Introduction: Good anticoagulant ability and good endothelial cells (ECs) compatibility were important to the cardiovascular implants. Recently, UV irradiation has been reported to easily improve the anticoagulant ability[1], which was related to the changes in the nature of the TiO2 film caused by the photo-generated ROS[2]. On the other hands, H2SO4 treatment has been reported to improve the cell compatibility, which was related to the enhancement of the positive charge of the TiO2 film[3].
In this study, the TiO2 films were treated successively with H2SO4 and the UV irradiation, then the materials detection and the biological detection was performed to determine: (1) whether the H2SO4 and the UV treatment improving the anticoagulant and the cell compatibility of the TiO2 film at the same time; (2) the relationship between the anticoagulant ability /cell compatibility and the changes in the nature of the TiO2 film.
Materials and methods: As shown in Fig. 1, TiO2 film on Si substratum was firstly treated by H2SO4 (67 wt %) in 120 °C for 5min; after that, the TiO2 film was UV-irradiated for 1h with UV light intensity of 16 mW/cm2 (λ = 365nm). The physicochemical properties of modified TiO2 surface were characterized. The anticoagulant ability and the cell compatibility were also evaluated.
Fig. 1. Preparation of H2SO4-treated and UV-irradiated TiO2 film
Results and Discussion: According to Fig.2, UV irradiation significantly shifted the shoulder peaks at about 288 eV to a higher bonding energy, indicating the oxidation of the hydrocarbon contaminants which adsorbed on the TiO2 surface. H2SO4 treatment slightly shifted the shoulder peaks to a higher bonding energy (Fig.2A), indicating the slightly oxidation of the hydrocarbon contaminants. Both UV irradiation and H2SO4 treatment reduced the atomic percentages of carbon on the TiO2 films and induced the increasing of positive charge. However, the H2SO4 treatment induced more positive charge on the TiO2 surface than UV irradiation (Fig. 2B). The results of platelet adhesion and fibrinogen adsorption showed the UV irradiation significantly improved the anticoagulant ability of TiO2 films by suppressing the fibrinogen adsorption and platelet adhesion. On the other hand, the H2SO4 improved the anticoagulant ability of TiO2 films slightly, which could be related to the slightly oxidation of the hydrocarbon contaminants adsorbed on the TiO2 surface (Fig. 2C). The results of ECs and Macrophages culture revealed that the H2SO4 treatment strongly enhanced the cellular adhesion and proliferation, which could be related to the increasing of the positive charge on the H2SO4-treated TiO2 surface (Fig 2D and E). According to the results above, the UV-irradiated and H2SO4-treated TiO2 films showed good anticoagulant ability and cell compatibility.
Fig. 2. The change of the physicochemical properties and the biocompatibility of modified TiO2 films: (A) The close-up view of the XPS C 1s peak. (B) The change of the atomic percentage of carbon and the surface charge. (C) Anticoagulant ability, (D) ECs adhesion. (E) Macrophages adhesion.
Conclusions: This study provides a novel and facile construction method for improving both the anticoagulant ability and cell compatibility of TiO2 film. The improving of the anticoagulant ability could be related to the oxidation of the adsorbed hydrocarbon contaminants which could be caused by the photo-generated ROS. On the other hand, the improving of the cell compatibility induced by the H2SO4 treatment could be related to the increasing of the positive charge of the TiO2 surface, which could be caused by the degradation of the adsorbed hydrocarbon contaminants on the TiO2 surface.
The National Natural Science Founda-tion of China (No. 31570963); The National Natural Science Founda-tion of China (No. 81401522)
References:
[1] Chen J, Zhao A, Chen H, Liao Y, Yang P, Sun H, et al. The effect of full/partial UV-irradiation of TiO2 films on altering the behavior of fibrinogen and platelets. Colloids and Surfaces B: Biointerfaces 2014;122:709-18.
[2] Chen J, Yang P, Liao Y, Wang J, Chen H, Sun H, et al. Effect of the Duration of UV Irradiation on the Anticoagulant Properties of Titanium Dioxide Films. ACS applied materials & interfaces 2015;7:4423-32.
[3] Att W, Hori N, Takeuchi M, Ouyang J, Yang Y, Anpo M, et al. Time-dependent degradation of titanium osteoconductivity: An implication of biological aging of implant materials. Biomaterials 2009;30:5352-63.