Fig. 3.

Intermediate-stage antibacterial efficacy evaluation in vivo and ex vivo. A) The changes of microstructure and surface morphology of the samples before and after soaking in Tris buffer (pH 7.4) for 12 weeks. The following pattern represent Zn²⁺ release-dependent antibacterial mechanism. B) Statistics of zinc content in Sr–Zn2@CaP sample dropped from 3.2% to 2.41% after soaking in the Tris buffer (pH 7.4) for 12 weeks. C) The daily zinc release of different samples in 2, 3, 4, 6, 8 and 12 weeks. D) SEM images of both S. aureus and E. coli morphology on the surfaces of various samples after soaking in the Tris buffer for 12 weeks. The last row shows the spread plate images of S. aureus seeding in the corresponding extraction solution. E) The primary procedure of rat knee model to mimic gonitis symptom where S. aureus were injected into the knee cavity 4 weeks after implantation. F) The macroscopic observation of knee-joint post-implantation and the ex vivo colony culture test for the knee joint eluate. G) H&E immunohistochemistry and Gram staining images in the regions of femur osteoepiphysis with different implant rods at 3 days after bacterial injection, respectively (scale bar: 50 μm). Circles represent lymphocytes and neutrophils infiltration. Red arrows represent inflammatory cells with bacteria.