Figure 5: Antibacterial properties of TPA NPs. Killing curves of (A) E. coli and (B) S. aureus grown in different concentrations of PTA NPs (2 to 50 μg mL-1) for 24 h at 37°C. Growth was determined by viable counts and is expressed in colony-forming units (CFU). Untreated bacteria and unloaded NPs (i.e., PMMA NPs) tested at a concentration of 50 μg mL-1 served as controls. Dashed lines (in A and B) represent the killing curves of E. coli (A) and S. aureus (B) exposed to free triclosan at concentrations of 0.36 and 0.44 μg mL-1, respectively. The triclosan concentrations tested in A and B were determined as the maximal concentrations of triclosan released from PTA NPs in the presence of E. coli and S. aureus, respectfully (see Figure 7). The supernatant curve line refers to E. coli (A) and S. aureus (B) grown in the supernatant of TSB or TSB-Glu previously incubated with PTA NPs (50 μg mL-1) for 24 h at 37°C. Error bars represent the standard deviation of three independent experiments conducted in triplicate.