Robust, Sprayable, and Multifunctional Hydrogel Coating through a Polycation Reinforced (PCR) Surface Bridging Strategy

A Sprayable Polyelectrolyte Coating to Mitigate the Foreign Body Response of Implants

The foreign body response (FBR) presents a significant challenge to biomedical implants, leading to fibrotic capsule formation that compromises implant functionality. In this study, we report a straightforward method for fabricating stable anti-fibrotic polyelectrolyte coatings on implant surfaces using industrialized ultrasonic spraying technology. The coating thickness and surface charge can be adjusted through variations in spraying time and polyelectrolyte ratio, respectively. We investigate the fibrotic response of polyelectrolyte-coated implants with varying surface charges and thicknesses. Our findings reveal that surface charge significantly influences the fibrotic response, while electronegative polyelectrolyte coatings most effectively inhibit FBR compared to electrically neutral, positively charged, and uncoated surfaces. Meanwhile, coating thickness beyond 10 μm resulted in thinner capsules than coatings at a 1 μm or nanometer scale. The simple and versatile polyelectrolyte coating method reported here holds great potential to enhance and extend the functionality of implants in a mass-produced manner by mitigating host responses to implantable biomaterials.

Photopatternable PEDOT:PSS Hydrogels for High-Resolution Photolithography

Conducting polymer hydrogels have been extensively explored toward diverse applications like bioelectronics and soft robotics. However, the fabrication resolution of conducting polymer hydrogels by typical techniques, including ink-jet printing, 3D-printing, etc., has been generally limited to >10 µm, significantly restricting rapid innovations and broad applications of conducting polymer hydrogels. To address this issue, a photosensitive biphasic conducting polymer hydrogel (PB-CH) is rationally designed and synthesized, comprising poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the conductive phase and a light-sensitive matrix as the mechanical phase. The formation of phase-separated structures within PB-CH preserves the integrity of the conductive channels during the photoinitiated cross-linking. This minimizes the conductivity loss, a common limitation in similar materials. Remarkably, the resultant PB-CH exhibits a combination of excellent electrical conductivity (≈30 S cm-1), robust mechanical performance (tensile strain up to 50%), and high photopatternability. A detailed investigation of the photolithography process identifies key technological parameters that enable high-resolution patterning of 5 µm. By simultaneously maintaining processability, conductivity, and mechanical flexibility, this PB-CH represents an ideal candidate for advanced flexible electronic applications, offering a new technique to fabricating high-performance conducting polymer hydrogels.

Adhesive and Conductive Hydrogels for the Treatment of Myocardial Infarction

Myocardial infarction (MI) is a leading cause of mortality among cardiovascular diseases. Following MI, the damaged myocardium is progressively being replaced by fibrous scar tissue, which exhibits poor electrical conductivity, ultimately resulting in arrhythmias and adverse cardiac remodeling. Due to their extracellular matrix-like structure and excellent biocompatibility, hydrogels are emerging as a focal point in cardiac tissue engineering. However, traditional hydrogels lack the necessary conductivity to restore electrical signal transmission in the infarcted regions. Imparting conductivity to hydrogels while also enhancing their adhesive properties enables them to adhere closely to myocardial tissue, establish stable electrical connections, and facilitate synchronized contraction and myocardial tissue repair within the infarcted area. This paper reviews the strategies for constructing conductive and adhesive hydrogels, focusing on their application in MI repair. Furthermore, the challenges and future directions in developing adhesive and conductive hydrogels for MI repair are discussed.

UV-Triggered Hydrogel Coating of the Double Network Polyelectrolytes for Enhanced Endothelialization

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.

Comparison study of surface-initiated hydrogel coatings with distinct side-chains for improving biocompatibility of polymeric heart valves

Polymeric heart valves (PHVs) present a promising alternative for treating valvular heart diseases with satisfactory hydrodynamics and durability against structural degeneration. However, the cascaded coagulation, inflammatory responses, and calcification in the dynamic blood environment pose significant challenges to the surface design of current PHVs. In this study, we employed a surface-initiated polymerization method to modify polystyrene-block-isobutylene-block-styrene (SIBS) by creating three hydrogel coatings: poly(2-methacryloyloxy ethyl phosphorylcholine) (pMPC), poly(2-acrylamido-2-methylpropanesulfonic acid) (pAMPS), and poly(2-hydroxyethyl methacrylate) (pHEMA). These hydrogel coatings dramatically promoted SIBS's hydrophilicity and blood compatibility at the initial state. Notably, the pMPC and pAMPS coatings maintained a considerable platelet resistance performance after 12 h of sonication and 10 000 cycles of stretching and bending. However, the sonication process induced visible damage to the pHEMA coating and attenuated the anti-coagulation property. Furthermore, the in vivo subcutaneous implantation studies demonstrated that the amphiphilic pMPC coating showed superior anti-inflammatory and anti-calcification properties. Considering the remarkable stability and optimal biocompatibility, the amphiphilic pMPC coating constructed by surface-initiated polymerization holds promising potential for modifying PHVs.