Figure 2

TBO with LED penetrating through soft tissue effectively kills P. gingivalis and F. nucleatum strains in vitro. (A,B) Design of antimicrobial test of PDT penetrating tissue depth. The 3 mm-thick artificial skin is placed between the LED device and the bacterial suspension to test whether LED irradiation at a wavelength of 650 nm penetrates through soft tissue, thereby activating the bactericidal effects of TBO. TBO in powder form was dissolved in PBS. TBO solutions were added to the bacterial suspension to obtain final concentrations of 0.16, 0.33, and 0.98 mM. After 5 min of incubation, TBO- containing wells were exposed to 3, 30, and 60 mW/cm² of LED irradiation at a 650 nm wavelength for 5 min. TBO-containing bacterial suspension wells were directly exposed to LED irradiation (C) for P. gingivalis and (E) for F. nucleatum, respectively. (D,F) TBO-containing bacterial suspension wells were exposed to LED irradiation through 3 mm-thick artificial skin (D) for P. gingivalis and (F) F. nucleatum, respectively. The data represent the mean ± the standard deviation (n = 2), *p < 0.05, **p < 0.01 vs. control (without TBO and without LED exposure). CFU, viable count colony forming unit.