Title : Liposomes containing moxifloxacin and functionalized with a siderophore analog for tuberculosis treatment
Tuberculosis (TB) is an infectious disease that affects millions of people annually and resistance to available antibiotics has worsened this scenario. Another particularity of Mycobacterium tuberculosis, the main etiologic agent of TB, is its ability to survive inside of macrophages. In a search for an effective, safe treatment that promotes a targeted delivery of the antibiotic to the site of infection, we proposed a nanotechnology approach based on functionalized liposomes, where its surface was modified with a siderophore analogue (Sid) to carry the antibiotic moxifloxacin (Mox). Siderophores are small and natural molecules that absorb iron and carry it into the cell . Four liposomes were synthesized: empty liposome (LipV); liposome containing Mox (LipMox); empty Sid-functionalized liposome (LipS) and Mox-containing Sid-functionalized liposome (LipSMox). The characterization of the liposomes was performed by the dynamic light scattering technique (DLS), nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). By all methods, we observed spherical and approximately 200 nm particles. NTA showed a concentration of ~1011 particles/mL. A method of quantification of Mox in high performance liquid chromatography was developed and validated to determine the encapsulation efficiency (EE) and release profile (RF). The EE was 51.31% for LipMox and 45.76% for LipSMox and the EL followed the model proposed by Korsmeyer-Peppas. The minimal inhibitory concentration (MIC) against M. tuberculosis was determined under standard conditions (pH 6.6 and [Fe] = 0.04 μg/mL) and different concentrations of iron (2x, 5x and 10x multiples of the medium). The MIC of LipMox and LipSMox were mostly less than 0.5% and no cytotoxicity was observed on macrophages (J774A.1), fibroblasts (MRC-5), liver (HepG-2) and intestinal (Caco-2) cells. In the assay of activity against intracellular M. tuberculosis, the system was able to reduce the concentration of bacteria inside the macrophage up to 2 Logs. Scanning electron microscopy (SEM) and TEM confirmed the phagocytosis of liposomal vesicles by macrophages, indicating once again the possibility of targeting the treatment when administered in nanoparticles. Since the permeability in intestinal cells, in addition to the already described fragility of the liposomes in the gastrointestinal tract, were undetectable, a pulmonary administration is suggested, facilitating the delivery of intact nanoparticles at the site of infection.
Audience Take Away:
- use of a Trojan horse-like bacterial pathogenesis mechanism by siderophores;
- New nanotechnology system based on siderophores, liposomes and antibiotics;
- New system could help improve TB treatment;
- Finally, the public will be able to learn about cytotoxic assays with different types of cells on a nanotechnology system.