The in vivo targeting ability of each nanoprobe was established by imaging mice bearing subcutaneous tumors expressing one of three biomarkers of relevance in breast cancer: caveolin 1 (CAV1), C-X-C chemokine receptor type 4 (CXCR4), and Folate Receptor alpha (FRα) (Table 1). The gene discussed is FOLR1; the disease is breast cancer.