Characterization of neutrophil adhesion to different titanium surfaces

Although titanium (Ti) is known to elicit a foreign body response when implanted into humans, Ti implant healing resembles normal wound healing in terms of inflammatory cell recruitment and inflammation persistence. Rough implant surfaces may present better conditions for protein adsorption and for the adhesion of platelets and inflammatory cells such as neutrophils. Implanted biomedical devices initially interact with coagulating blood; however, direct contact between the oxide layer of the implant and neutrophils has not been completely described. The aim of the present study is to compare the behaviours of neutrophils in direct contact with different Ti surfaces. Isolated human neutrophils were placed into contact with Ti discs, which had been rendered as ‘smooth’ or ‘rough’, following different surface treatments. Scanning electron microscopy and flow cytometry were used to measure cell adhesion to the surfaces and exposure of membrane proteins such as CD62L and CD11b. Topographic roughness was demonstrated as higher for SLA treated surfaces, measured by atomic force microscopy and elemental analysis was performed by energy dispersive X-ray, showing a similar composition for both surfaces. The adhesion of neutrophils to the ‘rough’ Ti surface was initially stronger than adhesion to the ‘smooth’ surface. The cell morphology and adhesion marker results revealed clear signs of neutrophil activation by either surface, with different neutrophil morphological characteristics being observed between the two surface types. Understanding the cellular mechanisms regulating cell–implant interactions should help researchers to improve the surface topography of biomedical implant devices.