Non-adhesive cyanoacrylate as an embolic material for endovascular neurosurgery

Polymerisation of cyanoacrylates: The effect of sclero-embolic and contrast agents

OBJECTIVES

The objective is to investigate the interaction of sclero-embolic and contrast agents with the polymerisation of medical grade n-butyl-cyanoacrylates.

METHODS

An in vitro spectrophotometric absorbance method was developed to detect changes in light transmission to measure n-BCA polymerisation. The initiation and the rate-of-polymerisation of mixtures of n-BCA with sclero-embolic and contrast agents were investigated.

RESULTS

Initiation of polymerisation: VENABLOCK™ and HISTOACRYL® were the fastest agents to polymerise, while VENASEAL™ was the slowest. Rate of polymerisation: Hypertonic saline inhibited the polymerisation of all n-BCAs, while hypertonic glucose prolonged the polymerisation rate. ETHANOL and detergent sclerosants had no effect. Contrast agents OMNIPAQUE™ and ULTRAVIST® initiated and prolonged the polymerisation of n-BCA, but in contrast, LIPIODOL® failed to initiate the process.

CONCLUSIONS

The commercially available medical cyanoacrylates differ in their polymerisation rates. These polymerisation rates are further affected when these products are used in conjunction with other compounds, such as sclero-embolic and contrast agents.

The Advantages of Non-Adhesive Gel-like Embolic Materials in the Endovascular Treatment of Benign Hypervascularized Lesions of the Head and Neck

OBJECTIVES

The use of non-adhesive gel-like embolic materials (NAGLEMs) in the endovascular treatment of hypervascularized formations in the head and neck is gaining in popularity because of a number of important characteristics involved. Their primary benefits are their capacity to penetrate diseased vasculature, effectively distribute, and, most importantly, remain controllable during the process. We reviewed the literature and evaluated the results of using NAGLEMs in comparison to other embolizing substances (namely, coils, glue, and particles) as alternative embolizing agents for patients receiving care at our clinic. The process comprised evaluating the safety, effectiveness, and technological elements of endovascular therapy used to treat two categories of hypervascular pathological abnormalities that were surgically corrected between 2015 and 2023. Arteriovenous malformations (AVMs) located in the head, neck, and paragangliomas with jugular/carotid body localization are combined by intense shunting blood flow and shared requirements for the embolic agent used in endovascular treatment (such as penetration, distribution, delayed polymerization, and controllability). An analysis of the literature was also conducted. Results showed 18 patients diagnosed with neck paragangliomas of the carotid body and jugular type. Five patients with arteriovenous malformation (AVM) of the face and neck were included, consisting of sixteen females and seven males with an average age of 55 ± 13 years. Endovascular procedures were performed using NAGLEMs (ONYX (Medtronic, Irvine, CA, USA), SQUID (Balt, Montmorency, France), and PHIL (Microvention, Tustin, CA, USA)) and dimethyl sulfoxide (DMSO)-compatible balloon catheters. All patients achieved complete or partial embolization of hypervascularized formations using one or more stages of endovascular treatment. Additionally, three AVMs of the face and two paragangliomas of the neck were surgically excised following embolization. In other instances, formations were not deemed necessary to be removed. The patients' condition upon discharge was assessed by the modified Rankin Scale (mRs) and rated between 0 and 2.

CONCLUSION

Currently, NAGLEMs are predominantly used to treat hypervascularized formations in the neck and head due to their fundamental properties. These properties include a lack of adhesion and a delay in predictable polymerization (after 30-40 min). NAGLEMs also exhibit excellent distribution and penetration throughout the vascular bed of the formation. Adequate controllability of the process is largely achieved through the presence of embolism forms of different viscosity, as well as excellent X-ray visualization.

Large, Wide-Neck, Side-Wall Aneurysm Treatment in Canines Using NeuroCURE: A Novel Liquid Embolic

BACKGROUND

Untreated intracranial aneurysms can rupture and result in high rates of morbidity and mortality. Although there are numerous approved endovascular aneurysm treatment devices, most require dual anti-platelet therapy, are minimally biocompatible, or are prone to recanalization. Neurovascular Controlled Uniform Rapid Embolic (NeuroCURE) is an innovative polymer gel material with long-term stability, biocompatibility, and hemocompatibility developed for the treatment of large, wide-neck aneurysms.

METHODS

Sidewall aneurysms were surgically created in 10 canines and NeuroCURE was injected through a 0.025 microcatheter under a single balloon inflation period. Aneurysm treatment was angiographically assessed post-embolization and pre-term with Raymond-Roy occlusion classification and a qualitative flow grade scale. Aneurysm neck stability and biocompatibility was histologically assessed to grade platelet/fibrin thrombus, percent endothelialization, and neointimal formation. Aneurysm sac stability was assessed by NeuroCURE sac content, inflammation, and neo-angiogenesis scales.

RESULTS

Explanted aneurysms exhibited a smooth surface at the aneurysm neck with nearly complete neointimal coverage at 3-months. By 6-months, neck endothelialization was 100% in all animals (average Raymond-Roy occlusion classification of 1.2), with no instances of aneurysm recanalization or parent vessel flow compromise. Biocompatibility assessments verified a lack of inflammatory response, neo-angiogenesis, and platelet/fibrin thrombus formation.

CONCLUSION

The NeuroCURE material promotes progressive occlusion of wide-necked side wall aneurysms over time without the need for dual antiplatelet agents. NeuroCURE also promotes neointimal tissue infill without dependence on thrombus formation and thus resists aneurysm recanalization. NeuroCURE remains a compelling investigational device for the treatment of intracranial aneurysms.

X-ray Microtomography to Assess Determinants of In Vivo N-Butyl Cyanoacrylate Glubran®2 Polymerization: A Rabbit-Model Study

Although introduced decades ago, few cyanoacrylate glues have been approved for endovascular use, despite evidence of their usefulness, notably for complex procedures suchas hemostatic embolization. Indications include massive bleeding requiring emergent hemostasis and prevention of severe bleeding during scheduled surgery to remove a hypervascular tumor. Adding radiopaque Lipiodol Ultra Fluid® (LUF) modulates glue polymerization and allows fluoroscopic guidance, but few comparative in vivo studies have assessed the impact of the resulting change in glue concentration or of other factors such as target-vessel blood flow. In a rabbit model, we used ex vivo X-ray microtomography to assess the results of in vivo renal-artery embolization by various mixtures of N-butyl cyanoacrylate (NBCA), metacryloxysulfolane, and LUF. Overall, penetration to the superficial interlobular arteries was achieved in about two-thirds of cases and into the capillaries in nearly half the cases, while cast fragmentation was seen in slightly more than half the cases. Greater NBCA dilution and the blocked-blood-flow technique were independently associated with greater distality of penetration. Blocked-blood-flow injection was independently associated with absence of fragmentation, capillary penetration, a shorter cast-to-capsule distance, and higher cast attenuation. A larger mixture volume was independently associated with higher indexed cast ratio and deeper penetration. Finally, microtomography is an adapted tool to assess ex vivo distribution of glue cast.

Gluing blood into gel by electrostatic interaction using a water-soluble polymer as an embolic agent

Liquid embolic agents are widely used for the endovascular embolization of vascular conditions. However, embolization based on phase transition is limited by the adhesion of the microcatheter to the embolic agent, use of an organic solvent, unintentional catheter retention, and other complications. By mimicking thrombus formation, a water-soluble polymer that rapidly glues blood into a gel without triggering coagulation was developed. The polymer, which consists of cationic and aromatic residues with adjacent sequences, shows electrostatic adhesion with negatively charged blood substances in a physiological environment, while common polycations cannot. Aqueous polymer solutions are injectable through clinical microcatheters and needles. The formed blood gel neither adhered to the catheter nor blocked the port. Postoperative computed tomography imaging showed that the polymer can block the rat femoral artery in vivo and remain at the injection site without nontarget embolization. This study provides an alternative for the development of waterborne embolic agents.

In Vivo Experimental Endovascular Uses of Cyanoacrylate in Non-Modified Arteries: A Systematic Review

Cyanoacrylates were first used for medical purposes during World War II to close skin wounds. Over time, medical applications were developed, specifically in the vascular field. Uses now range from extravascular instillation in vascular grafting to intravascular injection for embolization. These applications were made possible by the conduct of numerous preclinical studies involving a variety of tests and outcome measures, including angiographic and histological criteria. Cyanoacrylates were first harshly criticized by vascular surgeons, chiefly due to their fast and irreversible polymerization. Over the past five years, however, cyanoacrylates have earned an established place in endovascular interventional radiology. Given the irreversible effects of cyanoacrylates, studies in animal models are ethically acceptable only if supported by reliable preliminary data. Many animal studies of cyanoacrylates involved the experimental creation of aneurysms or arteriovenous fistulas, whose treatment by endovascular embolization was then assessed. In clinical practice, however, injection into non-modified arteries may be desirable, for instance, to deprive a tumor of its vascular supply. To help investigators in this field select the animal models and procedures that are most appropriate for their objectives, we have reviewed all published in vivo animal studies that involved the injection of cyanoacrylates into non-modified arteries to discuss their main characteristics and endpoints.

Targeted Propolis-Loaded Poly (Butyl) Cyanoacrylate Nanoparticles: An Alternative Drug Delivery Tool for the Treatment of Cryptococcal Meningitis

In this study, we describe a nano-carrier system for propolis that is able to cross an in vitro model of the blood-brain barrier (BBB) and effectively reduce the virulence of Cryptococcus neoformans in animal models. Antimicrobial properties of propolis have been widely studied. However, propolis applications are limited by its low water solubility and poor bioavailability. Therefore, we recently formulated novel poly (n-butyl cyanoacrylate) nanoparticles (PBCA-NP) containing propolis. PBCA-NP are biocompatible, biodegradable and have been shown to effectively cross the BBB using apolipoprotein E (ApoE) as a ligand. Prepared nanoparticles were characterized for particle size, zeta potential, propolis entrapment efficiency and in vitro release. Additionally, the PBCA-NP were functionalized with polysorbate 80, which then specifically adsorbs ApoE. Using an in vitro BBB model of human brain microvascular endothelial cells hCMEC/D3, it was shown that fluorescence labelled ApoE-functionalized PBCA-NP were internalized by the cells and translocated across the cell monolayer. Propolis-loaded PBCA-NP had in vitro, antifungal activity against C. neoformans, which causes meningitis. To utilize the invertebrate model, Galleria mellonella larvae were infected with C. neoformans and treated with propolis-loaded PBCA-NP. The larvae exhibited normal behavior in toxicity testing, and treatment with propolis-loaded PBCA-NP increased survival in the C. neoformans-infected larvae group. In addition, following cryptococcal infection and then 7 days of treatment, the tissue fungal burden of mice treated with propolis-loaded PBCA-NP was significantly lower than control groups. Therefore, our ApoE-functionalized propolis-loaded PBCA-NP can be deemed as a potential targeted nanoparticle in the therapeutic treatment of cerebral cryptococcosis.

Balloon-Assisted Embolization of Wide-Neck Aneurysms Using a Mixture of n-Butyl Cyanoacrylate, Lipiodol, and Ethanol in Swine: A Comparison of Four n-Butyl Cyanoacrylate Concentrations

PURPOSE

To determine the optimal ratio of n-butyl cyanoacrylate (NBCA)-Lipiodol-ethanol (NLE) mixture for balloon-assisted embolization of wide-neck aneurysms.

MATERIALS AND METHODS

We created 32 wide-neck aneurysms on both the common carotid arteries and external iliac arteries in eight female swine. Eight aneurysms were randomly assigned to four groups. Under balloon occlusion, the aneurysms were packed using NLE at one of four ratios of NLE: 2:2:1 (NLE221; 40%NBCA); 3:6:1 (NLE361; 30%NBCA); 2:7:1 (NLE271; 20%NBCA); and 1:5:1 (NLE151; 14.3%NBCA). We performed angiography before and after embolization to assess the aneurysms, and we compared adhesion between NLE and the balloon and assessed NLE migration. Three days after embolization, the aneurysms were removed for histopathologic evaluation.

RESULTS

Embolization was performed in 27 aneurysms. Adhesion between NLE and the balloon was not observed in any group. NLE migration was found in 0/7 aneurysms in the NLE221 group, 0/6 in the NLE361 group, 5/6 in the NLE271 group, and 7/8 in the NLE151 group. NLE migration was significantly lower in the NLE221 group than in the NLE271 and NLE151 groups (P = 0.0047 and 0.0014, respectively) and was significantly lower in the NLE361 group than in the NLE271 and NLE151 groups (P = 0.0152 and 0.0047, respectively). Media necrosis of the arterial wall close to the aneurysms was observed in all groups.

CONCLUSION

NLE with an NBCA concentration of ≥ 30% is a safe and feasible embolic material for balloon-assisted embolization of wide-neck aneurysms in swine in the short term up to 3 days after embolization.

Is the Cessation of Blood Flow Faster than the Polymerization of an n-Butyl Cyanoacrylate-Lipiodol Mixture? An In Vitro Phantom Study

PURPOSE

To compare the polymerization time of n-butyl cyanoacrylate (NBCA) and lipiodol mixture in a static model and a pulsating flow model simulating embolization procedure of small caliber arteries.

MATERIALS AND METHODS

The polymerization time of NBCA-lipiodol mixture was measured by the morphological changes of a glue droplet in a petri dish. For the flow model, we used a 2-mm-inner-diameter polyvinyl alcohol tube connected to a pulsation pump. Bovine serum was supplied from the pump and circulated into the system at 30 ml/min and 60 bpm. A 0.64-mm-inner-diameter silicon microcatheter was inserted into this system, and then, 0.5 ml of glue was injected into the tube. The flow cessation time was defined as the time it took to stop the serum draining from the end of the tube. Six samples of 100, 66, 50, 40, 33, and 20 vol% NBCA were assessed.

RESULTS

The median polymerization times for each concentration were 0.12, 3.72, 12.30, 27.41, 57.68, and 63.67 s, respectively. The median flow cessation times were 0.28, 0.78, 1.43, 3.75, 4.50, and 9.29 s, respectively. The flow cessation time was significantly shorter than the polymerization time for all samples except for 100 vol% cyanoacrylate (p < 0.05).

CONCLUSION

The flow cessation time of cyanoacrylate glue was significantly shorter than the polymerization time in an in vitro experiment. The injected glue possibly stops the blood flow before the completion of polymerization in the vascular system.

From poly(alkyl cyanoacrylate) to squalene as core material for the design of nanomedicines

This review article covers the most important steps of the pioneering work of Patrick Couvreur and tries to shed light on his outstanding career that has been a source of inspiration for many decades. His discovery of biodegradable poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs) has opened large perspectives in nanomedicine. Indeed, NPs made from various types of alkyl cyanoacrylate monomers have been used in different applications, such as the treatment of intracellular infections or the treatment of multidrug resistant hepatocarcinoma. This latest application led to the Phase III clinical trial of Livatag^®, a PACA nanoparticulate formulation of doxorubicin. Despite the success of PACA NPs, the development of a novel type of NP with higher drug loadings and lower burst release was tackled by the discovery of squalene-based nanomedicines where the drug is covalently linked to the lipid derivative and the resulting conjugate is self-assembled into NPs. This pioneering work was accompanied by a wide range of novel applications which mainly dealt with the management of unmet medical needs (e.g. pancreatic cancer, brain ischaemia and spinal cord injury).

In Vitro Evaluation of the Polymerization Properties of N-Butyl Cyanoacrylate/Iodized Oil Mixtures for Lymphatic Interventions

PURPOSE

To evaluate polymerization of N-butyl cyanoacrylate (NBCA)/iodized oil mixtures for lymphatic interventions in vitro.

MATERIALS AND METHODS

Polymerization times of different NBCA/iodized oil mixtures (ratios of 1:0-1:7) were investigated in a static and dynamic experimental setup (performed in a lymph flow model in a silicone tube). Eight lymphatic samples with different triglyceride (TG) concentrations (low TGs, < 50 mg/dL; medium TGs, approximately 100-400 mg/dL; high TGs, > 700 mg/dL) were investigated. Morphologic changes during NBCA polymerization were monitored and recorded by video. Statistical analysis was performed with intergroup comparisons (Kruskal-Wallis test) and multiple regression analysis.

RESULTS

Static experiments showed increasing polymerization times with increasing concentrations of iodized oil as well as increasing concentrations of TGs. In the low-TG group, polymerization time increased from 14 s at a 1:1 ratio of NBCA to iodized oil to 1,336 s at a 1:7 ratio; times in the medium-TG group increased from 21 s (1:1) to 2,546 s (1:7), and those in the high TG group increased from 168 s (1:1) to 16,530 s (1:7). In dynamic experiments, prolongation of polymerization time was less pronounced. For low- and medium-TG groups, total occlusion of the silicon tube was observed in all cases during the embolization procedure at between 26 seconds (1:1 ratio) and 52 seconds (1:7). In the high-TG group, polymerization took considerably longer (between 43 s [1:1] and 467 s [1:7]) or failed completely.

CONCLUSIONS

Polymerization time of NBCA/iodized oil in lymph seems to be prolonged by increasing iodized oil and TG concentrations.

Biocompatible alkyl cyanoacrylates and their derivatives as bio-adhesives

Cyanoacrylate adhesives and their homologues have elicited interest over the past few decades owing to their applications in the biomedical sector, extending from tissue adhesives to scaffolds to implants to dental material and adhesives, because of their inherent biocompatibility and ability to polymerize solely with moisture, thanks to which they adhere to any substrate containing moisture such as the skin.

A Case of Common Peroneal Nerve Palsy Associated with Internal Iliac Artery Embolization by Using N-butyl-2-cyanoacrylate (NBCA)

A 64-year-old man was scheduled to undergo endovascular aneurysm repair for an abdominal aortic aneurysm (AAA). Since preoperative computed tomography showed an AAA with common iliac artery and internal iliac artery (IIA) aneurysms, IIA embolization was scheduled. Embolization using a coil was supposed to be performed; however, the lateral sacral artery could not be selected. For this reason, IIA embolization using N-butyl-2-cyanoacrylate (NBCA) was undertaken. During embolization, the median sacral artery was unexpectedly embolized through the lateral sacral artery. The patient complained of drop foot just after embolization; he was diagnosed with iatrogenic common peroneal nerve palsy. We have learned that sciatic nerve palsy can occur in cases of embolization with a liquid NBCA-Lipiodol mixture to the lateral or sacral median artery.

Efficacy and safety of Innoseal for air leak after pulmonary resection: a case-control study

BACKGROUND

Prolonged air leak is one of the most common complications after lung surgery and the cause of prolonged hospital stay frequently associated with major postoperative morbidity and thus responsible for even higher hospital costs. This case-control study was designed to test the sealing efficacy and safety of Enable-Innoseal TP4 in patients undergoing pulmonary resection for lung cancer.

METHODS

This was a case-control trial enrolling patients with primary or single site metastatic lung cancer scheduled for elective anatomic or nonanatomic pulmonary resection presenting intraoperative grade 1 or 2 air leak at water submersion test; the study group population was then matched 1:1 according to surgical procedure, male/female ratio, preoperative FEV1, and age.

RESULTS

In the study population, 21 patients (70.0%) presented intraoperative grade 1 air leak and 9 patients grade 2 (30.0%) air leak; after comparison with the control group, we observed a significant shorter time for chest drain removal in the study population (P = 0.0050), whereas no difference was registered in terms of number of days needing for discharge (P = 0.0762).

CONCLUSIONS

Enable-Innoseal TP4 was effective in treating limited intraoperative air leaks after pulmonary resection and preventing prolonged postoperative air leaks in patients receiving either anatomic or nonanatomic lung resections. Further randomized double-arm studies are required to confirm the efficacy of Enable-Innoseal TP4 demonstrated by this pilot study.

In situ precision electrospinning as an effective delivery technique for cyanoacrylate medical glue with high efficiency and low toxicity

The side effects or toxicity of cyanoacrylate used in vivo have been argued since its first application in wound closure. We propose an airflow-assisted in situ precision electrospinning apparatus as an applicator and make a detailed comparison with traditional spraying via in vitro and in vivo experiments. This novel method can not only improve operational performance and safety by precisely depositing cyanoacrylate fibers onto a wound, but significantly reduce the dosage of cyanoacrylate by almost 80%. A white blood cell count, liver function test and histological analysis prove that the in situ precision electrospinning applicator produces a better postoperative outcome, e.g., minor hepatocyte injury, moderate inflammation and the significant ability for liver regeneration. This in situ precision electrospinning method may thus dramatically broaden both civilian and military applications of cyanoacrylates.

The efficacy and risks of preoperative embolization of spinal tumors

Background

The goal of preoperative embolization of spinal tumors is to improve surgical outcomes by diminishing the vascular supply to the tumor to reduce intraoperative blood loss and operative time.

Objective

To report our institutional experience with spinal tumor embolization and review the present literature.

Methods

Clinical records from January 1, 2001 to December 31, 2012 were reviewed and analyzed. Angiograms were used to calculate the percentage reduction in tumor vascularity, and relevant clinical and operative data were collected and analyzed.

Results

Thirty-seven patients underwent preoperative spinal tumor embolization (24 metastatic and 13 primary lesions) and were included in the study. One complication resulted in transient lower extremity weakness and was attributed to post-embolization swelling, which fully resolved after surgical resection. The transient neurological complication rate was 1/37 (3%) and the permanent rate was 0/37 (0%). The average surgical estimated blood loss (EBL) was 1946 mL (100–7000 mL) and the average operative time was 330 min (range 164–841 min). After embolization, tumor blush was reduced by 83% on average. Average pre- and postoperative modified Rankin Scale scores were 2.10 and 1.36, respectively (p=0.03). Cases in which tumor blush was decreased by ≥90% (classes 1 or 2) after embolization had significantly less operative blood loss than those cases in which <90% (classes 3 or 4) was achieved (mean EBL 1391 vs 2296 mL, respectively, p=0.05).

Conclusions

Spinal tumor embolization is a safe procedure, is associated with few complications, and may improve surgical outcomes by limiting intraoperative blood loss and reducing operative time.

Epirubicin loading in poly(butyl cyanoacrylate) nanoparticles manifests via altered intracellular localization and cellular response in cervical carcinoma (HeLa) cells

OBJECTIVE

Drug loading into nanocarriers is used to facilitate drug delivery to target cells and organs. We have previously reported a change in cellular localization of epirubicin after loading to poly(butyl cyanoacrylate) (PBCA) nanoparticles. We aimed to further investigate the altered cellular localization and cellular responses to the described drug formulation.

MATERIALS AND METHODS

HeLa cells were treated with epirubicin-loaded PBCA nanoparticles prepared by the pre-polymerization method. A systematic study was performed to evaluate the formulation cytotoxicity. Cellular localization and uptake of the formulation as well as cellular response to the treatment were evaluated.

RESULTS

Our studies revealed decreased cytotoxicity of the nanoparticle-formulated epirubicin compared to the free drug as well as a noticeable change in the drug's intracellular localization. Epirubicin-loaded nanoparticles were internalized via endocytosis, accumulated inside endosomal vesicles and induced a two-fold stronger pro-apoptotic signal when compared to the free drug. The level of the tumor suppressor protein p53 in HeLa cells increased significantly upon treatment with free epirubicin, but remained relatively unchanged when cells were treated with equivalent dose of nanoparticle-loaded drug, suggesting a possible shift from p53-dependent DNA/RNA intercalation-based induction of cytotoxicity by free epirubicin to a caspase 3-induced cell death by the epirubicin-loaded PBCA formulation.

Guidelines for the use of NBCA in vascular embolization devised by the Committee of Practice Guidelines of the Japanese Society of Interventional Radiology (CGJSIR), 2012 edition

Cyanoacrylates are a group of fast-acting adhesives. They form low viscosity liquids in the monomer state and instantly polymerize to become adhesive upon contact with ionic substances. Since the 1950s, they have been used around the world for industrial and household purposes. N-butyl cyanoacrylate (NBCA) is a cyanoacrylate that is commonly used for medical care, and the closure of skin wounds with NBCA has been found to promote hemostasis. However, in Japan, the intravascular injection of NBCA is considered to be off-label use, except during the treatment of gastric varices under endoscopy. The use of NBCA in embolotherapy is considered when the target vessels cannot be cannulated superselectively, for vascular diseases that require long segments of the target vessel to be embolized, or for patients in a hypocoagulable state. NBCA-based embolotherapy can be used to treat vascular malformations, acute hemorrhaging, tumors, and venous disease. The complications associated with NBCA-based embolotherapy include tissue ischemia, hemorrhaging, systemic or local reactions, and catheter adhesion to blood vessels. NBCA is mixed with Lipiodol to make it radiopaque and to adjust its polymerization time. Since there are various technical aspects to performing NBCA-based embolotherapy safely, it should be carried out by, or with the assistance of, proficient interventional radiologists.

Miniemulsion polymerizations of n-butyl cyanoacrylate via two routes: towards a control of particle degradation

This study aimed at determining the influence of the mechanism of polymerization on the molar mass and degradation of poly(n-butyl cyanoacrylate) (PBCA) nanoparticles obtained by miniemulsion polymerization. Therefore, nanoparticles of poly(n-butyl cyanoacrylate) were synthesized via radical and/or anionic miniemulsion polymerization stabilized by Brij®78, a POE based surfactant. Polymerization conditions had little influence on the final diameter while it severely affected the final molar masses of PBCA. An increase of the temperature and of the pH of the continuous phase led to higher molar masses. A further increase was observed when a radical initiator was added in the monomer. The evolution of the molar mass of the synthesized poly(n-butyl cyanoacrylate) was followed as a function of time at pH 7.4 by Size Exclusion Chromatography. As expected, the degradation kinetics strongly depended on the polymerization mechanism (anionic or radical).

Shape memory polymer foams for cerebral aneurysm reparation: effects of plasma sterilization on physical properties and cytocompatibility

Shape memory polyurethanes (SMPUs) represent promising candidate materials for aneurysm embolization, since they could enable clinical problems still associated with these clinical procedures to be overcome. In this work, we report on the characterization of physicochemical, thermomechanical and in vitro interface properties of two SMPU foams (Cold Hibernated Elastic Memory, CHEM), proposed as a material for embolization devices in minimally invasive procedures. Moreover, because device sterilization is mandatory for in vivo applications, effects on the properties of the foams after plasma sterilization were also evaluated. Both foams (CHEM 3520 and CHEM 5520) showed excellent shape recovery ability (recovery rate, R(r), up to 99%) in conventional shape recovery tests, performed at constant heating rate. Transition temperatures (T(trans)), determined by tandelta peaks in dynamic mechanical analysis (DMA), were 32.2 and 45.1 degrees C, for CHEM 3520 and 5520, respectively. The value of T(trans) affects shape memory ability in the recovery test at 37 degrees C, which simulates the behavior after implantation of the device: in fact, R(r) was significantly higher for lower T(trans) foam (R(r) approximately 82% and R(r) approximately 46%, respectively, for CHEM 3520 and CHEM 5520). After plasma sterilization performed by a Sterrad sterilization system, an increase in open porosity was observed: this is probably due to the sterilization cycle; however, no effects on shape recovery behavior were observed. Furthermore, plasma treatment had no significant effect on L929 cells in in vitro cytotoxicity tests, performed on cell culture medium extracts in contact with foams for up to 7 days. Moreover, direct cytocompatibility tests showed a good colonization and growth from L929 cells on CHEM foams, suggesting the effectiveness of an in vivo healing process. All these results seem to suggest that CHEM foams could be advantageously used for manufacturing devices for mini-invasive embolization procedures of aneurysms.

Endovascular embolization of a recurrent cervical giant cell neoplasm using N-butyl 2-cyanoacrylate

Pre-operative endovascular embolization of spinal giant cell tumors (GCTs) has been an effective strategy to reduce blood loss during surgical resection. Traditionally, spinal GCTs have been embolized with polyvinyl acetate (PVA) particles. We present the pre-operative embolization of a recurrent cervical GCT with N-butyl 2-cyanoacrylate (NBCA) rather than PVA. The patient was a 17-year-old female who, 3 months prior, had undergone a surgical resection of a cervical GCT without pre-operative embolization. She returned with tumor recurrence in the approximate location. Resection was recommended, and pre-operative embolization was requested. The tumor was embolized with NBCA. Post-embolization angiography demonstrated significantly decreased tumor "blush" and a significant reduction of the vascular supply. This is the first reported use of NBCA for the pre-operative embolization of a cervical GCT. The benefits of NBCA over PVA particles include superior penetration, permanent tumor embolization and lower exposure to radiation due to shorter procedure time.

Experimental comparative study in rabbits of three different ways of cartilage graft fixation: suture, gelatin-resorcin-formaldehyde and butyl-2-cyanoacrylate

CONCLUSION

The compound gelatin-resorcin-formaldehyde (GRF) was a better stabilizing material for cartilage grafts in rabbits than butyl-2-cyanoacrylate. GRF was also better than the suture when comparing fixation of cartilage to the periosteum and inflammatory reaction.

OBJECTIVE

Cartilage grafting is an interesting option for refinements on rhinoplasties. The objective of this study was to compare butyl-2-cyanoacrylate to GRF and suture to determine the efficacy of these methods in restraining grafted cartilage in rabbits.

MATERIALS AND METHODS

Fifteen male adult New Zealand rabbits underwent surgery with the aim of collecting six auricular cartilage grafts from each animal. Two of these grafts in each animal were glued together with butyl-2-cyanoacrylate, two were glued together with compound GRF, and two were sewn together with nylon suture. These sandwich grafts were then glued or sutured to the periosteum of the glabella. After 2, 6, and 12 weeks, groups of five animals were sacrificed and histological analysis for inflammation was performed. Cartilage graft migration, adhesion, and deformities of the grafts were also evaluated.

RESULTS

There was less migration of the cartilages glued with GRF than with cyanoacrylate and suture. GRF showed statistically less inflammatory reaction and angiogenesis than the other two methods. The three methods showed a tendency to decrease of fibrosis, inflammation, and angiogenesis as weeks passed. There was no detachment or deformity in the cartilage sandwiches sutured to the glabella's periostium. The majority of detached and deformed cartilages were those glued with cyanoacrylate. The number of detached cartilages was directly related to the number of deformed cartilages. The data were statistically significant (p<0.05).

Endovascular embolization of the swine rete mirabile with Eudragit-E 100 polymer

BACKGROUND AND PURPOSE

Both adhesive and nonabrasive embolic agents are available for arteriovenous malformation (AVM) embolization. The purpose of this study was to evaluate a novel ethanol-based nonadhesive liquid embolic material in a swine AVM model.

MATERIALS AND METHODS

Eudragit (copolymer of methyl and butyl methacrylate and dimethylaminoethyl methacrylate) was dissolved in 50% ethanol and 50% iopamidol. Eudragit was injected into 9 retia mirabilia (RMs). Ethanol and iopamidol mixture were injected into 4 RMs for comparison. Three RMs embolized with Eudragit mixture were evaluated both angiographically and histopathologically acutely (3-24 hours) and at 30 days and 90 days after embolization.

RESULTS

No procedural complications from Eudragrit embolization were noted, including retention or adhesion of the microcatheter. Various degrees of inflammation were observed in the acute and 30-day specimens. Two RMs showed partial recanalization on both histopathology and follow-up angiography in the 30-day group. Arterial fibrosis and calcification were observed in the 30- and 90-day specimens. The internal elastic lamina was disrupted in the 30- and 90-day specimens, but there was no evidence of Eudragit extravasation or hemorrhage. Endothelial damage was seen in all specimens and was particularly severe in the 30- and 90-day specimens.

CONCLUSION

Eudragit polymer induced inflammation in thrombosis similar to n-butyl 2-cyanoacrylate, but without the disadvantages of perivascular hemorrhage and extravasation of embolization material. Although recanalization of some embolized RMs was noted, further investigation into Eudragit as a potentially useful embolic material for brain AVMs is warranted.

SURGICAL APPLICATIONS OF CYANOACRYLATE ADHESIVES: A REVIEW OF TOXICITY

Cyanoacrylate (CA) and its homologues have a variety of medical and commercial applications as biological adhesives and sealants. Homologues of CA are being widely promoted in surgery as a tissue adhesive to replace traditional suturing techniques. Potential benefits of using CA adhesives include better cosmetic results, more rapid wound closure, and perhaps most significantly, the potential for significant reductions in percutaneous injuries from suture needles, which would in turn also reduce the risk of transmission of infectious diseases. Nevertheless, certain concerns have been raised regarding the potential toxicity of CA within patients, as well as among health professionals who are occupationally exposed when using CA compounds. Reported toxicity of CA in the workplace may result in dermatological, allergic and respiratory conditions. To help reduce the occupational burden, therefore, medical staff using CA adhesives should avoid direct contact with the compound and use appropriate personal protective measures at all times. Maintaining higher levels of humidity, optimizing room ventilation and using special air conditioning filters in surgical suites and operating theatres may also be useful in minimizing the exposure to volatile CA adhesives.

Surgical Endovascular Neuroradiology in the 21st Century: What Lies Ahead?

FEW COULD HAVE imagined the tremendous growth of endovascular surgery over the past 40 years. Endovascular therapy has greatly enhanced the care of the patient in neurosurgery, spine surgery, and head and neck surgery. Progress in technology and techniques continue to push forward the boundaries of what is deemed “treatable,” assuming acceptable risk. This article will briefly review the current state of endovascular surgery and speculate about what its role will be in the near and far future. Endovascular therapy provides a minimally invasive approach to the central nervous system and other systems via natural and, at times, highly selective pathways. Maximizing the accessibility of these routes to highly specific regions of the central nervous system provides an elegant and minimalist approach to treating diseases of the central nervous system with almost no “footprints” of ever having accessed the region. In the future, safe, efficient and intelligent delivery systems that may enhance or alter the tissue's response may result in successful treatment of cerebrovascular diseases, as well as other diseases of the craniospinal axis. The growth of nanotechnology, metallurgy, synthetic polymers, imaging, and training will all combine to help grow the technology and the science that is surgical endovascular neuroradiology.

Endovascular Treatment of Cerebral Arteriovenous Malformations

The modern management of cerebral arteriovenous malformations (AVMs) is based on three therapeutic modalities: microneurosurgery, endovascular embolization, and stereotactic radiosurgery. Embolization facilitates subsequent radiosurgery by reducing the volume of the nidus, prepares the resection of surgically accessible AVMs, and immediately addresses the risks related to associated intra/extranidal aneurysms and arteriovenous fistulas. We discuss in this article the current state of AVM endovascular therapy.

Biomaterials Used in Injectable Implants (Liquid Embolics) for Percutaneous Filling of Vascular Spaces

The biomaterials currently used in injectable implants (liquid embolics) for minimally invasive image-guided treatment of vascular lesions undergo, once injected in situ, a phase transition based on a variety of physicochemical principles. The mechanisms leading to the formation of a solid implant include polymerization, precipitation and cross-linking through ionic or thermal process. The biomaterial characteristics have to meet the requirements of a variety of treatment conditions. The viscosity of the liquid is adapted to the access instrument, which can range from 0.2 mm to 3 mm in diameter and from a few centimeters up to 200 cm in length. Once such liquid embolics reach the vascular space, they are designed to become occlusive by inducing thrombosis or directly blocking the lesion when hardening of the embolics occurs. The safe delivery of such implants critically depends on their visibility and their hardening mechanism. Once delivered, the safety and effectiveness issues are related to implant functions such as biocompatibility, biodegradability or biomechanical properties. We review here the available and the experimental products with respect to the nature of the polymer, the mechanism of gel cast formation and the key characteristics that govern the choice of effective injectable implants.

Poly(alkylcyanoacrylates) as biodegradable materials for biomedical applications

This review considers the use of poly(alkylcyanoacrylates) (PACAs) as biomedical materials. We first present the different aspects of the polymerization of alkylcyanoacrylate monomers and briefly discuss their applications as skin adhesives, surgical glues and embolitic materials. An extensive review of the developments and applications of PACAs as nanoparticles for the delivery of drugs is then given. The methods of preparation of the nanoparticles are presented and considerations concerning the degradation, in vivo distribution, toxicity and cytotoxicity of the nanoparticles are discussed. The different therapeutic applications are presented according to the route of administration of the nanoparticles and include the most recent developments in the field.

Cold hibernated elastic memory foams for endovascular interventions

Cold hibernated elastic memory (CHEM) polyurethane-based foam is a new shape memory polymeric self-deployable structure. Standard cytotoxicity and mutagenicity tests were conducted on CHEM in vitro, to ensure biocompatibility before studying potential medical applications. In vivo, lateral wall aneurysms were constructed on both carotid arteries of eight dogs. Aneurysms were occluded per-operatively with CHEM blocks. In two dogs, CHEM embolization was compared with gelatin sponge fragment embolization. Internal maxillary arteries (Imax) were also occluded with CHEM using a 6F transcatheter technique. Angiography and pathology were used to study the evolution of aneurysms and Imax at 3 and 12 weeks. Imax embolized with CHEM foam remained occluded at 3 weeks. Most aneurysms embolized with CHEM showed a small residual crescent of opacification at initial angiography, but angiographic scores were significantly better at 3 weeks. Thick neointima formation over the CHEM at the neck of aneurysms was demonstrated at pathology. The foamy nature of CHEM favours the ingrowth of cells involved in neointima formation. New devices for endovascular interventions could be designed using CHEM's unique physical properties.

Flow properties of liquid calcium alginate polymer injected through medical microcatheters for endovascular embolization

The flow properties of liquid calcium alginate injections were investigated for application in endovascular embolization. Alginate shear properties were assessed with a rheometer and a controlled injection system. The experimental results were used to model the flow properties and predict alginate's flow characteristics within various medical microcatheter delivery systems. The results suggest that alginates undergo shear-thinning effects with increasing shear. A flow comparison of 2.0 wt % alginate and a Newtonian fluid (82 cP) injected from the same microcatheter had similar flow rates at low injection pressure (100 kPa). However, at high injection pressure (2100 kPa), the alginate was injectable at a flow rate 100% higher than was the Newtonian fluid. Further analysis of injections through microcatheters resulted in a flow model for predicting viscosity changes, flow rates, and injection pressures of liquid alginate at medium-to-high shear rates. The predicted injection pressures and flow rates had an average variance of less than 15% from that of the experimental flow data. This study indicates that calcium alginate has the requisite flow properties for successful delivery to vascular lesions via endovascular injection. Possible uses of alginates include treating arteriovenous malformations (AVMs), aneurysms, blood flow to tumors, and vascular hemorrhages.

Calcium alginate gel: a biocompatible and mechanically stable polymer for endovascular embolization

The development and optimization of calcium alginate for potential use in endovascular occlusion was investigated by testing its in vitro and in vivo mechanical stability and biocompatibility. The compressive resistance, rheology, and polymer yield of reacted alginate, and the polymer viscosity of unreacted alginate, were assessed. Biocompatibility was tested by injecting calcium alginate into the kidney capsule of rats. The reactivity of alginates with various structures and levels of purity were compared visually and histologically. Results suggest that calcium alginate is a biocompatible and mechanically stable gel for endovascular applications. Purified alginates exhibited compressive strength of 22 kPa and above at 40% compression, with no significant loss in elasticity. Purified alginate strength was significantly higher than that of crude alginates (p < 0.08). Purified alginates also exhibited significantly lower tissue reaction than crude alginates (p < 0.05). Of the alginates tested, purified high guluronic acid alginates (PHG) exhibited optimal strength and polymer yield, increased biocompatibility, and decreased viscosity. Clinical embolization treatments may be improved with the development of stable and biocompatible polymers such as calcium alginate. Possible uses of improved endovascular polymers include treating arteriovenous malformations (AVMs), aneurysms, blood flow to tumors, and vascular hemorrhaging.