When selecting biological models for testing inhalation products, careful consideration must be made regarding the area of the respiratory tract that is the target site for a product. Once the appropriate cellular models are selected, there are several cell culture techniques that can be utilized to mimic the physiologically relevant conditions.
Currently, several cellular models are available commercially that can be used for in vitro testing of inhalation products targeting the respiratory system. These include immortalized cells lines that can proliferate indefinitely through passaging and primary cells that are freshly isolated directly from donor organs that have a finite life span. Once the appropriate cellular models are selected, there are several cell culture techniques that can be utilized to mimic the physiologically relevant conditions for testing of inhalation products. They can be sub-categorized into 2-dimensional (2-D) and 3-dimensional (3-D) cell culture.