Study of optical properties of gold nanoparticles embedded in normal, benign, and malignant breast tissues

Abstract

In this work, the complex dielectric permittivity of breast tissue is calculated for different growth rates of benign and malignant tumors using the Maxwell Garnett (MG) effective medium theory. The results show a wide variability of the dielectric properties depending on the nature and the volume fraction of the cancer cells. The benign-normal and malignant-normal heterostructures are denoted respectively x-B/N and x-M/N where x is the volume fraction of cancer cells in the breast tissue. The real and imaginary parts of dielectric permittivity increases when the growth rates of benign and malignant tumors increase and decrease when the microwave frequency increases from 0.5 to 8 GHz. In the aim to use the gold nanoparticles (GNPs) in breast cancer therapy, both for a better image diagnostic and photothermal therapy (PTT), we present here a study on the optical properties of GNPs embedded in normal, benign and malignant breast tissue in the frequency range from 0.5 GHz to 8 GHz. optical band gap energy for GNP is located in [0.5eV−1.46eV](±0.06eV), [0.72eV−1.20eV](±0.04eV) and [0.11eV−0.74eV](±0.02eV) ranges for Normal, Benign and Malignant breast tissues, respectively. We use the Finite Element Method (FEM) to evaluate the spectra of the dielectric and optical parameters of GNPs namely: complex dielectric permittivity, absorption cross section, reflectivity, dielectric loss function and conductivity, the surface plasmons resonance (SPR) properties are deduced from these spectra. The obtained results show that the SPR-peak of the GNPs is located in the Visible (Vis), near infrared (NIR) and short wavelength infrared (SWIR) bands when they are embedded respectively in the normal, benign and malignant breast tissue. For these three tissues when the microwave frequency increases from 0.5 to 8 GHz, the SPR-peak position λmax shifts towards the short wavelengths. The calculations show that in the vicinity of λmax the dielectric loss function take a maximum value and the reflectivity change strongly. These results show that the absorption and dielectric loss peaks are less wide for the high microwave frequencies and very wide for the low frequencies, which also influences the difference between the asymptotic values of the real part of permittivity and of the reflectivity. These results make it possible to identify the nature of the breast tumor using the GNPs in the sensors based on the of SPR phenomenon. The optical properties of GNPs depending on their size and on the tumor growth rate in the breast tissue are also studied and discussed. The study carried out represents a feasibility proposal for the use of GNPs for determining the degree of breast tumor progression and estimate the good performance of using the GNPs for the selective destruction of breast cancer cells.