# Low-Temperature Plasma Activation of Biomaterials and Its Stability over Time and Post-Sterilisation Effects

## TL;DR

Low-temperature plasma improves metal implant wettability, but its effects fade over time and are reduced by sterilization.

## Contribution

The study reveals the time-dependent stability of plasma-induced wettability and its sensitivity to steam sterilization.

## Key findings

- Low-temperature plasma activation significantly reduces contact angles, improving wettability of implant materials.
- Plasma-induced wettability diminishes over time and is strongly reduced when followed by steam sterilization.
- Steam sterilization alone has moderate and stable effects on surface wettability.

## Abstract

Low-temperature plasma (LTP) activation is increasingly used as a surface modification technique to enhance the wettability and biological performance of metallic implants. However, the stability of plasma-induced surface changes and their interaction with standard sterilisation procedures remain insufficiently understood. This study aimed to evaluate the effects of LTP activation, steam sterilisation, and their combination with the wettability of metallic implant materials, as well as the temporal stability of these effects. Samples manufactured from Ti6Al4V sheet, additively manufactured Ti6Al4V, and additively manufactured cobalt–chromium alloy were subjected to low-temperature plasma activation, steam sterilisation, or both procedures. Surface wettability was assessed by measuring the contact angle of canine blood droplets immediately after treatment and over a five-day observation period. Low-temperature plasma activation resulted in a substantial reduction in the contact angle for all tested materials, indicating a pronounced increase in surface wettability. However, this effect gradually diminished over time. Steam sterilisation alone moderately improved wettability and showed relatively stable effects. When steam sterilisation was applied after plasma activation, the plasma-induced enhancement was significantly attenuated and rapidly lost during storage. These findings demonstrate that while LTP activation effectively improves surface wettability, its benefits are highly time-dependent and strongly influenced by subsequent sterilisation. Plasma activation should therefore be performed immediately before implantation or combined with sterilisation and storage strategies that preserve surface modifications.