Progress in Magnetic Fe3o4 Nanomaterials in Magnetic Resonance Imaging
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Nanotechnology Reviews 2020; 9: 1265–1283 Review Article Hongcai Li#, Shuanqiang Yang#, David Hui, and Ruoyu Hong* Progress in magnetic Fe3O4 nanomaterials in magnetic resonance imaging https://doi.org/10.1515/ntrev-2020-0095 received August 4, 2020; accepted September 30, 2020 1 Introduction Abstract: At present, high-sensitivity, high-penetration- Nowadays, the early diagnosis of various difficulty and depth, and accurate tissue resolution clinical imaging miscellaneous diseases, such as cancer and septicemia, effect are required, while computer transverse scanning, hasalwaysbeenadifficult problem in medicine. Therefore, microwave imaging, and fluorescence imaging (FL) cannot the key to solve this problem is the effective auxiliary meet the requirements of clinical imaging, but the mag- diagnosis method [1]. Magnetic resonance imaging ( ) - netic resonance imaging MRI can meet the require (MRI) is one of the most powerful medical diagnosis ff ments of clinical dissecting details. The e ect of MRI methods because of the images provided by MRI with ( ) imaging is closely related to the contrast agent CA .As excellent anatomical details based on soft tissue contrast an important type of CA, Fe3O4 and its analogues have and functional information in noninvasive, real-time been widely concerned because of their low toxicity and monitoring manner [2]. Compared with computer trans- relatively low price. In this review, we summarize the verse (CT), sonography, nuclear scintigraphy, and X-ray development and improvement of CAs based on Fe3O4 imaging, MRI causes no radiation damage and provides T - and its analogues from 2 imaging mode and develop high soft tissue resolution, and hence can be applied to ment limitation in the initial single modulus imaging diagnose a variety of diseases [3]. However, conventional mode, to T imaging mode overcoming the limitations 1 MRI contrast agent (CA) is expensive, low in spatial reso- of T imaging and the limitations of its own in applica- 2 lution, which fails to detect early tiny tumors, and cannot tion, to the later development of dual modulus imaging distinguish between benign and malignant tumors form, and to the current multi-modulus imaging form. because of current CAs having only a single imaging Simultaneously, we demonstrate the research progress, mode [4]. The results of the MRI are determined by not preparation methods, and future trends based on Fe O 3 4 only the precision instrument and different imaging and its analogues CAs for MRI, the current application methods, but also the CA, which can significantly improve status is preliminarily summarized, and the future devel- the contrast of the biological targets around the tissue [5]. opment trend is prospected. Therefore, the development of new CAs can effectively Keywords: RI, Fe3O4 nanoparticles, preparation, imaging improve the imaging effect. mode, imaging effect From the application point of view, CAs can be divided into two categories, one is the longitudinal relaxation T1 signal CA (r1) that produces the bright field as a positive CA, and the other is the transverse relaxation T2 signal CA (r2) that produces the dark field as a negative # These authors contributed equally to this review. CA [6]. The T1 signal is generated by the interaction between the outermost electron cloud of the magnetic * Corresponding author: Ruoyu Hong, College of Chemical element and the protons in the water to produce a bright T Engineering, Fuzhou University, Fuzhou, Fujian 350108, China, signal, whereas the 2 signal is a darker signal owing to e-mail: [email protected] the magnetic unevenness caused by the strong magnetic Hongcai Li: College of Chemical Engineering, Fuzhou University, moment [7]. In terms of production mode, relaxation Fuzhou, Fujian 350108, China direction, and field of view, the two categories of CAs Shuanqiang Yang: Institute of Industrial Technology, Fujian Jiangxia are totally different; however, the division method is gen- University, Fuzhou, Fujian 350108, China - David Hui: Department of Mechanical Engineering, University of New erally accepted, especially for products with better circu Orleans, New Orleans, LA 70148, United States of America lation in the market [8]. Open Access. © 2020 Hongcai Li et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 International License. 1266 Hongcai Li et al. Gadolinium has been a popular product in the is a naturally occurring ferrite in which the metal ion (M) 2+ market on account of its T1 signal as an MRI CA [9]; is a ferrous iron (Fe ). More importantly, the outermost however, the recent FDA warning about the increased layer of iron atom contains five electrons similar to gado- risk of nephrogenic systemic fibrosis and nephrogenic linium, which can change the relaxation time of protons fibrosing dermopathy in patients who suffer from renal and engender greater r1 and r2 relaxation effects, thus failure and are subjected to enhanced contrast MRI showing certain potential in MRI applications [21].So exams has given rise to concern [10]. Therefore, the far, there are three kinds of iron CAs using the T2 sign −1 −1 development of new CAs to meet clinical needs has imaging on the market, Feridex (r2 = 120 mM s ), Reso- −1 −1 −1 −1 attracted much attention. Super-paramagnetic iron oxide vist (r2 = 186 mM s ), and Combidex (r2 = 65 mM s ), magnetic nanoparticles (SPIONs) and uniform ferrite respectively [22]. The following is in introduction to the nanoparticles such as Fe3O4 and Fe2O3 are widely applied current T2 CA study. in magnetic nanoparticle (MNP)-based CAs because of The stability of CAs is one of the key problems their non-toxicity and biodegradability [11].Different affecting the application of CA [23]. Researchers have forms of ferrite MNPs have been well reported in the tried various ways in which to improve the stability literature for decades because of their countless biome- without changing the magnetic imaging performance. dical applications, including MRI [12], targeted drug delivery Among them, the copolymerization of an organic polymer [13], photothermal [14], and magnetic fluid hyperthermia is a relatively direct and an effective method [24]. There cancer therapy [15]. These applications are based on are two preparation methods available: (i) one is to first excellent features, such as super para-magnetism, possi- synthesize nanoparticles and then to modify the coating bility of tuning of particle size (for desired electrical, with an organic polymer, and (ii) one-pot method by optical, and magnetic properties)[16], mono-dispersity, thermal precipitation copolymerization method [25] stability, biocompatibility, large surface areas that can be (Figure 1). easily functionalized [17], improved magnetic sensitivity, Certainly, there are other ways, for example, Kluenker and range of different synthesis methods [18]. In this et al. [26] presented a solution phase seed mediated review, the synthesis methods, outsourcing materials, synthesis of iron oxide superparticles colloidal with and doping metal methods of ferroferric oxide nanopar- flower- and hedgehog-like morphologies starting at dis- ticles are described. From the perspective of imaging persible spherical maghemite and nanoplate hematite methods, combined with the description of biological (HEX) templates to overcome the drawbacks of particle applications, a detailed discussion of the problem, cur- assemblies for functional nanodevices such as low rent solutions, and prospects for the application of ferro- mechanical stability, lack of interfacial electronic com- ferric oxide for MRI imaging were provided. munication, and poor processability [27]. Changes in solvent, type of iron salts, and temperatures have been used to synthesize different types of nanomaterials (Figure 2; the NPs are mostly spherical and faceted, and 2 Single modulus imaging an average particle size is 18–20 nm). As for the higher effective radius and anisotropy and inhomogeneity of the Because the FDA announced the toxicity of gadolinium to particle-generated magnetic field, both longitudinal and the kidneys, MNPs have attracted more attention [19]. transversal relaxation sign effects show obvious enhance- −1 −1 The outermost layer of iron has five electrons with strong ment (r1 and r2 values are 0.093 and 1.774 mM s for HEX magnetism, so can generate vivid MRI signals, allowing SPs).Ther2 relaxivity could be increased by a factor rapid development of MNPs. 2.5–64.36 mM−1 s−1 showing the potential for application 2.1 T sign imaging of Fe O nanomaterials 2 3 4 - , 0H 2+ 3+ Fe /Fe ot Ferrites are crystalline iron oxides whose magnetic prop- one-p erties were recognized for their commercial importance as early as 1933 [20]. Ferrites have the general formula Fe3O4 NPs polymer polymer in outer 3+ 2+ Fe2 O3·M O, where M is a divalent metal ion such as manganese, nickel, iron, cobalt, or magnesium. Magnetite Figure 1: Preparation methods of iron CAs. Progress in magnetic Fe3O4 nanomaterials in magnetic resonance imaging 1267 al hetan OED 3+ leate/ Fe ium o c/sod TMAO/OAc/OAm/OED/Fe(CO) OA seed particles 5 ethanol s od SPH NPs SPH SPs ium seed mediated growth milli-Q-water a cet ate Hex NPs Hex SPs SPH=spherical, HEX=hexagonal, NPs=nanoparticles, SPs=superparticles OAc=oleic acid,OED=1-octadecene,TMAO=trimethylamine N-oxide,OAm=oleylaine Figure 2: Flow diagram of solvent planting process [26]. as a T2 CA. Generally, the viabilityofthecellsdecreaseswith improve its magnetic properties while achieving targeted increasing Fe concentration and reaches a minimum of properties. Monoclonal antibodies (MAbs) could distin- 70–80% at 100 μg/mL NPs, which exhibits less virulence. guish malignant tumors from normal tissue and could be Certainly, this preparation method also provides a new way used for selective targeting [37]. Kubovcikova et al. [38] for industrial production. coated ferric material with poly-lysine (MFPLL, Sd = Early organic polymer coating with dextran, poly- 85 nm, and a hydrodynamic diameter (Hd) of 119.2 nm) ethylene glycol (PEG)[28], polyvinyl alcohol, and chit- to improve the stability in aqueous solution, and then osan as an outer cladding has been reported [29].