Development and characterization of intravesical mucoadhesive nanoparticulate formulations of paclitaxel and docetaxel for postoperative chemotherapy in non-muscle-invasive bladder cancer

The present work describes the development, in vitro and in vivo evaluation of mucoadhesive nanoparticulate formulations of paclitaxel (PTX) and docetaxel (DTX) for intravesical bladder cancer therapy. The nanoparticles developed for PTX and DTX delivery consisted of hyperbranched polyglycerol (HPG), which were hydrophobically derivatized with alkyl chains (C₈/₁₀) in the core to allow drug loading and were further derivatized with methoxy polyethylene glycol (MePEG) and primary amine groups in the shell (HPG-C₈/₁₀-MePEG-NH₂) to increase their mucoadhesiveness. Human urothelial carcinoma cell lines were treated with various concentrations of PTX and DTX formulations in vitro. Mice with established KU7-luc tumors were intravesically treated with various concentrations of PTX and DTX formulations or control vehicles. Drug uptake was conducted using LC/MS/MS and tumor microenvironment and uptake of rhodamine labeled HPGs was assessed by immunohistochemistry-based tumor mapping and fluorescence microscopy. The effects of HPG nanoparticles on the urinary bladder wall were studied on isolated porcine bladder tissues as well as in live mouse bladders. To investigate the toxicity and tolerability, histopathological evaluations were preformed following a single intravesical instillation with empty HPG nanoparticles in healthy female nude mice. In vitro, PTX and DTX loaded HPG nanoparticles were found to have equivalent cytotoxicities as their commercial formulations of Taxol® and Taxotere®, respectively. The surface modification of HPG-C₈/₁₀-MePEG with amine groups resulted in highly positive charged nanoparticles (HPG-C₈/₁₀-MePEG-NH₂) with improved mucoadhesive properties. A single intravesical instillation with DTX loaded HPG-C₈/₁₀-MePEG-NH₂ at a lower dose significantly inhibited tumor growth and increased drug uptake in mouse bladder tissues. HPG-C₈/₁₀-MePEG-NH₂ nanoparticles were found to significantly increase the uptake of DTX in both isolated pig bladder as well as in live mouse bladder tissues likely resulting from changes to the urothelial barrier function and morphology through opening of tight junctions and exfoliation of the superficial umbrella cells. Our preliminary studies suggest that this exfoliation was triggered by an apoptosis mechanism followed by a rapid recovery of the urothelium within 24 h post-instillation. Overall, our data show promising in vivo anti-tumor efficacy and provide preclinical proof-of-principle for intravesical application of these nanoparticulate formulations in the treatment of non-muscle-invasive bladder cancer.Pharmaceutical Sciences, Faculty ofGraduat