Novel Surface Modification Techniques to Enhance Biocompatibility of Metallic Materials for Medical Implants

Four different novel surface modification techniques have been investigated to enhance the cell growth behavior in metallic implantable materials. The potential of each technique has been studied for improving current treatments in a target disease. The first surface modification technique is the creation of nanoscale grain surfaces on stainless steel 316L material via linear plane-strain machining. The in vitro cell adhesion study demonstrates the enhanced osteoblast adhesion and growth on the native oxide layer formed on the material with the smallest grain size (i.e., created by 0° rake angle). This result represents a high potential of nanoscale grain surface in stainless steel for improving the bone bonding for orthopedic biomaterials. The second surface modification technique is a rapid endothelialization of thin film nitinol through electrostatic cell seeding process. This technique utilizes dielectrophoresis supplying for temporarily created positive surface charges on thin film nitinol. In vitro cell adhesion assays have demonstrated the enhanced seeding of endothelial cells on thin film nitinol under the optimal electrical conditions (i.e., 5V applied voltage for 30 minutes) which shows the potential use of the technique for thin film nitinol based low-profile endovascular graft. In the third technique, a thin layer of silk is deposited on the thin film nitinol substrate using electrospinning technique to facilitate the surface endothelialization and to enhance the hemocompatibility. The proof-of-concept in vitro test results have demonstrated that the integrated thin film nitinol and electrospun silk represents a high-potential candidate material for small-diameter vascular grafts owning to favorable properties of thin film nitinol and silk. The last technique introduces the micropatterned thin film nitinol as a novel low-profile cover for stents in treating carotid artery stenosis disease. A sputter deposition technique along with a lift-off process was used to create various microscale features in thin film nitinol. The micropatterned thin film nitinol effectively captured the embolic particles dislodged from the carotid artery stenosis in vitro model. Besides, the micropatterned thin film nitinol has significantly enhanced endothelial cell adhesion and growth. Therefore, four surface modification techniques showed advancement in cellular behavior with the various metallic biomaterials used in treating critical diseases