Bacterial and osteoblast behavior on titanium, cobalt–chromium alloy and stainless steel treated with alkali and heat: A comparative study for potential orthopedic applications

•Ti, Co–Cr, and SS substrates were treated with alkali and heat.•For Ti, the treatment results in increased hydrophilicity and anatase formation.•Surface anatase generates ROS, resulting in both bactericidal and apoptotic effects.•For SS and Co–Cr substrates, the treatment increases surface hydrophilicity.•The treated SS and Co–Cr reduce bacterial adhesion without apoptotic effects.

HypothesisAnatase-modified titanium (Ti) substrates have been found to possess antibacterial properties in the absence of ultraviolet irradiation, but the mechanism is not known. We hypothesize that this is due to the bactericidal effects of reactive oxygen species (ROS) generated by the surface anatase.ExperimentsAlkali and heat treatment was used to form anatase on Ti surface. The generation of ROS, and the behavior of bacteria and osteoblasts on the anatase-modified Ti were investigated. Cobalt–chrome (Co–Cr) alloys and stainless steel (SS) were similarly treated with alkali and heat, and their surface properties and effects on bacteria and osteoblasts were compared with the results obtained with Ti.FindingsThe anatase-functionalized Ti substrates demonstrated significant bactericidal effects and promoted apoptosis in osteoblasts, likely a result of ROS generated by the anatase. The alkali and heat-treated Co–Cr and SS substrates also reduced bacterial adhesion but were not bactericidal. This effect is likely due to an increase in hydrophilicity of the surfaces, and no significant ROS were generated by the alkali and heat-treated Co–Cr and SS substrates. The treated Co–Cr and SS substrates did not induce significant apoptosis in osteoblasts, and thus with these properties, they may be promising for orthopedic applications.

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