Nanoparticle formulations in pulmonary drug delivery

The advent of nanotechnology has reignited interest in the lungs as a major route of drug delivery for both systemic and local treatments. The large surface area of the lungs and the minimal barriers impeding access to the lung periphery make this organ a suitable portal for a variety of therapeutic interventions. Nanoparticles provide new formulation options for both dispersed liquid droplet dosage forms such as metered dose inhalers and nebulizers, and dry powder formulations. Nanoparticle formulations have many advantages over traditional dosage forms, such as enhanced dissolution properties and the potential for intracellular drug delivery. Specifically, pure drug nanoparticles, polymeric nanoparticles, polyelectrolyte complexes, and drug-loaded liposomes offer some encouraging results for delivering drugs to and through the lungs. Methods are also being investigated to produce nanoparticles with properties suitable for improving access to the peripheral lung. Traditional techniques such as spray drying and grinding, and more recent advances in supercritical fluid extraction, precipitation, and solvent extraction have been employed to produce nanoparticle formulations for pulmonary delivery. Here, the benefits of nanoparticle formulations and current progress are compared in light of the practical encumbrances of producing formulations, and possible toxicological effects of these materials.