Design and in vitro assessment of chitosan nanocapsules for the pulmonary delivery of rifabutin

Tuberculosis (TB) is a life-threatening disease and a main cause of death worldwide. It mainly affects the lungs, and it is attributed to the infection with Mycobacterium tuberculosis (MTB). Current treatments consist of the oral administration of combinations of antibiotics including rifabutin, in high doses and for long periods of time. These therapeutic regimens are associated with many side effects and high rates of drug resistance. To overcome these problems, this study aims at developing a nanosystem for the improved delivery of antibiotics, with potential application in pulmonary delivery. Chitosan-based nanomaterials are widely used in biomedical applications, due to their biodegradability and biocompatibility, as well as their potential antimicrobial effects and lack of toxicity. In addition, this polymer is particularly attractive for mucosal delivery due to its bioadhesive properties. Therefore, the structure of the proposed nanocarrier consists of a chitosan shell and a lipid core with a combination of different oils and surfactants to allow optimal association of the hydrophobic drug rifabutin. These nanocapsules were characterized in terms of size, polydispersity index, surface charge, morphology, encapsulation efficiency and biological stability. The release kinetics of the drug-loaded nanostructures was evaluated in simulated lung media. Moreover, in vitro studies in different cell models (A549 and Raw 264.7 cells) demonstrated the safety of the nanocapsules as well as their efficient internalization. An antimicrobial susceptibility test was performed to evaluate the efficacy of the rifabutin-loaded nanocapsules against Mycobacterium phlei. This study indicated complete inhibition for antibiotic concentrations within the expected susceptibility range of Mycobacterium (≤ 0.25-16 mg/L).

Development and Evaluation of Chitosan Microparticles Based Dry Powder Inhalation Formulations of Rifampicin and Rifabutin

BACKGROUND

The lung is the primary entry site and target for Mycobacterium tuberculosis; more than 80% of the cases reported worldwide are of pulmonary tuberculosis. Hence, direct delivery of anti-tubercular drugs to the lung would be beneficial in reducing both, the dose required, as well as the duration of therapy for pulmonary tuberculosis. In the present study, microsphere-based dry powder inhalation systems of the anti-tubercular drugs, rifampicin and rifabutin, were developed and evaluated, with a view to achieve localized and targeted delivery of these drugs to the lung.

METHODS

The drug-loaded chitosan microparticles were prepared by an ionic gelation method, followed by spray-drying to obtain respirable particles. The microparticles were evaluated for particle size and drug release. The drug-loaded microparticles were then adsorbed onto an inhalable lactose carrier and characterized for in vitro lung deposition on an Andersen Cascade Impactor (ACI) followed by in vitro uptake study in U937 human macrophage cell lines. In vivo toxicity of the developed formulations was evaluated using Sprague Dawley rats.

RESULTS

Both rifampicin and rifabutin-loaded microparticles had MMAD close to 5 μm and FPF values of 21.46% and 29.97%, respectively. In vitro release study in simulated lung fluid pH 7.4 showed sustained release for 12 hours for rifampicin microparticles and up to 96 hours for rifabutin microparticles, the release being dependent on both swelling of the polymer and solubility of the drugs in the dissolution medium. In vitro uptake studies in U937 human macrophage cell line suggested that microparticles were internalized within the macrophages. In vivo acute toxicity study of the microparticles in Sprague Dawley rats revealed no significant evidence for local adverse effects.

CONCLUSION

Thus, spray-dried microparticles of the anti-tubercular drugs, rifampicin and rifabutin, could prove to be an improved, targeted, and efficient system for treatment of tuberculosis.

Agglomerates containing pantoprazole microparticles: modulating the drug release

Pantoprazole-loaded microparticles were prepared using a blend of Eudragit S100 and Methocel F4M. The accelerated stability was carried out during 6 months at 40 degrees C and 75% relative humidity. In order to improve technological characteristics of the pantoprazole-loaded microparticles, soft agglomerates were prepared viewing an oral delayed release and gastro-resistant solid dosage form. The agglomeration was performed by mixing the pantoprazole microparticles with spray-dried mannitol/lecithin powders. The effects of factors such as the amount of lecithin in the spray-dried mannitol/lecithin powders and the ratio between pantoprazole microparticles and spray-dried mannitol/lecithin powders were evaluated. The pantoprazole-loaded microparticles present no significant degradation in 6 months. The agglomerates presented spherical shape, with smooth surface and very small quantity of non-agglomerated particles. The agglomerates presented different yields (35.5-79.0%), drug loading (58-101%), and mechanical properties (tensile strength varied from 44 to 69 mN mm(-2)), when the spray-dried mannitol/lecithin powders with different lecithin amounts were used. The biopharmaceutical characteristics of pantoprazole microparticles, i.e., their delayed-release properties, were not affected by the agglomeration process. The gastro-resistance of the agglomerates was affected by the amount of spray-dried mannitol/lecithin powders. The ratio of lecithin in the spray-dried mannitol/lecithin powders was the key factor in the agglomerate formation and in the drug release profiles. The agglomerates presenting better mechanical and biopharmaceutical characteristics were prepared with 1:2 (w/w) ratio of pantoprazole-loaded microparticles and mannitol/lecithin (80:20) powder.

Effects of Fungal-derived High Molecular Weight Chitosan on 5-Fluorouracil-induced Adverse Reactions

The effects of fungal-derived high molecular weight chitosan (HMWC) on the prevention of 5-fluorouracil (5-FU)-induced side-effects were studied in a sarcoma-bearing mice model. 5-FU (12.5mg/kg) was gargled into the mice with or without HMWC (25, 75, and 150mg/kg) every 12 h for consecutive 8 or 16 days in different experiments. The HMWC (25—150 mg/kg) exerted no toxicity and did not interfere with the anti-tumor activity of 5-FU on sarcoma-bearing mice. HMWC in a higher dose (150 mg/kg) partially protected 5-FU-induced cytotoxicity on peripheral leukocytes, lymphocytes, and bone marrow CD-19 positive cells. HMWC reversed the 5-FU suppression of intestine sucrase activity and attenuated the 5-FU-induced diarrhea. Bone marrow cells micronucleus and DNA comet assays demonstrated that HMWC significantly reversed 5-FU-induced genome toxicity to marrow cells. These results suggested that fungal-derived HMWC attenuated the 5-FU-induced bone marrow and gastrointestinal toxicity, and has the potential for clinical applications in the future.

Pharmaceutical particle engineering via spray drying

This review covers recent developments in the area of particle engineering via spray drying. The last decade has seen a shift from empirical formulation efforts to an engineering approach based on a better understanding of particle formation in the spray drying process. Microparticles with nanoscale substructures can now be designed and their functionality has contributed significantly to stability and efficacy of the particulate dosage form. The review provides concepts and a theoretical framework for particle design calculations. It reviews experimental research into parameters that influence particle formation. A classification based on dimensionless numbers is presented that can be used to estimate how excipient properties in combination with process parameters influence the morphology of the engineered particles. A wide range of pharmaceutical application examples—low density particles, composite particles, microencapsulation, and glass stabilization—is discussed, with specific emphasis on the underlying particle formation mechanisms and design concepts.