In situ formation and thermographical analysis of nanoparticle chain-like arrangements in polyacrylamide phantom during hyperthermia experiments

DANIELA P. VALDÉS; TEOBALDO E. TORRES; ANA C. MALDONADO; MARCELA S. NADAL; EMILIO DE BIASI; ROBERTO D. ZYSLER; GERARDO F. GOYA; ENIO LIMA JR.

Svetlogorsk

Conferencia; IV International Baltic Conference on Magnetism 2021 - IBCM 2021; 2021

The formation and control of magneticnanoparticle (MNP) arrangements during the hyperthermia experiment (HE) forviscosities similar to those of the intracellular environment is relevant forthe enhancement of the specific power absorption [1]. A gel with adjustableviscosity such as polyacrylamide gel may work as a phantom to emulateintracellular viscosity [2].In this work,γ-Fe2O3 MNPs with 25 nm diameter(σ = 7 nm) were prepared through the thermal decomposition method with asubsequent annealing. We determined the saturation magnetization (MS= 68 emu g−1 at room temperature), the mean blocking temperature (<TB>∼ 10 K) and the effective anisotropyconstant (K ∼ 1 ×104 erg cm−3).The hydrophobic character of the as-synthesized nanoparticles was changed tohydrophilic by a post-synthesis glucose coating. Two typesof 4% polyacrylamide gel phantoms with dispersed MNPs were prepared: one conventionallyjellified (dispersed MNPs) and another one jellified during the HE with an ac field with amplitude H0 =200 Oe and frequency f = 630 kHz, each one at MNP concentrations of 0.1 and 0.5% wt. Images were taken with a cryo-focused electron and ion beam (Cryo-FIB-SEM)microscope, where the formation of chains-like structures was confirmed forgels exposed to the ac field (see Figure 1). Power absorption experiments were performedunder ac magnetic fields with amplitude H0 = 550 Oe and frequency f= 400 kHz. The temperature evolution was monitored through a thermographic cameraand spatio-temporal profiles were obtained from the videos. Qualitative andquantitative differences were observed between the gel phantoms.To conclude, we obtained considerabletemperature increments for MNPs dispersed in cytosol-viscosity emulating mediumand confirmed the formation of chain-like arrangements for samples jellified insitu in the HE, which is of great importance to optimize the application incells. [1]D.P. Valdés, Phys. Rev. Applied 14, 014023 (2020)[2] T. Yano, Biosci. Biotechnol. 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