Arabic gum plus colistin coated moxifloxacin-loaded nanoparticles for the treatment of bone infection caused by Escherichia coli

Osteomyelitis is an inflammatory process of bone and bone marrow that may even lead to patient death. Even though this disease is mainly caused by Gram-positive organisms, the proportion of bone infections caused by Gram-negative bacteria, such as Escherichia coli, has significantly increased in recent years. In this work, mesoporous silica nanoparticles have been employed as platform to engineer a nanomedicine able to eradicate E. coli- related bone infections. For that purpose, the nanoparticles have been loaded with moxifloxacin and further functionalized with Arabic gum and colistin (AG+CO-coated MX-loaded MSNs). The nanosystem demonstrated high affinity toward E. coli biofilm matrix, thanks to AG coating, and marked antibacterial effect because of the bactericidal effect of moxifloxacin and the disaggregating effect of colistin. AG+CO-coated MX-loaded MSNs were able to eradicate the infection developed on a trabecular bone in vitro and showed pronounced antibacterial efficacy in vivo against an osteomyelitis provoked by E. coli. Furthermore, AG+CO-coated MX-loaded MSNs were shown to be essentially non-cytotoxic with only slight effect on cell proliferation and mild hepatotoxicity, which might be attributed to the nature of both antibiotics. In view of these results, these nanoparticles may be considered as a promising treatment for bone infections caused by enterobacteria, such as E. coli, and introduce a general strategy against bone infections based on the implementation of antibiotics with different but complementary activity into a single nanocarrier. Statement of significance: In this work, we propose a methodology to address E.coli bone infections by using moxifloxacin-loaded mesoporous silica nanoparticles coated with Arabic gum containing colistin (AG+CO-coated MX-loaded MSNs). The in vitro evaluation of this nanosystem demonstrated high affinity toward E. coli biofilm matrix thanks to the Arabic gum coating, a disaggregating and antibacterial effect of colistin, and a remarkable antibiofilm action because of the bactericidal ability of moxifloxacin and colistin. This anti-E. coli capacity of AG+CO-coated MX-loaded MSNs was brought out in an in vivo rabbit model of osteomyelitis where the nanosystem was able to eradicate more than 90% of the bacterial load within the infected boneFinancial support from the Eu-ropean Research Council through ERC-2015-AdG-694160 (VERDI) grant. AM is funded by grants from Instituto de Salud Carlos III through the “Miguel Servet” program (CP15/00053