Curative treatment of cerebral arteriovenous malformations by embolisation using cellulose acetate polymer followed by surgical resection

In-situ injectable physically and chemically gelling NIPAAm-based copolymer system for embolization

The goal of this work is to make an injectable physically and chemically cross-linking NIPAAm-based copolymer system for endovascular embolization. A copolymer with N-isopropylacrylamide (NIPAAm) and hydroxyethyl methacrylate (HEMA) was synthesized and converted to poly(NIPAAm-co-HEMA-acrylate) functionalized with olefins. When poly(NIPAAm-co-HEMA-acrylate) was mixed with pentaerythritol tetrakis 3-mercaptopropionate (QT) stoichiometrically in a 0.1 N PBS solution of pH 7.4, it formed a temperature-sensitive hydrogel with low swelling through the Michael-type addition reaction and showed improved elastic properties at low frequency compared to physical gelation. This material could be useful for applications requiring water-soluble injection but lower swelling and lower creep properties than available with other soluble in-situ-gelling materials.

Gel strength and solution viscosity of temperature-sensitive, in-situ-gelling polymers for endovascular embolization

The goal of this work was to investigate the relationship of the gel strength and stiffness (at 37 degrees C) to solution viscosity (at 25 degrees C) in poly(N-isopropylacrylamide-co-acrylic acid) solutions with regard to acid content, molecular weight and solution concentration. It was hypothesized that the gel strength could be maximized while minimizing the increase in solution viscosity. If so, there would be motivation to investigate these materials for arteriovenous malformation embolization. The co-polymers were synthesized with 0-2 mol% content of acrylic acid (AAc) in benzene, dioxane, THF, 50:50 benzene/dioxane, or 50:50 dioxane/THF to obtain polymers of different molecular weight. The polymers were characterized for molecular weight by GPC/light scattering, for acrylic acid content by acid titration, for lower critical solution temperature by differential scanning calorimetry, and for solution viscosity (at 25 degrees C) and gel strength (at 37 degrees C) by rheometry. Solutions of lower-molecular-weight polymers were shown to have lower viscosities while possessing higher strengths as gels than the highest manageable concentrations of higher-molecular-weight polymers. This work demonstrates that the mechanical properties of poly(N-isopropylacrylamide-co-acrylic acid) can be increased while minimizing the increase in solution viscosity.

Mechanical Optimization of an Arteriovenous Malformation Embolization Material: A Predictive Model Analysis

Arteriovenous malformations (AVMs) pose a constant danger of hemorrhages, seizures, and headaches to patients; they also disrupt oxygen-rich blood flow entering capillaries of the brain. We have utilized a linear model to mechanically characterize and optimize a water-borne, reverse emulsion, self-reactive, in situ cross-linking material, which we propose clinical use as an embolization material. The material is formed by cross-linking various acrylate and thiol multifunctional precursors with NaOH supplemented PBS. We compared theoretical elastic modulus values to modulus values observed during compression testing to determine the cross-linking efficiency of the material. Empirically determined elastic moduli for various material compositions ranged from 0.76 to 2.26 MPa, with corresponding cross-link efficiencies averaging 55+/-4%. We predict a reduction in theoretical circumferential stress exerted on AVM vasculature from 4933 to 10.9 Pa after embolization with the optimal material configuration. Theoretical risk of AVM rupture, as defined by Hademenos et al., was reduced below 1.0% for extreme variations of vessel modulus, thickness, and blood pressure after embolization with the optimized material. We will be using this material configuration to embolize swine rete mirabile AVM models and further assess the clinical viability of this potential embolization material.