Noble metal, oxide and chalcogenide-based nanomaterials from scalable phototrophic culture systems

Phototrophic cell or tissue cultures can produce nanostructured noble metals, oxides and chalcogenides at ambient temperatures and pressures in an aqueous environment and without the need for potentially toxic solvents or the generation of dangerous waste products. These "green" synthesized nanobiomaterials can be used to fabricate biosensors and bio-reporting tools, theranostic vehicles, medical imaging agents, as well as tissue engineering scaffolds and biomaterials. While successful at the lab and experimental scales, significant barriers still inhibit the development of higher capacity processes. While scalability issues in traditional algal bioprocess engineering are well known, such as the controlled delivery of photons and gas-exchange, the large-scale algal synthesis of nanomaterials introduces additional parameters to be understood, i.e., nanoparticle (NP) formation kinetics and mechanisms, biological transport of metal cations and the effect of environmental conditions on the final form of the NPs. Only after a clear understanding of the kinetics and mechanisms can the strain selection, photobioreactor type, medium pH and ionic strength, mean light intensity and other relevant parameters be specified for an optimal bioprocess. To this end, this mini-review will examine the current best practices and understanding of these phenomena to establish a path forward for this technology.