Enhanced cellular uptake and intracellular drug controlled release of VESylated gemcitabine prodrug nanocapsules

Abstract

Gemcitabine, 2′,2′-difluoro-2′-deoxycytidine (dFdC), is the first-line antitumor agent in the treatment of pancreatic tumors. However, it possesses certain drawbacks, such as poor biological half-life resulted from rapid metabolism and the induction of resistance, leading to its restricted therapeutic potential. With the purpose of overcoming the above drawbacks, we developed a novel VESylated gemcitabine (VES-dFdC) prodrug by coupling the N4-amino group of the pyrimidine ring of dFdC to the carboxylic group of vitamin E succinate (VES). The resulting amphiphilic compound could protect the N4-amino group of the pyrimidine ring of dFdC from being degraded by cytidine deaminase. What is more, the prodrug was able to form nanocapsules in aqueous media (similar to the structure of cytomembrane), confirmed by transmission electron microscope (TEM). Their average particle size is about 107nm with zeta potential of −33.4mV measured by dynamic light scattering (DLS). VES-dFdC nanocapsules showed accelerated accumulative drug release profile in simulated lysosome environment (sodium acetate buffer pH 5+cathepsin B, an enzyme in lysosome), due to the easily hydrolyzed property of amide bond by cathepsin B, while rather stable in PBS (pH 7.4) or sodium acetate buffer (pH 5.0) without cathepsin B, indicating their enhanced intracellular drug controlled release manner. Besides, VES-dFdC prodrug nanocapsules showed enhanced cellular uptake ability, and the amount of cellular uptake of the nanocapsules by the pancreatic cancer cell line BxPC-3 is seventy times higher than that of native gemcitabine in the first 1.5h. Compared with free gemcitabine, VES-dFdC nanocapsules showed essentially increased growth inhibition activity against BxPC-3 cells, indicating its great potential as prodrug for pancreatic tumor therapy with improved antitumor activity.