Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Doctor of Philosophy


Biomedical Engineering


Zhu, Jesse


Chronic respiratory diseases, particularly asthma and chronic obstructive pulmonary disease (COPD), are worldwide public health challenges due to the high prevalence and mortality, affecting millions of people globally. Orally inhaled therapy through dry powder inhalation (DPI) has proven to be an effective, non-invasive, and convenient way to deliver medications to the lungs in the treatment of respiratory diseases and systemic diseases. The in-vitro performance and in-vivo efficacy of DPI systems are mainly affected by inhalers, formulations, and patients. However, the performance is not satisfactory due to variable and low lung delivery (10%-30%) of medications as well as high mouth-throat deposition. Therefore, the primary objective of the project is to investigate DPI formulation-device system to improve pulmonary delivery efficiency.

The key design parameters of a 3D-printed inhaler, including grid structure, gas inlet, grid mesh, “pierce-and-hole” design, mouthpiece length, and diameter were studied by experimental and numerical analysis, providing a comprehensive understanding of the designs in powder dispersion. Improved dispersion and aerosolization performance could be achieved by narrowing mouthpiece diameter and gas inlet size as well as generating intensive grid meshes with relatively small aperture size to introduce less vortexed airstreams and high turbulent flow. With satisfactory fine particle fraction and inhaler resistance as criteria for inhaler optimization, the final modified DPI has improved fine particle fraction (FPF) to approximately 41% compared with the model inhaler.

The influence of tertiary components on DPI formulations was investigated by particle engineering during formulation development and optimization. Spray-dried and jet-milled drug particles could achieve particle micronization with inhalable size but in spherical and irregular shapes, respectively. With 10% of fine lactose (geometric mean diametermicrons) incorporated in the formulation, the API-fine lactose-coarse lactose showed improved aerosolization performance with fine lactose physically blending with carrier lactose first. Moreover, other tertiary components, such as L-leucine and magnesium stearate, also showed their capability to improve dispersion and FPF. The optimal L-SS formulation has achieved a significantly increased FPF, up to 47%.

In summary, the levosalbutamol DPI system was successfully developed. With the optimal L-SS formulation working with the improved inhaler, the final levosalbutamol dry powder inhalation system has achieved an increased FPF to 51% with satisfactory delivery dose uniformity.

Summary for Lay Audience

Chronic pulmonary diseases, especially the most common asthma and chronic obstructive pulmonary disease (COPD), affect billions of people around the whole world. Orally inhaled therapy of medications has become the mainstream to treat diseases by delivering therapeutic ingredients to the lungs. One of the most popular delivering platforms is dry powder inhalers (DPIs), aiming to deliver powdered drug aerosol with an aerodynamic size of 1-5 microns to pulmonary sites. However, the low (10-30%) and inconsistent delivery percentage of medications to the lungs is a primary issue for DPIs, which would cause unexpected clinical therapy outcomes.

To improve the drug delivery efficiency of DPIs, studies on devices and formulations have been performed in the project. With a typical capsule-based DPI as the model inhaler, its key design parameters, such as mouthpiece length and diameter, gas inlet, grid mesh, and piercing pins, were investigated by in-vitro aerosolization testing and computational modeling. As for the DPI formulations, the carrier, α-monohydrate lactose, is a frequently used and well-accepted excipient to improve flow behaviors and handling of cohesive fine drug particles. In addition to the drug and carrier particles, third components like lactose, L-leucine, and magnesium stearate, are also proven to increase powder dispersion and delivery efficiency. Therefore, by studying the concentration, adding order, and size of the third component of lactose, an overall understanding of the influence of the tertiary component was obtained. Additionally, the methods to prepare fine drug particles were also studied, including spray drying and jet milling, since the size of fine drug particles plays a critical role in formulation performance. In addition to particle micronization, other factors that may affect drug delivery were also investigated, such as capsule material, filling weight, mixing, and ambient humidity.

After the comprehensive studies on both inhalers and formulations, an optimal device-formulation system was developed, achieving an improved in-vitro drug delivery efficiency to as high as 51% with a satisfactory dose delivered uniformity.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Available for download on Tuesday, August 17, 2027