Non-thermal argon plasma enhances wettability of Ti-6Al-4V biomaterial surfaces without detectable elemental alteration

This in vitro study evaluated whether non-thermal argon plasma could improve the wettability of Grade 5 titanium alloy (Ti-6Al-4V) surfaces without producing detectable changes in elemental composition. Ninety commercially sourced Ti-6Al-4V discs were allocated to one of three surface conditions: machined, nitric acid-treated, or hydrochloric acid-treated. For wettability analysis, each surface condition was evaluated either without plasma treatment or after 60 s of non-thermal argon plasma exposure at 22 °C, with 13 independent discs per subgroup. Water contact angle was measured using the sessile-drop method, and the mean of the left and right contact angles was used as the specimen-level outcome. Surface morphology and elemental composition were evaluated qualitatively by scanning electron microscopy and energy-dispersive X-ray spectroscopy before plasma exposure and immediately and at 30 and 60 min after treatment. Argon plasma significantly reduced the water contact angle in all surface groups (p < 0.0001), indicating a marked increase in wettability. Mean contact angle decreased from 162.6° to 32.74° on machined surfaces, from 150.5° to 12.96° on nitric acid-treated surfaces, and from 110.0° to 21.87° on hydrochloric acid-treated surfaces. Plasma-treated acid-conditioned surfaces exhibited lower contact angles than plasma-treated machined surfaces. Scanning electron microscopy indicated that plasma exposure made pre-existing topographic features more visually distinct, particularly on acid-treated surfaces, whereas energy-dispersive X-ray spectroscopy revealed no appreciable changes in elemental composition. These findings support non-thermal argon plasma as a short-term surface-activation strategy for Ti-6Al-4V biomaterials; however, the durability and biological relevance of this effect require further investigation.