Brain-targeted delivery of PEGylated nano-bacitracin A against Penicillin-sensitive and -resistant Pneumococcal meningitis: formulated with RVG<sub>29</sub> and Pluronic<sup>®</sup> P85 unimers

<p>Pneumococcal meningitis (PM), caused by <i>Streptococcus pneumonia</i>, remains a high-burden disease in developing countries. Antibiotic therapy has been limited due to the inefficiency of drug transport across the blood-brain barrier (BBB) and the emergence of drug-resistant strains. In our preliminary study, PEGylated nano-self-assemblies of bacitracin A (PEGylated Nano-BA<sub>12K</sub>) demonstrated a strong antibacterial potency against <i>S. pneumonia</i>. In this study, the potential application of this micelle for the treatment of both Penicillin-sensitive and -resistant PM was studied. To address BBB-targeting and -crossing issues, PEGylated Nano-BA<sub>12K</sub> was formulated with a specific brain-targeting peptide (rabies virus glycopeptide-29, RVG<sub>29</sub>) and a P-glycoprotein inhibitor (Pluronic<sup>®</sup> P85 unimers) to construct a mixed micellar system (RVG<sub>29</sub>-Nano-BA<sub>P85</sub>). RVG<sub>29</sub>-Nano-BA<sub>P85</sub> demonstrated a strong antibacterial potency against 13 clinical isolates of <i>S. pneumonia</i>, even higher than that of Penicillin G, a conventional anti-PM agent. RVG<sub>29</sub>-Nano-BA<sub>P85</sub> had more cellular uptake in brain capillary endothelial cells (BCECs) and higher BBB-crossing efficiency than single formulated Nano-BAs as shown in an <i>in vitro</i> BBB model. The enhanced BBB-permeability was attributed to the synergetic effect of RVG<sub>29</sub> and P85 unimers through receptor-mediated transcytosis, exhaustion of ATP, and reduction in membrane microviscosity. <i>In vivo</i> results further demonstrated that RVG<sub>29</sub>-Nano-BA<sub>P85</sub> was able to accumulate in brain parenchyma as confirmed by <i>in vivo</i> optical imaging. In addition, RVG<sub>29</sub>-Nano-BA<sub>P85</sub> exhibited high therapeutic efficiencies in both Penicillin-sensitive and -resistant PM mouse models with negligible systemic toxicity. Collectively, RVG<sub>29</sub>-Nano-BA<sub>P85</sub> could effectively overcome BBB barriers and suppressed the growth of both drug-sensitive and -resistant <i>S. pneumonia</i> in the brain tissues, which demonstrated its potential for the treatment of PM.</p>