Controlling and Monitoring Intracellular Drug Delivery Using PHPMA-Based Polymer Nanomedicines

Polymer nanomedicine is an attractive approach for the delivery of anticancer drugs. Firstly designed to increase drug bioavailability, polymer conjugates and polymer nanoparticles have rapidly emerged in the field of cancer therapy after the discovery of the enhanced permeation and retention (EPR) effect. The leaky and disordered tumor neovascularization provides opportunities to guide the accumulation of polymer nanomedicines to the tumor tissue therefore enhancing therapy selectivity and reducing off-target-associated side effects. However, since many chemotherapeutics act on targets that are located in well-defined subcellular compartments, controlling the intracellular fate of polymer nanomedicines and/or their payload is another important factor that contributes to therapy efficiency. Polymer conjugates and polymer nanoparticles generally access the cell interior via endocytosis. The physiochemical and biochemical parameters that distinguish the endolysosomal compartments from the extracellular environment have been widely exploited to trigger intracellular drug release from the polymer carriers. Amongst a range of other polymers and polymer nanoparticles that have been investigated over the past 30 years, poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA)-based conjugates have been extensively explored for the endolysosomal release of anticancer drugs. While the modern polymer chemistry toolbox provides many opportunities to tailor the molecular weight and functionality of PHPMA and to introduce features that allow the polymer to respond to the different endolysosomal environments, the development of tools and methods to monitor these processes is also crucial for the future development of advanced delivery systems. The aim of this Thesis is to design dual-functional PHPMA polymers that offer the possibility to control the endolysosomal release of anticancer drug combinations as well as to monitor the PHPMA endolysosomal trafficking. Chapter 1 of this Thesis provides an overview of the different approaches that have been described in literature to control and monitor the intracellular delivery of polymer nanomedicines. Chapter 2 describes a synthetic approach to prepare alpha- and alpha,omega-fluorine labeled pentafluorophenyl methacrylate (PPFMA) polymers via reversible addition fragmentation chain transfer (RAFT) polymerization. In Chapter 3 post-polymerization modification of the alpha-fluorine labeled PPFMA precursor will be used to prepare a series of PHPMA conjugates carrying either the anticancer drug doxorubicin (Dox) or the P-glycoprotein inhibitor zosuquidar (Zos) or both drugs at the polymer side chains. The ability of the conjugates to overcome doxorubicin efflux and therefore reverse P-gp-mediated multidrug resistance in resistant ovarian carcinoma cells will be assessed. Finally, Chapter 4 will study the cellular internalization and endolysosomal trafficking of PHPMA. The synthesis of a dual-labeled PHPMA polymer containing both a fluorescent as well as a fluorinated label will be used for flow cytometry and confocal fluorescence microscopy studies and to demonstrate the potential of nanoscale secondary ion mass spectrometry (NanoSIMS) to map and localize fluorine-containing polymers in cells.