Studying IR Photohyperthermia Sensitized by Titanium Nitride Nanoparticles Using Tissue-Equivalent Phantoms

Abstract

Purpose: To use tissue-equivalent phantom for studies of thermal fields in biological tissues during IR photo hyperthermia with plasmonic titanium nitride nanoparticles (TiN NPs). Material and methods: Gel phantom based on polyacrylamide (PAA) with addition of naphtol green dye and intralipid 10% was created. Optical properties (reduced scattering coefficient) of phantom ingredients were determined using added absorber technique. Thermal field distribution was studied with IR thermal imaging technique. 50 nm plasmonic TiN NPs, synthetized by laser ablation in liquids, were used as sensitizers of photothermic action. Photothermal experiments were performed using two phantoms: a phantom with homogeneous optical parameters, which are relevant to biological tissues (absorption coefficient µa=0.35 сm-1, reduced scattering coefficient µ's=30 сm-1), and a phantom containing 0.02 mg/ml of TiN NPs, which increased absorption coefficient by Dµa=0.65 сm-1. The part of phantom with the NPs was located under 5 mm layer of NPs-free phantom. Photothermal effect was excited by CW laser irradiation of 830 nm wavelength and 16 W/cm2 intensity (900 mW, beam diameter: 1.3 mm) for 2 min. Thermal field distribution inside the phantom was measured by IR thermal camera. Results: A tissue-equivalent gel phantom with independently tunable absorption and scattering coefficients was designed. The phantom had cubic shape with 30 30 30 mm size. Results of photothermal experiments showed that the use of TiN NPs as sensitizers IR photohyperthermia leads to a significant increase in tissue temperature (up to 5 degrees Celsius) at distances up to 15 mm under the phantom surface. In addition, a simple experimental setup for measuring scattering coefficient of a liquid phantom ingredients was described. Conclusion: A simple method for preparation of PAA phantom for modelling photothermal heating of biological tissues and studying thermal fields distributions was described. The phantom is handy and allows one to quickly experimentally simulate the photothermal response of biological tissues, including tissues containing various spatial distributions of photosensitive NPs. TiN NPs experimentally confirmed to be an effective sensitizer of IR photothermal effect.