Reduction of Thrombosis and Bacterial Infection via Controlled Nitric Oxide (NO) Release from S-Nitroso-N-acetylpenicillamine (SNAP) Impregnated CarboSil Intravascular Catheters

Abstract

Nitric oxide (NO) has many important physiological functions, including its ability to inhibit platelet activation and serve as potent antimicrobial agent. The multiple roles of NO in vivo have led to great interest in the development of biomaterials that can deliver NO for specific biomedical applications. Herein, we report a simple solvent impregnation technique to incorporate a nontoxic NO donor, S-nitroso-N-acetylpenicillamine (SNAP), into a more biocompatible biomedical grade polymer, CarboSil 20 80A. The resulting polymer-crystal composite material yields a very stable, long-term NO release biomaterial. The SNAP impregnation process is carefully characterized and optimized, and it is shown that SNAP crystal formation occurs in the bulk of the polymer after solvent evaporation. LC-MS results demonstrate that more than 70% of NO release from this new composite material originates from the SNAP embedded CarboSil phase, and not from the SNAP species leaching out into the soaking solution. Catheters prepared with CarboSil and then impregnated with 15 wt % SNAP provide a controlled NO release over a 14 d period at physiologically relevant fluxes and are shown to significantly reduce long-term (14 day) bacterial biofilm formation against Staphylococcus epidermidis and Pseudonomas aeruginosa in a CDC bioreactor model. After 7 h of catheter implantation in the jugular veins of rabbit, the SNAP CarboSil catheters exhibit a 96% reduction in thrombus area (0.03 ± 0.01 cm2/catheter) compared to the controls (0.84 ± 0.19 cm2/catheter) (n = 3). These results suggest that SNAP impregnated CarboSil can become an attractive new biomaterial for use in preparing intravascular catheters and other implanted medical devices.

Antimicrobial nitric oxide releasing surfaces based on S-nitroso-N-acetylpenicillamine impregnated polymers combined with submicron-textured surface topography

“…The solvent impregnation technique described herein allows SNAP incorporation into CarboSil polymer via a one-step method, and the impregnated SNAP molecules are embedded in the entire bulk of the material as the solvent evaporates. 39 Since SNAP can partially dissolve in the CarboSil polymer with a solubility limit of ~3.4–4 wt%, 30 the SNAP is present in the materials in the form of both dissolved SNAP as well as crystalline SNAP, the latter which forms a stable polymer-crystal composite that can enable long-term NO release.…”

“…The former SNAP-doped textured film was prepared by the layer-by-lay spin-coating method previously reported 38 . As shown in Figure 5, after the solvent impregnation process, the SNAP molecules/crystals are “inserted” into the interspace between CarboSil 20 80A polymer chains, 39 with a lamellae structure of the PDMS phase and the polycarbonate/polyurethane hard segment mixed phase. 42 This process may result in a slightly less uniform crystal distribution in the 5 % SNAP-impregnated films when compared to the 5 wt% SNAP-doped films prepared by the previously reported spin coating technique.…”

“…42 This process may result in a slightly less uniform crystal distribution in the 5 % SNAP-impregnated films when compared to the 5 wt% SNAP-doped films prepared by the previously reported spin coating technique. 39 …”

“…As described previously, 39 the films were soaked in solutions (70 % MEK and 30 % MeOH) containing different SNAP concentrations (35, 65 and 110 mg/mL) to achieve 5, 10 and 15 wt% SNAP loading in Carbosil PU films, respectively. 39 After 2 h of impregnation, the films were removed from the impregnation solution, quickly washed with methanol to remove any residual SNAP solution on the film surface, and allowed to dry up in the ambient environment protected from light exposure.…”

“…39 Briefly, films with diameter of ~10 mm were placed in the sample vessel immersed in PBS containing 100 μM EDTA at 37°C. Nitric oxide emitted from the film was continuously purged from the buffer and swept from the headspace using nitrogen gas and a bubbler into the chemiluminescence detection chamber of the NOA.…”