Gentamicin-loaded silk/nanosilver composite scaffolds for MRSA-induced chronic osteomyelitis

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) often induces chronic osteomyelitis and then bone defects. Here, gentamicin-loaded silk/nanosilver composite scaffolds were developed to treat MRSA-induced chronic osteomyelitis. AgNO₃ was reduced with silk as a reducing agent in formic acid, forming silver nanoparticles in situ that were distributed uniformly in the composite scaffolds. Superior antibacterial properties against MRSA were achieved for the composite scaffolds, without the compromise of osteogenesis capacity. Then gentamicin was loaded on the scaffolds for better treatment of osteomyelitis. In vivo results showed effective inhibition of the growth of MRSA bacteria, confirming the promising future in the treatment of chronic osteomyelitis.

Keywords: osteomyelitis; silk scaffold; silver nanoparticles.

Figure 1.

Preparation and morphology of SF-AgNPs materials. (a) Schematic diagram of the preparation of SF-AgNPs materials. (b) The appearance and SEM observation for the SF, SF-0.1%AgNPs, SF-0.5%AgNPs and SF-1%AgNPs.

Figure 2.

SEM observation for the morphology and distribution of AgNPs (a) and the EDS spectra of SF-1%AgNPs (b).

Figure 3.

FTIR spectra (a) and XRD patterns (b) of SF (i), SF-0.1%AgNPs (ii), SF-0.5%AgNPs (iii) and SF-1%AgNPs (iv).

Figure 4.

Biocompatibility of materials and osteoblasts. The CLSM image of osteoblasts on SF (a), SF-0.1%AgNPs (b), SF-0.5%AgNPs (c) and SF-1%AgNPs (d) after 5 days; there was little difference in cell morphology between materials. CCK-8 results (e); ALP activity (f) and Runx2 activity (g). SF scaffolds with 1% concentration AgNPs show time-dependent cytotoxicity (*p < 0.05).

Figure 5.

Inhibition zones of the SF scaffolds with different concentration AgNPs against MRSA (a), the zones of inhibition of SF-0.1%AgNPs, SF-0.5%AgNPs and SF-1%AgNPs were 10.5, 11.4 and 13.2 mm. The inhibition rate converted by bacterial growth curve (b) showed the SF scaffolds with 0.5% and 1% concentration AgNPs significantly inhibited bacterial growth.

Figure 6.

The change of body weight (a) and white blood cell (b) count at the day before osteomyelitis model, the day before surgery, and one, two and three weeks after the surgery.

Figure 7.

Lateral radiographs and histological examination of no implants after debridement (a,f), SF (b,g), SF-AgNPs (c,h), SF + Gentamicin (d,i), SF-AgNPs + Gentamicin (e,j) after three weeks of treatment. Inflammatory cells (wide arrow), ruptured cortex (narrow arrow) and new bone formation (triangle).

Figure 8.

Quantitative microbiological analyses of samples between groups. SF-0.5%AgNPs could significantly inhibit the growth of MRSA bacteria in osteomyelitis compared with the blank control group and SF group (**p < 0.01).