Thermoplasmonics of Platinum nanoparticles

Plasmonic nanoparticles can absorb part of incident laser energy and liberate it into the local environment in the form of heat . This effect can be used in an advantageous manner, for thermoplasmonic applications in the life... [ view full abstract ]

Plasmonic nanoparticles can absorb part of incident laser energy and liberate it into the local environment in the form of heat . This effect can be used in an advantageous manner, for thermoplasmonic applications in the life sciences, nano-medicine, and bio-medical engineering. Current efforts focus on the development of NIR resonant plasmonic nanoparticles with, sizes optimized for delivery into tumors (d=50-100 nm), higher light-to-heat conversion efficiency and less toxicity for bio-applications.

Here, we quantify the extraordinary thermoplasmonic properties of Platinum Nanoparticles, PtNPs (d=50-70 nm), via both experiment and simulation, and their efficiency in photothermal cancer therapy demonstrated in vitro. 

Using a novel bio-compatible assay, we directly quantified the temperature profile of individual irradiated PtNP and results are backed-up by Finite Element Modeling (FEM). Toxicity and photothermal cancer therapy of PtNPs for human SK-OV-3 ovarian cancer cells assessed in vitro.⁵  

We find that PtNPs (d=50-70 nm), are capable of reaching temperatures as high as 700 °C while maintaining structural integrity (Figure 1), under NIR irradiation which can penetrate deeper into the bio-material, e.g., tumor tissue. Thus, the plasmonic properties of PtNPs and their low toxicity, in connection with the commercial availability of high quality PtNPs, makes the future bright for utilizing these exceptional particles for hot bio-engineering purposes.

Caption: 

(a) Illustration (not to scale) of temperature measurements. A tightly focused 1064 nm laser (red cone) irradiates a PtNP immobilized onto a coverslip coated with a lipid-bilayer (dark green) incorporating phase-sensitive fluorophores which partition into the melted area (light green). r_m denotes the radius of the melted area around the heated NP and T_m is the phase transition temperature. (b) Confocal images showing the partitioning of phase-sensitive fluorophores into the melted area around an irradiated 70 nm PtNP. The laser powers used are 85 mW, 195 mW and 315 mW, respectively, from left to right. Scale bar is 10 μm. (c) Temperature profile around a 70 nm PtNP irradiated by a 1064 nm laser with 195 mW. The white symbols are experimentally determined temperature profile (n = 7 experiments) and the red solid line shows the temperature profile predicted via FEM.