Micro-nano delivery systems for an efficient cystic fibrosis treatment

INTRODUCTION Cystic fibrosis (CF) is an autosomal recessive disease, which is the result of a genetic defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Pulmonary disease accounts for over 90% of the morbidity and mortality associated with CF. The main challenge for an efficient CF pharmacologic treatment is the mucus obstruction of the airway in CF patients that impairs lung function, increases the inflammation/infection processes, and limits delivery of inhaled drugs1. Micro and nano delivery systems are currently being investigated as an efficient way to penetrate the viscous and highly complex mucus barrier. In this work, novel drug delivery systems based on microparticles incorporating a depolymerising agent were prepared and tested for their mucolytic activity towards the tenacious CF sputum. EXPERIMENTAL METHODS A natural water-soluble polysaccharide (gellan, GL) and a synthetic copolymer (poly(lactic-co-glycolic) acid, PLGA) were used to prepare two different classes of microparticles (MPs) through procedures based on water/oil emulsion techniques. The preparation of MPs was optimized to have suitable dimensions in agreement with the CF airway caliber and anatomy. A complete morphological and physicochemical characterization was carried out on both MPs using SEM, DSC, TGA and FTIR Chemical Imaging. Artificial sputum (AS) was produced and its rheological properties compared with sputum from CF patients. In vitro cytocompatibility tests were performed on both MPs using the human lung cancer cell line A459. MPs were loaded with a mucolytic agent (N-acetyl cysteine, NAC) and their release kinetics was evaluated using HPLC. Rheological analysis was carried out to evaluate the effect of NAC on the AS viscosity after NAC-loaded MPs addition. RESULTS AND DISCUSSION PLGA MPs present a spherical shape and dimensions in line with application requirements (Fig 1a). GL MPs show a sponge structure, responsible for the high capability of these particles to swell in water and dissolve rapidly into mucus. In vitro biocompatibility tests demonstrated that GL and PLGA MPs did not interfere with neither A549 human lung epithelial cell viability nor proliferation. NAC loading efficiency was 73% for GL MPs and 98% for PLGA MPs. NAC was released from GL MPs with a rapid kinetics: 87% of released amount was detected after 5 min in agreement with hydrophilic and porous structure of GL MPs. Concerning PLGA MPs, the release is more gradual and controlled; a value of 57% after 72 h was found. The effect of drug delivery systems on AS degradation was analysed by comparing viscosity vs shear rate of pure AS, AS loaded with PLGA or GL MPs, AS loaded with free NAC and NAC-loaded MPs. For PLGA MPs, a reduction of viscosity compared to pure AS was detected in all three cases (Fig 1b). But, the highest viscosity reduction was achieved for NAC-loaded MPs. These results confirm the release of the depolymerising agent from MPs and its diffusion directly into the mucus. Fig 1 a. SEM image of PLGA MPs; b. Viscosity vs shear rate of AS before and after addition of PLGA MPs CONCLUSION PLGA and GL MPs were evaluated as platforms for delivery of NAC, a depolymerising agent currently limited in use in its free form due to poor pharmacokinetic properties. Both MPs efficiently encapsulated NAC and provided its sustained release. The cytocompatible NAC-loaded MPs were capable of disrupting the AS. This work demonstrates the potential for GL and PLGA MPs as a vehicle for mucolytic drug release and establishes the utility of these platforms for improving local drug bioavailability, such as anti-inflammatory agents, for CF treatment.