Development Towards a Clinically Relevant Gemcitabine Loaded Ultrasound Contrast Agent
Thursday, September 20, 2018
1:00 PM-3:00 PM
BIOMED Master's Thesis Defense
Title:
Development Towards a Clinically Relevant Gemcitabine Loaded Ultrasound Contrast Agent
Speaker:
David Karl Brown, MS Candidate, School of Biomedical Engineering, Science and Health Systems, Drexel University
Advisor:
Margaret Wheatley, PhD, John M. Reid Professor, School of Biomedical Engineering, Science and Health Systems, Drexel University
Abstract:
Injectable ultrasound contrast agents (UCAs) are being research 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 a 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-MB and GEM-loaded nanoshards (GEM-Nsh) were observed against MIA-PaCa-2 cancer cells and compared to controls daily for 7 days. While unloaded MBs possess no effect on cell growth, GEM-MB killed cells similar to free GEM at 750nM GEM concentration. After 7 days, cells treated with control media, free GEM and GEM-MB 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-MB 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 method was found to be 155.77±89.95 µgGEM/mgAuNP. 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 µgGEM/mgMB compared to 4.29±0.33 µgGEM/mgMB (p=0.03). Increasing GEM concentration may allow GEM-AuNP MBs to better penetrate pancreatic stroma and induce a stronger cytotoxic response.
Contact Information
Ken Barbee
215-895-1335
barbee@drexel.edu