Abstract
Nanotechnology is that sphere of technology that involves the participation of biology, chemistry, physics, and engineering sciences. Nanoscale science defines the chemistry and physics of structures lying in the range of 1-100 nm. Among the nanosystems researched, magnetic nanosystems are highlighted due their unique ability, which enables their targeting to specific locations on application of an external magnetic field. The exhibited property of these magnetic nanosystems being super-paramagnetism, there is no retention of magnetic property on removal of the magnetic field, thus enabling a reversion of the targeting process. For effective utilization of these nanosystems, they should be reduced to nanosizes, layered with biocompatible entities, stabilized, and functionalized. In the chapter, synthesis and functionalization and stabilization are elucidated. The biomedical applications such as targeted delivery, MRI, magnetic hyperthermia, tissue engineering, gene delivery, magnetic immunotherapy, magnetic detoxification, and nanomagnetic actuation are discussed.
TopIntroduction
Novel technologies with innovative ideas that modify drug attributes and therapeutic strategies for increased efficacy and cost-effective products to patients is the need of the hour. Nanotechnology in combination with novel delivery systems opens up possibilities for effective treatment regimens (Lyer, Singh, Tietze & Alexiou, 2015). Nanotechnology is a multifaceted area in research and development that brings together the various facets of science viz. chemistry, biology, engineering, and medicine (Banerjee, Katsenovich, Lagos, McIintosh, Zhang, & Li, 2010). Nanoscale science defines the chemistry and physics of structures lying in the range of 1-100 nm, or < 100 nm (Nikalje, 2015) (Figure 1 is adapted from Nikalje, 2015). Magnetic nanoparticles (MNPs) principally comprise of metals (iron and cobalt), alloys (spinel type ferromagnetic substances viz. magnesium ferrite (MgFe2O4), manganese ferrite (MnFe2O4), cobalt ferrite (CoFe2O4) and oxides such as iron oxide magnetite (Fe3O4) and maghemite (γ-Fe2O3). Magnetic materials can be classified based on magnetic susceptibility, which is defined as magnetism induced on application of an external magnetic field (Barakat, 2009). Based on the response of the intrinsic MNP magnetic dipole and the net magnetization in the presence and absence of an applied magnetic field, commonly there are five types of magnetic materials (Issa, Obaidat, Albiss & Haik, 2013) (Kolhatkar, Jamison, Litvinov, Wilson & Lee, 2013).
Figure 1. Size of particles in nanoscale
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Ferromagnetic materials possess a net magnetic moment due to presence of unpaired electrons. These will orient themselves in the direction of an applied magnetic field giving rise to a large net magnetic moment. On removal of the magnetic field these materials will tend to disorient but sustain a residual magnetic moment. Some examples of ferromagnetic materials are, iron, cobalt and nickel.
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Paramagnetic materials are characterized by unpaired electrons and do not contain magnetic domains. They align themselves weakly to an external magnetic field and lose their magnet moment on removal of the field. E.g. gadolinum, magnesium, lithium and tantalum.
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Diamagnetic materials have atoms with no unpaired electrons and lack a net magnetic moment. These atoms repel an external magnetic field, resulting in an alignment opposite to the direction of the field. Some examples of diamagnetic substances are copper, silver and gold.
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Antiferromagnetic materials are composites consisting of two different atoms that position themselves at different areas of a lattice. These two atoms cancel out each others magnetic moments as a result these compounds possess a zero net magnetic moment; for example cobalt oxide (CoO), nickel oxide (NiO), magnesium oxide (MgO).
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Ferrimagnetic materials (such as Fe3O4 and γ-Fe2O3) are compounds of different atoms residing on different lattice sites with anti-parallel magnetic moments. Since the atoms of the compounds possess magnetic moments of different magnitudes, magnetic moments do not get cancelled. A spontaneous net magnetic moment is thus a characteristic of these composites.