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

D. VALDÉS; T. TORRES MOLINA; A.C. MORENO MALDONADO; NADAL, MARCELA S.; E. DE BIASI; R.D. ZYSLER; G.F. GOYA; E. LIMA JR.

Svetlogorsk

Congreso; International Baltic Conference on Magnetism (IBCM 2021); 2021

Immanuel Kant Baltic Federal University

The formation and control of magnetic nanoparticle (MNP) arrangements during thehyperthermia experiment (HE) for viscosities similar to those of the intracellular environment is relevant for the enhancement of the specific power absorption [1]. A gel with adjustable viscosity such as polyacrylamide gel may work as a phantom to emulate intracellular viscosity [2]. In this work, maghemite MNPs with 25 nm diameter (σ = 7 nm) were prepared through the thermal decomposition method with a subsequent annealing. We determined the saturation magnetization (MS = 68 emu g−1 at room temperature), the mean blocking temperature (<TB> ∼ 10 K) and the effective anisotropy constant (K ∼ 1 ×104 erg cm−3). The hydrophobic character of the as-synthesized nanoparticles was changed to hydrophilic by a post-synthesis glucose coating. Two types of 4% polyacrylamide gel phantoms with dispersed MNPs were prepared: one conventionally jellified (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 for gels exposed to the ac field (see Figure 1). Power absorption experiments were carried out under ac magnetic fields with amplitude H0 = 550 Oe and frequency f = 400 kHz. The temperature increment was monitored through a thermographic camera and spatio-temporal profiles were obtained from the videos. Qualitative and quantitative differences were observed between gels.To conclude, we obtained considerable temperature increments for MNPs dispersed in cytosol-viscosity emulating medium and confirmed the formation of chain-like arrangements for samples jellified in situ in the HE, which is of great importance to optimize the application in cells.