Escherichia coli-mediated palladium nanoparticle synthesis

Palladium nanoparticles (Pd NPs) offer a wide range of novel and exciting applications in catalysis, medicine, engineering, and electronics. Currently, these NPs are synthesized using conventional physical and chemical methods. These methods have several disadvantages as the physical methods usually require energy-intensive processes, and the chemical methods often involve harmful solvents or produce toxic by-products. Lately, more environmentally friendly approaches for the synthesis of NPs have emerged using microorganisms. Several bacteria were reported for their ability to biosynthesize Pd NPs. In this process, Pd ions are biologically transported into the bacterial cells and subsequently reduced to metallic Pd, forming Pd NPs. The current knowledge on the proteins, enzymes, or pathways involved in the transport and reduction of Pd is very limited, which hinders the ability to genetically engineer bacterial strains capable of producing Pd NPs with fine-tuned properties. This thesis provides new insights on the genes that might be responsible for the transport of Pd ions in E. coli, the toxicological effects of Pd, and the potential detoxification strategies that E. coli employ to deal with Pd stress. In addition, this thesis describes an E. coli-mediated approach for the synthesis of 1-2 nm Pd and Pd-Fe NPs displaying novel ferromagnetic properties. At the same time, this thesis shows different methods for the characterization of the magnetic properties of these NPs in biological samples.