Self-assembly of biogenic gold nanoparticles and their use to enhance drug delivery into cells.

Integration of the principles of green chemistry into nanotechnology is one of the key issues in nanobio-science research. There is a growing need for development of a synthesis method for producing environmentally harmless nanoparticles in order to avoid adverse effects in medical applications. Here, we report the use of a simple and rapid in vivo biosynthesis method for the preparation of gold nanoparticles (AuNPs) using heavy metal binding proteins (HMBPs) in recombinant Escherichia coli. The HMBPs were found to act as reducing, stabilizing, and capping agents to form the spherical nanoparticles with 5-20 nm in diameter. The size and the shape of AuNPs were modulated by varying the concentration ratio of recombinant proteins in the medium. Only 20 min was required to form AuNPs at room temperature, suggesting that the reaction rate of the proposed method is faster than that of the chemical methods commonly used for nanoparticle synthesis. The AuNPs could be applied as drug carriers in therapeutic applications to improve drug delivery, since they exhibit higher biocompatibility and less toxic effects than chemically synthesized materials. To achieve high cytotoxicity for cancer chemotherapy, doxorubicin (Dox) was released from AuNPs, which can be a more efficient anti-cancer agent than free Dox.