2.7. In vitro antibacterial experiments
Methicillin-resistant Staphylococcus aureus (MRSA) andK.pneumoniae were cultivated separately overnight at 37 °C in Luria–Bertani broth (LB broth). The antibacterial effect of the nanomaterials was determined by the agar diffusion method. Briefly, 100 μL bacterial suspension (108 CFU mL-1) of MRSA or K.pneumoniae was spread homogeneously on the agar plate. Then, 25 μL of sample (PBS, HMPB NPs, ofloxacin and OHH NPs) dropped to a filter paper on MRSA andK.pneumoniae -coated agar plates. The agar plates were transferred into the 37 °C incubator. After incubation for 12 h, the diameters of inhibition area were measured to assess the bactericidal activity.
The plate counting method was adopted to test in vitroantibacterial efficiency of sample (PBS, HMPB NPs, ofloxacin and OHH NPs) combined with NIR laser irradiation. 200 μL of bacterial suspension (1×104 CFU mL-1) was incubated with PBS (control), HMPB, ofloxacin or OHH NPs and then irradiated with/without 808 nm laser at a power density of 1 W/cm2 for 5 min. Afterwards, 100 μL of appropriately diluted bacterial suspension was spread on LB agar plate followed by incubated at 37°C for 24 h. Bacterial colony forming units were counted and antibacterial efficiency was calculated according to the following equation:
Survival ratio (%) = CFUsample/CFUcontrol×100%