Prof. Younan Xia, Washington University, St. Louis MO

Putting Nanomaterials to Work for Biomedical Research

Nanomaterials are finding widespread use in diagnosis and treatment of various diseases. In this talk, I will focus on gold nanocages, a novel class of nanomaterials with hollow interiors and porous walls that can be conveniently prepared through a galvanic replacement reaction between silver nanocubes and HAuCl4 in an aqueous solution. By controlling the molar ratio of silver to HAuCl4, the localized surface plasmon resonance peaks of the resultant nanostructures can be continuously tuned from the blue (400 nm) to the near-infrared (1200 nm). These nanostructures are characterized by extraordinarily large cross-sections for absorption and scattering of light. Optical measurements indicate that the 35-nm gold nanocage has a scattering cross section of ~0.8x10-15 m2 and an absorption cross section of ~7.3x10-15 m2; both of them are more than five orders of magnitude greater than those of typical organic chromophores. Due to the photothermal effect, exposure of gold nanocages to a camera flash in air resulted in the instant melting and conversion of gold nanocages into spherical nanoparticles. Gold nanocages can be easily bioconjugated with ligands to target the receptors on specific cancer cells. Currently, we are developing this novel class of nanomaterials as both a contrast agent for optical imaging in early-stage detection of cancer and as a therapeutic agent for photothermal treatment of cancer, and as nanoscale capsules for targeted drug delivery. If time allows, I will also briefly talk about our recent work related to the design of novel scaffolds based on electrospun nanofibers for tissue engineering applications.