Iron Oxide Nanoparticles: A Review on the Province of Its Compounds, Properties and Biological Applications

Abstract

Materials science and technology, with the advent of nanotechnology, has brought about innumerable nanomaterials and multi-functional materials, with intriguing yet profound properties, into the scientific realm. Even a minor functionalization of a nanomaterial brings about vast changes in its properties that could be potentially utilized in various applications, particularly for biological applications, as one of the primary needs at present is for point-of-care devices that can provide swifter, accurate, reliable, and reproducible results for the detection of various physiological conditions, or as elements that could increase the resolution of current bio-imaging procedures. In this regard, iron oxide nanoparticles, a major class of metal oxide nanoparticles, have been sweepingly synthesized, characterized, and studied for their essential properties; there are 14 polymorphs that have been reported so far in the literature. With such a background, this review's primary focus is the discussion of the different synthesis methods along with their structural, optical, magnetic, rheological and phase transformation properties. Subsequently, the review has been extrapolated to summarize the effective use of these nanoparticles as contrast agents in bio-imaging, therapeutic agents making use of its immune-toxicity and subsequent usage in hyperthermia for the treatment of cancer, electron transfer agents in copious electrochemical based enzymatic or non-enzymatic biosensors and bactericidal coatings over biomaterials to reduce the biofilm formation significantly.

Keywords: bio-imaging; biomaterials; electrochemical biosensors; iron oxide polymorphs; nanoparticles; properties.

Figure 1

Overview of synthesis methods, properties and biological applications of iron oxide nanoparticles that have been extensively discussed in the current review.

Figure 2

Crystal structures of different polymorphs of iron oxide (a) Magnetite (b) Hematite (c) Maghemite (d) $\mathsf{\beta }$-Fe₂O₃ (Reprinted with permission from Ref. [43] Copyright 2013, American Chemical Society) (e) $\mathsf{\zeta }$ -Fe₂O₃ [5] (f) Goethite (g) Ferrihydrite (h) Wüstite (i) Akaganeite (j) Lepidocrocite.

Figure 3

SEM images of magnetite nanoparticles synthesized at different p values (A) p = 0.57 (B) p = 0.56 (C) p = 0.21 (D) p = 0.16 (Reprinted with permission from Ref. [47] Copyright 2019 Elsevier).

Figure 4

Mossbauer spectrum of (a) magnetite (Reprinted with permission from Ref. [21] Copyright 2008 Elsevier) (b) maghemite (Reprinted with permission from Ref. [49] Copyright 2002, American Chemical Society).

Figure 5

X-band Electron magnetic spectra of magnetite nanoparticles prepared by co-precipitation method (Reprinted with permission from Ref. [45] Copyright 2019 Elsevier).

Figure 6

(a) FT-IR spectra for magnetite, maghemite and hematite nanoparticles (b) XPS spectra of Fe2p from magnetite, maghemite and hematite nanoparticles (Reprinted with permission from Ref. [43] Copyright 2017 Elsevier).

Figure 7

Morphological characterization of hematite nanoparticles that were synthesized using different concentrations of surfactants—S1, S2 and S3 (left to right) (Reprinted with permission from Ref. [55] Copyright 2019 Elsevier).

Figure 8

Raman spectra for (a) hematite (b) maghemite nanoparticles (Reprinted with permission from Ref. [64] Copyright 2010 American Chemical Society).

Figure 9

Tauc plots of hematite films deposited on unheated (RS) and heated (HS) substrates showing (a) direct band gaps and (b) indirect band gaps (Reprinted with permission from Ref. [108] Copyright 2012 Elsevier).

Figure 10

Illustration of mitochondria-mediated autophagy induced by Fe@Au composite material for cancer cell specific cytotoxicity (Reprinted with permission from Ref. [153] Copyright 2011 Elsevier).

Figure 11

(a) DPV response of immunoelectrode (BSA/Anti-VD/Fe₃O₄-PANnFs/ITO) as a function of antigen concentrations (b) Calibration graph between current peak and antigen concentration (Reprinted with permission from Ref. [206] Copyright 2018 Elsevier).

Figure 12

Cyclic Voltagramm plots of Nafion/GOx/CA-IONPs/ITO bioelectrode (a) in absence of glucose (b–f) in 1, 2, 4, 6 and 8 mM glucose into 0.1 M PBS (pH 7.0) at scan rate 100 mV/s. Inset: Calibration curve of current obtained as a function of glucose concentration (Reprinted with permission from Ref. [208] Copyright 2016 Elsevier).

Figure 13

Amperometric response (A) CAT/Fe₃O₄/Au (B) CAT/CNT/Au (C) CAT/Fe₃O₄–CNT/Au hybrid electrode for successive addition of 1.2 M hydrogen peroxide, at a constant potential of −0.05 V using phosphate buffer solution (pH 7.4) as electrolyte (Reprinted with permission from Ref. [209] Copyright 2015 Elsevier).

Figure 14

Differential pulse voltammograms (A) and calibration curve (B) (from 3 independent measurements at each concentration) for levodopa at GCE modified with (0.2% Fe₂O₃ 1% MWCNT), in 0.1 M PB solution, pH 6.0. Scan rate 4 mV/s; step potential 2 mV. Concentration of levodopa: (a) 0.1; (b) 0.2; (c) 0.4; (d) 0.6; (e) 0.8; (f) 0.9; (g) 1.0; (h); 2.0; (i) 3.0; (j) 4.0; (l) 8.0 mM (Reprinted with permission from Ref. [210] Copyright 2018 John Wiley and Sons).

Figure 15

Schematic of the quantification of miRNA assay. Magnetically purified and separated miRNA from the extracted RNA sample pool were adsorbed directly on the magnetically bound GO/IO hybrid- modified SPCE. A significant electrocatalytic signal amplification was achieved via the chronocoulometric (CC) charge interrogation of target miRNA-bound [Ru(NH3)6]3+- [Fe(CN)6]3- electrocatalytic assay system (Reprinted with permission from Ref. [211] Copyright 2018 John Wiley and Sons).

Figure 16

Schematic representation of the electrochemical biosensor developed for detection of MCF-7 exosomes along with the detection mechanism (Reprinted with permission from Ref. [198] Copyright 2022 Elsevier).