Structural and Thermomagnetic Properties of Gallium Nanoferrites and Their Influence on Cells In Vitro

Abstract

Magnetite and gallium substituted cuboferrites with a composition of Ga_xFe_3-xO₄ (0 ≤ x ≤ 1.4) were fabricated by thermal decomposition from acetylacetonate salts. The effect of Ga³⁺ cation substitution on the structural and thermomagnetic behavior of 4-12 nm sized core-shell particles was explored by X-ray and neutron diffraction, small angle neutron scattering, transmission electron microscopy, Mössbauer spectroscopy, and calorimetric measurements. Superparamagnetic (SPM) behavior and thermal capacity against increasing gallium concentration in nanoferrites were revealed. The highest heat capacity typical for Fe₃O₄@Ga_0.6Fe_2.4O₄ and Ga_0.6Fe_2.4O₄@Fe₃O₄ is accompanied by a slight stimulation of fibroblast culture growth and inhibition of HeLa cell growth. The observed effect is concentration dependent in the range of 0.01-0.1 mg/mL and particles of Ga_0.6Fe_2.4O₄@Fe₃O₄ design have a greater effect on cells. Observed magnetic heat properties, as well as interactions with tumor and healthy cells, provide a basis for further biomedical research to use the proposed nanoparticle systems in cancer thermotherapy (magnetic hyperthermia).

Keywords: Mössbauer spectroscopy; X-ray and neutron diffraction; calorimetric measurements; in vitro cell culture; small angle neutron scattering; superparamagnetic nanoparticles.

Figure 1

Structural (a) and magnetic (b) ordering in M@Ga_0.6 (10 K). In the left panel, the blue dots represent the Td sublattice while the red dots correspond to the Oh sublattice. In the right panel, the red arrows illustrate Fe²⁺ magnetic moments, while the blue and green arrows are related to Fe³⁺ moments.

Figure 2

X-ray diagrams collected at room temperature: (a) set of both series of nanoparticle patterns with the inset legend of nominal compositions; (b) lattice constant and crystalline size versus gallium content, where the curves are guides to the eye only; (c) neutron data refinement of M@Ga_0.2 core-shell system at 10 K and (d) iron in-site magnetic moment dependence versus gallium content of M@Ga_x series collected at 10 K. The red triangles correspond to Fe²⁺ magnetic moments on the Oh sublattice, while the blue triangles correspond to Fe³⁺ moments occupying the Th sublattice.

Figure 3

The square structure factors ${\left|F_{\left(hkl\right)}\right|}^2$ of structural reflections, (311)—dotted curves, and (220)—solid curves as a function of gallium content for series M@Ga_x were obtained from X-ray (red symbols) and neutron (blue symbols) data analysis. The curves are guides to the eye only.

Figure 4

TEM images of nanosystems: Ga_0.2@M (a) and M@Ga_1.0 (b).

Figure 5

SANS data collected at the temperature range of 20–50 °C for selected core–shell gallium ferrite nanoparticles: (a) M@Ga0.2, and Ga0.2@M; (b) M@Ga1.0, and Ga1.0@M. The panels illustrate the refinements (solid lines) of the experimental data (symbols).

Figure 6

Mössbauer spectra (black dots) collected at room temperature for (a) M@Ga_x and (b) Ga_x@M series of shell@core type nanoparticles. The percentage contributions of hyperfine magnetic fields associated with Td (pink triangle down) and Oh (blue triangle up) magnetic sublattices as well as slow (red circles) and fast (green hexagons) superparamagnetic fluctuations as the result of deconvolution of experimental spectra of (c) M@Ga_x and (d) Ga_x@M series. For better readability, the fractions of fast and slow magnetic fluctuations were summed to the common percentage contribution (black squares). The lines are to guide the eye only.

Figure 7

Heating characteristics of samples with a concentration of 10 mg/mL with gallium in the core and jacket (a) and SAR coefficients depending on the concentration of Ga (b).

Figure 8

Morphology of cells undergoing experiment. (A)—HeLa control culture, (B)—HeLa culture with 0.01 mg/mL of M@Ga_0.6, (C)—HeLa culture with 0.01 mg/mL of Ga_0.6@M, all after 3 days of culture. (D)—Fibroblast control culture, (E)—Fibroblast culture with 0.01 mg/mL of M@Ga_0.6, (F)—Fibroblast culture with 0.01 mg/mL of Ga_0.6@M. The arrows indicate detaching cells, bar = 20 µm.

Figure 9

Changes in total amount of HeLa cells depending on the content and type of nanoparticles (% of control ± SE). The stars represent student’s t-test for a single sample = 100%, p < 0.01, n = 6.

Figure 10

Changes in total amount of fibroblast cells depending on the content and type of nanoparticles (% of control ± SE). The stars represent student’s t-test for a single sample = 100%, p < 0.01, n = 6.