Advanced cardiovascular stent coated with nanofiber.

ABSTRACT

Nanofiber was explored as a stent surface coating substance for the treatment of coronary artery diseases (CAD). Nanofibers loaded with nanoparticles containing ß-estradiol were developed and exploited to prevent stent-induced restenosis through regulation of the reactive oxygen species (ROS). Eudragit S-100 (ES), a versatile polymer, was used as a nanoparticle (NP) base, and the mixtures of hexafluoro-2-propanol (HFIP), PLGA and PLA at varying ratios were used as a nanofiber base. ß-Estradiol was used as a primary compound to alleviate the ROS activity at the subcellular level. Nile-Red was used as a visual marker. Stent was coated with nanofibers produced by electrospinning technique comprising the two-step process. Eudragit nanoparticles (ES-NP) as well as 4 modified types of NP-W (ES-NP were dispersed in H2O, which was mixed with HFIP (11 (v/v) and then subsequently added with 15% PLGA), NP-HW (ES-NP were dispersed in H2O, which was mixed with HFIP (11 (v/v)) already containing 15% PLGA), NP-CHA (ES-NP with a chitosan layer were added in H2O, which was mixed with HFIP (11 (v/v)) containing 15% PLGA), and NP-CHB (ES-NP with a chitosan layer were added in H2O, which was mixed with HFIP (11 (v/v)) containing the mixture of PLGA and PLA at a ratio of 41) were developed, and their properties, such as the loading capacity of ß-estradiol, the release profiles of ß-estradiol, cell cytotoxicity and antioxidant responses to ROS, were characterized and compared. Among composite nanofibers loaded with nanoparticles, NP-CHB had the maximal yield and drug-loading amount of 66.5 ± 3.7% and 147.9 ± 10.1 µg, respectively. The nanofibers of NP-CHB coated on metallic mandrel offered the most sustained release profile of ß-estradiol. In the confocal microscopy study, NP-W exhibited a low fluorescent intensity of Nile-Red as compared with NP-HW, indicating that the stability of nanoparticles decreased, as the percentage volume of the organic solvent increased. Nanofibers incorporated with ß-estradiol yielded a high endothelial proliferation rate, which was about 3-fold greater than the control (without ß-estradiol). The cells treated with the enhanced level of H2O2 (>1 mM as ROS source) were mostly nonviable (81.1 ± 12.4%, p < 0.01), indicating that ROS induce cell apoptosis and trigger the rupture of atheroma thin layer in a concentration dependent manner. Nanofibers containing ß-estradiol (0.5 mM) lowered cellular cytotoxicity from 25.2 ± 4.9% to 8.1 ± 1.4% in the presence of 600 µM H2O2, and from 86.8 ± 8.4% to 59.4 ± 8.7% in the presence of 1.0 mM H2O2, suggesting that ß-estradiol efficiently protected hPCECs from ROS induced cytotoxicity. The level of NO production in hPCECs in the presence of ß-estradiol after 6 days of incubation was much greater than that of the control without ß-estradiol. In summary, nanofibers loaded with nanoparticles containing ß-estradiol could be used as a suitable platform for the surface coating of a cardiovascular stent, achieving enhanced endothelialization at the implanted sites of blood vessels.