Evaluation of synergistic bioinhibitory effect between low-level laser irradiation and gold nanoparticles on MCF-7 cell line

Low-level laser therapy (LLLT) has been used in cancer therapy by either activating chemicals, known as photodynamic treatment (PDT), or by heating the cancer cells through laser photon energy, known as photothermal therapy (PTT). In order to improve the effectiveness of LLLT, gold nanoparticles (AuNPs) are promising candidates that can serve as photo-absorbing agents. The current study evaluated the synergistic bioinhibitory effect of 532 nm green laser irradiation and AuNPs on MCF-7 cell line. The photo-absorption of AuNPs in visible and near-infrared regions can potentially improve low-level laser therapy. In this work, cells were treated with AuNPs (50 ± 0.15nm) at concentrations of 20 μg/ml and 50 μg/ml prior to irradiation with 0.002, 0.020, 0.060, and 0.100 W at different time frames (60–900 s). In the absence of AuNPs during laser therapy, cell inhibition was ranged at 25–40%. Interestingly, when cells were irradiated with the lowest dose of 2.40 J.cm−2 (0.002 W at 60 s) in the presence of AuNPs at the highest concentration of 50 μg/ml, a dramatic drop in cell density of more than 90% was observed (p < 0.05). Considering this discovery, AuNPs-assisted low-level laser therapy seems to be a promising alternative to therapy using high power laser.