Plasmonic Nanocages as Photothermal Transducers for Nanobubble Cancer Therapy

Plasmonics is emerging from among the most promising means for generating and controlling thermal energy at the nanoscale. In this approach, metallic nanoparticles are laser heated at plasmon resonant wavelengths that depend on the size, shape and properties of the particles. Key attributes of this method include remote optical activation, nanoscale resolution and efficient photothermal transduction. In this presentation we examine photothermal transduction using laser-pulsed colloidal gold nanocage and nanoframe structures. We explore fundamental aspects of this process using computational models that predict the absorption spectra of the nanoparticles, photothermal transduction at plasmon resonance, heat transfer to the fluid and the dynamics of bubble generation under conditions of superheating. We demonstrate that gold nanocages and nanoframes have a substantial absorption cross-section in the NIR that is essentially independent of orientation. In addition, our thermofluidic analysis indicates that by carefully tuning applied power and pulse duration, the generation of controlled nanobubbles is possible without damaging the nanoparticles. Hence, gold nanocages and nanoframes could offer immediate and very selective therapeutic options when properly uptaken since explosive nanobubbles can cause immediate lysis of targeted cells while preventing damage to nearby healthy tissue due to strong cooperative heating effects.