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%