Abstract
Delivering drug through inhalation is a very superior approach for treating diseases localized in lungs, trachea, and bronchi. The history of inhalation therapy has been developed for a long time and can be traced back to 1500 BC. The first inhaler device for inhalation therapy was developed in 1860s and many pharmaceutical companies have shown their efforts to design novel inhaler to enhance efficacy of inhalation therapy in recent decades. However, drug deposition rate in lung are far from perfect (usually less than 30 %) because of not only mis-operating of but also very few studies paid close attention to modified drug formulation for inhaling medicine. To further improve the drug delivery of inhaling medicine, we aim to develop a drug carrier equipped with nano-structure on the surface of microsphere. We succeed in preparing protein-based microspheres with different roughness and integrity of surface, which was capable of carrying Tiotropium Bromide, the model drug in this study and also one of the long –acting bronchodilator drugs was for chronic obstructive pulmonary disease (COPD) therapy. To investigate deposition rate in lungs after intratracheal instillation for animals, fluorescent moiety was conjugated with protein molecules for tracing the microsphere in vivo and ex vivo by fluorescent imaging technique. Furthermore, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) imaging technique was applied for visualizing the presence of Tiotropium Bromide in tissue dissections. In this study, microspheres modified with rough (roughness: 30-40 nm) and smooth (roughness: <3.0 nm) surface can be produced, the former shows better deposition in lung than the later (49 % versus 33 %). The addition of cross-linker maintains surface integrity for both of rough and smooth microspheres but surprisingly lead to significant changes of adhesion property which dramatically elevate deposition rate to more than 65 %. With the corss-linking additives, both of rough and smooth microspheres provide the niche of sustained release, by which the Tiotropium can be gradually release for at least 6 days. Furthermore, MALDI-TOF MS imaging technique again was proven the concept of sustained release for microspheres containing cross-linker. The protein-based microsphere shown in present work is biocompatible drug carrier and demonstrates pretty good biodisposition through inhalation by increasing surface roughness and adhesion properties, which give us insight into adding nano-structure and intrinsic properties for microspheres can effectively improve inhaling medicine.