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We previously explored the use of antibody-conjugated, antibiotic-loaded gold nanocages for the treatment of bacterial infections. Using Staphylococcus aureus as a proof-of-principle pathogen, we confirmed that nanocages coated with polydopamine and loaded with daptomycin could be effectively targeted to bacterial cells using an antibody targeting S. aureus surface-associated protein A. We also confirmed that laser irradiation could then be used to achieve a lethal photothermal effect and localized release of the antibiotic, the synergistic effect of which was capable of eradicating viable bacteria even from a therapeutically recalcitrant biofilm. To assess the possibility that this comes at the cost of adverse side effects, we used multispectral optoacoustic tomography (MSOT) to track the biodistribution of our nanocages following intravenous administered and determined whether their administration was associated with toxic side effects. The results of our MSOT analysis confirmed that our nanocages accumulate primarily in the liver, spleen and kidney irrespective of infection status. However, in an infected animal, they also confirmed that nanocages ultimately do reach the site of infection. MSOT results were consistent with studies involving the direct analysis of these tissues, which confirmed the correlation between MSOT signals and the presence of gold nanocages. More importantly, they also demonstrated that the presence of nanocages was not associated with appreciable histopathology in the spleen, liver, kidney, lung or heart. This suggests that our use of antibody-conjugated, antibiotic-loaded gold nanocages for the treatment of infection offers significant promise that would not be compromised by systemic toxicity.
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