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On-demand degradable embolic microspheres for immediate restoration of blood flow during image-guided embolization procedures.

ABSTRACT: Degradable embolic agents that provide transient arterial occlusion during embolization procedures have been of interest for many years. Ideally, embolic agents are visible with standard imaging modalities and offer on-demand degradability, permitting physicians to achieve desired arterial occlusion tailored to patient and procedure indication. Subsequent arterial recanalization potentially enhances the overall safety and efficacy of embolization procedures. Here, we report on-demand degradable and MRI-visible microspheres for embolotherapy. Embolic microspheres composed of calcium alginate and USPIO nanoclusters were synthesized with an air spray atomization and coagulation reservoir equipped with a vacuum suction. An optimized distance between spray nozzle and reservoir allowed uniform size and narrow size distribution of microspheres. The fabricated alginate embolic microspheres crosslinked with Ca²⁺ demonstrated highly responsive on-demand degradation properties in vitro and in vivo. Finally, the feasibility of using the microspheres for clinical embolization and recanalization procedures was evaluated with interventional radiologists in rabbits. Digital subtraction angiography (DSA) guided embolization of hepatic arteries with these embolic microspheres was successfully performed and the occlusion of artery was confirmed with DSA images and contrast enhanced MRI. T2 MRI visibility of the microspheres allowed to monitor the distribution of intra-arterial (IA) infused embolic microspheres. Subsequent on-demand image-guided recanalization procedures were also successfully performed with rapid degradation of microspheres upon intra-arterial infusion of an ion chelating agent. These instant degradable embolic microspheres will permit effective on-demand embolization/recanalization procedures offering great promise to overcome limitations of currently available permanent and biodegradable embolic agents.

SUBMITTER: Choi H

PROVIDER: S-EPMC7673262 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Rationale: Intraoperative bleeding impairs physicians' ability to visualize the surgical field, leading to increased risk of surgical complications and reduced outcomes. Bleeding is particularly challenging during endoscopic-assisted surgical resection of hypervascular tumors in the head and neck. A tool that controls bleeding while marking tumor margins has the potential to improve gross tumor resection, reduce surgical morbidity, decrease blood loss, shorten procedure time, prevent damage to surrounding tissues, and limit postoperative pain. Herein, we develop and characterize a new system that combines pre-surgical embolization with improved visualization for endoscopic fluorescence image-guided tumor resection. Methods: Silk-elastinlike protein (SELP) polymers were employed as liquid embolic vehicles for delivery of a clinically used near-infrared dye, indocyanine green (ICG). The biophysical properties of SELP, including gelation kinetics, modulus of elasticity, and viscosity, in response to ICG incorporation using rheology, were characterized. ICG release from embolic SELP was modeled in tissue phantoms and via fluorescence imaging. The embolic capability of the SELP-ICG system was then tested in a microfluidic model of tumor vasculature. Lastly, the cytotoxicity of the SELP-ICG system in L-929 fibroblasts and human umbilical vein endothelial cells (HUVEC) was assessed. Results: ICG incorporation into SELP accelerated gelation and increased its modulus of elasticity. The SELP embolic system released 83 ± 8% of the total ICG within 24 hours, matching clinical practice for pre-surgical embolization procedures. Adding ICG to SELP did not reduce injectability, but did improve the gelation kinetics. After simulated embolization, ICG released from SELP in tissue phantoms diffused a sufficient distance to deliver dye throughout a tumor. ICG-loaded SELP was injectable through a clinical 2.3 Fr microcatheter and demonstrated deep penetration into 50-µm microfluidic-simulated blood vessels with durable occlusion. Incorporation of ICG into SELP improved biocompatibility with HUVECs, but had no effect on L-929 cell viability. Principle Conclusions: We report the development and characterization of a new, dual-functional embolization-visualization system for improving fluorescence-imaged endoscopic surgical resection of hypervascular tumors.

Project description:PurposeTransarterial chemoembolization is accepted therapy for hepatocellular carcinoma (HCC). No randomized trial has demonstrated superiority of chemoembolization compared with embolization, and the role of chemotherapy remains unclear. This randomized trial compares the outcome of embolization using microspheres alone with chemoembolization using doxorubicin-eluting microspheres.Materials and methodsAt a single tertiary referral center, patients with HCC were randomly assigned to embolization with microspheres alone (Bead Block [BB]) or loaded with doxorubicin 150 mg (LC Bead [LCB]). Random assignment was stratified by number of embolizations to complete treatment, and assignments were generated by permuted blocks in the institutional database. The primary end point was response according to RECIST 1.0 (Response Evaluation Criteria in Solid Tumors) using multiphase computed tomography 2 to 3 weeks post-treatment and then at quarterly intervals, with the reviewer blinded to treatment allocation. Secondary objectives included safety and tolerability, time to progression, progression-free survival, and overall survival. This trial is currently closed to accrual.ResultsBetween December 2007 and April 2012, 101 patients were randomly assigned: 51 to BB and 50 to LCB. Demographics were comparable: median age, 67 years; 77% male; and 22% Barcelona Clinic Liver Cancer stage A and 78% stage B or C. Adverse events occurred with similar frequency in both groups: BB, 19 of 51 patients (38%); LCB, 20 of 50 patients (40%; P = .48), with no difference in RECIST response: BB, 5.9% versus LCB, 6.0% (difference, -0.1%; 95% CI, -9% to 9%). Median PFS was 6.2 versus 2.8 months (hazard ratio, 1.36; 95% CI, 0.91 to 2.05; P = .11), and overall survival, 19.6 versus 20.8 months (hazard ratio, 1.11; 95% CI, 0.71 to 1.76; P = .64) for BB and LCB, respectively.ConclusionThere was no apparent difference between the treatment arms. These results challenge the use of doxorubicin-eluting beads for chemoembolization of HCC.

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On-demand degradable embolic microspheres for immediate restoration of blood flow during image-guided embolization procedures.

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