title: Enhancement of endothelialisation of coronary stents by laser surface engineering.
abstract: OBJECTIVE
  Coronary stents have been widely used in the treatment of coronary heart disease. However, complications have hampered the long-term success of the device. Bare-metal stents (BMS) have a high rate of restenosis and poor endothelialisation. The drug-eluting stents (DES), although dramatically reduce restenosis, significantly prevent endothelialisation leading to late thrombosis and behave the same way as BMS after drug releasing. Rapid adhesion and growth of endothelial cells on the stent surface is a key process for early vascular healing after coronary stenting which contributes to the reduction of major complications. Surface properties manipulate cell growth and directly determine the success and life-span of the implants. However, the ideal surface properties of coronary stents are not yet fully understood. The objective of this research is to understand how surface micro/nano textures and associated material chemistry changes generated by a laser beam affect the behavior of endothelial cells on bare metal 316L stents.
  
  
  METHODS
  A high power laser beam was applied to modifying the surface properties of 316L coronary stent material and the commercial coronary stents, followed by examination of the adhesion and proliferation of human coronary endothelial cells that were growing on the surfaces. Surface properties were examined by scanning electron microscopy, contact angle measurement, and X-ray photoelectron spectroscopy.
  
  
  RESULTS
  A novel surface with combined micro/nano features was created on stent material 316L and coronary stent with a specific surface chemistry. This surface gives rise to a threefold increase in the adhesion and eightfold increase in the proliferation of endothelial cells. Interestingly, such effects were only observed when the surface texture was produced in the nitrogen atmosphere suggesting the importance of the surface chemistry, including the dramatic increase of chromium nitride, for the interaction of endothelial cells with the material surface. This novel surface is also super-hydrophilic with close to zero water/cell culture fluid contact angles and low cytotoxicity.
  
  
  CONCLUSIONS
  A novel surface created by laser surface-engineering with a combination of defined surface texture and surface chemistry was found beneficial for the improvement of coronary stent endothelialisation. The technology presented here could work with both DES and BMS with added benefit for the improvement of the biocompatibility of current coronary stents.
authors.affiliation: Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, and Photon Science Institute, The University of Manchester, Manchester, M13 9PL, UK.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Nazanin
authors.initials: N
authors.lastname: Mirhosseini
authors.forename: Alun
authors.initials: A
authors.lastname: Michael
authors.forename: Zhu
authors.initials: Z
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
mesh_terms: D000818:Animals; D001698:Biomedical Engineering; D002448:Cell Adhesion; D049109:Cell Proliferation; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology; D042783:Endothelial Cells / Q000502:physiology*; D006801:Humans; D053844:Lasers, Solid-State; D062645:Percutaneous Coronary Intervention / Q000295:instrumentation*; D056951:Photoelectron Spectroscopy; D051381:Rats; D017207:Rats, Sprague-Dawley; D015607:Stents
keywords: biocompatibility; cell adhesion and proliferation; endothelialisation; laser surface-texturing; surface chemistry