Non–fourier thermal transport induced structural hierarchy and damage to collagen ultrastructure subjected to laser irradiation

Abstract

Comprehending the mechanism of thermal transport through biological tissues is an important factor for optimal ablation of cancerous tissues and minimising collateral tissue damage. The present study reports detailed mapping of the rise in internal temperature within the tissue mimics due to NIR (1064 nm) laser irradiation, both for bare mimics and with gold nanostructures infused. Gold nanostructures such as mesoflowers and nano spheres have been synthesized and used as photothermal converters to enhance the temperature rise, resulting in achieving the desired degradation of malignant tissue in targeted region. Thermal history was observed experimentally and simulated considering non–Fourier dual phase lag (DPL) model incorporated Pennes bio-heat transfer equation using COMSOL Multiphysics software. The gross deviation in temperature i.e. rise from the classical Fourier model for bio-heat conduction suggests additional effects of temperature rise on the secondary structures and morphological and physico-chemical changes to the collagen ultrastructures building the tissue mass. The observed thermal denaturation in the collagen fibril morphologies have been explained based on the physico–chemical structure of collagen and its response to thermal radiation. The large shift in frequency of amide A and B are pronounced at depth of maximum temperature rise compared to other positions in tissue phantom. Observations for change in band of Amide I, Amide II, and Amide III respectively are found to be responsible for damage to collagen ultra-structure. Variation in concentration of gold nanostructures shows the potentiality of localized hyperthermia treatment subjected to NIR radiation through a proposed free radical mechanism.