Key factors influencing magnetic nanoparticle-based photothermal therapy: physicochemical properties, irradiation power, and particle concentration .

A collection of magnetic nanoparticles with average particle sizes in the range between 9 and 78 nm were prepared using several synthetic approaches that also provided different particle morphologies (spherical, octahedral and flowers). Some of these particles were also subsequently coated with different molecules in order to generate a set of materials that allowed us to evaluate the impact that the particle size, shape and coating had on the heating capacity of the nanoparticles when exposed to near infrared (NIR) laser light. Moreover, one of the prepared materials (octahedral particles of ∼32 nm coated with dextran) was used to perform an assay to study the possible use of this material in the frame of photothermal treatments to trigger cell death. It was found that both the laser power and the particle concentration played a significant role in the reduction of the cell viability. Under the most extreme conditions of laser power and nanoparticle concentration, cell viability was reduced to 11% of the whole cell population using only 10 min exposure to laser light. These results open the possibility of further studies of photothermal treatments using magnetic nanoparticles, a material already approved for clinical practice.