Manipulating metal uptake to tune quantum dot synthesis in living bacteria

Bacteria have been shown to synthesize a variety of metallic and semiconductor nanomaterials. Bacterial naturally have pathways that interact with and transport metal ions, including iron, manganese, and selenium, and often these pathways have promiscuous activity towards less biologically relevant metals such as cadmium and arsenic. For material synthesis inside of cells, it is key to create a suitable chemical environment with sufficient metal ion concentrations for nucleation and growth of particles. Towards this goal, we have investigated how multiple transport proteins within bacterial cells impact the internal concentration of cadmium ions. We have identified several metal ion transport proteins that import or export cadmium across the inner membrane of the cell. These transport pathways are both active and passive. Through a combination of experimental measurements and theoretical modeling, we have identified how different combinations of these proteins establish the concentration of cadmium during particle synthesis. We then leverage these results to engineer cells for the synthesis of cadium sulfide nanoparticles inside of living cells, using biological parameters to tune the properties of the resultant nanoparticles.