Accessing BCG in infected macrophages by antibody-mediated drug delivery system and tracking by surface-enhanced Raman scattering spectroscopy

[Display omitted] •Au nanoparticles modified with antibody, carrying rifampicin to infected macrophages.•Antibiotic drug delivery led to the combat of BCG bacteria infecting macrophages.•The uptake of gold nanocarrier in macrophage was monitored by SERS spectroscopy.•Anti-folic acid was anchored on gold surface bonding to previous adsorbed folic acid.•Antibody modifying gold surface interacted with macrophages by non-specific portions. Gold nanoparticles (AuNP) modified with antibody and rifampicin (RP) were tested against Mycobacterium bovis Bacillus Calmette-Guérin (BCG), which previously generated in vitro infection of macrophages from mice. Such a drug delivery system works as nanocarrier for RP and presented lower toxicity for macrophages cells than each separated component. Surface-enhanced Raman scattering (SERS) spectroscopy and fluorescence microscopy were used as analytical tools for the characterization of the internalization of gold nanocarriers into macrophage cells. The effective antibiotic action of RP, when combined with gold nanocarrier, was confirmed by dead-live assay of BCG bacteria lysed from macrophages after incubation. Such results indicate the delivery of RP to BCG bacteria, which were infecting macrophages, occurred with remarkable efficiency. It was rationalized based on the strategy used for the adsorption of antibody molecules on gold surface.