A pharmaceutical study on nebulizable delivery systems for pulmonary administration

Abstract

Lung cancer is considered one of the most common killer cancer types worldwide and is accompanied with very poor prognosis. The most commonly available treatment options for lung cancer include surgery, radiotherapy and chemotherapy mostly through I.V. and oral route. However, owing to the several side effects accompanying these different options and routes, pulmonary administration of relatively safe therapeutic moieties with anti-cancer activity will offer many advantages including higher patient compliance, avoidance of the hepatic first pass metabolism, low enzymatic activity compared to oral route and the possibility of achieving direct local therapeutic effect on the respiratory tract with possibility of systemic absorption which, will be beneficial in controlling cases with cancer metastasis. Nanotechnology-based delivery systems have been widely used for passive targeting of different cancer types owing to their diverse advantages, including drugs protection from enzymatic degradation and endocytosis clearance by macrophages, controlled and targeted drug delivery relying on the Enhanced permeability and retention (EPR) effect, in addition to reduction of toxicity and side effects of the delivered drugs.

The purpose of the first chapter was to formulate PLGA polymer-based nanoparticles co-encapsulating the novel combination of the herbal compound naringin with the COX-2 inhibitor celecoxib for treatment of lung cancer. Modified combined nanoprecipitation homogenization / solvent evaporation method was used to prepare different PLGA nanoparticulate formulations using different grades of PLGA polymer and incorporation of poloxamer 188, was tried as well. The prepared PLGA nanoparticulate formulations were characterized with respect to their particle size, zeta potential, entrapment efficiency, in vitro release and in vitro stability. The selected PLGA nanoparticulate formulations were characterized for morphology using transmission electron microscopy, cytotoxicity on A549 lung cancer cells, physicochemical properties related to nebulization and their aerosolization / nebulization behaviors. Thein vivo biodistribution upon pulmonary aerosolization and safety on healthy lung tissue were determined as well. PLGA nanoparticulate formulations were successfully prepared and were able to entrap both naringin and celecoxib together with moderate and high EE%, respectively. They displayed particle sizes ranging from 215 – 267 nm (within suitable range for cancerous cells passive targeting relying on EPR effect, and for avoiding pulmonary mucociliary and alveolar macrophages clearance), narrow particle size distributions, zeta potential values ranging from -18.3 to -25.9 mV (which is expected to provide higher resting potential in the lungs), biphasic in vitro release patterns for naringin and more controlled in vitro release patterns for celecoxib. The selected PLGA nanoparticulate formulation (P8) which, showed the highest EE% for naringin and the best in vitro stability profiles, showed also spherical shape with a clear evident poloxamer coat, and displayed superior cytotoxicity on A549 lung cancer cells than (naringin - celecoxib) combination solution in DMSO (emphasizing the merit of colloidal nanoparticles application in increasing drugs concentration gradients around and directly inside the cells). Also, the selected PLGA nanoparticulate formulation (P8) showed high stability and suitability for nebulization using air-jet nebulizers generating aerosol droplets with small volume median diameter (VMD) and mass median aerodynamic diameter (MMAD) lower than 6 µm, small span and geometric standard deviation (GSD) values, high aerosol output, aerosol output rate and drug outputs, and higher deposition in lower stages of Twin Impinger (TI) and multistage Next Generation Impactor (NGI).In vivo biodistribution studies for the selected PLGA nanoparticulate formulation (P8) showed high accumulation of naringin and celecoxib per gram organ in lung tissues with favorable distribution to the bones, liver and brain, which are common metastatic sites for lung cancer and also, showedin vivo safety on lung tissues of animal models, suggesting suitability for pulmonary administration for the aim of local lung cancer treatment and systemic metastasis control. Additionally, in the second chapter of the thesis, (naringin – celecoxib) co-loaded o/w nanoemulsion formulations wereprepared by homogenization / solvent evaporation method using labrafac lipophile or soybean oil as oily phase, tween 80 as surfactant (with different concentrations and addition methods), ethanol as solvent and normal saline (NaCl 0.9%) as the aqueous phase. The prepared nanoemulsion formulations were characterized with respect to their particle size, zeta potential, in vitro release and in vitro stability. The selected nanoemulsion formulation was characterized for morphology using transmission electron microscopy, cytotoxicity on A549 lung cancer cells, physicochemical properties related to nebulization and their aerosolization / nebulization behaviors. Thein vivo biodistribution upon pulmonary aerosolization and safety on healthy lung tissue were determined as well.