Methylene Blue-Loaded NanoMOFs: Accumulation in Chlamydia trachomatis Inclusions and Light/Dark Antibacterial Effects

Abstract

Metal–organic framework nanoparticles (nanoMOFs) are promising nanomaterials for biomedical applications. Some of them, including biodegradable porous iron carboxylates are proposed for encapsulation and delivery of antibiotics. Due to the high drug loading capacity and fast internalization kinetics, nanoMOFs are more beneficial for the treatment of intracellular bacterial infections compared to free antibacterial drugs, which poorly accumulate inside the cells because of the inability to cross membrane barriers or have low intracellular retention. However, nanoparticle internalization does not ensure their accumulation in the cell compartment that shelters a pathogen. This study shows the availability of MIL-100(Fe)-based MOF nanoparticles to co-localize with Chlamydia trachomatis, an obligate intracellular bacterium, in the infected RAW264.7 macrophages. Furthermore, nanoMOFs loaded with photosensitizer methylene blue (MB) exhibit complete photodynamic inactivation of C. trachomatis growth. Simultaneous infection and treatment of RAW264.7 cells with empty nanoMOFs resulted in a bacterial load reduction from 100 to 36% that indicates an intrinsic anti-chlamydial effect of this iron-containing nanomaterial. Thus, our findings suggest the use of iron-based nanoMOFs as a promising drug delivery platform, which contributes to antibacterial effect, for the treatment of chlamydial infections.