Abstract-Terahertz three-dimensional monitoring of nanoparticle-assisted laser tissue soldering

Junliang Dong, Holger Breitenborn, Riccardo Piccoli, Lucas V. Besteiro, Pei You, Diego Caraffini, Zhiming M. Wang, Alexander O. Govorov, Rafik Naccache, Fiorenzo Vetrone, Luca Razzari, and Roberto Morandotti

Schematic showing the range of simultaneous photothermal reactions during nanoparticle-assisted laser tissue soldering.

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-11-4-2254

In view of minimally-invasive clinical interventions, laser tissue soldering assisted by plasmonic nanoparticles is emerging as an appealing concept in surgical medicine, holding the promise of surgeries without sutures. Rigorous monitoring of the plasmonically-heated solder and the underlying tissue is crucial for optimizing the soldering bonding strength and minimizing the photothermal damage. To this end, we propose a non-invasive, non-contact, and non-ionizing modality for monitoring nanoparticle-assisted laser-tissue interaction and visualizing the localized photothermal damage, by taking advantage of the unique sensitivity of terahertz radiation to the hydration level of biological tissue. We demonstrate that terahertz radiation can be employed as a versatile tool to reveal the thermally-affected evolution in tissue, and to quantitatively characterize the photothermal damage induced by nanoparticle-assisted laser tissue soldering in three dimensions. Our approach can be easily extended and applied across a broad range of clinical applications involving laser-tissue interaction, such as laser ablation and photothermal therapies.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Turning light energy into heat to fight disease

IMAGE: SENSING THE SIZE-DEPENDENT LIGHT-TO-HEAT CONVERSION EFFICIENCY OF NANOPARTICLES BY TERAHERTZ RADIATION. 

CREDIT: ROBERTO MORANDOTTI

Scientists have developed a method involving terahertz radiation to monitor temperature changes when laser light is focused on tiny gold particles in water

https://www.eurekalert.org/pub_releases/2019-12/aiop-tle121619.php

WASHINGTON, D.C., December 17, 2019 -- An emerging technology involving tiny particles that absorb light and turn it into localized heat sources shows great promise in several fields, including medicine. For example, photothermal therapy, a new type of cancer treatment, involves aiming infrared laser light onto nanoparticles near the treatment site.

Localized heating in these systems must be carefully controlled since living tissue is delicate. Serious burns and tissue damage can result if unwanted heating occurs in the wrong place. The ability to monitor temperature increases is crucial in developing this technology. Several approaches have been tried, but all of them have drawbacks of various kinds, including the need to insert probes or inject additional materials.

In this week's issue of APL Photonics, from AIP Publishing, scientists report the development of a new method to measure temperatures in these systems using a form of light known as terahertz radiation. The study involved suspensions of gold nanorods of various sizes in water in small cuvettes, which were illuminated by a laser focused on a small spot within the cuvette.

The tiny gold rods absorbed the laser light and converted it to heat that spread through the water by convection. "We are able to map out the temperature distribution by scanning the cuvette with terahertz radiation, producing a thermal image," co-author Junliang Dong said.

The study also looked at the way the temperature varied over time. "Using a mathematical model, we are able to calculate the efficiency by which the gold nanorod suspensions converted infrared light to heat," said co-author Holger Breitenborn.

The smallest gold particles, which had a diameter of 10 nanometers, converted laser light to heat with the highest efficiency, approximately 90%. This value is similar to previous reports for these gold particles, indicating the measurements using terahertz radiation were accurate.

Although the smaller gold rods had the highest light-to-heat conversion efficiency, the largest rods -- those with a diameter of 50 nanometers -- displayed the largest molar heating rate. This quantity has been recently introduced to help evaluate the use of nanoparticles in biomedical settings.

"By combining measurements of temperature transients in time and thermal images in space at terahertz frequencies, we have developed a noncontact and noninvasive technique for characterizing these nanoparticles," co-author Roberto Morandotti said. This work offers an appealing alternative to invasive methods and holds promise for biomedical applications.

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The article, "Quantifying the photothermal conversion efficiency of plasmonic nanoparticles by means of terahertz radiation," is authored by H. Breitenborn, J. Dong, R. Piccoli, A. Bruhacs, L.V. Besteiro, A. Skripka, Z. Wang, A.O. Govorov, L. Razzari, F. Vetrone, R. Naccache and R. Morandotti. The article will appear in the journal APL Photonics on Dec. 17, 2019 (DOI: 10.1063/1.5128524). After that date, it can be accessed at https://aip.scitation.org/doi/10.1063/1.5128524.

Abstract-Multi-dimensional Imaging in the Terahertz Regime for Theranostic Applications

Holger Breitenborn, Rafik Naccache, Anna Mazhorova, Matteo Clerici, Riccardo Piccoli, Larousse K. Khorashad, Alexander O. Govorov, Luca Razzari, Fiorenzo Vetrone, and Roberto Morandotti

https://www.osapublishing.org/abstract.cfm?uri=cleo_at-2017-ATu3A.6&origin=search

We demonstrate a novel terahertz radiation-based joint thermal-hyperspectral imaging method for theranostic applications. Hyperspectral imaging of a drug formulation was realized in the stratum granulosum of skin, in the presence of plasmonically heated gold nanoparticles.