Biocompatibility Studies of the Nitinol Thin Films

Abstract

Pulsed Laser Deposition method (PLD) was used to grow nitinol (NiTi) thin films with goal of investigating their biocompatibility. High purity Ni and Ti targets were alternatively ablated in vacuum with a laser beam (λ=355 nm, 10 Hz) and the material was collected on room temperature Ti substrates. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy analyses have been performed to investigate the chemical composition, crystalline structure and surface morphology of the NiTi films. The nitinol layers biocompatibility has been tested using as a metric the extent to which the cells adhere during the culture period on the surface of NiTi layers deposited on Ti substrates. Vero and fibroblast cell lines dispersed into MEM (Eagle) solution containing 8% fetal bovine serum, at 37° C, were used for tests. Preliminary studies indicate that the interaction at the interface is specifically controlled by the surface morphology, (especially by surface roughness), and by the chemical state of the surface. Cell behavior after contact with NiTi/Ti structure for different intervals (18, 22 and 25 days for the Vero cells, and after 10 and 25 days for fibroblasts) supports the conclusion that NiTi is a very good candidate as a biocompatible material.

Monitorizing nitinol alloy surface reactions for biofouling studies

“…The experimental set-up used for the nitinol thin film deposition was already described elsewhere [20,21]. Briefly, two high purity Ni and Ti disks (99.99%) were placed on a multi-target system and irradiated at 458 by a frequency tripled Nd:YAG pulsed laser (l = 355 nm, 5 ns) operating in vacuum (10 À6 mbar), a fluence of 4 J/cm 2 and a repetition rate of 5 Hz.…”

“…These changes induce internal-stress plasticity [12] and superelasticity [16] that in turn increase alloy use in biomedical applications [17]. Different techniques have been employed for deposition of nitinol thin films: DC plasma assisted sputtering [18], sequential multilayer deposition of Ni and Ti layers followed by metal interdiffusion via annealing [19] or pulsed laser deposition technique (PLD) [20,21]. PLD is a highly non-equilibrium process that produces an intense plasma to ablate and transfer the target composition to a proximal substrate.…”