Fig. 2

a Zeta potential of bacteria before and after incubation with GCS-PDA@GNRs and Ag⁺-GCS-PDA@GNRs at pH 6.3 or pH 7.4. SEM images of (b) bacteria (pH 6.3 & pH 7.4) and (d) HaCat cells and NIH 3T3 fibroblasts (pH 7.4) before and after incubation with GCS-PDA@GNRs and Ag⁺-GCS-PDA@GNRs. The red arrows indicated the GNRs. cThe amount of NP bound on the bacteria at different pH conditions (pH 7.4 and 6.3) after 4 h co-incubation with Ag⁺-GCS-PDA@GNRs and on the cells (pH 7.4) after 24 h co-incubation with Ag⁺-GCS-PDA@GNRs. The significant difference was compared between the bacteria at pH 7.4 condition and at pH 6.3 condition. * and ** present p < 0.05 and p < 0.01, respectively