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Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications

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ABSTRACT

This review focuses on the recent development and various strategies in the preparation, microstructure, and magnetic properties of bare and surface functionalized iron oxide nanoparticles (IONPs); their corresponding biological application was also discussed. In order to implement the practical in vivo or in vitro applications, the IONPs must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of IONPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The new functionalized strategies, problems and major challenges, along with the current directions for the synthesis, surface functionalization and bioapplication of IONPs, are considered. Finally, some future trends and the prospects in these research areas are also discussed.

No MeSH data available.


A facile ligand-exchange approach, which enables sequential surface functionalization and phase transfer of colloidal NCs while preserving the NC size and shape. (Reprinted with permission from A Dong et al 2010 J. Am. Chem. Soc.133 998. Copyright 2010 American Chemical Society.)
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Figure 12: A facile ligand-exchange approach, which enables sequential surface functionalization and phase transfer of colloidal NCs while preserving the NC size and shape. (Reprinted with permission from A Dong et al 2010 J. Am. Chem. Soc.133 998. Copyright 2010 American Chemical Society.)

Mentions: Another way is to use a ligand exchange procedure to change the polarity of the hydrophobic layer to being hydrophilic [141–143]. It involves adding an excess of ligand to the nanoparticle solution, resulting in the displacement of the original ligand on the surface of NPs. For instance, Dong et al reported a facile ligand-exchange approach, which is enabled for sequential surface functionalization and phase transfer of colloidal IONPs while preserving the NPs’ size and shape. Nitrosonium tetrafluoroborate (NOBF4) is used to replace the original organic ligands attached to the NPs’ surface, stabilizing the NPs in various polar and hydrophilic media for years, without aggregation or precipitation (shown in figure 12). Significantly, as illustrated in figure 12, the hydrophilic NPs obtained by NOBF4 treatment can readily undergo secondary surface modification due to the weak binding affinity of BF4− anions to the surface of NPs, allowing fully reversible phase transfer of NPs between hydrophobic and hydrophilic media [144]. Ninjbadgar and Brougham have reported a novel and efficient method to produce water dispersible superparamagnetic Fe3O4 NPs by ring opening coupling reactions. Fe3O4 NPs prepared by non-hydrolytic organic phase methods were subsequently functionalized with (3-glycidyloxypropyl) trimethoxysilane, the linker between the Fe3O4 NPs and organic molecule prevent aggregation, and it also is available for subsequent coupling reactions with a wide range of polymers and biomolecules. Ring opening coupling reactions were used to coat the epoxy-functionalized Fe3O4 NPs with aminated polymers (polyetheramines) or small molecules (arginine). The obtained NPs, with hydrodynamic size of 13 nm, are found to be very stable over extended periods in water or PBS due to the presence of a dense stabilizer layer covalently anchored onto the surface. Exceptionally high spin-lattice relaxivity, low r2/r1 ratios were exhibited in the clinical MRI frequency range, irrespective of the molecule selected for nanoparticle stabilization. As a result, the dispersions are excellent candidates for incorporation into multifunctional assemblies or for use as a positive contrast agent for MRI [145].


Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications
A facile ligand-exchange approach, which enables sequential surface functionalization and phase transfer of colloidal NCs while preserving the NC size and shape. (Reprinted with permission from A Dong et al 2010 J. Am. Chem. Soc.133 998. Copyright 2010 American Chemical Society.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036481&req=5

Figure 12: A facile ligand-exchange approach, which enables sequential surface functionalization and phase transfer of colloidal NCs while preserving the NC size and shape. (Reprinted with permission from A Dong et al 2010 J. Am. Chem. Soc.133 998. Copyright 2010 American Chemical Society.)
Mentions: Another way is to use a ligand exchange procedure to change the polarity of the hydrophobic layer to being hydrophilic [141–143]. It involves adding an excess of ligand to the nanoparticle solution, resulting in the displacement of the original ligand on the surface of NPs. For instance, Dong et al reported a facile ligand-exchange approach, which is enabled for sequential surface functionalization and phase transfer of colloidal IONPs while preserving the NPs’ size and shape. Nitrosonium tetrafluoroborate (NOBF4) is used to replace the original organic ligands attached to the NPs’ surface, stabilizing the NPs in various polar and hydrophilic media for years, without aggregation or precipitation (shown in figure 12). Significantly, as illustrated in figure 12, the hydrophilic NPs obtained by NOBF4 treatment can readily undergo secondary surface modification due to the weak binding affinity of BF4− anions to the surface of NPs, allowing fully reversible phase transfer of NPs between hydrophobic and hydrophilic media [144]. Ninjbadgar and Brougham have reported a novel and efficient method to produce water dispersible superparamagnetic Fe3O4 NPs by ring opening coupling reactions. Fe3O4 NPs prepared by non-hydrolytic organic phase methods were subsequently functionalized with (3-glycidyloxypropyl) trimethoxysilane, the linker between the Fe3O4 NPs and organic molecule prevent aggregation, and it also is available for subsequent coupling reactions with a wide range of polymers and biomolecules. Ring opening coupling reactions were used to coat the epoxy-functionalized Fe3O4 NPs with aminated polymers (polyetheramines) or small molecules (arginine). The obtained NPs, with hydrodynamic size of 13 nm, are found to be very stable over extended periods in water or PBS due to the presence of a dense stabilizer layer covalently anchored onto the surface. Exceptionally high spin-lattice relaxivity, low r2/r1 ratios were exhibited in the clinical MRI frequency range, irrespective of the molecule selected for nanoparticle stabilization. As a result, the dispersions are excellent candidates for incorporation into multifunctional assemblies or for use as a positive contrast agent for MRI [145].

View Article: PubMed Central - PubMed

ABSTRACT

This review focuses on the recent development and various strategies in the preparation, microstructure, and magnetic properties of bare and surface functionalized iron oxide nanoparticles (IONPs); their corresponding biological application was also discussed. In order to implement the practical in vivo or in vitro applications, the IONPs must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of IONPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The new functionalized strategies, problems and major challenges, along with the current directions for the synthesis, surface functionalization and bioapplication of IONPs, are considered. Finally, some future trends and the prospects in these research areas are also discussed.

No MeSH data available.