D. S. Pender1, A. Khanal1, S. Hudson1, L. McNally1 1University Of Louisville,Louisville, KY, USA
Introduction: Modern methods of pancreatic cancer diagnosis and treatment are severely lacking and have failed to provide effectual treatment options for patients. The root cause of this inadequacy stems from the hypovascularized nature of pancreatic cancer, making traditional chemotherapeutics and cancer detecting contrast agents nearly obsolete. A potential solution for tumor-targeting difficulties is through the implementation of nanotechnology, specifically targeting ligand capped, theranostic nanoparticles. We hypothesize that pH-responsive chitosan-capped mesoporous silica nanoparticles (MSNs) with the targeting ligand, urokinase plasminogen activator (UPA) will serve as theranostic agents for treatment and diagnosis of pancreatic cancer.
Methods: MSNs were synthesized by employing cetyl trimethylammonium bromide (CTAB), tetraethyl orthosilicate (TEOS) and chitosan through the sol-gel method. The synthesized MSNs were characterized by transmission electron microscopy (TEM) and zeta-potential measurements. Afterwards, gemzar chemotherapeutic drug was encapsulated into these nanoparticles to observe the pH dependent release profiles in vitro. Furthermore, MSNs were tagged with UPA to increase the binding efficiency of these nanoparticles towards the pancreatic tumor cells (S2CP9 and S2VP10). The binding efficiency of both tagged and non-tagged MSNs was observed at various pHs (7.4 to 6.5) by employing fluorescence microscopy, Odyssey infrared imaging and tissue phantoms. For that, various types of dyes were used, such as, rhodamine B and indocyanine green (ICG). Finally, UPA-tagged MSNs with ICG were injected into mice infected with S2CP9 tumors cells to observe the distribution of these nanoparticles in-vivo through multispectral photoacoustic Tomography system (MSOT).
Results: TEM pictures showed that the synthesized MSN had a size around 120 nm. Zeta-potential measurements revealed that charge density of MSN was dependent on pH. The release experiments showed that these nanoparticles were pH-sensitive because the release of gemazar depended on the pH. Gemzar released ~2x the quantity from MSNs at pH 6.5 in comparison to pH 7.4. Fluorescence microscopy, Odyssey infrared imaging and tissue phantoms showed that uptake of MSNs by pancreatic tumor cells depended on the pH and tagging of UPA. Lowering pH and tagging a ligand drastically increased the uptake of MSNs in pancreatic tumor cell in vitro. Specifically in tissue phantoms, UPA-ICG loaded MSNs at pH 6.5 demonstrated 20X and 7X more cell signal than without ligand or at pH 7.4, respectively. Furthermore, UPA-ICG loaded MSNs were successfully detected in orthotopic pancreatic tumor of mice within 6 hours of imaging time by MSOT.
Conclusion: UPA tagged, pH sensitive MSNs demonstrate potential as a theranostic nanoparticle for pancreatic cancer.