“…Specifically, stimuliresponsive delivery systems have been created to target the acidic pH and/or hypoxic environment characteristic of tumor cells [210] (Figure 5). In this respect, polymeric nanoparticles have been investigated as carriers towards various tumor cells, including breast [44,[211][212][213], colon [91,[214][215][216][217], gastric [169,[218][219][220], liver [116,221,222], bladder [46,223], skin [224,225], lung [36,92,226], prostate [94,[227][228][229], and ovarian [230][231][232] cancer cells (Table 2). In this respect, polymeric nanoparticles have been investigated as carriers towards various tumor cells, including breast [44,[211][212][213], colon [91,[214][215][216][217], gastric [169,[218]…”