1. Tissue Biocompatibility of Variously Treated DLC-coated NiTi Fragments using Rat Model Shin JH 1, Kim TH 1, Kim EY 1, Song HY 1, Moon MW 2, Lee KR 2, Han DK 3 1 Department of Radiology, University of Ulsan, College of Medicine Asan Medical Center, Seoul, Korea 2 Future Convergence Technology Lab., 3 Biomaterials Research Center, KIST (Korea Institute of Science and Technology), Seoul, Korea

2. Introduction Problems with a biomedical device - Biocompatibility, hematocompatibility, & cytotoxicity Ideal Biomaterials - Chemically and biologically inert to the surrounding tissues - Hard and wear-resistant with low friction - No release of toxic and carninogenic elements ** ‘surface properties’ are very important Introduction

3. DLC (diamond-like carbon) coatings - High hardness, low frictional coefficient, high wear & corrosion resistance, chemical inertness, high electrical resistivity, and excellent smoothness - Promising as a hemocompatible material - Doping or surface treatment is helpful for better mechanical properties and biocompatibility Introduction

4. To evaluate tissue biocompatibility of the variously treated DLC coated NiTi fragments by in-vivo experiments using rat model Purpose

5. Materials and Methods Test Specimens - Sample size: 5mm x 5mm, rectangular - NiTi-control (n=6) NiTi/Si-DLC (n=6) NiTi/Si-DLC/PEG (n=6) NiTi/Si-DLC/N 2 (n=6) NiTi/Si-DLC/CF 4 (n=6) NiTi Si DLC Materials and Methods PEG

6. Animal Experiment - Six for each test specimen, so total 30 specimens - Rat thigh muscle model (n=15) - Anesthesia with intraperitoneal injection of ketamine (100mg/kg) and xylazine (15mg/kg) - Fixation of the hind leg - Bilateral thigh muscle dissection - Implantation of test specimens into muscle belly - Suture of the incision site Materials and Methods

8. Follow-up and Histopathology - 6 weeks of follow-up to allow tissue response to the implanted specimens - Sacrifice with removal of each specimen and surrounding skeletal muscle Materials and Methods

9. - H & E staining for the skeletal muscle - Measurement of ‘fibrotic tissue thickness’ which indicates tissue response Materials and Methods

10. Statistics - Measure ‘fibrotic tissue thickness’ 3 times for each specimen - ANOVA test to evaluate significant difference of fibrotic tissue thickness between the five groups Materials and Methods

11. Results All rats tolerated the surgery well Post-implantation period was uncomplicated Implantation site healed without any complications Implanted specimens could be removed easily Fibrotic tissue was observed as a capsule around the implantation site Results

12. Fibrotic tissue thickness sample Mean fibrotic tissue thickness NiTi-control 85.40 ㎛ (5 th ) NiTi/Si-DLC 76.00 ㎛ (4 th ) NiTi/Si-DLC/PEG 61.60 ㎛ (1 st ) NiTi/Si-DLC/N 2 72.70 ㎛ (3 rd ) NiTi/Si-DLC/CF 4 69.10 ㎛ (2 nd ) Results

13. NiTi-control Mean - 85.40 ㎛ NiTi/Si-DLC Mean - 76.00 ㎛ NiTi/Si-DLC/PEG Mean - 61.60 ㎛ No significant difference between five groups ; p=0.063 (ANOVA) (x100) Results

14. Minimal lymphocytic infiltration and fibrosis, suggesting chronic inflammation (x200) NiTi/Si-DLC/PEG

15. Discussion NiTi/Si-DLC/PEG showed the best tissue biocompatibility. - PEG is hydrophilic as a water-soluble polymer - PEG is flexible (high chain motility) - PEG has steric stabilization having exclude volume, - difficult for blood components to get close

16. Conclusion NiTi/Si-DLC/PEG showed the best tissue biocompatibility. Variously treated DLC coated NiTi specimens showed less tissue reaction compared with NiTi-control. This observation provides basis for feasibility of application of the stents made of treated DLC coated NiTi.

17. Acknowledgement Kim TH, Kim EY – Dept. of Radiology, Asan Medical Center Park CS - Dept. of Pathology, Asan Medical Center Lee KR, Moon MW - Future Convergence Technology Lab., KIST Han DK, Park K - Biomaterials Research Center, KIST Thank you for your attention !