Fig. 2. Bactericidal activity in vitro. (a) SEM images of PA after treatment with PBS, HMnO₂ and HMnO₂@NM nanoparticles. (b) Bacteria-killing kinetics of PBS (control), HMnO₂@NM, PMB and PMB@HMnO₂@NM. (c) Illustrative fluorescence images for live/dead bacterial staining assay of MDR PA after treatment with PBS (control), HMnO₂@NM, PMB and PMB@HMnO₂@NM. Scale bar: 20 μm. (d) Representative SEM images of MDR PA at 4 h after treatment with PBS (control), HMnO₂@NM, PMB and PMB@HMnO₂@NM (47.08 μg mL⁻¹ of PMB).