Fig. 4

SEM images of (a) MRSA (pH 6.3) and (c) E. coli (pH 6.3) treated with (a1, c1) PBS, (a2, c2) AgNO₃, (a3, c3) GCS-PDA@GNRs, (a4, c4) Ag⁺-GCS-PDA@GNRs, (a5, c5) PBS + NIR, (a6, c6) AgNO₃ +NIR, (a7, c7) GCS-PDA@GNRs + NIR and (a8, c8) Ag⁺-GCS-PDA@GNRs + NIR, respectively. The red arrows indicate the lesions and collapse of bacteria. Images of Live/Dead staining assay for (b) MRSA (pH 6.3) and (d) E. coli (pH 6.3) treated by (b1, d1) PBS, (b2, d2) AgNO₃, (b3, d3) GCS-PDA@GNRs, (b4, d4) Ag⁺-GCS-PDA@GNRs, (b5, d5) PBS + NIR, (b6, d6) AgNO₃ + NIR, (b7, d7) GCS-PDA@GNRs + NIR and (b8, d8) Ag⁺-GCS-PDA@GNRs + NIR, respectively. e Bacterial viability of MRSA treated by different dose of AgNO₃ and Ag⁺-GCS-PDA@GNRs for 4 h. f Bacterial viability of MRSA treated with Ag⁺-GCS-PDA@GNRs under NIR laser (0.5 W cm⁻², 7 min) of different power density. g Bacterial viability of MRSA treated by water bath (50 °C) before and after combinational therapy of AgNO₃ or Ag⁺-GCS-PDA@GNRs. * and ** present p < 0.05 and p < 0.01, respectively