Introduction
Application of near-infrared absorbing nanostructures can induce hyperthermia, in addition to providing more efficient  photothermal effects. Gold-gold sulfide (GGS) is considered as one of these nanostructures. This study was performed on a tissue-equivalent optical-thermal phantom to determine the temperature profile in the presence and absence of GGS and millisecond pulses of a near-infrared laser. Moreover, the feasibility of hyperthermia induction was investigated in a simulated tumor.
Materials and Methods
A tumor with its surrounding tissues was simulated in a phantom made of Agarose and Intralipid. The tumor was irradiated by 30 laser pulses with durations of 30, 100, and 400 ms and fluences of 40 and 60 J/cm². Temperature variations in the phantom with and without GGS were recorded, using fast-response sensors of a digital thermometer, placed at different distances from the central axis at three depths. The temperature rise was recorded by varying duration and fluence of the laser pulses.
Results
The rise in temperature was recorded by increasing laser fluence and number of pulses for three durations. The temperature profile was obtained at each depth. The presence of GGS resulted in a significant increase in temperature in all cases (P<0.035). Also, the laser temperature had a slower reduction in the presence of GGS, compared to its absence after turning the laser off (P<0.001).
Conclusion
The millisecond laser pulses could induce hyperthermia in a relatively large target tissue volume. GGS as a simple and cost-effective synthesized nanostructure could induce localized hyperthermia in the desired region during near-infrared laser irradiation.