Nitric Oxide Releasing Tygon Materials: Studies in Donor Leaching and Localized Nitric Oxide Release at a Polymer-Buffer Interface

Abstract

Tygon is a proprietary plasticized poly(vinyl chloride) polymer that is used widely in bioapplications, specifically as extracorporeal circuits. To overcome issues with blood clot formation and infection associated with the failure of these medical devices upon blood contact, we consider a Tygon coating with the ability to release the natural anticlotting and antibiotic agent, nitric oxide (NO), under simulated physiological conditions. These coatings are prepared by incorporating 20 w/w% S-nitrosoglutathione (GSNO) donor into a Tygon matrix. These films release NO on the order of 0.64 ± 0.5 × 10(-10) mol NO cm(-2) min(-1), which mimics the lower end of natural endothelium NO flux. We use a combination of assays to quantify the amount of GSNO that is found intact at different time points throughout the film soak, as well as monitor the total thiol content in the soaking solution due to any analyte that has leached from the polymer film. We find that a burst of GSNO is released from the material surface within 5 min to 1 h of soaking, which only represents 0.25% of the total GSNO contained in the film. After 1 h of film soak, no additional GSNO is detected in the soaking solution. By further considering the total thiol content in solution relative to the intact GSNO, we demonstrate that the amount of GSNO leached from the material into the buffer soaking solution does not contribute significantly to the total NO released from the GSNO-incorporated Tygon film (<10% total NO). Further surface analysis using SEM-EDS traces the elemental S on the material surface, demonstrating that within 5 min -1 h soaking time, 90% of the surface S is removed from the material. Surface wettability and roughness measurements indicate no changes between the GSNO-incorporated films pre- to postsoak that will be significant toward the adsorption of biological components, such as proteins, relative to the presoaked donor-incorporated film. Overall, we demonstrate that, for a 20 w/w% GSNO-incorporated Tygon film, relatively minimal GSNO leaching is experienced, and the lost GSNO is from the material surface. Varying the donor concentration from 5 to 30 w/w% GSNO within the film does not result in significantly different NO release profiles. Additionally, the steady NO flux associated with the system is predominantly due to localized release from the material, and not donor lost to soaking solution. The surface properties of these materials generally imply that they are useful for blood-contacting applications.

Reduction in thrombosis and bacterial adhesion with 7 day implantation of S-nitroso-N-acetylpenicillamine (SNAP)-doped Elast-eon E2As catheters in sheep

“…37 Despite these promising literature reports, many of these NO-releasing polymers have not been clinically applied due to instability of the NO donor species within the polymers during storage or sterilization, significant leaching of unbound NO donors, or the requirement of complex chemistry to covalently bind the NO donor to the polymer. 30,38 For example, S-nitrosothiol-modified polyesters were effective at reducing platelet adhesion/activation and had antimicrobial effect against Staphylococcus aureus and the multi-drug resistant Pseudomonas aeruginosa strains, but the NO release capability was significantly influenced by ethylene oxide sterilization. 39,40 In addition, most of the NO-releasing materials reported to date have been tested in vitro or in short-term animal models for their hemocompatibility properties, so testing these materials in longerterm animal models would be beneficial to evaluate more clinically relevant situations.…”

Evaluation of experimental methods for nitric oxide release from cardiovascular implants; bypass grafts as an exemplar

“…This method was adapted from that of Jolish and colleagues [Joslin et al 2013]. A series of standard solutions of SNAP (1 nM to 10 μM) in PBS (pH = 7.4) and EDTA (1 mM) was prepared and the calibration curve plotted.…”

Multivalent manganese complex decorated amphiphilic dextran micelles as sensitive MRI probes

“…37 Despite these promising literature reports, many of these NO-releasing polymers have not been clinically applied due to instability of the NO donor species within the polymers during storage or sterilization, significant leaching of unbound NO donors, or the requirement of complex chemistry to covalently bind the NO donor to the polymer. 30, 38 For example, S- nitrosothiol-modified polyesters were effective at reducing platelet adhesion/activation and had antimicrobial effect against Staphylococcus aureus and the multi-drug resistant Pseudomonas aeruginosa strains, but the NO release capability was significantly influenced by ethylene oxide sterilization. 39, 40 In addition, most of the NO-releasing materials reported to date have been tested in vitro or in short-term animal models for their hemocompatibility properties, so testing these materials in longer-term animal models would be beneficial to evaluate more clinically relevant situations.…”