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Fundamental studies of ultra-high ductility multi-phase Mg-Li based alloys for biodegradable tracheal stent application

Wu, Jingyao (2019) Fundamental studies of ultra-high ductility multi-phase Mg-Li based alloys for biodegradable tracheal stent application. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Airway obstruction though uncommon in the pediatric age group is however, extremely difficult and challenging to handle. Current gold standard treatment therapies include tracheal intubation with prolonged mechanical ventilation, implementation of surgical procedures, and intraluminal airway stents. All the current treatment options are associated with high complications and failure rates. Commercially available airway stents provide immediate relief and reduced morbidity and risks, albeit are unsatisfactory in long-term effectiveness. Due to the obvious deficiencies of currently available treatment options, there is a significant clinical need for the generation and use of a biodegradable medical device, which maintains airway patency while safely degrading overtime. Previous preclinical and clinical studies have focused on designing polymeric scaffolds as extraluminal splint or intraluminal stents. Despite the promising clinical results, an open surgery is always required to place the extraluminal stents. As for intraluminal stents, one of the major pitfalls is that the remnants of the degraded stents might migrate to the bronchi causing progressing dyspnea.
The objectives of this dissertation were to explore the feasibility of a biodegradable magnesium alloy-based tracheal stents. Six ultra-high ductility multi-phase Mg-Li-Zn-(Al) alloys were accordingly designed and fabricated. These alloys display ultra-high ductility due to the co-existence of both α (HCP) and β (BCC) phases. Further characterization of the six alloys for microstructure, mechanical properties and in vitro degradation demonstrated superior overall performance of the Mg-Li-Zn-(Al) alloys. In addition, all the selected alloys exhibited high cell viability and low cell apoptosis although possibly inhibiting the proliferation of human bronchial epithelial cells due arrest of cells in the G2/M phase. In vivo subcutaneous implantation of all the six alloys in mouse further proved the efficacy of these alloys demonstrating low corrosion rate and excellent tissue compatibility of the Mg-Li-Zn-(Al) alloys. Finally, prototype stents were fabricated and evaluated both in a bioreactor system and in a rabbit airway model. The stents showed significantly higher corrosion resistance under flow environments in vitro and safely degraded in vivo without affecting further growth of the rabbit airway. Both the alloy matrix and degradation products were well tolerated by the airway tissue without exhibiting noticeable local and systematic toxicity. In conclusion, the studies demonstrated the feasibility of using Mg-Li-Zn-(Al) alloy biodegradable magnesium alloy for tracheal stent application. It is anticipated that this novel approach and the promising results of the study will likely lead to a new treatment method for airway obstruction.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Wu, Jingyaojywu90@gmail.comjiw85
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKumta,
Committee MemberChi,
Committee MemberChun,
Committee MemberWagner,
Date: 24 January 2019
Date Type: Publication
Defense Date: 12 September 2018
Approval Date: 24 January 2019
Submission Date: 29 October 2018
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 186
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Magnesium, Tracheal stent, Airway, Biodegradable, Lithium
Date Deposited: 24 Jan 2020 06:00
Last Modified: 24 Jan 2024 06:15


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