Towards the Standardization of Photothermal Measurements of Iron Oxide Nanoparticles in Two Biological Windows

A systematic study on laser-induced heating carried out in two biological windows (800 nm and 1053 nm) for Fe3O4 nanoparticles in water suspension showed evidence of the strong dependence of the specific absorption rate (SAR) on extrinsic parameters such as the vessel volume or laser spot size. The results show that a minimum of 100 mu L must be used in order to obtain vessel-size-independent SARs. In addition, at a constant intensity but different laser powers and spot size ratios, the SARs can differ by a three-fold factor, showing that the laser power and irradiated area strongly affect the heating curves for both wavelengths. The infrared molecular absorber IRA 980B was characterized under the same experimental conditions, and the results confirm the universality of the SARs' dependence on these extrinsic parameters. Based on these results, we propose using solutions of IRA 980B as a standard probe for SAR measurements and employing the ratio SAR(iron oxide)/SAR(IRA 980B) to compare different measurements performed in different laboratories. This measurement standardization allows us to extract more accurate information about the heating performance of different nanoparticles.

Automated summary

A systematic study on laser-induced heating was conducted on Fe3O4 nanoparticles in water suspension in two biological windows (800 nm and 1053 nm). It was found that the specific absorption rate (SAR) strongly depends on extrinsic parameters such as vessel volume or laser spot size. Utilizing solutions of IRA 980B as a standard probe for SAR measurements and comparing different measurements in different laboratories using the ratio SAR(iron oxide)/SAR(IRA 980B) allows for more accurate evaluation of the heating performance of different nanoparticles.