Thesis
Development towards a clinically relevant gemcitabine loaded ultrasound contrast agent
Master of Science (M.S.), Drexel University
Sep 2018
DOI:
https://doi.org/10.17918/etd-8035
Abstract
Injectable ultrasound contrast agents (UCAs) are being researched as a vehicle for ultrasound sensitive targeted drug delivery. Chemotherapeutic drugs such as gemcitabine (GEM) can be loaded into the poly(lactic acid) (PLA) shell of an echogenic microbubble (MB) limiting side effects from undesired interactions with GEM and healthy tissue. Upon insonation, GEM-loaded MBs (GEM-MBs) shatter into drug-loaded nanoshards (Nsh) which can pass through the leaky vasculature of the tumor. Pancreatic cancer is known for displaying a dense fibrous stroma surrounding the tumor inhibiting perfusion of chemotherapeutic treatment. Increasing GEM concentration through GEM-MBs may overcome this limitation. Acoustic properties of GEM-MBs were characterized by maximum enhancement and stability under ultrasound (0.45MPa). GEM-MBs reached a maximum enhancement of 18.40±1.78 dB with a half-life of 9.89±3.76 minutes. This confirms that GEM-MBs can successfully reflect ultrasound and is stable enough to travel through the circulatory system. In vitro, cytotoxicity of GEM-MBs and GEM-loaded nanoshards (GEM-Nsh) was observed against MIA PaCa-2 human pancreatic cancer cells and compared to controls daily for 7 days. While unloaded MBs possess no effect on cell growth, GEM-MBs killed cells similar to free GEM at a GEM concentration of 750nM. After 7 days, cells treated with control media, free GEM and GEM-MBs exhibited dsDNA concentrations of 419.63±204.98 ng/mL, 9.92±3.73 ng/mL and 17.89±11.82 ng/mL confirming cytotoxic effects of GEM-MBs in vitro; however, literature suggests that in vitro success does not predict in vivo cytotoxicity. To increase GEM loading, incorporating GEM-bound gold nanoparticles (AuNPs) (GEM-AuNPs) into the MBs was explored. Four methods of synthesizing GEM-AuNPs were compared for size and aggregation. GEM-loading for the final AuNP protocol was found to be 155.77±89.95 [mu]gGEM/mgAuNP on average. These GEM-AuNPs were loaded into polymer MBs at a concentration of 1mg per 0.1g PLA to create GEM-loaded GEM-AuNP-loaded MBs (GEM-AuNP MBs). These MBs were characterized acoustically for maximum enhancement (17.33±2 dB) and half-life (>15 minutes) under constant insonation at 0.42MPa. Compared to GEM-MBs, GEM-AuNPs display similar enhancement with increased stability. GEM-AuNP MBs were found to load significantly more GEM per mg MB than GEM-MBs with 5.51±1.38 [mu]gGEM/mgMB compared to 4.29±0.33 [mu]gGEM/mgMB (p=0.03). Increasing GEM concentration may allow treatment to better penetrate pancreatic stroma and induce a stronger cytotoxic response.
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Details
- Title
- Development towards a clinically relevant gemcitabine loaded ultrasound contrast agent
- Creators
- David Karl Brown - DU
- Contributors
- Adrian C. Shieh (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xii, 57 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems (1997-2026); Drexel University
- Other Identifier
- 8035; 991014632236804721