Page - (000358) - in Biomedical Chemistry: Current Trends and Developments

Figure 3.5.3: Stimulus-responsive delivery strategies for tumor targeting. Abbreviations: EPR, enhanced permeability and retention effect; GSH, glutathione. Reprinted with permission from (Zhu, 2013). Among the nanosystems generated to trigger the release of cargos in a pH-dependent manner, many systems have been developed taking into account the difference in pH values existing between the healthy tissues (pH = 7.4) and the extracellular environment of solid tumors (pH = 6.5– 6.8) (Helmlinger, 2002). Other systems exploit the pH values of the internal cellular organelles, such as lysosomes and endosomes (Sorkin, 2002). It is well-known that, environmentally, these cellular compartments have characteristic features, such as lower pH and reductive potential, which are divergent from the extracellular surroundings, offering a chance to exploit these special properties to release actively the cargos intracellularly, inside endosomal vesicles and/or lysosomal organelles (Elzoghby, 2012; MacEwan, 2010). For example, mesoporous silica nanoparticles (MSN) have been widely used for stimuli-responsive drug delivery in cancer therapeutics and were proved to be a versatile, easily functionalized platform, enabling an easy