Tissue Biocompatibility of Variously Treated DLC-coated NiTi Fragments

using Rat Model

Shin JH1, Kim TH1, Kim EY1,

Song HY1, Moon MW2, Lee KR2, Han DK3

1Department of Radiology, University of Ulsan, College of Medicine

Asan Medical Center, Seoul, Korea2Future Convergence Technology Lab., 3Biomaterials Research Center,

KIST (Korea Institute of Science and Technology), Seoul, Korea

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

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

To evaluate tissue biocompatibility of the

variously treated DLC coated NiTi fragments

by in-vivo experiments using rat model

Purpose

Purpose

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/N2 (n=6)

NiTi/Si-DLC/CF4 (n=6)

NiTiSi

DLC

Materials and Methods

PEG

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

Materials and Methods

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

- H & E staining for the skeletal muscle

- Measurement of ‘fibrotic tissue thickness’ which indicates tissue response

Materials and Methods

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

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

Fibrotic tissue thickness

sample Mean fibrotic tissue thickness

NiTi-control 85.40 ㎛ (5th)

NiTi/Si-DLC 76.00 ㎛ (4th)

NiTi/Si-DLC/PEG 61.60 ㎛ (1st)

NiTi/Si-DLC/N2 72.70 ㎛ (3rd)

NiTi/Si-DLC/CF4 69.10 ㎛ (2nd)

Results

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) (x100)(x100)

Results

Results

Minimal lymphocytic infiltration and fibrosis, suggesting chronic inflammation

(x200)

NiTi/Si-DLC/PEG

Discussion

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

Conclusion

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.

AcknowledgementKim 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 !