Hu et al. developed a hyaluronic acid–cysteamine–polylactic acid–glycolic acid (HA–SS–PLGA) polymer nano-delivery system to deliver doxorubicin (DOX) and cyclopamine to breast cancer cells with CD44 overexpression.67 They found that the intake of PLGA–DOX and HA–SS–PLGA–DOX into MCF-7 cells was similar. Here, CD44 is linked to breast cancer.