Comparison of Diazeniumdiolated Dialkylhexanediamines as Nitric Oxide Release Agents on Nonthrombogenicity in an Extracorporeal Circulation Model

A dual-action nitric oxide-releasing slippery surface for extracorporeal organ support: Dynamic in vitro hemocompatibility evaluation

Numerous biomaterials have been developed for application in blood-contacting medical devices to prevent thrombosis; however, few materials have been applied to full-scale devices and evaluated for hemocompatibility under clinical blood flow conditions. We applied a dual-action slippery liquid-infused (LI) nitric oxide (NO)-releasing material modification (LINO) to full-scale blood circulation tubing for extracorporeal lung support and evaluated the tubing ex vivo using swine whole blood circulated for 6 h at a clinically relevant flow. LINO tubing was compared to unmodified tubing (CTRL) and isolated LI and NO-releasing modifications (n = 9/group). The primary objective was to evaluate safety and blood compatibility of this approach, prior to progression to in vivo testing of efficacy in animal models. The secondary objective was to evaluate coagulation outcomes relevant to hemocompatibility. No untoward effects of the coating, such as elevated methemoglobin fraction, were observed. Additionally, LINO delayed platelet loss until 6 h versus the reduction in platelet count in CTRL at 3 h. At 6 h, LINO significantly reduced the concentration of platelets in an activated P-selectin expressing state versus CTRL (32 ± 1% decrease, p = .02). Blood clot deposition was significantly reduced on LINO blood pumps (p = .007) and numerically reduced on tubing versus CTRL. Following blood exposure, LINO tubing continued to produce a measurable NO-flux (0.20 ± 0.06 × 10^-10  mol cm^-2  min^-1 ). LINO is a potential solution to reduce circuit-related bleeding and clotting during extracorporeal organ support, pending future extended testing in vivo using full-scale extracorporeal lung support devices.

Current and Future Engineering Strategies for ECMO Therapy

Extracorporeal membrane oxygenation (ECMO) is a last resort therapy for patients with respiratory failure where the gas exchange capacity of the lung is compromised. Venous blood is pumped through an oxygenation unit outside of the body where oxygen diffusion into the blood takes place in parallel to carbon dioxide removal. ECMO is an expensive therapy which requires special expertise to perform. Since its inception, ECMO technologies have been evolving to improve its success and minimize the complications associated with it. These approaches aim for a more compatible circuit design capable of maximum gas exchange with minimal need for anticoagulants. This chapter summarizes the basic principles of ECMO therapy with the latest advancements and experimental strategies aiming for more efficient future designs.

Improved Polymer Hemocompatibility for Blood-Contacting Applications via S-Nitrosoglutathione Impregnation

Blood-contacting medical devices (BCMDs) are inevitably challenged by thrombi formation, leading to occlusion of flow and device failure. Ideal BCMDs seek to mimic the intrinsic antithrombotic properties of the human vasculature to locally prevent thrombotic complications, negating the need for systemic anticoagulation. An emerging category of BCMD technology utilizes nitric oxide (NO) as a hemocompatible agent, as the vasculature's endothelial layer naturally releases NO to inhibit platelet activation and consumption. In this paper, we report for the first time the novel impregnation of S-nitrosoglutathione (GSNO) into polymeric poly(vinyl chloride) (PVC) tubing via an optimized solvent-swelling method. Material testing revealed an optimized GSNO-PVC material that had adequate GSNO loading to achieve NO flux values within the physiological endothelial NO flux range for a 4 h period. Through in vitro hemocompatibility testing, the optimized material was deemed nonhemolytic (hemolytic index <2%) and capable of reducing platelet activation, suggesting that the material is suitable for contact with whole blood. Furthermore, an in vivo 4 h extracorporeal circulation (ECC) rabbit thrombogenicity model confirmed the blood biocompatibility of the optimized GSNO-PVC. Platelet count remained near 100% for the novel GSNO-impregnated PVC loops (1 h, 91.08 ± 6.27%; 2 h, 95.68 ± 0.61%; 3 h, 97.56 ± 8.59%; 4 h, 95.11 ± 8.30%). In contrast, unmodified PVC ECC loops occluded shortly after the 2 h time point and viable platelet counts quickly diminished (1 h, 85.67 ± 12.62%; 2 h, 54.46 ± 10.53%; 3 h, n/a; 4 h, n/a). The blood clots for GSNO-PVC loops (190.73 ± 72.46 mg) compared to those of unmodified PVC loops (866.50 ± 197.98 mg) were significantly smaller (p < 0.01). The results presented in this paper recommend further investigation in long-term animal models and suggest that GSNO-PVC has the potential to serve as an alternative to systemic anticoagulation in BCMD applications.

Anti-thrombogenic Surface Coatings for Extracorporeal Membrane Oxygenation: A Narrative Review

Extracorporeal membrane oxygenation (ECMO) is used in critical care to manage patients with severe respiratory and cardiac failure. ECMO brings blood from a critically ill patient into contact with a non-endothelialized circuit which can cause clotting and bleeding simultaneously in this population. Continuous systemic anticoagulation is needed during ECMO. The membrane oxygenator, which is a critical component of the extracorporeal circuit, is prone to significant thrombus formation due to its large surface area and areas of low, turbulent, and stagnant flow. Various surface coatings, including but not limited to heparin, albumin, poly(ethylene glycol), phosphorylcholine, and poly(2-methoxyethyl acrylate), have been developed to reduce thrombus formation during ECMO. The present work provides an up-to-date overview of anti-thrombogenic surface coatings for ECMO, including both commercial coatings and those under development. The focus is placed on the coatings being developed for oxygenators. Overall, zwitterionic polymer coatings, nitric oxide (NO)-releasing coatings, and lubricant-infused coatings have attracted more attention than other coatings and showed some improvement in in vitro and in vivo anti-thrombogenic effects. However, most studies lacked standard hemocompatibility assessment and comparison studies with current clinically used coatings, either heparin coatings or nonheparin coatings. Moreover, this review identifies that further investigation on the thrombo-resistance, stability and durability of coatings under rated flow conditions and the effects of coatings on the function of oxygenators (pressure drop and gas transfer) are needed. Therefore, extensive further development is required before these new coatings can be used in the clinic.

S-Nitroso-N-acetyl-l-cysteine Ethyl Ester (SNACET) Catheter Lock Solution to Reduce Catheter-Associated Infections

Antimicrobial-lock therapy is an economically viable strategy to prevent/reduce the catheter-related bloodstream infections (CRBSI) that are associated with central venous catheters (CVCs). Herein, we report the synthesis and characterization of the S-nitroso-N-acetyl-l-cysteine ethyl ester (SNACET), a nitric oxide (NO)-releasing molecule, and for the first time its application as a catheter lock solution to combat issues of bacterial infection associated with indwelling catheters. Nitric oxide is an endogenous gasotransmitter that exhibits a wide range of biological properties, including broad-spectrum antimicrobial activity. The storage stability of the SNACET and the NO release behavior of the prepared lock solution were analyzed. SNACET lock solutions with varying concentrations exhibited tuneable NO release at physiological levels for >18 h, as measured using chemiluminescence. The SNACET lock solutions were examined for their efficacy in reducing microbial adhesion after 18 h of exposure toStaphylococcus aureus (Gram-positive bacteria) andEscherichia coli (Gram-negative bacteria). SNACET lock solutions with 50 and 75 mM concentrations were found to reduce >99% (ca. 3-log) of the adhered S. aureus and E. coli adhesion to the catheter surface after 18 h. The SNACET lock solutions were evaluated in a more challenging in vitro model to evaluate the efficacy against an established microbial infection on catheter surfaces using the same bacteria strains. A >90% reduction in viable bacteria on the catheter surfaces was observed after instilling the 75 mM SNACET lock solution within the lumen of the infected catheter for only 2 h. These findings propound that SNACET lock solution is a promising biocidal agent and demonstrate the initiation of a new platform technology for NO-releasing lock solution therapy for the inhibition and treatment of catheter-related infections.