Deposition of nebulized liposomal carriers within an upper airways replica

abstract

en

Lung cancer is the most deadly cancer disease (18 % of deaths are caused by cancer) (Sung et al., 2021). Cancer treatment is connected with severe side effects due to whole-body exposure to strong cytotoxic anticancer drugs (Zhang et al., 2018). Inhalation treatment could decrease the exposure of the healthy organs and eliminate the side effects. Liposomal carrier systems are a perspective option of inhalation delivery of anticancer drugs, because of their biocompatibility, the longer retention in the lung, or targeted cellular therapy (Young et al., 2015). The liposome from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) stabilized by cholesterol phosphatidic acid (PA) was nebulized by Pari LC Sprint Star nebulizer (Pari GmbH, Germany). MMAD (Mass Median Aerodynamic Diameter) of generated aerosol measured by Aerodynamic Particle Sizer (APS, TSI Inc., Minnesota) was 7.27±0.26 µm and GSD (Geometric Standard Deviation) was 1.54±0.01 µm. The deposition of a nebulized system in a replica of the human upper airway was investigated. Specifically, the replica of the extrathoracic (ET) airway and the trachea described in (Lizal et al., 2012) were used. Liposomal vesicles were labelled by fluorescence dye ATTO 488 (bounded to phospholipid) to enable the detection of deposited aerosol after exposure. The membrane filter was connected below the airway replica to capture the aerosol which penetrates below the trachea. Two breathing modes were investigated: 1. A steady inspiration with 20 l/min flowrate corresponding to the averaged tidal breathing pattern; and 2. A realistic normal breathing pattern from a study of Farkas et al. (Farkas et al., 2020) was generated by a breathing simulator. The nebulizer worked with a 4.5 l/min air flowrate. In the case of the steady inspiration, the nebulizer mouthpiece was connected directly to the mouth of the model. In the case of realistic breathing, the branching was placed between the mouthpiece and the airway model. The inspiration was performed through the branch with airways, whereas the exhaled aerosol was led to the nebulizer through the second branch to bypass the airway replica. In other words, the air was passing through the airway only during the inspiration. Deposited aerosol was extracted from the airway model, nebulizer mouthpiece, and a membrane filter by distilled water. The amount of dye deposited in each segment was evaluated by spectrofluorimeter FS5 (Edinburg Instruments Ltd, UK). A significant difference in deposition was identified between the steady inhalation and the realistic inspiration. Approximately 90 % of the mass of liposomes penetrated below the airway replica (deposited on the filter) during steady inhalation, which means they were able to reach the bronchial airway region. On the other hand, only approximately 40 % of liposomes reached the filter in the case of realistic inspiration. This difference is caused by the rapid increase of the deposited fraction on the mouthpiece exhalation valve in the case of the realistic breathing cycle. However, nebulizers are commonly tested by the next-generation impactor using a constant flow rate.

Lung cancer is the most deadly cancer disease (18 % of deaths are caused by cancer) (Sung et al., 2021). Cancer treatment is connected with severe side effects due to whole-body exposure to strong cytotoxic anticancer drugs (Zhang et al., 2018). Inhalation treatment could decrease the exposure of the healthy organs and eliminate the side effects. Liposomal carrier systems are a perspective option of inhalation delivery of anticancer drugs, because of their biocompatibility, the longer retention in the lung, or targeted cellular therapy (Young et al., 2015). The liposome from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) stabilized by cholesterol phosphatidic acid (PA) was nebulized by Pari LC Sprint Star nebulizer (Pari GmbH, Germany). MMAD (Mass Median Aerodynamic Diameter) of generated aerosol measured by Aerodynamic Particle Sizer (APS, TSI Inc., Minnesota) was 7.27±0.26 µm and GSD (Geometric Standard Deviation) was 1.54±0.01 µm. The deposition of a nebulized system in a replica of the human upper airway was investigated. Specifically, the replica of the extrathoracic (ET) airway and the trachea described in (Lizal et al., 2012) were used. Liposomal vesicles were labelled by fluorescence dye ATTO 488 (bounded to phospholipid) to enable the detection of deposited aerosol after exposure. The membrane filter was connected below the airway replica to capture the aerosol which penetrates below the trachea. Two breathing modes were investigated: 1. A steady inspiration with 20 l/min flowrate corresponding to the averaged tidal breathing pattern; and 2. A realistic normal breathing pattern from a study of Farkas et al. (Farkas et al., 2020) was generated by a breathing simulator. The nebulizer worked with a 4.5 l/min air flowrate. In the case of the steady inspiration, the nebulizer mouthpiece was connected directly to the mouth of the model. In the case of realistic breathing, the branching was placed between the mouthpiece and the airway model. The inspiration was performed through the branch with airways, whereas the exhaled aerosol was led to the nebulizer through the second branch to bypass the airway replica. In other words, the air was passing through the airway only during the inspiration. Deposited aerosol was extracted from the airway model, nebulizer mouthpiece, and a membrane filter by distilled water. The amount of dye deposited in each segment was evaluated by spectrofluorimeter FS5 (Edinburg Instruments Ltd, UK). A significant difference in deposition was identified between the steady inhalation and the realistic inspiration. Approximately 90 % of the mass of liposomes penetrated below the airway replica (deposited on the filter) during steady inhalation, which means they were able to reach the bronchial airway region. On the other hand, only approximately 40 % of liposomes reached the filter in the case of realistic inspiration. This difference is caused by the rapid increase of the deposited fraction on the mouthpiece exhalation valve in the case of the realistic breathing cycle. However, nebulizers are commonly tested by the next-generation impactor using a constant flow rate.

Aerosol, deposition, airway, liposom, nebulizer

04.09.2022

Atény, Grécko

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