Hybrid magnetic nanoparticles as efficient nanoheaters in biomedical applications

Abstract

Heating at the nanoscale is the basis of several biomedical applications, including magnetic hyperthermia therapies and heat-triggered drug delivery. The combination of multiple inorganic materials in hybrid magnetic nanoparticles provides versatile platforms to achieve an efficient heat delivery upon different external stimuli or to get an optical feedback during the process. However, the successful design and application of these nanomaterials usually require intricate synthesis routes and their magnetic response is still not fully understood. In this review we give an overview of the novel systems reported in the last few years, which have been mostly obtained by organic phase-based synthesis and epitaxial growth processes. Since the heating efficiency of hybrid magnetic nanoparticles often relies on the exchange-interaction between their components, we discuss various interface-phenomena that are responsible for their magnetic properties. Finally, followed by a brief comment on future directions in the field, we outline recent advances on multifunctional nanoparticles that can boost the heating power with light and combine heating and temperature sensing in a single nanomaterial.

Fig. 1. (A) Design of multigrain Mn₃O₄ shells grown on Co₃O₄ nanocubes. The upper panel shows the orientation relationship between the cubic core and the tetragonal shell by mapping the outer (green) and inner (red) spots of the FFT region (indicated by a purple square) obtained from the associated HAADF-STEM image. The lower panel summarizes the grain boundaries between adjacent Mn₃O₄ grains with a misorientation angle of ∼8.4°. Adapted with permission from Nature, ref. , Copyright 2020 Nature (B) high-resolution TEM and STEM-EELS elemental mapping images confirm a coherent interface between Fe₃O₄ and CoFe₂O₄ in core/shell hybrid nanoparticles. Adapted with permission from ref. , Copyright 2020 American Chemical Society (C) evolution from metal Fe to Fe/Fe-oxide core/shell and Fe-oxide hollow nanoparticles and associated TEM images. Adapted with permission from ref. , Copyright 2016 Royal Society of Chemistry (D) TEM image of Janus Fe-oxide-Au nanostars. Adapted with permission from ref. , Copyright 2020 Wiley-VCH (E) TEM image and EDS elemental mapping of Ag/Fe₃O₄ nanoflowers. Adapted with permission from ref. , Copyright 2016 American Chemical Society.

Fig. 2. (A) Comparison between DC and AC hysteresis loops for superparamagnetic nanoparticles. The relevant parameters defining the hysteresis losses (M_s, H_C, and M_R) have been explicitly indicated (B) electron cryotomography image of the chain of magnetosomes of M. gryphiswaldense and experimental and simulated AC hysteresis loops measured at 500 kHz for bacteria dispersed in water (25 °C). Reproduced from ref. and under a Creative Commons (CC BY 3.0) License. (C) 2D schematic representation of the different regions in a FM/FIM core/shell spherical nanoparticle, and SAR of core/shell hybrid nanoparticles with different shapes: spherical (black), cubic (red), octahedral (green), and truncated cuboctahedral (blue), and size distributions: log-normal size distribution (solid lines) and uniform particle size (dotted lines). Adapted from ref. with permission from The Royal Society of Chemistry.

Fig. 3. (A) Cation-inversion gradient in the shell of a Mn₃O₄ domain grown on Fe₃O₄ nanoparticles. Reprinted with permission from ref. , Copyright 2018 American Chemical Society (B) Monte Carlo simulations of the spin configurations for spherical defected (upper panel) and defect-free (lower panel) nanoparticles. From left to right the diagrams indicate the configuration under a positive field and two different reversal fields, while core, surface and defect spins are represented in red, blue and black, respectively. The bottom inset indicates the comparison of the simulated SAR values for both cases. Reprinted from ref. under a Creative Commons Attribution 4.0 International Licence (C) FePt/Fe₃O₄ core/shell nanocubes: TEM images, 3D-TEM tomography and off-axis electron holography at the remanence state indicating a magnetic vortex magnetic flux configuration. Adapted with permission from ref. , Copyright 2018 Wiley-VCH.

Fig. 4. (A) HAADF-STEM image and elemental mapping of SiO₂-encapsulated Fe-oxide and upconversion NaYF₄:Yb³⁺,Er³⁺ nanoparticles (scale bars = 50 nm). Temperature dependence of the excitation spectra and temperature change at the surroundings of the hybrid nanoparticles and at the whole medium under the application of an alternating magnetic field. Adapted with permission from ref. , Copyright 2014, American Chemical Society (B) TEM images of Fe-oxide/CuS hybrid nanoflowers and intermediate products (scale bars = 100 nm). Temperature rise (ΔT) as a function of the Fe and Cu concentration for Fe-oxide/CuS hybrid (spiky) nanoflowers at an applied alternating magnetic field (AMF, 471 kHz and 180 Oe), a laser excitation (λ = 1064 nm, 1 W cm⁻²) or a dual-excitation set-up (AMF + laser). Adapted from ref. under Creative Commons Attribution-NonCommercial 4.0 License.

Gabriel C. Lavorato

Raja Das

Javier Alonso Masa

Manh-Huong Phan

Hariharan Srikanth