Effect of different wave-length ultraviolet light-treated micro-arc oxidation titanium surfaces on the physicochemical properties and bioactivity in vitro

Abstract

To study the effects of ultraviolet (UV) light-treatment on the physicochemical properties and bioactivity of micro-arc oxidation (MAO) titanium surfaces in vitro. The pure titanium were prepared using MAO. MAO titanium samples were treated with 15 W bactericidal lamp UVC [λ = (250 ± 20) nm] or 15 W mercury lamp [λ = (360 ± 20) nm] for 24 h under ambient conditions. Three sample groups were prepared: MAO, UVA treated after MAO (MAO + UVA), UVC treated after MAO (MAO + UVC). The surface physicochemical properties were evaluated using scanning electron microscopy (SEM), contact angle measuring device, energy dispersive X-ray spectrometer (EDX), and X-ray diffraction (XRD). Bicinchoninic acid (BCA) based colorimetric detection was used to quantify the percentage of albumin adsorption after 2 h, 6 h, and 24 h incubation on the titanium surfaces. The rates of MG-63 cells attached to each group titanium surfaces were calculated by nucleus immunofluorescence using Hoechst 33342 after 1 h, 2 h, and 4 h incubation. SEM was used to observe cell morphology on titanium surfaces in each group. No obvious differences in surface topography, TiO(2) crystal and elemental composition were detected on titanium surfaces with or without UV treatment. Statistically significant difference in contact angles among MAO + UVC group (65.34 ± 1.16)°, MAO + UVA group (44.64 ± 1.28)°, and MAO group (3.41 ± 0.48)° were found (P < 0.001). The percentage of albumin adsorption reached the plateau after 2 h incubation on MAO + UVC titanium surfaces (48.16 ± 1.24)%, which was higher than those in MAO [(8.22 ± 2.99)%] and MAO + UVA groups [(5.29 ± 2.27)%, P < 0.001]. The rates of cells attached to the surfaces of MAO + UVC titanium was greater than that on MAO surfaces and MAO + UVA surfaces after 1 h [(40.71 ± 4.08)%], 2 h [(53.72 ± 2.38)%], 4 h [(70.32 ± 2.85)%] incubation (P < 0.05). The MAO + UVC surfaces remarkably enhanced the spread of MG-63 cells, however, there was no significant difference between the group of MAO and MAO + UVA. Pretreatment of micro-arc oxidation titanium with UVC light considerably improved the surface bioactivity to MG-63 cells, which showed an increase in cellular attachment and spread.