Transcatheter arterial embolization of aneurysm with metal microcoils is notoriously prone to recanalization arising from the low filling ratio due to their extreme rigidity. Smart hydrogel microcoils with tunable modulus may essentially significantly improve the therapeutic efficacy. Here, a radiopaque highly stiff body‐temperature‐triggered shape memory (SM) hydrogel is fabricated for the first time by introducing reversible hydrophobic dipole pairing microdomains in the flexibly crosslinked network, followed by BaSO4 precipitation. This radiopacification does not affect their mechanical performances as well as the SM effect. It is demonstrated that the mechanical properties of SM hydrogels are comparable to those of rubbers and can be modulated by adjusting temperature ranging from 20 to 40 °C. Benefiting from the thermoresponsive mechanical properties, the stiff radiopaque hydrogel strip can easily pass through a catheter under the protection of cool saline for delivery into pig's renal artery, and spontaneously and rapidly transformed into a microcoil upon contacting blood. Real‐time angiogram reveals that continuous delivery of several hydrogel microcoils can efficiently occlude the blood supply. The kidneys are atrophied considerably over three month postoperative follow‐up, and no recanalization occurs throughout the experimental time. These novel hydrogel microcoils are promising to be developed as novel permanent embolic agents for treating aneurysm.
An aneurysm is a life-threatening vascular disease. Embolization with shape memory (SM) hydrogel coils is promising for the treatment of the intractable aneurysms. However, single temperature-triggered SM is softened in a catheter, and delivery of multiple coils is required, which may clog the catheter and complicate operation procedure. Here, a radiopaque temperature/pH dual responsive shape memory hydrogel with self-tuned stiffness is fabricated by copolymerizing acrylonitrile (AN, dipole-dipole interaction monomer), N-acryloyl 2-glycine (ACG, pH-sensitive H-bonding monomer), and polyethylene glycol diacrylate. Under slightly acidic conditions without eliciting cytotoxicity, additional supramolecular PACG hydrogen bonds combined with cyano dipole-dipole pairings contribute to the body temperature-triggered SM effect with an unprecedented high 430 MPa (10 °C) and 16 MPa (37 °C) Young's modulus. A carotid aneurysm is created in a dog to test the embolization of this SM hydrogel. At 37 °C, the hydrogel's high stiffness ensures its smooth delivery through a catheter. After being transported into the aneurysm sac, secondary swelling occurs concurrent with appropriate decrease of stiffness upon contacting neutral blood, thus enhancing the packing density and reducing recanalization rate and delivery times. This stiffness adaptive SM hydrogel holds its great potential as permanent embolic agents for treating a variety of aneurysms.
Our team has previously reported a high strength thermoplastic supramolecular polymer hydrogel. However, the hydrogel required injection temperatures outside the physiological range therefore preventing its use in a living environment. In this article, we reported a thermoresponsive supramolecular copolymer hydrogel p(N-acryloyl glycinamide-co-acrylamide) (PNAGA-PAAm), which can be injected at temperatures within the physiological range. We used rheological measurements to demonstrate that the transition temperature (upper critical solution temperature) of both the moduli and gel-sol could be finely adjusted by controlling both the ratio and concentration of the monomer. Adding iohexol (contrast agent) in PNAGA-PAAm hydrogels contributed to the decreased moduli and gel-sol transition temperature due to weakening of the hydrogen bonding interactions. The cytocompatible and hemocompatible PNAGA-PAAm sol mixed with iohexol was injected into the renal arteries of rabbits through a microcatheter at a temperature within the high biological range. The transition from the injection temperature (high biological range) to body temperature (basal for the animals) quickly solidified the embolic agent without the occurrence of dehydration, therefore overcoming the main limitation of LCST-typed poly(N-isopropylacrylamide) previously reported. Angiography and histological examination demonstrated the successful embolization of both renal arteries and no recanalization was observed after 8 weeks. The PNAGA-based supramolecular copolymer hydrogel is a novel embolic agent that allows for the occlusion of larger sized arteries in a biocompatible environment.
Mixed reality (MR) merges virtual information into the real world through computer technology, in which the real environment and virtual objects can get spliced in the same image or space at real time so that it can effectively express and integrate the virtual and real worlds and allow high feedback interaction. This technology combines the many advantages of virtual realityand augmented reality, and has a promising future in the medical field. At present, MR technology is just at the beginning stage in the medical field in the world, whose application in neurosurgery is also rarely reported. Given this, the authors described the research progress of MR in neurosurgery including preoperative planning and intraoperative guidance, doctor-patient communication, teaching rounds, physician training, and so on.
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