Abstract:

Objective To explore the regulatory effect of ultrasonic power on the dispersibility of graphene oxide （GO）， to reveal the correlation between GO dispersibility and the microstructure as well as biological properties of GO/zinc film composite coating materials， and to optimize the preparation process of GO-based biomedical coatings. Methods GO powder （purity≥99%） and zinc film were used as raw materials. GO dispersion systems and GO/zinc film composite coating materials were prepared by a stirring-coupled ultrasonic dispersion-dip coating process， with three ultrasonic power gradients set at 100 W， 300 W， and 600 W. Scanning electron microscope （SEM） and Raman spectroscopy were used to analyze the surface dispersion morphology， surface sheet size， coating porosity， and structural defects of GO on the GO/zinc film composite coating materials under different ultrasonic powers. Live/dead cell staining and cell counting kit-8 （CCK-8） method were used to evaluate the survival and the proliferative activities of mouse mesenchymal stem cells （MSCs） in various groups treated with GO dispersions prepared under different ultrasonic powers. Plate counting method was used to determine the survival rates of Escherichia coli （E.coli） and Staphylococcus aureus （S.aureus） in various groups after treatment with GO dispersions prepared under different ultrasonic powers. Results The SEM observation showed that the ultrasonically dispersed GO coating achieved uniform and continuous coverage on zinc film surface； the GO/zinc film coating material in 300 W group exhibited a smooth and dense surface. The surface sheet size and rate of porosity of the GO/zinc film material in 300 W group were moderate， which were lower than those in 100 W group and higher than those in 600 W group （P<0.05）. The Raman spectroscopy analysis results revealed that the ratio of intensities of defect peak and graphitic peak （I_D/I_G） of the GO/zinc film material in 300 W group was higher than that in 100 W group but lower than that in 600 W group， indicating moderate graphitization degree and structural defects. The results of live/dead cell staining showed that a high proportion of survived cells with well-spread morphology and clear pseudopodia was observed in MSCs in 300 W group； a small number of dead cells， with surviving cells exhibiting contracted cell bodies and limited spreading range was observed in the MSCs in 100 W group， while more dead cells were seen in the MSCs in 600 W group. The results of CCK-8 method demonstrated that after 108 h of intervention， compared with 100 W group and 600 W group， the proliferative activity of mouse MSCs in 300 W group was significantly increased （P<0.05）. The results of plate counting method showed that compared with 100 W group， the survival rates of E.coli and S.aureus in 300 W group were significantly decreased （P<0.05）； compared with 600 W group， the survival rate of S.aureus in 300 W group was significantly decreased （P<0.05）. Conclusion 300 W is identified as the optimal ultrasonic power for preparing GO/zinc film composite coating materials. This parameter can precisely regulate the dispersibility of GO， simultaneously optimize the interfacial bonding performance and biological activity of the coating， and synergistically improve biosafety and antibacterial performance. The findings provide the key process parameters and theoretical basis for the industrial production and clinical translation of GO-based biomedical coatings.

Key words: Graphene oxide, Ultrasonic power, Dispersibility, Biological property, Antibacterial performance