Inhalation of aerosolized drugs holds promise as a means to treat localized disease states within the lung and may also represent an ideal method for drug delivery to the systemic circulation. The use of polymer-based aerosol carriers for controlled drug delivery via the lung is an approach that may improve the duration and effectiveness of drugs delivered to the respiratory tract. However, the ability to optimize new formulations for pulmonary drug delivery has been limited by the inability to closely mimic the conditions the particles encounter in the various regions of the lung.

Conventional "complete immersion" methods used to characterize microparticle water uptake rates, polymer degradation kinetics, and drug diffusion rates may not be relevant for particles designed for inhalation due to the extremely thin aqueous layers in the lungs. In this paper, I discuss the forces on a particle at the air-surfactant-particle interface used to determine the extent of submersion. Then, I model the water uptake into particles completely immer

Force analysis on a particle at the solid-liquid-gas interface

Concentration profiles for 5 mm particles completely submerged in an aqueous solution showed the concentration within the particles increases with time until a steady value is reached in approximately 67 hours. Water uptake into particles submersed in humidified air depends on adsorption and condensation of water on the particle surface as well as the diffusivity into the particle. Because of the low water vapor concentration and adsorption rate, water uptake by humidified air will be extremely slow compared to that in an aqueous solution. Therefore, water uptake into a particle deposited on a thin fluid film can be assumed to occur only from the submersion liquid. To model this situation appropriately, water uptake in the r and q-directions needs to be solved.

Some common words found in the essay are:
Introduction Inhalation, Using Langmuir-Wilhelmy, Calculations Force, Abstract Inhalation, surface tension, water uptake, drug delivery, aqueous layers, surfactant film, line tension, particles submersed, larger particles, particles diameter, respiratory tract, Transport December, improve duration effectiveness, water uptake spherical, water uptake particles, particles partially submersed, uptake spherical particles,
Approximate Word count = 4407
Approximate Pages = 18 (250 words per page double spaced)