Spray-Dried, Nanoencapsulated, Multi-Drug Anti-Tuberculosis Therapy Aimed at Once Weekly Administration for the Duration of Treatment.

Aiming to improve the treatment outcomes of current daily tuberculosis (TB) chemotherapy over several months, we investigated whether nanoencapsulation of existing drugs would allow decreasing the treatment frequency to weekly, thereby ultimately improving patient compliance. Nanoencapsulation of three first-line anti-TB drugs was achieved by a unique, scalable spray-drying technology forming free-flowing powders in the nanometer range with encapsulation efficiencies of 82, 75, and 62% respectively for rifampicin, pyrazinamide, and isoniazid. In a pre-clinical study on TB infected mice, we demonstrate that the encapsulated drugs, administered once weekly for nine weeks, showed comparable efficacy to daily treatment with free drugs over the same experimental period. Both treatment approaches had equivalent outcomes for resolution of inflammation associated with the infection of lungs and spleens. These results demonstrate how scalable technology could be used to manufacture nanoencapsulated drugs. The formulations may be used to reduce the oral dose frequency from daily to once weekly in order to treat uncomplicated TB.

Protein-polysaccharide complexes for enhanced protein delivery in hyaluronic acid templated calcium carbonate microparticles.

The controlled delivery of proteins within calcium carbonate (CaCO3) particles is currently widely investigated. The success of these carriers is driven by ionic interactions between the encapsulated proteins and the particles. This poses a great limitation on the successful loading of proteins that have no ionic affinity to CaCO3. In this study, we explored the use of polysaccharide-protein interactions to strongly enhance the encapsulation of proteins in CaCO3 microparticles. Previously, Vandevenne and colleagues inserted a human chitin binding domain (ChBD) that has intrinsic affinity for hyaluronic acid (HA) into a ß-lactamase (BlaP). This generated chimeric protein, named BlaPChBD, was shown to be fully bifunctional. In this study we showed that this hybrid protein can associate with HA and be successfully loaded into vaterite CaCO3 microparticles using supercritical CO2 (ScCO2) technology aided by the templating effect of HA on CaCO3. The presence of ChBD inserted into BlaP increased the encapsulation of the protein by 6-fold when complexed with HA. Furthermore, thrombin cleavage sites were engineered on both sides of the inserted ChBD in the chimeric BlaP to achieve release of the protein from the microparticles by protease cleavage. Our results showed that thrombin cleavage increased the release of the protein from the microparticles within 36 hours from <20% to 87%. In conclusion, the presence of ChBD successfully improved the encapsulation yield of the protein while retaining up to 82% of its activity and efficient release of the protein from the microparticles was achieved by protease cleavage.

Mycolic acids, a promising mycobacterial ligand for targeting of nanoencapsulated drugs in tuberculosis.

The appearance of drug-resistant strains of Mycobacterium tuberculosis (Mtb) poses a great challenge to the development of novel treatment programmes to combat tuberculosis. Since innovative nanotechnologies might alleviate the limitations of current therapies, we have designed a new nanoformulation for use as an anti-TB drug delivery system. It consists of incorporating mycobacterial cell wall mycolic acids (MA) as targeting ligands into a drug-encapsulating Poly dl-lactic-co-glycolic acid polymer (PLGA), via a double emulsion solvent evaporation technique. Bone marrow-derived mouse macrophages, either uninfected or infected with different mycobacterial strains (Mycobacterium avium, Mycobacterium bovis BCG or Mtb), were exposed to encapsulated isoniazid-PLGA nanoparticles (NPs) using MA as a targeting ligand. The fate of the NPs was monitored by electron microscopy. Our study showed that i) the inclusion of MA in the nanoformulations resulted in their expression on the outer surface and a significant increase in phagocytic uptake of the NPs; ii) nanoparticle-containing phagosomes were rapidly processed into phagolysosomes, whether MA had been included or not; and iii) nanoparticle-containing phagolysosomes did not fuse with non-matured mycobacterium-containing phagosomes, but fusion events with mycobacterium-containing phagolysosomes were clearly observed.

Effects of protein binding on the biodistribution of PEGylated PLGA nanoparticles post oral administration.

The surface of nanoparticles is often functionalised with polymeric surfactants, in order to increase systemic circulation time. This has been investigated mainly for intravenously administered nanoparticles. This study aims to elucidate the effect of surface coating with various concentrations of polymeric surfactants (PEG and Pluronics F127) on the in vitro protein binding as well as the tissue biodistribution, post oral administration, of PLGA nanoparticles. The in vitro protein binding varied depending on the polymeric surfactant used. However, in vivo, 1% PEG and 1% Pluronics F127 coated particles presented similar biodistribution profiles in various tissues over seven days. Furthermore, the percentage of PEG and Pluronics coated particles detected in plasma was higher than that of uncoated PLGA particles, indicating that systemic circulation time can also be increased with oral formulations. The difference in the in vitro protein binding as a result of the different poloxamers used versus similar in vivo profiles of these particles indicates that in vitro observations for nanoparticles cannot represent or be correlated to the in vivo behaviour of the nanoparticles. Our results therefore suggest that more studies have to be conducted for oral formulations to give a better understanding of the kinetics of the particles.