Macrophage-targeted amphiphilic peptide nanocarrier for intracellular MRSA infection therapy

Intracellular bacterial infections pose a significant challenge due to limited cellular internalization, low intracellular antibiotic efficacy, and bacterial sequestration within specific cellular compartments. In this study, we designed an amphiphilic peptide drug delivery system (RFP@TVYV) for sequential targeting of macrophages and intracellular bacteria eradication. By modifying the macrophage-targeting molecule tuftsin, RFP@TVYV facilitates rapid internalization by macrophages. Additionally, the incorporation of Val-Cit fragments, responsive to lysosomal cathepsin B, enables the controlled release of the cell-penetrating peptide YGRKKRRQRRR (TAT) and rifampin (RFP). The inclusion of TAT further enhances subcellular targeting, directing RFP to the bacterial cytoplasm to effectively disrupt intracellular pathogens. Synthesis and characterization studies confirmed that RFP@TVYV self-assembles into stable nanomicelles through hydrogen bonding and hydrophobic interactions. Antibacterial assays demonstrated the nanoplatform’s potent activity against Staphylococcus aureus, while flow cytometry (FC) and immunofluorescence (IF) confirmed increased macrophage uptake efficiency and intracellular targeting. Both in vitro and in vivo studies showed that RFP@TVYV significantly reduces intracellular bacterial load more effectively than free RFP, with minimal cytotoxicity. These findings underscore the potential of RFP@TVYV as an advanced drug delivery platform for combating intracellular bacterial infections, particularly those caused by drug-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA).