The synergistic effect of photodynamic therapy and photothermal therapy in the presence of gold-gold sulfide nanoshells conjugated Indocyanine green on HeLa cells.

BACKGROUND: Photodynamic therapy (PDT) and photothermal therapy (PTT) are two known optical remedies of cancer. PTT can be combined with other therapies. One of the limitations of optical therapies is the penetration of light into biological tissues, which reduces its effectiveness due to usage of photosensitizers and PTT agents, which are absorbed in the NIR region that provides the maximum penetration. For instance, Indocyanine green (ICG) serves as a photosensitizer and Gold nanostructures as agents for PTT. GGS is a gold nanoshell with two absorption peaks in the NIR and visible regions. The aim of this study is to evaluate the synergistic effect of PDT and PTT in the presence of GGS conjugated with ICG.

METHODS: After synthesizing GGS, ICG was conjugated with GGS. The specifications and cytotoxicity of agents were identified. Cells were irradiated by an 808nm laser with or without the agents and three laser outputs were achieved, with each having four different exposure times. The viability of treated cells was determined via MTT assay.

RESULT: The irradiation of the laser did not produce any significant effect by itself or in the presence of GGS. The maximum cell death recorded for GGS, ICG and GGS-ICG were 15±7%, 50±3% and 31±3% respectively. ICG and GGS-ICG differs significantly for exposures higher than 2250J/cm(2).

CONCLUSION: The conjugate was provided through a simple process and a greater chemical stability compared to GGS was achieved. Moreover, it induced a stronger photodynamic and photothermal effect on the cells. This is a promising result which can help enhance the effectiveness of a minimally invasive treatment.