Surface modification and cellular uptake evaluation of Au-coated Ni ₈₀ Fe ₂₀ nanodiscs for biomedical applications

Abstract

A nanofabrication technique based on self-assembling of polystyrene nanospheres is used to obtain magnetic Ni 80 Fe 20 nanoparticles with a disc shape. The free-standing nanodiscs (NDs) have diameter and thickness of about 630 nm and 30 nm, respectively. The versatility of fabrication technique allows one to cover the ND surface with a protective gold layer with a thickness of about 5 nm. Magnetization reversal has been studied by room-temperature hysteresis loop measurements in water-dispersed free-standing NDs. The reversal shows zero remanence, high susceptibility and nucleation/annihilation fields due to spin vortex formation. In order to investigate their potential use in biomedical applications, the effect of NDs coated with or without the protective gold layer on cell growth has been evaluated. A successful attempt to bind cysteine-fluorescein isothiocyanate (FITC) derivative to the gold surface of magnetic NDs has been exploited to verify the intracellular uptake of the NDs by cytofluorimetric analysis using the FITC conjugate.

Influence of shape, size and magnetostatic interactions on the hyperthermia properties of permalloy nanostructures

“…The attention is first focused on disk-shaped nanostructures, for which we present a detailed comparison between experimental and numerical results. The studied nanodisks, with diameters ranging from 270 nm to 680 nm, are prepared by means of a nanolithography technique based on the self-assembling of polystyrene nanospheres 43,44 . Hysteresis loop measurements are performed on samples in two spatial configurations, namely in 2D array form (nanodisks still attached on the substrate) and dispersed in an ethanol solution (free-standing nanodisks).…”

Au-Coated Ni80Fe20 Submicron Magnetic Nanodisks: Interactions With Tumor Cells

“…The presence of the NDs within or in contact with the cells was proven by different imaging techniques: with SEM, it was possible to clearly localize and distinguish the presence of several NDs retained by the cells and distributed in small clusters with no specific space arrangement. Note that the formation of small ND ensemble does not affect the peculiar magnetic properties induced by geometrical parameters of a single ND (Barrera et al, 2016).…”

“…The Au layers deposited on the top and bottom faces of the nanodisks have the purpose of coating the magnetic core with a biocompatible surface reducing the toxic effect of the Ni element contained in the Ni 80 Fe 20 magnetic alloy (Bar-Ilan et al, 2009). In addition, Au coating improves not only the biocompatibility of the magnetic nanodisks but also provides a useful surface to potentially bind chemical and biological entities maintaining unaltered the magnetic behavior of the particles (Li et al, 2011;Barrera et al, 2016).…”

“…The fraction of surface area occupied by nanodisks array with respect to the whole substrate area (packing density, η = 0.62) and the area number density (ρ = 1.2 × 10 8 nanodisks cm −2 ) were evaluated taking several scanning electron microscopy (SEM) images in different regions of the samples (Barrera et al, 2016) in order to prepare a magnetic ND solution with a known nominal concentration, resulting in 58 µg ml −1 , which was then diluted in order to prepare ND solution for the biological assays at 11.60, 1.16, and 0.12 µg ml −1 .…”

“…In the last decade, NPs consisting of soft ferromagnetic alloys, such as FeNi, FePd, received much interest for their ability to stabilize a controllable magnetic vortex domain configuration when they are prepared in discoidal shape (Rozhkova et al, 2009;Kim et al, 2010;Leulmi et al, 2015;Tiberto et al, 2015Tiberto et al, , 2016Barrera et al, 2016) within a proper selected range of diameters and aspect ratio (Tiberto et al, 2016;Peixoto et al, 2020). This magnetic vortex configuration induces peculiar magnetic properties to the discoidal NPs, not present in the more conventional iron oxide-based spherical ones, such zero remanence, high magnetic saturation and susceptibility, as well as the presence of a hysteresis at high field (Kim et al, 2010;Tiberto et al, 2015;Barrera et al, 2016).…”