CD44 and breast cancer: Xu et al. functionalized HA through Au–S bonds to gold nanorods (GNR), and then coupled 5-aminolevulinic acid (ALA), Cy7.5 and anti-HER2 antibody onto HA moiety for photodynamic therapy (PDT), fluorescence imaging and active targeting, respectively (Fig. 8).106 Experiments showed that the dual targeting strategy of HER2 and CD44 could significantly enhance the endocytosis of GNR–HA–ALA/Cy7.5-HER2 in human breast cancer cell MCF-7.