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(743d) Photo-Activation of Near Infra-Red Light Absorbing Nanoparticles : Continuous Wave and Pulse Irradiation

Authors: 
Shin, J., University of Minnesota
Zasadzinski, J. A., University of Minnesota
Ogunyankin, M. O., University of Minnesota

Currently, a popular area in nanomedicine is the implementation of plasmonic gold nanoparticles for cancer treatment. The wide-ranging implementation of gold nanoparticles for medical applications is based largely on the unique and highly tunable optical properties that gold nanomaterials provide. Hollow gold nanoparticles (HGNs) have been appealing to medical applications, since the HGN-absorbance maximum can be easily tuned to 700 – 900 nm, near infra-red (NIR) light, by adjusting the ratio of the shell thickness to the nanoparticle diameter. The advantage of NIR is that it can penetrate several centimeters of soft tissues without showing any significance harmful effect on tissues. In previous works, the HGN synthesis, which involves the galvanic exchange of gold on a silver nanoparticle template, provides a relatively polydisperse population, which broadens the absorption maximum. We have developed new methods of creating monodispersed hollow gold nanoparticles in different sizes (25 – 40 nm) and shapes (nanospheres and nanocubes). Moreover, we optimized the reaction to synthesize nanoparticles as small as 10 nm, by adjusting the reaction time. We use NIR light in two different ways to irradiate the HGNs, continuous wave and pico-second pulsed laser light. We show two different mechanism that the HGNs are photo-activated. We present the effect of size, shape, and concentration of HGNs at a specific power density with both continuous wave and pico-second pulsed laser irradiation.  Nanoparticles were continuously irradiated with NIR for certain amount of time (e.g., 5 min) at a specific power density; substantial increments in temperature were observed. We compared the size, shape, and concentration effect of nanoparticles on heating. On the other way, nanoparticles were irradiated with picosecond NIR pulses. The generation of nanobubbles around nanoparticles were detected as evidence of fast (picoseconds) NIR absorption. We compared the threshold energy for nanobubble generation in different sizes of nanoparticles.