Spraying of Cell Colloids in Medical Atomizers

Abstract

Aerosols are conveniently used for delivery of medicines to the human body. The most common application is inhalation of anti-asthmatic or anti-inflammatory drugs, nevertheless the spectrum of therapeutic agents that may be administered via the respiratory system is continuously expanding. Aerosols are also used topically (on skin) as a method of speeding up the healing. In this context, bio-colloids (e.g., cell suspensions) are considered as the material for which the proper atomization method must be established to assure that local hydrodynamic stresses related to droplet formation will not destroy the living cells. In this work we test the influence of selected spraying techniques on the integrity and survival of different types of cells after the atomization process using medical atomizers. Medical nebulizers and spray devices were characterized in respect of emitted droplet size distribution and used to aerosolize model bio-colloids (suspensions of yeast, bacteria and mouse fibroblasts). Cell viability after spraying was determined via direct microscopic observations and specific microbiological assays. Commonly used medical inhalers produce droplets which are too small (Dv50 ˜ 4-5.5 µm) to contain whole living cells. As generation of such fine droplets is related to high local hydrodynamic stresses, cell viability in the suspension is strongly reduced even for small and mechanically resistant cells. Nasal atomizer (spray pump) and mechnical Microsprayer produce larger droplets (Dv50 ˜ 50-80 µm) which are capableof carrying intact fibroblast cells. Due to a lower shear during atomization process in these devices, the cells remain viable and active. Based on the results of experimental study, only selected techniques can be proposed for bio-colloid atomization in medical applications.