Biocompatible, smooth, plasma-treated nickel-titanium surface--an adequate platform for cell growth

Area of Science:

• Biomaterials Science
• Materials Engineering
• Cell Biology

Background:

• Nickel-titanium (Ni-Ti) alloys offer valuable shape memory and pseudoelastic properties for biomedical applications like spinal implants.
• High nickel content in Ni-Ti alloys raises concerns regarding nickel toxicity and limits their biomedical use.
• Improving Ni-Ti alloy biocompatibility is crucial for expanding its clinical applications.

Purpose of the Study:

• To investigate the biocompatibility of native and surface-modified nickel-titanium alloys.
• To determine how surface treatments affect nickel release and cell response.
• To identify surface characteristics that promote cell differentiation and minimize nickel-induced toxicity.

Main Methods:

• Investigated four surface conditions: smooth ground, thermal oxidation, alkali treatment, and plasma sputtering.
• Analyzed surface chemistry, nickel release, surface roughness (R(a)), and layer adhesion.
• Evaluated cell response, including cytoskeleton development and differentiation, on the different surfaces.

Main Results:

• Alkali treatment and thermal oxidation (at 600 °C) increased nickel release and surface roughness.
• Plasma sputtering and grinding resulted in smooth surfaces (R(a)=4 nm) with low nickel release.
• Cellular analysis revealed less developed cytoskeletons on surfaces with high nickel content or release.
• Ground and plasma-sputtered surfaces demonstrated the most favorable cell responses and supported cell growth.

Conclusions:

• Smooth surfaces, particularly plasma-sputtered Ni-Ti, enhance biocompatibility by minimizing nickel release.
• Surface modification techniques significantly impact nickel ion release and cellular interactions.
• Optimizing surface properties of Ni-Ti alloys is key to overcoming nickel toxicity concerns for biomedical applications.