[Effects of different fibre diameter of polypyrrole after direct current stimulation on adhesion and proliferation of cells and bacteria].

OBJECTIVE: To study the effects of cells'and bacteria's adhesion and proliferation on different fiber diameters of polypyrrole coating with electricity.

METHODS: Titanium coated with polypyrrole was divided into no electrical stimulation and stimulation groups, each group had 30-60 nm, 70- 100 nm, 130-170 nm diameters of the fiber. MC3T3 cells and Staphylococcus aureus (S. aureus) were inoculated on different fiber diameters of polypyrrole coating with and without electric stimulation. We gave the electrical stimulation group 100 mV for 1 h and every 24 hours gave it 1 h stimulation, and no electrical stimulation group was not managed. We used scanning electron microscope (SEM) to observe the cells'and bacteria's morphology. The cells were given 20 mL CCK-8 solutions after 1,3,7 days' cultivation, then incubated for 2 h, the solution was transferred to 96-well plate, we measured the cells' CCK-8 of the 30-60 nm, 70-100 nm, and 130-170 nm groups by Elisa. The cells on different fiber diameters were also stained by live-dead cell staining kit, TritonX-100 and DAPI. We used PBS to wash and glycerin to seal them. The live-dead situation and morphology were tested by co focal microscope. The bacterial were stained by Live/dead baclight bacterial viability kits, we detect the suspension's D of the 30-60 nm, 70-100 nm, and 130-170 nm groups, and also observed the bacteria's survival situation by co focal microscope.

RESULTS: The CCK-8 of the cells with direct current stimulation was higher than that of the unpowered group (F=12.248, P=0.006). The smaller the fiber diameter, the better was the cell's adhesion and proliferation (F=9.261, P=0.005). The bacterial suspension's D of the electric group was lower than that of the unpowered group, and the fiber diameter had no significant effect on the bacteria's growth(F=9.641, P=0.036).

CONCLUSION: Polypyrrole coating with electricity can promote the cell's proliferation and inhibit the bacteria's proliferation, and the cell growth on small fiber diameter coating is better. There is no difference in the bacterial growth of different fiber diameter coatings.