The antibacterial activity of the samples was determined using
Escherichia coli ATCC 25922 (E. coli, gram negative). Gentamicin
(10 mg/mL) and sterile distilled water were the positive and negative
control, respectively. All the samples (1 cm2
) were sterilized in
humid vapor (121 C, 1 atm). A 7 lL suspension of the bacteria
(107 colony-forming units) [31] was dropped on each sterilized
sample, and covered with parafilm to spread the bacteria uniformly
for 1 h at 37 C. The samples were washed thoroughly with
1 mL of a 0.87% NaCl solution in order to remove the adhered bacteria
and placed in individual wells of 24-well culture plates. A
1 mL Brain and Heart Infusion (BHI; Difco) solution (3.7%) was
added in each well, and the samples were incubated at 37 C for
6 h. The absorbance of each well content was measured with a
Spectra Count spectrophotometer (Packard). The relative eradication
of the bacteria was determined as
Eð%Þ¼ð1 ðD=FÞÞ 100; ðwhere E is relative eradication of the bacteria (%), D is the mean
number of bacteria on the analyzed sample, and F is the mean number
of bacteria on the control sample.
The antibacterial experiments were performed under sun light
and in darkness in order to compare the action of TiO2-DLC films
under UV light. In both cases, the experiments were carried out
in quintuplicate and repeated at least three times in order to con-
firm the reproducibility.