Abstract
The objective of this study was to evaluate microwave heating enhancements offered by iron/iron oxide nanoparticles dispersed within tissue-mimicking media for improving efficacy of microwave thermal therapy. The following dopamine-coated magnetic nanoparticles (MNPs) were considered: 10 and 20 nm diameter spherical core/shell Fe/Fe3O4, 20 nm edge-length cubic Fe3O4, and 45 nm edge-length/10 nm height hexagonal Fe3O4. Microwave heating enhancements were experimentally measured with MNPs dissolved in an agar phantom, placed within a rectangular waveguide. Effects of MNP concentration (2.5–20 mg/mL) and microwave frequency (2.0, 2.45 and 2.6 GHz) were evaluated. Further tests with 10 and 20 nm diameter spherical MNPs dispersed within a two-compartment tissue-mimicking phantom were performed with an interstitial dipole antenna radiating 15 W power at 2.45 GHz. Microwave heating of 5 mg/mL MNP-agar phantom mixtures with 10 and 20 nm spherical, and hexagonal MNPs in a waveguide yielded heating rates of 0.78 ± 0.02 °C/s, 0.72 ± 0.01 °C/s and 0.51 ± 0.03 °C/s, respectively, compared to 0.5 ± 0.1 °C/s for control. Greater heating enhancements were observed at 2.0 GHz compared to 2.45 and 2.6 GHz. Heating experiments in two-compartment phantoms with an interstitial dipole antenna demonstrated potential for extending the radial extent of therapeutic heating with 10 and 20 nm diameter spherical MNPs, compared to homogeneous phantoms (i.e., without MNPs). Of the MNPs considered in this study, spherical Fe/Fe3O4 nanoparticles offer the greatest heating enhancement when exposed to microwave radiation. These nanoparticles show strong potential for enhancing the rate of heating and radial extent of heating during microwave hyperthermia and ablation procedures.
Highlights
Several clinical trials have demonstrated the benefit of moderate hyperthermia (40 ◦C < T < 45 ◦C) adjuvant to radiation and/or chemotherapy for cancer therapy [1,2]
The results presented here indicate significant heating enhancements offered by 10 nm and 20 nm diameter spherical Fe/Fe3O4 magnetic nanoparticles (MNPs) similar to that reported with single-walled carbon nanotubes (SWCNT) in [26]
Microwave heating enhancements with spherical Fe/Fe3O4, hexagonal Fe3O4, and cubic Fe3O4 MNPs mixed within tissue-mimicking phantoms were experimentally evaluated
Summary
Several clinical trials have demonstrated the benefit of moderate hyperthermia (40 ◦C < T < 45 ◦C) adjuvant to radiation and/or chemotherapy for cancer therapy [1,2]. Heating within this temperature range increases tumor blood perfusion, thereby alleviating tumor hypoxia and facilitating improved chemotherapeutic delivery, as well as stimulates a mild anti-tumor immune response [3]. A significant challenge associated with hyperthermia and thermal ablation treatments is the localized delivery of therapeutic energy to minimize thermal damage to healthy tissue, while ensuring adequate thermal dose delivery to the tumor target
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