α-Tocopherol Succinate-Anchored PEGylated Poly(amidoamine) Dendrimer for the Delivery of Paclitaxel: Assessment of in Vitro and in Vivo Therapeutic Efficacy

Abstract

This study involves development of a dendrimer-based nanoconstruct by conjugating α-tocopheryl succinate (α-TOS) and polyethylene glycol (PEG) on a poly(amidoamine) dendrimer (G4 PAMAM) to improve intracellular delivery of a poorly water-soluble chemotherapeutic drug, paclitaxel (PTX). The conjugates were characterized by NMR, and PTX-loaded nanocarriers (G4-TOS-PEG-PTX) were evaluated for hydrodynamic diameter, polydispersity index (PDI), zeta potential, percentage encapsulation efficiency (%EE), and percentage drug loading (%DL). A hemolysis study was performed, which indicated that the synthesized dendrimer conjugates were not toxic to red blood cells; hence, they were biocompatible. A cellular uptake study in (B16F10 and MDA MB231) monolayer cells and 3D spheroids showed that α-TOS conjugation improved the time dependent uptake of nanosized dendrimer conjugates. The cell viability assay revealed that G4-TOS-PEG-PTX enhanced the cytotoxicity of PTX as compared to free PTX and PTX-loaded G4-PEG (G4-PEG-PTX) at tested concentrations. Correspondingly, the α-TOS-anchored dendrimer induced more apoptosis as compared to free PTX and G4-PEG-PTX. Moreover, the fluorescently labeled G4-TOS-PEG penetrated deeper into MDA MB231 3D spheroids as visualized by confocal microscopy. G4-TOS-PEG-PTX showed significant growth inhibition in 3D spheroids as compared to free PTX and G4-PEG-PTX. Further, the in vivo efficacy study using B16F10 xenografted C57Bl6/J mice indicated that the G4-TOS-PEG localized in tumor sections. G4-TOS-PEG-PTX reduced the tumor growth significantly compared to free PTX and G4-PEG-PTX. G4-TOS-PEG-PTX had more apoptotic potential in tumor sections as analyzed by TUNEL assay. Hence, the newly developed dendrimer conjugate, G4-TOS-PEG, has the potential to target loaded drug to the tumor, and G4-TOS-PEG-PTX has the potential to be utilized successfully in cancer treatment.

Keywords: 3D spheroids; G4 PAMAM dendrimer; PEGylation; in vivo therapeutic efficacy; paclitaxel; α-TOS.