Magnetite-Silica Core/Shell Nanostructures: From Surface Functionalization towards Biomedical Applications—A Review

Abstract

The interconnection of nanotechnology and medicine could lead to improved materials, offering a better quality of life and new opportunities for biomedical applications, moving from research to clinical applications. Magnetite nanoparticles are interesting magnetic nanomaterials because of the property-depending methods chosen for their synthesis. Magnetite nanoparticles can be coated with various materials, resulting in “core/shell” magnetic structures with tunable properties. To synthesize promising materials with promising implications for biomedical applications, the researchers functionalized magnetite nanoparticles with silica and, thanks to the presence of silanol groups, the functionality, biocompatibility, and hydrophilicity were improved. This review highlights the most important synthesis methods for silica-coated with magnetite nanoparticles. From the presented methods, the most used was the Stöber method; there are also other syntheses presented in the review, such as co-precipitation, sol-gel, thermal decomposition, and the hydrothermal method. The second part of the review presents the main applications of magnetite-silica core/shell nanostructures. Magnetite-silica core/shell nanostructures have promising biomedical applications in magnetic resonance imaging (MRI) as a contrast agent, hyperthermia, drug delivery systems, and selective cancer therapy but also in developing magnetic micro devices.

Magnetic Core-Shell Iron Oxides-Based Nanophotocatalysts and Nanoadsorbents for Multifunctional Thin Films

“…Nanoparticles size for samples M1 and M1-S1/2 ranges from 26–33, 22–29 and 16–26 nm, respectively, while for M2 and M2-S1/2 it varies from 16–24 to 12–20, and 16–32 nm, respectively. As expected [ 27 , 28 , 29 ], smaller particles depicted in the M1-S(1/2) samples point out that SiO 2 and Zn-doped SiO 2 covers prevented agglomeration of the M1 cores. The same reasoning is valid for M2-S1 sample.…”

“…Ultrasonic assisted co-precipitation method allows better control of particle shape [ 24 , 25 ], while oxygen-free atmosphere is often preferred to hinder magnetite oxidation [ 24 ]. In order to control nanoparticle size, chemical stability, carrier mobility in semiconductor structures and to prevent agglomeration, coating of the IONPs has been carried out using organic or inorganic polymers, multifunctional organic and organic molecules, and carbon nanostructures [ 1 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Surface functionalization with SiO 2 (shell) of the superparamagnetic iron oxide (core) is one of the most used and is easy to achieve and does not introduce toxic compounds [ 27 ].…”

“…In order to control nanoparticle size, chemical stability, carrier mobility in semiconductor structures and to prevent agglomeration, coating of the IONPs has been carried out using organic or inorganic polymers, multifunctional organic and organic molecules, and carbon nanostructures [ 1 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Surface functionalization with SiO 2 (shell) of the superparamagnetic iron oxide (core) is one of the most used and is easy to achieve and does not introduce toxic compounds [ 27 ]. Presence of Si-OH silanol groups on the surface of the magnetite nanoparticles coated with silica allows various subsequent surface functionalization, which can result in a large class of complex hybrid nanostructured compounds and applications [ 27 , 28 , 29 ].…”

“…Surface functionalization with SiO 2 (shell) of the superparamagnetic iron oxide (core) is one of the most used and is easy to achieve and does not introduce toxic compounds [ 27 ]. Presence of Si-OH silanol groups on the surface of the magnetite nanoparticles coated with silica allows various subsequent surface functionalization, which can result in a large class of complex hybrid nanostructured compounds and applications [ 27 , 28 , 29 ]. Fe 3 O 4 /SiO 2 core–shell nano-cubes have confirmed the ability to bind to biomolecules and to be suitable for biosensing applications [ 30 ].…”

An overview into advantages and applications of conventional and unconventional hydro(solvo)thermal approaches for novel advanced materials design

“…Current research has been moving towards the new configuration development of heterostructured materials with increasingly complex structures to maximize their properties. Thus, the heterostructured materials by definition are usually based on the combination of two or more components to form composite structures, which can also be classified into decorated (or open-shell), core-shell, yolk-shell and Janus-like structures according to their configurations exhibit superior physical properties [434][435][436][437][438][439][440][441][442][443][444][445][446][447][448].…”