Search

The left atrial appendage (LAA) occluder is an important medical device for closing the LAA and preventing stroke. The device-related thrombus (DRT) prevents the implantation of the occluder in exerting the desired therapeutic effect, which is primarily caused by the delayed endothelialization of the occluder. Functional coatings are an effective strategy for accelerating the endothelialization of occluders. However, the occluder surface area is particularly large and structurally complex, and the device is subjected to a large shear friction in the sheath during implantation, which poses a significant challenge to the coating. Herein, a hydrogel coating by the in situ UV-triggered polymerization of double-network polyelectrolytes is reported. The findings reveal that the double network and electrostatic interactions between the networks resulted in excellent mechanical properties of the hydrogel coating. The sulfonate and Arg-Gly-Asp (RGD) groups in the coating promoted hemocompatibility and endothelial growth of the occluder, respectively. The coating significantly accelerated the endothelialization of the LAA occluder in a canine model is further demonstrated. This study has potential clinical benefits in reducing both the incidence of DRT and the postoperative anticoagulant course for LAA closure., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

The sprayable hydrogel coatings that can establish robust adhesion onto diverse materials and devices hold enormous potential; however, a significant challenge persists due to monomer hydration, which impedes even coverage during spraying and induces inadequate adhesion post-gelation. Herein, a polycation-reinforced (PCR) surface bridging strategy is presented to achieve tough and sprayable hydrogel coatings onto diverse materials. The polycations offer superior wettability and instant electrostatic interactions with plasma-treated substrates, facilitating an effective spraying application. This PCR-based hydrogel coatings demonstrate tough adhesion performance to inert PTFE and silicone, including remarkable shear strength (161 ± 49 kPa for PTFE), interfacial toughness (198 ± 27 J m -2 for PTFE), and notable tolerance to cyclic tension (10 000 cycles, 200% strain, silicone). Meanwhile, this method can be applied to various hydrogel formulations, offering diverse functionalities, including underwater adhesion, lubrication, and drug delivery. Furthermore, the PCR concept enables the conformal construction of durable hydrogel coatings onto sophisticated medical devices like cardiovascular stents. Given its simplicity and adaptability, this approach paves an avenue for incorporating hydrogels onto solid surfaces and potentially promotes untapped applications., (© 2024 Wiley‐VCH GmbH.)

Endothelialization has proved to be critical for maintaining long-term success of implantable vascular devices. The formation of monolayer of endothelial cells (ECs) on the implant surfaces is one of the most important factors for the endothelialization. However, endothelial function of regenerated EC monolayer, which plays a much more important role in preventing the complications of post-implantation, has not received enough attention. Here, a vascular endothelial growth factor (VEGF)-incorporated poly(l-lysine)/hyaluronan (PLL/HA) polyelectrolyte multilayer film was fabricated. Through varying the crosslinking degree, stiffness of the film was manipulated, offering either soft or stiff film. We demonstrated that ECs were able to adhere and proliferate on both soft and stiff films, subsequently forming an integrated EC monolayer. Furthermore, endothelial functions were evaluated by characterizing EC monolayer integrity, expression of genes correlated with the endothelial functions, and nitric oxide production. It demonstrated that EC monolayer on the soft film displayed higher endothelial function compared to that on the stiff film. Our study highlights the influence of substrate stiffness on endothelial function, which offers a new criterion for surface design of vascular implants., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Periodic porous structures have been introduced into functional films to meet the requirements of various applications. Though many approaches have been developed to generate desired structures in polymeric films, few of them can effectively and dynamically achieve periodic porous structures. Here, a facile way is proposed to introduce periodic stratified porous structures into polyelectrolyte films. A photo‐crosslinkable polyelectrolyte film of poly(ethylenimine) (PEI) and photoreactive poly(acrylic acid) derivative (PAA‐N3) is prepared by layer‐by‐layer (LbL) self‐assembly. Stratified crosslinking of the PEI/PAA‐N3 film is generated basing on standing‐wave optics. The periodic stratified porous structure is constructed by forming pores in noncrosslinked regions in the film. Thanks to the dynamic mobility of polyelectrolytes, this structural controlment can be repeated several times. The size of pores corresponding to the layer spacing of the film contributes to the structural colors. Furthermore, structural color patterns are fabricated in the film by selective photo‐crosslinking using photomasks. Although the large‐scale structural controlment in thick (micron‐scale and above) films needs to be explored further, this work highlights the periodic structural controlment in polymeric films and thus presents an approach for application potentials in sensor, detection, and ink‐free printing. [ABSTRACT FROM AUTHOR]

Layer-by-layer (LbL) self-assemblies have inherent potential as dynamic coatings because of the sensitivity of their building blocks to external stimuli. Here, humidity serves as a feasible trigger to activate the self-healing of a microporous polyethylenimine/poly(acrylic acid) multilayer film. Microporous structures within the polyelectrolyte multilayer (PEM) film are created by acid treatment, followed by freeze-drying to remove water. The self-healing of these micropores can be triggered at 100% relative humidity, under which condition the mobility of the polyelectrolytes is activated. Based on this, a facile and versatile method is suggested for directly integrating hydrophobic drugs into PEM films for surface-mediated drug delivery. The high porosity of microporous film enables the highest loading (≈303.5 μg cm−2 for a 15-bilayered film) of triclosan to be a one-shot process via wicking action and subsequent solvent removal, thus dramatically streamlining the processes and reducing complexities compared to the existing LbL strategies. The self-healing of a drug-loaded microporous PEM film significantly reduces the diffusion coefficient of triclosan, which is favorable for the long-term sustained release of the drug. The dynamic properties of this polymeric coating provide great potential for its use as a delivery platform for hydrophobic drugs in a wide variety of biomedical applications. [ABSTRACT FROM AUTHOR]

Controlled and stimulated release of small drug molecules from polyelectrolyte multilayers is still a challenge due to the limitations to incorporate and control the interactions between small molecules and multilayers. Herein we reported a facile method to fabricate polyelectrolyte multilayers with pH-sensitive controlled release of doxorubicin (DOX). A pH-responsive polyelectrolyte was prepared by conjugating DOX onto hyaluronan (HA) via pH-responsive hydrazone bond with an 8% grafting degree. The HA-DOX was then incorporated into the multilayers via the layer-by-layer assembly with poly- l -lysine (PLL). The growth of the multilayers was tracked by spectroscopic ellipsometry. The morphology and structure of the films were characterized by scanning electron microscopy and UV–vis spectroscopy, respectively. The in vitro drug release experiments indicated that the release of DOX was pH-dependent: there was almost no release at pH 7.4, while the releases were significantly promoted at pH 6.0 and 5.0. Furthermore, human hepatoma (HepG2) cells were remarkably inhibited under the conditions at pH 5.0 when they were cultured with the (HA-DOX/PLL) multilayers. The multilayers with the properties of pH-sensitive DOX release would be potentially applied to the biomedical devices for tumor treatments. [ABSTRACT FROM AUTHOR]

In addition to the topographical features and chemical properties of substrates, the mechanical properties are known as a vital regulator of cellular processes such as adhesion, proliferation, and migration, and have received considerable attention in recent years. In this work, electrochemical redox multilayers made of ferrocene-modified poly(ethylenimine) (PEI-Fc) and deoxyribonucleic acid (DNA) with controlled stiffness were used to investigate the effects of the mechanical properties of multilayers on fibroblast cell (NIH/3T3) behaviors. Redox PEI-Fc plays an essential role in inducing swelling in multilayers under an electrochemical stimulus, resulting in distinct changes in the stiffness of the multilayers. The Young's modulus varied from 2.05 to 1.07 MPa for the (PEI-Fc/DNA) multilayers by changing the oxidation time of the electrochemical treatment. We demonstrated that the adhesion, proliferation, and migration of fibroblast cells depended on the multilayers' stiffness. These results indicate that cell behaviors can be precisely controlled by electrochemical treatment, which provides a new way to prepare thin films with tunable mechanical properties with potential biomedical applications. [ABSTRACT FROM AUTHOR]

Introducing roughness features onto materials' surface can serve as an efficient strategy for novel or enhanced surface functionality. Surface roughness can be developed spontaneously on exponentially growing polyelectrolyte multilayer films without any postassembly treatment. This is essentially a pressure‐induced wrinkling behavior, which is associated with the diffusion of polyelectrolyte chains into the films during the assembling process. Here, this wrinkling behavior is suppressed by applying a pre‐cross‐linking process, which can produce steric hindrance within the films against the diffusion of oncoming polyelectrolytes. With the aid of photolithography, the wrinkling behavior can be "turned off" regioselectively and confined on the areas unexposed to UV irradiation, thus leading to a film with patterned surface wrinkles and paving the way for novel applications. [ABSTRACT FROM AUTHOR]

A coating of implanted medical devices with antifouling ability, preferable mechanical property and stability in the physiological environment proves beneficial for their clinical use. Here we develop a flexible bilayer hydrogel coating with self-healing, antifouling, and lubricating functions. Our bilayer coating consists of two functional layers: i) an adhesive flexible polyelectrolyte hydrogel layer, ii) an antifouling and lubricous polyzwitterionic layer. The bilayer hydrogel coating is prepared in two steps dip-coating and in situ UV photopolymerization. Our results demonstrate that the prepared bilayer hydrogel coating has proper mechanical properties, favorable hydrophilicity, and lower surface friction. We demonstrate that the bilayer hydrogel coating maintains hydrophilicity under extreme condition (1 h sonicating or 5000 times repeating bending). The as-prepared bilayer hydrogel coating resists non-specific protein adsorption, inhibits cell and platelet adhesion, and prevents thrombosis. This work provides a reliable coating on the medical materials, showing a promising practical application in diversified implantable medical devices. [Display omitted] [ABSTRACT FROM AUTHOR]