBER SEL-P) relative to ethylene-vinyl alcohol copolymer (EVOH, Onyx) in a healthy swine endovascular model.

MATERIALS AND METHODS

Twenty-five swine underwent rete mirabile and bilateral kidney embolization with PA or EVOH and were followed up for 24 hours (n = 5) and 30 days (n = 10), and 3 (n = 10) months. Angiographic features (penetrability, radiopacity, catheter entrapment, fragmentation, occlusion, and vasospasm) were evaluated. Necropsy and histology were used to evaluate the nontarget embolization, safety, and target embolization effectiveness by recanalization and analyze the vascular response.

RESULTS

No adverse events occurred during the embolization process or study period. The angiographic performance confirmed a significant positive effect of PA compared with that of EVOH in terms of penetrability (P = .007), catheter entrapment (P = .007), fragmentation (P = .007), vascular occlusion (P = .038), vasospasm (P = .038), and follow-up vascular occlusion (P = .038). Prenecropsy angiography found no vascular recanalization in the organs treated with PA, whereas it was detected at 3 months in 2 samples treated with EVOH. Histologically, PA was classified as nonirritant compared with EVOH under the study conditions according to ISO 10993-6:2016 as modified. No systemic effects during necropsy were detected in the animals treated with these agents.

CONCLUSIONS

This in vivo study found that the angiographic behavior of PA had advantages compared with EVOH. The embolization and biocompatibility of PA were similar to those of EVOH. PA was safe and effective for transarterial embolization in an acute, subacute, and chronic endovascular embolization animal models.

Biomedical applications of functional hydrogels: Innovative developments, relevant clinical trials and advanced products

Functional hydrogels are used for numerous biomedical applications such as tissue engineering, wound dressings, lubricants, contact lenses and advanced drug delivery systems. Most of them are based on synthetic or natural polymers forming a three-dimensional network that contains aqueous media. Among synthetic polymers, poly(meth)acrylates, polyethyleneglycols, poly(vinylalcohols), poly(vinylpyrrolidones), PLGA and poly(urethanes) are of high relevance, whereas natural polymers are mainly polysaccharides such as hyaluronic acid, alginate or chitosan and proteins such as albumin, collagen or elastin. In contrast to most synthetic polymers, natural polymers are biodegradable. Both synthetic and natural polymers are often chemically modified in order to improve or induce favorable properties and functions like high mechanical strength, stiffness, elasticity, high porosity, adhesive properties, in situ gelling properties, high water binding capacity or drug release controlling properties. Within this review we provide an overview about the broad spectrum of biomedical applications of functional hydrogels, summarize innovative approaches, discuss the concept of relevant functional hydrogels that are in clinical trials and highlight advanced products as examples for successful developments.

Intravascular Casting Radiopaque Hydrogel Systems for Transarterial Chemo/Cascade Catalytic/Embolization Therapy of Hepatocellular Carcinoma

This paper introduces catheter-directed intravascular casting hydrogels for transarterial chemo/starvation/chemodynamic embolization (TACSCE) therapy of hepatocellular carcinoma (HCC). Comprising Mn ion-crosslinked hyaluronic acid-dopamine (HD) with glucose oxidase (for glucose decomposition to H2O2 in starvation therapy), doxorubicin (for chemotherapy), and iopamidol (for X-ray imaging), these hydrogels are fabricated for transarterial embolization therapy guided by X-ray fluoroscopy. Mn4+ (from MnO2) demonstrates strong coordination with the catechol group of HD, providing hypoxia relief through O2 generation and cellular glutathione (GSH) consumption, compared to the OH radical generation potential of Mn2+. The gelation time-controlled, catheter-injectable, and rheologically tuned multitherapeutic/embolic gel system effectively reaches distal arterioles, ensuring complete intravascular casting with fewer complications related to organic solvents. Glucose deprivation, cascade reactive oxygen species (ROS) generation, GSH depletion, and sustained release profiles of multiple drug cargos from the hydrogel system are also achieved. The combined chemo/starvation/chemodynamic efficacies of these designed hydrogel systems are confirmed in HCC cell cultures and HCC-bearing animal models. The developed radiopaque/injectable/embolic/sol-to-gel transformable systems for TACSCE therapy may offer enhanced therapeutic efficacies compared to typical transarterial embolization and transarterial chemoembolization procedures for HCC.

Advancements in hydrogel-based embolic agents: Categorized by therapeutic mechanisms

BACKGROUND

Transcatheter arterial embolization (TAE) is a crucial technique in interventional radiology. Hydrogel-based embolic agents show promise due to their phase transition and drug-loading capabilities. However, existing categorizations of these agents are confusing.

AIMS

This review tackles the challenge of categorizing hydrogel-based embolic agents based on their therapeutic mechanisms, including transportation, accumulation, interaction, and elimination. It also addresses current challenges and controversies in the field while highlighting future directions for hydrogel-based embolicagents.

MATERIALS AND METHODS

We conducted a systematic review of papers published in PUBMED from 2004 to 2024, focusing primarily on preclinical trials.

RESULTS

Various kinds of hydrogel embolic agents were introduced according to their therapeutic mechanisms.

DISCUSSION

Most hydrogel embolic agents were specifically designed for effective accumulation and interaction. Recent advancement highlight the potential of multifunctional hydrogel embolic agents.

CONCLUSION

This new categorizations provided valuable insights into hydrogel embolic agents, potentially guiding material scientists and interventional radiologists in the development of novel hydrogel embolic agents in transarterial embolization.

Renal Artery Coil Embolization as an Endovascular Approach for Establishing a Rabbit Model of Chronic Kidney Disease

PURPOSE

To investigate the safety and feasibility of renal artery coil embolization for establishing chronic kidney disease (CKD) in rabbits.

MATERIALS AND METHODS

Ten male adult New Zealand rabbits underwent renal artery coil embolization. Initially, the main renal artery on 1 side was completely embolized, followed by embolization of approximately two-thirds of the primary branches of the contralateral renal artery 1 week later. Four rabbits were randomly chosen for sacrifice at 4 weeks after embolization, whereas the remaining 6 were sacrificed at 8 weeks after embolization. The assessment encompassed the animals' general condition, angiography, biochemical parameters, inflammatory markers, and histopathological examination of the kidneys and hearts.

RESULTS

Four weeks after embolization, serum creatinine level showed a substantial increase (2.4 mg/dL [SD ± 0.6]; P = .009 vs baseline), with a subsequent 4.12-fold elevation at 8 weeks after embolization (4.9 mg/dL [SD ± 1.4]; P < .001 vs baseline). Additionally, considerable increases in serum blood urea nitrogen, calcium, and potassium ions were observed at 8 weeks after embolization (58.3 mg/dL [SD ± 19.0]; P < .001 vs baseline; 23.1 mg/dL [SD ± 4.4]; P < .001 vs baseline; and 6.3 mEq/L [SD ± 0.7]; P < .001 vs baseline, respectively). The completely embolized kidney exhibited notable atrophy, severe fibrosis, and cortical calcification, whereas the contralateral partially embolized kidney displayed compensatory hypertrophy, along with glomerulosclerosis, tubular dilation, tubular casts, and interstitial fibrosis.

CONCLUSIONS

Renal artery coil embolization proved to be effective and safe for establishing a CKD model in rabbits.

Liquid Embolic Agents for Endovascular Embolization: A Review

Endovascular embolization (EE) has been used for the treatment of blood vessel abnormalities, including aneurysms, AVMs, tumors, etc. The aim of this process is to occlude the affected vessel using biocompatible embolic agents. Two types of embolic agents, solid and liquid, are used for endovascular embolization. Liquid embolic agents are usually injectable and delivered into the vascular malformation sites using a catheter guided by X-ray imaging (i.e., angiography). After injection, the liquid embolic agent transforms into a solid implant in situ based on a variety of mechanisms, including polymerization, precipitation, and cross-linking, through ionic or thermal process. Until now, several polymers have been designed successfully for the development of liquid embolic agents. Both natural and synthetic polymers have been used for this purpose. In this review, we discuss embolization procedures with liquid embolic agents in different clinical applications, as well as in pre-clinical research studies.

Interventional oncology: new techniques and new devices

Interventional oncology is a rapidly emerging field in the treatment of cancer. Minimally invasive techniques such as transarterial embolization with chemotherapeutic and radioactive agents are established therapies and are found in multiple guidelines for the management of primary and metastatic liver lesions. Percutaneous ablation is also an alternative to surgery for small liver, renal, and pancreatic tumors. Recent research in the niche of interventional oncology has focused on improving outcomes of established techniques in addition to the development of novel therapies. In this review, we address the recent and current advancements in devices, technologies, and techniques of chemoembolization and ablation: thermal ablation, histotripsy, high-intensity focused ultrasound, embolization strategies, liquid embolic agents, and local immunotherapy/antiviral therapies.

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.

Evaluation of a Hydrogel Liquid Embolic in a Porcine Mesenteric Hemorrhage Model

PURPOSE

To evaluate a new liquid embolic in a porcine mesenteric artery hemorrhage model.

METHODS AND MATERIALS

An anticoagulated porcine mesenteric artery hemorrhage model was created using a transarterial approach. Arterial hemorrhage was the result of aspiration needle punctures and simultaneous radiofrequency (RF) current application. Ten mesenteric arteries injured in eight swine were treated. The hydrogel liquid embolic under investigation, an aqueous-based and in situ polymerizing liquid embolic, was used to treat actively bleeding sites. At seven days, confirmation angiography was performed followed by necropsy.

RESULTS

The mesenteric arterial injuries produced persistent and angiographically visible hemorrhage prior to initiating embolic therapy. Arteriovenous fistulas were observed in four cases. Embolization led to hemostasis in 10/10 bleeds (100%). The mean embolic delivery time was 5.3 minutes (range 1-15 minutes) with a mean embolic volume of 2.9mL (range 0.8-5.2 mL) delivered to achieve hemostasis. Notably, 40% of the treatments embolized the injury in the artery at the treatment site while leaving the native arterial lumen patent for the seven day term of survival. All animals survived with no clinical evidence of hemorrhage through seven days. Necropsy did not find evidence of ischemia within bowel, liver and lung.

CONCLUSION

A new hydrogel liquid embolic was found to safely obtain acute and durable hemostasis in an animal model of persistent angiographic hemorrhage.

A Phase I First in Human Study of Embrace™ a Polyethylene Glycol Based Liquid Embolic in the Embolization of Malignant and Benign Hypervascular Tumors

PURPOSE

To investigate the safety and efficacy of an aqueous polyethylene glycol (PEG) based liquid embolic Embrace HES in the treatment of benign and malignant hypervascular tumors.

MATERIAL AND METHODS

A prospective, single-arm, multicenter study included eight patients, 5 males and 3 females median age 58.5 (30-85), who underwent embolization in eight tumors between October 2019 and May 2020. Technical success was defined as successful delivery of HES to the index vessel with disappearance of >90% of the targeted vascular enhancement, or for portal vein embolization, occlusion of the portal branches to the liver segments for future resection. The volume of HES administered, ease of use (Likert scale), administration time and adverse events were recorded. Evaluation at 7, 30 and 90 days via clinical assessment and blood testing; and follow-up imaging at 30 days.

RESULTS

Eight patients were enrolled with 10 embolizations performed in 8 lesions. Tumors included Hepatocellular carcinoma (n=4), Renal Angiomyolipoma (n=3) and Intrahepatic Cholangiocarcinoma (n=1). Technical success was 100% and average ease of use was 3.3 +/- 1.0 standard deviation. HES delivery time was 1-28 minutes (median 16.5) and HES volume injected was 0.4-4.0mL (median 1.3). All patients reached 30 day follow-up with imaging and 6 reached 90 day follow-up. There were 3 serious adverse events in 2 patients which were unrelated to the embolic agent.

CONCLUSION

HES resulted in a 100% embolization technical success. Product ease of use was acceptable and no target vessel recanalization was noted in follow up imaging at 30 days.

Embolic Materials: Understanding the Ocean of Choices

Embolization is a fundamental procedure that interventional radiologists perform on a daily basis to treat a variety of diseases. The disease processes for which embolization is considered a safe and effective treatment are continuously expanding, as are the embolization materials available for use. To achieve optimal clinical outcomes and minimize complications, it is imperative that the interventional radiologist understands the properties, strengths, and weaknesses of each class of embolic and specific embolic products. This is a continuous process as new materials are always becoming available. This article reviews the different classes of embolic materials, discusses strengths and weaknesses, and reviews areas of innovation.

The Common but Complicated Tool: Review of Embolic Materials for the Interventional Radiologist

Embolization is an important and widely utilized technique in interventional radiology. There are a variety of different categories and individual products which can be utilized to perform embolization. Understanding the different classes of embolic agents, the important features of each of these classes including strengths and limitations, and the variation in individual products within the classes is critical for interventional radiologist to practice safely and effectively. This article reviews the different kinds of embolics and relays some of the pertinent physical and chemical properties of individual products which should be considered when determining which embolic to select for a given purpose.