Recent investigations have demonstrated that polydopamine (PDA)-modified surfaces were beneficial to the proliferation of endothelial cells (ECs). In this work, PDA coated 316L stainless steels (316L SS) were thermally treated at 50, 100, and 150 °C respectively (hereafter designated as Th50, Th100, and Th150) and consequently produced diverse surface chemical components. In vitro hemocompatibility and vascular cell-material interactions with ECs and smooth muscle cells (SMCs) affected by surface characteristics have been investigated. The Th150, rich in quinone, showed the best hemocompatibility and could effectively inhibit platelet adhesion, activation, and fibrinogen conformation transition. The polydopamine-modified surfaces were found to induce dramatic cell-material interaction with enhanced ECs proliferation, viability and migration, release of nitric oxide (NO), and reduced SMCs proliferation. The inhibitory effect of SMCs proliferation might be associated with the surface catechol content. The coating on Th150 showed a good resistance to the deformation of compression and expansion of vascular stents. These results effectively suggested that the Th150 coating might be promising when served as a stent coating platform.

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In this study, using polylactic acid-co-glycolic acid (PLGA) with a molecular weight of 95,800 Da as drug carrier, three dose (low, moderate, high) rapamycin-eluting stents and the corresponding coating films were prepared. The pre- and post-expansion morphology of the rapamycin-eluting stent was examined by scanning electron microscopy (SEM), indicating that the coating was very smooth and uniform. The coating had the ability to withstand the compressive and tensile strains imparted without cracking from the stent during expansion process. There were many voids on stent coating surface after released for 18 days in release medium. The thermodynamics data of the stent coating film measured by differential scanning calorimetry (DSC) showed a lack of measurable solubility of rapamycin in the PLGA matrix. The release behavior of rapamycin from stent surface had a two phase release profile with a burst release period of about 2 days, followed by a sustained and slow release phase. The mass loss behavior of PLGA appeared linear throughout most of the degradation period, corresponding to an approximately constant mass loss rate. The platelet adhesion tests showed that the rapamycin-eluting films may have a good blood compatibility compared with control samples. Take into these results account, this novel rapamycin-eluting may be a good candidate to resolve in-stent restenosis.

Local and continuous release of nitric oxide (NO) has been suggested to be a potential and desirable demand for blood contacting implants. However, the life time of NO release from polymer films is limited by the reservoir of loaded NO donor. In situ generation of NO via catalytic decomposing the endogenous S-nitrosothiols (RSNOs) at the blood/material interface is a novel and challenging approach. Herein, a copper-incorporated film was constructed with the copolymerization of catechols (catechol or epigallocatechin gallate (EGCG)) and collagen. FT-IR results suggested the successful deposition of catechol/collagen copolymer film. The XPS results demonstrated the existence of copper on the surfaces. AFM results demonstrated that copper particles were formed in the thin polymeric film. Copper-incorporated samples presented a capability of generating physiological levels of NO. Difference of the generated amount of NO was associated with the Cu (I) concentration during the testing period, demonstrated by micro-BCA assay. NO-generating films not only significant properties on inhibiting platelet activation and adhesion, but also dramatically decreased smooth muscle cell adhesion. Such copper-incorporated film might suggest potential in the design of vascular devices.