Magnetic nanoparticles introduction, synthesis and role in health care.pdf

Magnetic nanoparticles introduction, synthesis and role in health care

1. Magnetic
nano
particles

2. Magnetic nanoparticles
Magneticnanoparticles(MNPs) have gained interest in the field of drug delivery. These magnetic particles have
the ability to target specific cells thus lowering systemic exposure of cytotoxic compounds.

3. Introduction
Among many synthetic compounds the general public comes across with, in day-to-day life,
nanoparticles are considered highly advantageous in various applications. Nanoparticles in
diagnostics and as drug delivery vehicles are coming under the aforementioned beneficial
applications in the field of biomedical science. Various types of nanoparticles, for instance, gold
nanoparticles and iron oxide nanoparticles, are being used in biomedical operations. Due to its
magnetic properties and nanometer size, magnetic nanoparticles such as magnetite (Fe
3O
4) and
maghemite (γ-Fe
2O
3) are considered highly beneficial for diagnostics and in drug delivery systems. On
the other hand, inorganic nanoscale particles with semiconductor properties are becoming very
popular in such applications. These semiconductor nanoparticles, called quantum dot nanoparticles,
are equipped with extremely favorable characteristics such as high fluorescence and
photoluminescence. These nanoparticles have been tested to be used in diagnostics , and trials were
carried out at laboratory scale as therapeutics, that is, for drug delivery . At the same time, quantum
dots are found to be more beneficial over regular chemotherapy, radiation, and ionizing radiation
imaging which are used in cancer diagnosis and treatment.

4. Properties
Magnetic nanoparticles are nanomaterials consist of magnetic elements, such as iron, nickel, cobalt, chromium,
manganese, gadolinium, and their chemical compounds. Magnetic nanoparticles are superparamagnetic
because of their nanoscale size, offering great potentials in a variety of applications in their bare form or coated
with a surface coating and functional groups chosen for specific uses. Especially, ferrite nanoparticles are the
most explored magnetic nanoparticles, which can be greatly increased by clustering of a number of individual
superparamagnetic nanoparticles into clusters to form magnetic beads.
Magnetic nanoparticles can be selective attached to a functional molecules and allow transportation to a
targeted location under an external magnetic field from an electromagnet or permanent magnet. In order to
prevent aggregation and minimize the interaction of the particles with the system environment, surface coating
may be required. The surface of ferrite nanoparticles is often modified by surfactants, silica, silicones, or
phosphoric acid derivatives to increase their stability in solution. In general, coated magnetic nanoparticles
have been widely used in several medical applications, such as cell isolation, immunoassay, diagnostic testing
and drug delivery.

5. Properties
1. Magnetic Property
The properties of magnetic nanoparticles depend on the synthesis method and
chemical structure. In most cases, the magnetic nanoparticles range from 1 to 100
nm in size and can display superparamagnetism. Superparamagnetismis caused by
thermal effects that the thermal fluctuations are strong enough to spontaneously
demagnetize a previously saturated assembly; therefore, these particles have zero
coercivity and have no hysteresis. In this state, an external magnetic field is able to
magnetize the nanoparticles with much larger magnetic susceptibility. When the
field is removed, magnetic nanoparticles exhibit no magnetization. This property can
be useful for controlled therapy and targeted drug delivery.
2. Magnetocaloric Effect
Some magnetic materials heat up when they are placed in a magnetic field and cool
down when they are removed from a magnetic field, which is defined as the
magnetocaloric effect (MCE). Magnetic nanoparticles provide a promising alternative
to conventional bulk materials because of their particle size-dependent
superparamagnetic features. In addition, the large surface area in magnetic
nanoparticles has the potential to provide better heat exchange with the
surrounding environment. By careful design of core-shell structures, it would be
possible to control the heat exchange between the magnetic nanoparticles and the
surrounding matrix, which provide a possible way for improving therapy
technologies, such as hyperthermia.
Hyperthermia isan abnormally high
body temperature —or
overheating. It's the opposite of
hypothermia, when your body is
too cold. Hyperthermia occurs
when your body absorbs or
generates more heat than it can
release.

6. Magnetic
nanoparticles
synthesis
Magnetic core nanoparticles owing to their large surface area
and energy, are sensitive to agglomeration and oxidation. The
surface of the particles is rapidly oxidized in ambient conditions,
which has a dramatic effect on their magnetic properties. In
order to protect the particles from oxidation and forming
clusters, they are generally encapsulated or surface
functionalized by a biocompatible material. These materials also
help in altering the surface charge of the nanoparticle and
provide chemical functionalities for bioconjugation, affecting
their biodistribution and pharmacokinetics. Several natural
(dextran, albumin) and synthetic polymers (PEG, PAA) are
mostly used to coat the surface of magnetic nanoparticles,
either during the synthesis or after the synthesis. However, the
thickness of the coating can have a negative effect on the
magnetic response of the particle. Other coating materials
include inorganic molecules such as silica, gold, and carbon.
Liposomes, which are phospholipid bilayer membrane vesicles,
can encapsulate a large number of magnetic cores and deliver
them simultaneously.

7. Preparation Methods
During the last few years, a large portion of the published articles about MNPs have
described efficient routes to attain shape-controlled, highly stable, and narrow size
distribution MNPs. Up to date, several popular methods including co-precipitation,
microemulsion, thermal decomposition, solvothermal, sonochemical, microwave assisted,
chemical vapourdeposition, combustion synthesis, carbon arc, laser ablation and flame
pyrolysis synthesis have been reported for synthesis of MNPs.

9. Characterization
Post-synthesis-preparedmagneticnanoparticlesmustbethoroughlycharacterizedbyusingavarietyofcharacterization
techniquesbeforeemployingthemforvariousbiomedicalapplications.Thesurfacemorphologyandsizeofthemagnetic
nanoparticlescanaltertheirphysicochemicalproperties.Transmissionelectronmicroscopy(TEM)andscanningelectron
microscopy(SEM)aremostcommonlyusedforthedeterminationofparticlesizeandmorphologyof
nanoparticles/nanomaterials.TEMcanalsobeusedtovisualizeandmeasurethethicknessofthecoatingmaterialonthe
magneticcoreparticles,whichisnotpossibleusingSEM.Theatomicforcemicroscopy(AFM)techniqueisoftenemployedfor
determiningthesize,morphology,andsurfaceroughnessofthenanoparticles.Dynamiclightscattering(DLS)orphoton
correlationspectroscopy(PCS)isusedtofindthehydrodynamicdiameterandsizedistribution(polydispersity)oftheparticles.
Variousanalyticaltechniquessuchasenergy-dispersiveX-rayspectroscopy(EDS),X-rayfluorescence(XRF)spectroscopy,X-
rayphotoelectronspectroscopy(XPS),atomicabsorptionspectroscopy(AAS),andinductivelycoupledplasmamass
spectroscopy(ICP-MS)areemployedtodeterminetheelementalcompositionofthemagneticparticles.FT-IRspectroscopyis
employedforidentifyingsurfacefunctionalities(mainlyorganic).Thesesurfacecharacterizationtechniquesareusefulin
confirmingthepresenceofcoatingorattachmentoffunctionalitiesonthesurfaceofthemagneticcore.Inadditionto
determiningthermalstability,thermalgravimetricanalysis(TGA)canalsodeterminethebindingefficiencyandcoating
formationontheparticle’ssurface.
Themagneticpropertiesaregenerallyevaluatedusingavibratingsamplemagnetometer(VSM)andsuperconductingquantum
interferencedevice(SQUID).

10. Applications
1.Magnetic separation
In a biomedical study, Isolation and
separation of specific molecules
including DNAs, proteins, and cells
are prerequisites in most fields of
biosciences and biotechnology.
Among various bioseparationmethods, magnetic nanoparticles
based bioseparationis mostly documented and widely used
due to its unique magnetic separation mood and promising
efficiency. In the process, the biological molecules are labeled
by magnetic nanoparticles colloids and then subjected to
separation by an external magnetic field, which may be applied
for cell isolation, protein purification, RNA/DNA extraction, and
immunoprecipitation.
Magnetic nanoparticles particles such as beads have been
extensively used for separation and purification of cells and
biomolecules, due to their small size, promising separation
mood, and good dispersibility. One of the trends in this subject
area is the magnetic separation using antibodies conjugated
with beads to provide highly accurate antibodies that can
specifically bind to their matching antigens on the surface of
the targeted sites.

11. 2. Diagnostics
Non-invasive imaging methods have been developed by labeling stem cells using magnetic nanoparticles.
Among them, Magnetic Resonance Imaging (MRI) is widely used as diagnostic tools to present a high spatial
resolution and great anatomical detail to visualize the structure and function of tissues. Several kinds of
magnetic nanoparticles have been developed to improve contrast agents in MRI imaging, with significant
benefits of improved sensitivity, good biocompatibility and ready detection at moderate concentrations.
3. Sensors
Many types of magnetic nanoparticles-based biosensors have been surface functionalized to recognize specific
molecular targets, due to their unique magnetic properties which are not found in biological systems. Due to
different composition, size and magnetic properties, magnetic nanoparticles can be used in a variety of
instruments and formats for biosensing with an enhancement of sensitivity and the stability.

12. The magnetic nanoparticles first act as a carrier of the drug, which are attached to its outer surface or dissolve in the coating. Once
the drug coated particles have been introduced into the bloodstream of the patient, a magnetic field gradient is created by strong
permanent magnet to retain the particles at the targeted region. Moreover, magnetic nanoparticles coated with a drug could be
injected intravenously, transported, and retained at targeted sites, which make them highly promising system for drug delivery.
4. Drug delivery
Magnetic nanoparticles have been developed and applied in localized drug delivery to tumors.
Carbon nanotubes (CNTs) were
synthesized by Chen et al., which were
co-loaded with iron oxide nanoparticles
and CdTequantum dots. These carriers
effectively transferred doxorubicin
(DOX, an anticancer drug) under the
influence of an external magnet into the
cells

13. 5. Therapy
Magnetic nanoparticles have currently been explored as a technique for
targeted therapeutic heating of tumors, which is called hyperthermia. Various
types of superparamagnetic nanoparticles with different coatings and targeting
agents are used for specific tumor sites. Magnetic particle heating can be
accomplished at depths necessary for treatment of tumors located virtually
anywhere in the human body. In addition, magnetic nanoparticle hyperthermia
can also be used as an adjuvant to conventional chemotherapy and radiation
therapy, which shows great potential.