The current invention relates to development of new formulation containing gold nanoparticles (AuNPs) with bi-functional recombinant fusion proteins TRAF(C) for the delivery of anticancer drugs and nucleic acids to HER2+ cancers. Using the combinatorial approach, we designed gold nanoparticle-based targeted drug delivery system (TDDS) or (Au-TR-DX-si) by combining AuNPs with bi-functional recombinant fusion protein TRAF(C) (TR), doxorubicin (DX) and siRNA (si). The recombinant protein based gold nanoparticles formulations are stable and homogenous as revealed by several physicochemical studies. In addition, the engineered fusion protein TRAF (C) has the ability to target selectively to HER2+ receptors overexpressed in ovarian cancer cells (SK-OV-3).