Reduction of Late In-Stent Stenosis in a Porcine Coronary Artery Model by Cobalt Chromium Stents with a Nanocoat of Polyphosphazene (Polyzene-F)

The purpose of this study was to investigate the potential of nanoscale coating with the highly biocompatible polymer Polyzene-F (PZF), in combination with cobalt chromium and stainless steel stents, to reduce in-stent stenosis, thrombogenicity, and vessel wall injury and inflammation. One bare cobalt chromium, PZF-nanocoated stainless steel or PZF-nanocoated cobalt chromium stent was implanted in right coronary artery of 30 mini-pigs (4- or 12-week follow-up). Primary study end points were in-stent stenosis and thrombogenicity. Secondary study end points were vessel wall injury and inflammation as evaluated by microscopy and a new immunoreactivity score applying C-reactive protein (CRP), tumor-necrosis factor alpha (TNFα), and TGFβ. At 12 weeks, angiography showed a significantly lower average loss in lumen diameter (2.1% ± 3.05%) in PZF-nanocoated cobalt chromium stents compared with stents in the other groups (9.73% ± 4.93% for bare cobalt chromium stents and 9.71% ± 7% for PZF-nanocoated stainless steel stents; p = 0.04), which was confirmed at microscopy (neointima 40.7 ± 16 μm in PZF-nanocoated cobalt chromium stents, 74.7 ± 57.6 μm in bare cobalt chromium stents, and 141.5 ± 109 μm in PZF-nanocoated stainless steel stents; p = 0.04). Injury and inflammation scores were low in all stents and were without significant differences. PZF-nanocoated cobalt chromium stents provided the highest efficacy in reducing in-stent stenosis at long-term follow-up. The PZF nanocoat proved to be biocompatible with respect to thromboresistance and inflammation. Our data suggest that its combination with cobalt chromium stents might provide an interesting passive stent platform.