Plasmonic Photothermal Therapy in Third and Fourth Biological Windows

TL;DR

This paper introduces a novel nanoparticle design approach for plasmonic photothermal therapy in the 3rd and 4th biological windows, achieving smaller size and higher efficiency, enabling deeper tissue treatment with less collateral damage.

Contribution

It proposes a versatile design method for absorber-dominant nanostructures in new biological windows, reducing size and increasing absorption efficiency compared to traditional designs.

Findings

Up to 40% size reduction of nanoparticles.

Two-fold increase in absorption efficiency.

Photothermal performance boosted by 250% in the 4th window.

Abstract

The recently reported 3rd and 4th biological transparency windows located respectively at 1.6-1.9um and 2.1-2.3um promise deeper tissue penetration and reduced collateral photodamage, yet they haven't been utilized in photothermal therapy applications. Nanoparticle based plasmonic photothermal therapy poses a nontrivial optimization problem in which the light absorption efficiency of the nanoparticle has to be maximized subject to various constraints that are imposed by application environment. Upscaling the typical absorber-dominant nanoparticle designs (rod, sphere etc.) that operate in the 1st and 2nd transparency windows is not a viable option as their size gets prohibitively large for cell intrusion and they become scatterer-dominant. The present study addresses this issue and suggests a versatile approach for designing both lithography based and self-assembling absorber dominant nanostructures for the new transparency windows, while keeping their size relatively small. The proposed nanoparticles demonstrate up to 40% size reduction and 2-fold increase in absorption efficiency compared to the conventional nanobar design. The overall photothermal performance per nanoparticle in the 4th window is boosted up by 250% compared to the 2nd window.