Multivalent conjugates comprising the following formula: (STxB-linker A-S)x-GNS-(S-linker B-T)y wherein STxB is the B-subunit of Shiga toxin linker A is a noncleavable linker linker B is a cleavable linker used to release at least one T or a noncleavable linker GNS is a gold nanostructure S is a sulfhydryl group and x and y can vary from 1 to 8,000 and T is a molecule selected from the group of: contrast agents, cytotoxic agents, prodrugs and antigens and x and y can vary from 1 to 10,000. These multivalent conjugates can be used in therapy to treat cancer and in medical imaging. Methods to distinguish normal cells from abnormal cells and methods for treating cancer by photothermal therapy or photothermal therapy and cytotoxic therapy are also part of the present invention.
