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 nanospheres have been synthesised 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 amides A and B is pronounced at a depth of maximum temperature rise compared with other positions in tissue phantom. Observations for change in band of amide I, amide II, and amide III are found to be responsible for damage to collagen ultra-structure. Variation in the concentration of gold nanostructures shows the potentiality of localised hyperthermia treatment subjected to NIR radiation through a proposed free radical mechanism.

Keywords:

• Collagen
• laser
• bio-heat transfer
• hyperthermia
• photo thermotherapy
• structure
• denaturation

Acknowledgements

The authors thank late Dr. P.K. Sehgal of the Central Leather Research Laboratory, Chennai, India, for providing the collagen and Dr. Shamit Bakshi, Mechanical Engineering Department, IIT Madras for providing the laser. N. S. thanks Dr. T. Pradeep’s group, Chemistry Department, IIT Madras for help with the preparation of gold nanostructures.

Disclosure statement

The authors declare no conflict of interest with respect to the present paper.