Targeted Antitubercular Peptide Nanocarriers Prepared by Flash NanoPrecipitation with Hydrophobic Ion Pairing

The encapsulation of therapeutics into nanocarriers with specialized surface chemistries for targeting applications in the body is a major goal in the field of drug delivery. Here the encapsulation of an antitubercular peptide, ecumicin, into monodisperse nanocarriers 60 nm in diameter using a combination of Flash NanoPrecipitation and hydrophobic ion pairing is demonstrated. The lead formulation achieves 70% ecumicin encapsulation efficiency and 24% loading by mass. In vivo single-dose oral (PO), subcutaneous (SC), and intraperitoneal (IP) pharmacokinetics (PK) are measured in mice, and the dose-normalized area under the curve (AUC) of ecumicin nanocarriers dosed IP exceeded the dose-normalized AUC of unencapsulated ecumicin dosed IP by a factor of 2.5. Next, variations of the lead formulation stabilized with a custom-synthesized poly(caprolactone)-block-poly(ethylene glycol)-hexamannose polymer at three levels of mannose surface coverage (0%, 4%, and 74% of polymer chains terminating in hexamannose) for targeting to macrophages are prepared. These formulations are evaluated against Mycobacterium tuberculosis in a macrophage culture at multiple concentrations and found to reduce colony-forming units (CFU) counts by up to 3.8-log₁₀ units, with greater antitubercular ecumicin activity measured from formulations prepared with higher amounts of surface mannose coverage. Taken together, these results suggest that Flash NanoPrecipitation with hydrophobic ion pairing is an effective method for encapsulating ionizable peptide therapeutics into macrophage-targeted formulations for improved PK and targeted macrophage uptake in the body.