Development and In Vitro Whole Blood Hemocompatibility Screening of Endothelium-Mimetic Multifunctional Coatings

Surface Engineering for Endothelium-Mimicking Functions to Combat Infection and Thrombosis in Extracorporeal Life Support Technologies

Blood-contacting medical devices routinely fail from the cascading effects of biofouling toward infection and thrombosis. Nitric oxide (NO) is an integral part of endothelial homeostasis, maintaining platelet quiescence and facilitating oxidative/nitrosative stress against pathogens. Recently, it is shown that the surface evolution of NO can mediate cell-surface interactions. However, this technique alone cannot prevent the biofouling inherent in device failure with dynamic blood-contacting applications. This work proposes an endothelium-mimicking surface design pairing controlled NO release with an inherently antifouling polyethylene glycol interface (NO+PEG). This simple, robust, and scalable platform develops surface-localized NO availability with surface hydration, leading to a significant reduction in protein adsorption as well as bacteria/platelet adhesion. Further in vivo thrombogenicity studies show a decrease in thrombus formation on NO+PEG interfaces, with preservation of circulating platelet and white blood cell counts, maintenance of activated clotting time, and reduced coagulation cascade activation. It is anticipated that this bio-inspired surface design will enable a facile alternative to existing surface technologies to address clinical manifestations of infection and thrombosis in dynamic blood-contacting environments.

Nitric Oxide-Releasing Porous Coating with Antibacterial Activity and Blood Compatibility

Nitric oxide (NO)-releasing coating is promising to enhance the biocompatibility of medical devices. In this study, polyurethane (PU) and S-nitrosated keratin (KSNO) were dissolved with dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF) to prepare a coating solution. This solution is facile to form a porous coating on various substrates based on solvent-evaporation-induced phase separation (SEIPS). The coating could continuously release NO up to 200 h in the presence of ascorbic acid (Asc). In addition, the coating could accelerate endothelialization by promoting the viability of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation of human umbilical artery smooth muscle cells (HUASMCs). Furthermore, the coating had good antibacterial activity and blood compatibility. Taken together, this universal coating provides wider potential applications in the field of cardiovascular implants.

Unravelling Surface Modification Strategies for Preventing Medical Device-Induced Thrombosis

The use of biomaterials in implanted medical devices remains hampered by platelet adhesion and blood coagulation. Thrombus formation is a prevalent cause of failure of these blood-contacting devices. Although systemic anticoagulant can be used to support materials and devices with poor blood compatibility, its negative effects such as an increased chance of bleeding, make materials with superior hemocompatibility extremely attractive, especially for long-term applications. This review examines blood-surface interactions, the pathogenesis of clotting on blood-contacting medical devices, popular surface modification techniques, mechanisms of action of anticoagulant coatings, and discusses future directions in biomaterial research for preventing thrombosis. In addition, this paper comprehensively reviews several novel methods that either entirely prevent interaction between material surfaces and blood components or regulate the reaction of the coagulation cascade, thrombocytes, and leukocytes.

Gas station in blood vessels: An endothelium mimicking, self-sustainable nitric oxide fueling stent coating for prevention of thrombosis and restenosis

Stenting is the primary treatment for vascular obstruction-related cardiovascular diseases, but it inevitably causes endothelial injury which may lead to severe thrombosis and restenosis. Maintaining nitric oxide (NO, a vasoactive mediator) production and grafting endothelial glycocalyx such as heparin (Hep) onto the surface of cardiovascular stents could effectively reconstruct the damaged endothelium. However, insufficient endogenous NO donors may impede NO catalytic generation and fail to sustain cardiovascular homeostasis. Here, a dopamine-copper (DA-Cu) network-based coating armed with NO precursor L-arginine (Arg) and Hep (DA-Cu-Arg-Hep) is prepared using an organic solvent-free dipping technique to form a nanometer-thin coating onto the cardiovascular stents. The DA-Cu network adheres tightly to the surface of stents and confers excellent NO catalytic activity in the presence of endogenous NO donors. The immobilized Arg functions as a NO fuel to generate NO via endothelial nitric oxide synthase (eNOS), while Hep works as eNOS booster to increase the level of eNOS to decompose Arg into NO, ensuring a sufficient supply of NO even when endogenous donors are insufficient. The synergistic interaction between Cu and Arg is analogous to a gas station to fuel NO production to compensate for the insufficient endogenous NO donor in vivo. Consequently, it promotes the reconstruction of natural endothelium, inhibits smooth muscle cell (SMC) migration, and suppresses cascading platelet adhesion, preventing stent thrombosis and restenosis. We anticipate that our DA-Cu-Arg-Hep coating will improve the quality of life of cardiovascular patients through improved surgical follow-up, increased safety, and decreased medication, as well as revitalize the stenting industry through durable designs.

Derivatization of graphene oxide nanosheets with tunable nitric oxide release for antibacterial biomaterials

Graphene oxide (GO) nanosheets are a promising class of carbon-based materials suitable for application in the construction of medical devices. These materials have inherent antimicrobial properties based on sheet size, but these effects must be carefully traded off to maintain biocompatibility. Chemical modification of functional groups to the lattice structure of GO nanosheets enables unique opportunities to introduce new surface properties to bolster biological effects. Herein, we have developed nitric oxide (NO)-releasing GO nanosheets via immobilization of S-nitrosothiol (RSNO) moieties to GO nanosheets (GO-[NH]x -SNO). These novel RSNO-based GO nanosheets were characterized for chemical functionality via Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and colorimetric assays for functional group quantification. Stoichiometric control of the available RSNO groups functionalized onto the nanosheets was studied using chemiluminescence-based NO detection methods, showing highly tunable NO release kinetics. Studies of electrical stimulation and subsequent electrochemical reduction of the nanosheets demonstrated further tunability of the NO release based on stimuli. Finally, nanosheets were evaluated for cytotoxicity and antibacterial effects, showing strong cytocompatibility with human fibroblasts in parallel to broad antibacterial and anti-biofilm effects against both Gram-positive and Gram-negative strains. In summary, derivatized GO-(NH)x -SNO nanosheets were shown to have tunable NO release properties, enabling application-specific tailoring for diverse biomedical applications such as antimicrobial coatings and composite fillers for stents, sensors, and other medical devices.

Bio-inspired hemocompatible surface modifications for biomedical applications

When blood first encounters the artificial surface of a medical device, a complex series of biochemical reactions is triggered, potentially resulting in clinical complications such as embolism/occlusion, inflammation, or device failure. Preventing thrombus formation on the surface of blood-contacting devices is crucial for maintaining device functionality and patient safety. As the number of patients reliant on blood-contacting devices continues to grow, minimizing the risk associated with these devices is vital towards lowering healthcare-associated morbidity and mortality. The current standard clinical practice primarily requires the systemic administration of anticoagulants such as heparin, which can result in serious complications such as post-operative bleeding and heparin-induced thrombocytopenia (HIT). Due to these complications, the administration of antithrombotic agents remains one of the leading causes of clinical drug-related deaths. To reduce the side effects spurred by systemic anticoagulation, researchers have been inspired by the hemocompatibility exhibited by natural phenomena, and thus have begun developing medical-grade surfaces which aim to exhibit total hemocompatibility via biomimicry. This review paper aims to address different bio-inspired surface modifications that increase hemocompatibility, discuss the limitations of each method, and explore the future direction for hemocompatible surface research.