Single-Cell Photothermal Analysis Induced by MoS₂ Nanoparticles by Raman Spectroscopy

Area of Science:

• Nanomedicine
• Biophysics
• Materials Science

Background:

• Two-dimensional nanomaterials like molybdenum disulfide (MoS2) nanosheets are explored for cancer diagnosis and treatment.
• Understanding MoS2 nanosheet-cell interactions at the single-cell level is crucial for optimizing their therapeutic applications and assessing cytotoxicity.

Purpose of the Study:

• To investigate the photothermal effect of MoS2 nanosheets on single cancer cells using confocal micro-Raman spectroscopy.
• To map the temperature distribution within cells upon laser irradiation of MoS2 nanosheets.
• To explore the influence of MoS2 nanosheet aggregation on cellular heating.

Main Methods:

• Confocal micro-Raman spectroscopy was employed to analyze the water O-H stretching band (around 3,400 cm⁻¹).
• This Raman-based thermometry approach was used to create thermal maps of single human breast cancer MCF7 cells targeted with MoS2 nanosheets.
• The method avoids issues of fluorophore instability common in fluorescence-based temperature measurements under laser irradiation.

Main Results:

• Irradiation of MCF7 cells with MoS2 nanosheets induced a significant photothermal effect.
• The photothermal effect was notably enhanced in the presence of MoS2 nanosheet aggregates.
• Laser-induced heating was localized near aggregated MoS2 nanosheets, which tended to accumulate near the cytoplasmic membrane.

Conclusions:

• MoS2 nanosheets exhibit a potent photothermal effect in cancer cells, influenced by aggregation.
• Raman spectroscopy provides a robust method for measuring temperature changes at the single-cell level.
• These findings are vital for refining MoS2 nanosheet fabrication for improved cancer photothermal therapy.