The importance of interaction between particles for the application of powder for inhalation

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Agent particles for the therapy of bronchial asthma which can reach the fine alveoli of the lung through inhalation must have sizes between 1 micron and 5 micron. Such particle however are very cohesive, a poor flowability and are difficult to disperse. Consequently they are blended in a mixer with coarser particles which become coated. During the inhalation process the agent particles must be detached again from the carrier. Hence, the adhesion force between carrier and agent must be strong enough during the production and handling process, but on the other hand small enough to be detached from the carrier again in the inhaler device. For this reason the control of the adhesion force is very important. The objective of the first project period was the targeted modification of the adhesion force through surface treatment of the glass bead carrier. Furthermore, an objective of the first and second project period was the numerical flow simulation of the detachment probability on the basis of the Lattice-Boltzmann method using experimental information on the adhesion forces for different surface treatment. The main objective of the second project period was the consideration of size, shape and chemistry of different agent particles for providing a data base. This should allow a proper selection of the carrier particle, depending on the agent particle properties. The main goal of the proposed project is the optimization of the inhaler geometry in order to improve its efficiency (i.e. amount of agent particles reaching the lung). This shall be done on the basis of experimental studies using a modular facility and applying numerical flow calculations of the entire inhaler incorporating a developed detachment model. Thereby, all the properties of the powder inhalation influencing factors, which influence the agent detachment, can be targeted adjusted. With that, the development of powder inhalants so far based on try and error procedures will be replaced by a more scientific approach.