Poly(2-hydroxyethyl methacrylate) beads for the preoperative endovascular occlusion of branches of the hepatic artery in focal alterations of the liver

Fabrication of Highly Porous Nonspherical Particles Using Stop-Flow Lithography and the Study of Their Optical Properties

A microfluidic flow lithography approach was investigated to synthesize highly porous nonspherical particles and Janus particles in a one-step and high-throughput fashion. In this study, using common solvents as porogens, we were able to synthesize highly porous particles with different shapes using ultraviolet (UV) polymerization-induced phase separation in a microfluidic channel. We also studied the pore-forming process using operating parameters such as porogen type, porogen concentration, and UV intensity to tune the pore size and increase the pore size to submicron levels. By simply coflowing multiple streams in the microfluidic channel, we were able to create porous Janus particles; we showed that their anisotropic swelling/deswelling exhibit a unique optical shifting. The distinctive optical properties and the enlarged surface area of the highly porous particles can improve their performance in various applications such as optical sensors and drug loading.

Morphological and Functional Analysis of Hepatocyte Spheroids Generated on Poly-HEMA-Treated Surfaces under the Influence of Fetal Calf Serum and Nonparenchymal Cells

Poly (2-hydroxyethyl methacrylate) (HEMA) has been used as a clinical material, in the form of a soft hydrogel, for various surgical procedures, including endovascular surgery of liver. It is a clear liquid compound and, as a soft, flexible, water-absorbing material, has been used to make soft contact lenses from small, concave, spinning molds. Primary rat hepatocyte spheroids were created on a poly-HEMA-coated surface with the intention of inducing hepatic tissue formation and improving liver functions. We investigated spheroid formation of primary adult rat hepatocyte cells and characterized hepatic-specific functions under the special influence of fetal calf serum (FCS) and nonparencymal cells (NPC) up to six days in different culture systems (e.g., hepatocytes + FCS, hepatocytes – FCS, NPC + FCS, NPC – FCS, co-culture + FCS, co-culture – FCS) in both the spheroid model and sandwich model. Immunohistologically, we detected gap junctions, Ito cell/Kupffer cells, sinusoidal endothelial cells and an extracellular matrix in the spheroid model. FCS has no positive effect in the sandwich model, but has a negative effect in the spheroid model on albumin production, and no influence in urea production in either model. We found more cell viability in smaller diameter spheroids than larger ones by using the apoptosis test. Furthermore, there is no positive influence of the serum or NPC on spheroid formation, suggesting that it may only depend on the physical condition of the culture system. Since the sandwich culture has been considered a “gold standard” in vitro culture model, the hepatocyte spheroids generated on the poly-HEMA-coated surface were compared with those in the sandwich model. Major liver-specific functions, such as albumin secretion and urea synthesis, were evaluated in both the spheroid and sandwich model. The synthesis performance in the spheroid compared to the sandwich culture increases approximately by a factor of 1.5. Disintegration of plasma membranes in both models was measured by lactate dehydrogenase (LDH) release in both models. Additionally, diazepam was used as a substrate in drug metabolism studies to characterize the differences in the biotransformation potential with metabolite profiles in both models. It showed that the diazepam metabolism activities in the spheroid model is about 10-fold lower than the sandwich model. The poly-HEMA-based hepatocyte spheroid is a promising new platform towards hepatic tissue engineering leading to in vitro hepatic tissue formation.

Targeted chemoembolization of tumors with poly(2-hydroxyethyl methacrylate) particles

Thirty-four patients suffering from various kinds of tumors, including metastasis, were treated by selective embolization with both spherical and cylindrical poly(2-hydroxyethyl methacrylate) [poly(HEMA)] particles and topical chemotherapy. Treatment of a patient with carcinoid metastases in the liver is discussed. Immediately after embolization, 5-fluorouracil, and later, doxorubicin and Lipiodol, were selectively infused into the tumorous tissue for approximately 1 week. Patient received four cycles of this infusion. Chemoembolization proceeded against the background of anticoagulant therapy using small doses of heparin or its low-molecular-weight analogue, dalteparin. This was followed by transcutaneous transhepatic portography and embolization. Finally, the tumor-feeding artery and portal vein were sealed by a hydrogel. After 1.5 months, the affected liver lobe was resected. Although 4 years from the beginning of treatment, the patient is still alive. Embolization with poly(HEMA) hydrogel particles in conjunction with an anticancer drug infusion via catheter is recommended as an efficient method of tumor treatment. The therapeutic effect has been shown to be a function of ischemia and slow local infusion of drug into the tumor, and systemic drug levels can be kept low.

Poly(2-hydroxyethyl methacrylate) particles for preoperative endovascular occlusion of extensive angiodysplasias

The application of superselective endovascular occlusion in vascular radiology has broadened the scope of possible radical surgery of giant angiodysplasias by reducing considerably the risk of severe haemorrhage during the surgery. Occlusion was performed on 229 patients using spherical and cylindrical particles of porous poly(2-hydroxyethyl methacrylate). The treatment of a patient suffering from angiodysplasia of the pelvis is described as an example. The first day following endovascular occlusion a hypercoagulation reaction developed, with a decrease of both the level of fibrinolysis and of anticoagulant factors. This was mainly due to a decrease of the level of antithrombin III and activation of the factor XIII indicating a strong tendency of intravascular thrombosis. During the third day, the hypercoagulation reaction increased. However, on the fifteenth day, parameters of the haemostasis system were close to normal values. Only the activity of the factor XIII remained high suggesting the stabilization and the organization of fibrin clot in the embolized blood vessel territory.

Are superabsorbers useful for endovascular embolization of saccular aneurysms? An in vitro study

RATIONALE AND OBJECTIVES

The authors conducted in vitro evaluation of superabsorber for endovascular embolization of saccular aneurysms.

METHODS

The swelling properties of the superabsorber Sanwet IM-7000 were investigated in various solvents. The material used was granulate (group A: particle size approximately 459 microm; group B: particle size approximately 20 microm) as well as cubes with an edge length of 1 mm prepared from a block. With ascending concentrations of Sanwet IM-7000 held in suspensions made of Lipiodol and 96% ethanol, the injectability was determined using microcatheters (2.1 F/3 F). The behavior of Sanwet IM-7000 as occlusion material for aneurysms was examined in a sacciform glass-model aneurysm.

RESULTS

The granule showed no significant increase in size in Lipiodol and in 96% ethanol, so that they were chosen for catheter measurement. In Lipiodol suspension the maximum fraction of the granulate suitable for injection through a 3 F catheter was 3.2%. In 96% ethanol suspension the maximum fraction of granulate suitable for injection through a 3 F catheter was 0.8%. Suspended in Lipiodol Sanwet IM-7000 showed a moderate swelling in the aneurysm model, whereas the use of 96% ethanol resulted in a pronounced swelling of the granulate (100 vol%) after the 96% ethanol was washed off. Irrespective of the granulate size used, a rinse-off process of the granulate occurred in the model aneurysm at a flow rate above 200 mL x min(-1). Cubes prepared from a block of the base polymerisate of Sanwet IM-7000 showed a delayed increase in size. The final size in 0.9% NaCl solution was reached in the cubes after 220 min, in the granulate already after 20 mins. The cubes displayed a high form stability.

CONCLUSIONS

Due to the substance-related absence of intercorporeal cross-linking and the unpredictable increase in size, embolization of aneurysms using Sanwet IM-7000 granulate is inadvisable at present. In spite of a longer swelling time and because of its form consistency, the use of prepared cubes could provide a reasonable alternative.

Poly (2-hydroxyethyl methacrylate) particles for management of hemorrhage of complicated origin: treatment of hemobilia

Poly (2-hydroxyethyl methacrylate) (PHEMA) particles of cylindrical and spherical shape were developed as a preparation for tumor treatment or control of hemorrhage by blocking their blood supply. In this report, PHEMA particles were used for the management of hemobilia, that is, bleeding into biliary passages. The origin of hemobilia in 31 patients was localized by selective angiography. With the objective of prophylaxy of hemorrhage, selective embolization with PHEMA particles of the branches of the hepatic artery responsible for the supply of blood to the focus of damage was used in 18 patients. This low-trauma method allowed either a complete control of bleeding or, at least, intraoperative blood loss was reduced more than twice. Histological investigation of the occluded blood vessels showed that the thrombus was attached to the particles and was reinforced by the porous structure of the polymer. A hypercoagulation reaction was observed in the postembolization period. This allowed correction of the hypocoagulation in the hemostasis system.

Hydrogels in endovascular embolization. V. Antitumour agent methotrexate-containing p(HEMA)

The aminohexyl derivative of the copolymer of 2-hydroxyethyl methacrylate and ethylene dimethacrylate (p(HEMA)-Hex) in the form of regular spherical particles was used as a polymeric carrier for chemically sorbed methotrexate (MTX). The effect of the washed p(HEMA)-Hex-MTX carrier on the morphological structure of donor blood, on blood coagulation indicators and on responses of the living tissue surrounding the material which has been in the blood vessel of the rabbit for various periods of time was evaluated. MTX is capable of diffusion for several days from the embolic material.