Using Trastuzumab-conjugated nanogels (Trast-NG) encapsulating the DNA-damaging drug Doxorubicin (DOX) as a model chemotherapeutic, we demonstrate through in vitro and in vivo studies that HSP90 inhibition can indeed lead to an enhancement of targeted delivery of DOX specifically into ErbB2-overexpressing breast cancer cells. The gene discussed is ERBB2; the disease is breast cancer.