Iron oxide nanoparticle
They have attracted extensive interest due to their superparamagnetic properties and their potential applications in many fields (although cobalt and nickel are also highly magnetic materials, they are toxic and easily oxidized) including molecular imaging.
These applications require coating of the nanoparticles by agents such as long-chain fatty acids, alkyl-substituted amines, and diols.
[2] Magnetite has an inverse spinel structure with oxygen forming a face-centered cubic crystal system.
Maghemite differs from magnetite in that all or most of the iron is in the trivalent state (Fe3+) and by the presence of cation vacancies in the octahedral sites.
A ferrimagnetic material is similar to a ferromagnet but has two different types of atoms with opposing magnetic moments.
The ordering of magnetic moments in ferromagnetic, antiferromagnetic, and ferrimagnetic materials decreases with increasing temperature.
When the size gets small enough (<10 nm), thermal fluctuations can change the direction of magnetization of the entire crystal.
As iron oxide nanoparticles translate toward the magnetic field source, they experience Stokes' drag force in the opposite direction.
[8] The preparation method has a large effect on shape, size distribution, and surface chemistry of the particles.
Recently, many attempts have been made to develop processes and techniques that would yield "monodisperse colloids" consisting of nanoparticles uniform in size and shape.
For example, spherical magnetite particles of narrow size distribution with mean diameters between 30 and 100 nm can be obtained from a Fe(II) salt, a base and a mild oxidant (nitrate ions).
[9] The other method consists in ageing stoichiometric mixtures of ferrous and ferric hydroxides in aqueous media, yielding spherical magnetite particles homogeneous in size.
Being highly susceptibile to oxidation, magnetite (Fe3O4) is transformed to maghemite (γFe2O3) in the presence of oxygen:[3] The size and shape of the nanoparticles can be controlled by adjusting pH, ionic strength, temperature, nature of the salts (perchlorates, chlorides, sulfates, and nitrates), or the Fe(II)/Fe(III) concentration ratio.
[15][16] Iron oxide nanoparticles are used in cancer magnetic nanotherapy that is based on the magneto-spin effects in free-radical reactions and semiconductor material ability to generate oxygen radicals, furthermore, control oxidative stress in biological media under inhomogeneous electromagnetic radiation.
The magnetic nanotherapy is remotely controlled by external electromagnetic field reactive oxygen species (ROS) and reactive nitrogen species (RNS)-mediated local toxicity in the tumor during chemotherapy with antitumor magnetic complex and lesser side effects in normal tissues.
The combined influence of inhomogeneous constant magnetic and electromagnetic fields during nanotherapy has initiated splitting of electron energy levels in magnetic complex and unpaired electron transfer from iron oxide nanoparticles to anticancer drug and tumor cells.
In particular, anthracycline antitumor antibiotic doxorubicin, the native state of which is diamagnetic, acquires the magnetic properties of paramagnetic substances.
The experimental data was received about correlation between the frequency of electromagnetic field radiation with magnetic properties and quantity paramagnetic centres of complex.
In this method, the ferrofluid which contains iron oxide is injected to the tumor and then heated up by an alternating high frequency magnetic field.
