Figure 4. Antibacterial effect of unprotected AgNPs and AgNPs-PVP. A-C) Growth of NTHi (A), S. pneumoniae (B), andS. mutans (C) after 12 hours of incubation without or with varying concentrations of AgNPs and AgNPs-PVP, normalized by the growth without antimicrobials (i.e., 100% growth represents the growth of bacteria without AgNPs or AgNPs-PVP). MIC and IC50 are indicated with dashed lines. Data are mean ± SD. D-E) Summary of IC50 (D) and MIC (E) values of AgNPs and AgNPs-PVP against NTHi, S. pneumoniae and S. mutans . n=3 for each group.