Magnetic Separation: Industrial and Lab Scale Applications

Magnetic Separation: Industrial and Lab Scale Applications
Separation by means of magnetic field has been a mystery until the late 18 th century
though magnets were known since 6 th century BC (Livingston 1997 book). The magical
flow of the force exerted on a material by iron seemed supernatural in many ways.
Perhaps, that was the reason it wasn’t quite understood and designed for the good
everyday life.
Since the industrial revolution and mass production of steel, magnetic control became a
crucial piece of modern technology. Electronics, communication was in high demand of
magnetic technology as similar as the way magnetic ore refinement industry solely relied
on. Magnetic force seemed best petted into magnetic separation where its uncontrollable
power would be very handy. But it was only 1792 when a patent was filed by William
Fullarton on separating iron minerals with a magnet (Gunther 1909, Parker 1977).
The applications were in great interest mainly because magnetic force didn’t let the
gravity be the monopoly of the natural forces. In 1852, magnetite was separated from
apatite by a NY company on a conveyor belt separator (Gunther 1909). Later, with the
proven methods of beneficiation and refinement especially in the ores and minerals, a
new line of separators were introduced for separation of iron from brass fillings, turnings,
metallic iron from furnace products and magnetite from plain gangue (Gunther 1909). A
brief timeline can be seen in Figure 1.

First
Patent
on MS
1800
NY company
built a conveyor
belt separator
Over 300
patents filed
on MS
1900
First nano
separations
paper
First size
dependent
magnetic
separation
1792 1852 1909 1973 2006
Figure 1. Timeline of magnetic separation technology
A very broad but fitting and clear classification of magnetic separations can be done as
follows (Parker 1977):
1. Low intensity dry magnetic separations
2. Low intensity wet magnetic separations
3. High intensity dry magnetic separations
4. High intensity wet magnetic separations (i.e. High Gradient Magnetic Separation
(HGMS))
2000

A. Value of Magnetic Separation
Although the magnetic field would make no distinction between various magnetic
particles, magnetic separation handpicks those with magnetic affinity from physically
similar mixtures, i.e. in terms of density, shape, and size (Svoboda 2003).
Among many applications we’ll discuss briefly in the following pages, the following
ones would give a sense of how valuable magnetic separation could be. As early as 1970s
Delatour and Kolm (Delatour 1973 and 1975) treated water samples from the Charles
River (Fe3O4 seeding, 5ppm Al 3+ ) with a high flow velocity HGMS (Vo= 136 mms -1 ,
Ho=1T) to obtain the following reductions:
- coliform bacteria from 2.2x10 5 /l to 350/l
- turbidity by 75%
- color by 95%
- suspended solids by 78% (Gerber 1983 p 153)
Later, Bitton and Mitchell removed 95% of the viruses from water by magnetic filtration
following a 10 minutes of contact period with magnetite (added to be 250 ppm) (Gerber
1983 p 153). The following years, Boliden Kemi AB reduced phosphorus of water
supplies at least 87%. (Gerber 1983 p 154).
B. Physics of the process
a. Introduction of the concept

Magnetic separation, particularly the high gradient magnetic separation (HGMS), is the
method of entrapping magnetic particles from a non-magnetic medium by the virtue of
high gradient magnetic fields. The high gradients are obtained as a consequence of
distortion of the magnetic field by ferromagnetic wire matrix present in a separation
column.
b. Comparison to magnetic separation and applications which could not be done by
normal magnetic separation.
HGMS methods have been successful in separating weakly paramagnetic materials of the
order of microns, efficiently unlike traditional magnetic separation techniques (Parker
1981). HGMS has been successfully applied to remove cells (Safarik, 1999) and proteins
(Bucak 2003), organic (Moeser 2002) and inorganic contaminants using functionalized
magnetic materials, all of which will be exemplified in the related applications sections.
c. Physics and Fluid dynamics of the method.
Magnetic separation occurs on account of the force balance between the various
competing forces acting on a magnetic particle like hydrodynamic drag arising due to the
flow velocity, magnetic force due the applied field, diffusion force and inter-particle
forces like Helmotz double layer interaction, dipole-dipole interaction and Van Der
Waals attraction. The diffusion forces become important in the nanometer regime
because the energy required to move a particle, attains comparability with the thermal

energy of the Brownian motion, hence setting up a number density gradient (Fletcher
1998). Hence, the magnetic, dipole-dipole interaction and Van Der Waals forces aid the
process of separation, whereas, diffusion, double layer interaction and drag force act
against the separation.
Since the magnitude of magnetic (Fm), drag (Fh) and diffusional (Fd) forces are
prominent, we shall consider these for the force balance.
Fm + Fh + Fd = 0
Fm = μ VpMp
o ∇
H
where µo is the permeability of free space, Vp is the particle volume, Mp is the core
magnetization of the particle and grad H is the magnetic field gradient(order of Ms/a -
Parker 1981) in the vicinity of a capture center (e.g Ferromagnetic wire) (Gerber and
Birss, 1983).
Fh = 6πηbv
Where η is the viscosity of the solvent in which the nanosized magnetite particles are
dispersed, b is the particle radius and v is the flow velocity.

kT
Fd = − ∇n
n
W ⎛ K
n = no
exp( ⎜
kT ⎝ 2ra
4
1
+
ra
2
⎞
⎟
⎠
Where, ‘n’ denotes the particle number density, no is the bulk particle density away from
the wire, k the Boltzmann constant, T is the temperature, W = 2πMsHob3/3, K= Ms/2µoHo
and ra = r/a. (Fletcher 1991)
Gradient also given as dH/dx = -2Bo a 2 /b 3 (Oberteuffer 1974)
Explanation of force figure and graph will take one more paragraph.
C. Industrial (Column) Applications
As briefly mentioned above, separation by means of a magnet gained strong grounds
when high gradient magnetic separation (HGMS) was introduced. Its ability of handling
particles down to nanometer scale on a large scale and high flow rate with affordable cost
even inspired engineers to say: “Virtually every process in the chemical engineering
industry is a potential application (for HGMS). Many previously unthinkable processes
will now become practical, and many previously practical ones will become unthinkable.
It has already happened in the kaolin industry, and is beginning to happen elsewhere.”
(Henry Kolm, September 1975)(Kolm 1975 IEEE). Apart from kaolin, the “elsewhere”
would mainly be steel related applications. Thanks to the construction of industrial plants
where steel is heavily used, almost all piping builds up iron particulates. These can be
cleaned most efficiently by a magnet preferably with a ferromagnetic matrix, in other

words with a high gradient magnetic separator. Table 1 summarizes the general use of
magnetic separation in industry.
Fields of Application Objective
Chemical and allied industries
Food, drink and tobacco manufacturing
Coal processing
Metals industries
Industrial raw materials processing
(cement, refractory materials, glass sands,
etc.)
Removal of tramp metal for machinery
protection and avoidance of wear
Extraction of ferrous contamination,
including free iron, ferrosilicon, magnetite,
etc.
Mineral dressing industries Extraction or enrichment of magnetic ores
(magnetite, hematite, ilminite, etc.
Table 1. Industrial applications of magnetic separation (From Parker 1977 Contemp
Phys.)
a. Kaolin (clay) decolorization
Kaolin (a.k.a. china clay) is a clay mixture with the main component kaolinite
(Al2O2SiO2.2H2O or Al2Si2O5(OH)4) mineral (Gerber 1983 p131). Named from the
Kaoling Hills of the city of Ching-te chen where fine Chinese porcelains were produced,
kaolin quickly found its place in industries where resistance to acids and alkalis was
necessary. In today’s world, however, it’s mostly used (80%) for paper manufacturing
industry where it plays dual role:
1. as a filler between the pulp fibers
2. as a surface coating for a white glossy finish

(Saikia 2003, Iannicelli 2000, Gerber 1983 p132, China Clay Producers
Association)
Naturally colored due to the iron containing micas, tourmaline, pyrite, anatase and rutile,
kaolin needs to be magnetically cleaned before used in paper or porcelain (Oder 1973,
Oder 1976 IEEE, Gerber 1983 p132, Lofthouse 1981). Since the first magnetic removal
of impurities by J. M. Huber Corp. in 1969, kaolin is processed for coating quality
throughout the world with continuous high gradient magnetic separator (Figure 2).
Competing with the leaching process, where chemical resistance of impurities limits
usage, HGMS handles 75% of world production (Oder 1976). A typical plant would
have an HGMS with a filter diameter of about 2 m and capacity up to 20 tons/h
(Hirschbein 1982). Figure 3 shows kaolin mineral before and after the decolorization
process.

Figure 2. Metso® High Gradient Magnetic Separators (HGMS) are designed to recover
weakly magnetic material from non-magnetic matter and can be used for many
applications including the processing of clays, iron ores, rare earths and industrial
minerals. In addition to the strongly magnetic minerals of Fe, Co, and Ni, a vast number
of weakly magnetic minerals, which are not normally treatable by ordinary magnetic
separators, may be processed by High Gradient Magnetic Separators. Metso HGMS
separators are able to remove even weakly paramagnetic materials. (From Metso
Minerals)

Figure 3. Kaolin decolorizes to white after magnetic separation . Courtesy of
R.Weller/Cochise College and U.S. Geological Survey.
b. Steel production
Conventional methods for cleaning steel mill waste and process waters include
sedimentation, flocculation followed by sedimentation, and fixed bed filtration.
Sedimentation methods require large areas for settling tanks and clarifiers (Oberteuffer
1975). Table 2 lists some of the contaminants generated in a steel production process. On
average 1 ton of steel needs 151 tons of water for cooling, cleaning purposes. Apparently,
the process generates many magnetic particulates. Those particles, especially the ones in
the gas and hot water streams, need vast space and heavy machinery for removal by
regular methods, filtration, flocculation, etc. Magnetic separation, instead, offers great
time, space and cost savings (Oberteuffer 1975, Harland 1976, Gerber 1983 p133). In a
sample treatment at Kawasaki Steel Corporation of Japan, a 3 kOe field strength, 2.1 m

diameter magnetic filter removes 80% of contaminants from the cooling wastewater of
vacuum degassing process (Hirschbein 1982).
Sources Contaminants
Coke production Non-magnetic particles, dissolved organics, oil
Iron making Magnetic particles, dissolved organics
Steel making Magnetic particles
Hot forming Magnetic particles, oil, acids
Cold finishing Magnetic particles, oil
Table 2. Sources of contaminants in a steel production process (Oberteuffer 1975).
Power plants (both conventional and nuclear) with wastewater, steam and cooling
systems often requires filtering off the ferromagnetic or paramagnetic particulates
clumping on the thermal, process streams (Berger 1983 book page).
Fly ash from coal power plants has 18% iron oxides. Magnetic filtration is capable of
saving 15% of fly ash and recycling it. Estimates show that this can replace some of the
magnetite used in industry (Hirschbein 1982). Figure 4 shows an example of a ball mill
separator used in these operations.

Figure 4. A ball mill separator from Eriez. Separation of ball mill grinding ball segments
from the discharge.
c. Enrichment of ores – Mineral Beneficiation
Treatment of ores with magnetic separation carried out mostly for 2 purposes:
Enrichment of iron ores or cleaning non-iron ores from iron species. The very similar
density of transition metal minerals makes it challenging to use conventional methods of

separation. The magnetic nature of iron species, therefore, plays a crucial role in the
beneficiation of the ores.
Among the iron ores taconite leads for the need of magnetic beneficiation. From a
taconite ore (33% iron) kelland (kelland 1973) was able to recover iron at 95% on a 5
cm/sec flow rate. Today, Metso Minerals, Inc. (formerly Sala International AB) offers
magnetic separators that can separate iron from ores up to 100% (depending on the
particulate sizes, magnetic field and flow rate). Figure 5 shows a successful continuous
HGMS separator.
Figure 5. Continuous High Gradient Magnetic Separation for many low susceptibility
minerals that are associated with other minerals or have extra Fe in the crystals, and are
hence often possible to separate. (From Metso Minerals)

Magnetic separation of pyrite (FeS2) from coal for desulfurization is also very much
practiced by industrial means (Maxwell 1978). The weakly magnetic nature of pyrite,
however, led to pretreatments for better removal. The most useful procedure was found to
be the thermal conversion of pyrite (FeS2, Ms=0.3 emu/g) to pyrrohite (Fe7S8, Ms=22
emu/g). Up to 91% removal of sulfur from coal was achieved by microwave heating
followed by a magnetic separation (Uslu 2003). Figure 6 shows a picture of Eugene Hise
testing magnetic separation on pulverized coal. Figure 7 has an industrial scale drum
separator used in large scale applications.
Figure 6. Eugene Hise pours crushed coal into a magnetic separator designed to remove
contaminants from pulverized coal. (Courtesy of Oak Ridge National Laboratory
(ORNL). Ref: ORNL Review 1992 Vol 25 (3-4) Chapter 7)

Figure 7. An industrial scale drum separator used in large scale applications. From Eriez
manual.
d. Food industry

General use of magnetic separation in food industry is removing rare earth elements
from food ingredients. Similar to the ore beneficiation or desulfurization, the target
substances are weakly magnetic and need high magnetic fields applied to a continous
process of food production line.
Bunting Magnetics Co. offers magnetic metal separators and metal detectors for the
quality of food and extended service life of the processing equipment, especially for
cheese processing, chocolate plants, pet food processing, flour mills, spice plants,
vegetable processing. Removal of both ferrous and nonferrous tramp metals is achieved
by their line of food safety products for the food processing industry (For more
information visit www.buntingmagnetics.com). Figure 8, 9 and 10 show case studies
from Greenwood Magnetics Ltd. (For more information visit
www.greenwoodmagnetics.com).
Figure 8. A single row easy-clean grid box was supplied to a major international food
producer. Manufactured to specification, the grid was fitted with a perspex inspection

window and safety switches. The high-density rare earth easy-clean magnetic tubes
filter loose tea with a flow rate of 5tph. Internally the welds were fully laid, ground
smooth and crack and crevice free to food industry standards.
Figure 9. The Bullet magnet was specified by a leading flour producer. Flour flows
upwards through the 5” pipe and any ferrous contamination is removed by the high
intensity rare earth bullet magnet (8500 gauss min). This particular customer specified a
bolted flat door, so that the magnet could be completely removed when required.
Figure 10. A water-jacketed pipeline magnet was supplied to Fox’s Biscuits.
Manufactured to suit a 4” pipeline pressure resistant up to 10bar, nine high intensity rare
earth magnets (11500 gauss) filter liquid chocolate flowing at 300l/minute. The

pressurised heated water-jacket maintains the temperature of the chocolate. All 316
stainless steel, and manufactured to food industry standards.
e. Arsenic removal – Water treatment (JT)
[in progress]
D. Biotechnological (Batch) Applications
The ability to control remotely inspired many biotechnologists and medical scientists to
investigate magnetic solutions for several biochemical processes, such as protein and cell
separations and purifications, magnetic drug targeting and delivery, and enzyme based
bio-catalysis. Unlike industrial applications, in-lab or batch applications require tailor-
made magnetic materials but remain fine with steady, not continuous, bench-top or batch,
process solutions. First, we will give key components of a magnetic material to be used in
vivo and then review some of the biological applications of magnetic separation.
a. Materials requirement
In vivo applications of magnetic materials require biocompatibility. Thus, biochemists
tend to use naturally existing minerals, such as magnetic iron oxides (magnetite, Fe3O4
and maghemite, γ-Fe2O3), due to their biologically safe nature i.e. in the ferrofluids
(Tartaj 2003 J of Phy).

A summary of key requirements for a bio-magnetic separation material is as follows (also
depicted in Figure 8):
1. Biocompatibility
2. Suitable linkers
3. Functional layers on magnetic core
4. Protective layer
5. Antigen detection
6. Shape recognition
7. Fluorescent signaling

Figure 11. On a single particle, several necessary sections of a magnetic material that
could be used in biological systems is summarized. (from ref. [Salata 2004 Review] with
permission)
b. Protein purification
Magnetic separation of biological entities proven to be rapid and more effective for over
30 years now (Robinson 1973 Biotech, Lilly 1974 Biotech, Guesdon 1977
Immunochem, Hirschbein 1982 ApplBiochem, Hubbuch 2001). Proper coating and
labeling of the magnetic particles and the target species would yield hassle-free and
time-saver purifications with reduced costs (Setchell 1985, Safarik 2004
BiomagResTech). Although very effective, magnetic affinity separations need to be
very specific. Immobilization of ligands on the magnetic adsorbents for the capture of
the target species is crucial and perhaps because of this, though standard liquid column
chromatography is currently the most often used technique, magnetic separations will
prevail with significant research in magnetic affinity separations and biochemical
analysis (Safarik 2004 BiomagResTEch). Recent studies on magnetic materials for
protein separations involve silica coated magnetite with amino functionality for salmon
sperm DNA elution (Bruce 2005 Langmuir), phospholipid coated magnetite for
myoglobin recovery (Bucak 2003 BiotechnolProg), polyethylenimine coated magnetite
for purification of plasmid DNA from bacterial cells (Chiang 2005 J ChromatogB),
magnetic separation of erbium (III) attached biological particles (Evans 1981 Science),
magnetic polyacrylamide-agarose beads for measuring rabbit antibody (Guesdon 1977),

magnetic polymer latexes for isolation of trypsin from pancreatic extract (Khng 1998),
ProtA-immobilized magnetic immunomicrospheres for immunoaffinity purification of
antibodies IgG2a from mouse ascites (Liu 2004 JApplPolS), silica coated magnetite
with iminodiacetic acid functionality for bovine hemoglobin (BHb) and bovine serum
albumin (BSA) (Ma 2006 Coll), streptavidin-functionalized magnetic nanoparticles for
stimulant biotoxin (Mertz 2005 JMMM), magnetite and nickel particles for the
immobilization of a-chymotrypsin (Munro 1975 IEEE), Nickel-NiO-BSA-chymotrypsin
for casein hydrolysis (Munro 1981 BiotechBioeng), magnetic affinity support for
adsorption of lysozyme (Tong 2001 BiotechProg), streptavidin-biotin coated magnetic
beads for DNA-RNA isolation (Uhlen 1989 Nature), polyethyleneimine coated
magnetite for virus capture (Veyret 2005 AnalBiochem), carboxyl-modified magnetic
nanobeads for the isolation of genomic DNA from human whole blood (Xie 2004
JMMM), TeNT-linked iron oxide nanobeads with dextran coating for explaining the
relative capacity of the specific compartments of a cell resulting from endocytosis
through different receptors that promote antigen presentation and immune (Perrin-
Cocon 2001 JMMM). Figure 8 describes a standard setup for a bench-top magnetic
separation (Tartaj 2003 Review). Figure 9 shows a summary of the available magnetic
separators (Safarik 2004 BiomagResTech).

Figure 12. A simple, standard representation of a bio-magnetic separation. (From Tartaj
2003)

Figure 13. Examples of batch magnetic separators applicable for magnetic separation of
proteins and peptides. A: Dynal MPC -S for six microtubes (Dynal, Norway); B: Dynal
MPC – 1 for one test tube (Dynal, Norway); C: Dynal MPC – L for six test tubes
(Dynal, Norway); D: magnetic separator for six Eppendorf tubes (New England
BioLabs, USA); E: MagneSphere Technology Magnetic Separation Stand, two position
(Promega, USA); F: MagnaBot Large Volume Magnetic Separation Device (Promega,
USA); G: MagneSphere Technology Magnetic Separation Stand, twelve-position
(Promega, USA); H: Dynal MPC – 96 S for 96-well microtitre plates (Dynal, Norway);
I: MagnaBot 96 Magnetic Separation Device for 96-well microtitre plates (Promega,
USA); J: BioMag Solo-Sep Microcentrifuge Tube Separator (Polysciences, USA); K:
BioMag Flask Separator (Polysciences, USA); L: MagneSil Magnetic Separation Unit
(Promega, USA); M: MCB 1200 processing system for 12 microtubes based on MixSep
process (Sigris Research, USA); N: PickPen magnetic tool (Bio-Nobile, Finland).
Reproduced with the permission of the above mentioned companies; the photos were
taken from their www pages. (REF: Safarik 2004 Protein Review)
In an excellent review, Safarik and Safarikova discuss advantages and the equipment for
a successful protein purification via magnetic means with a full scan of magnetic
separation applications in isolation of enzymes, antibodies and proteins (Safarik 2004
Biomag Res Tech). The efforts for the industrial scale applications are noteworthy and
can be applied for a few biological molecules (Hubbuch 2002 BiotechBioeng, Safarik
2001 BiotechLett).

Magnetic separation based protein analysis and detection systems on chips are of great
interest for early diagnosis for fatal infections. Biobarcoded magnetic beads (Nam 2003
Science), microfluidic biochemical detection system (Choi 2002 LabOnaChip),
micromachined magnetic particle separator (Ahn 1996) are prominent examples of this
field.
Recently, nanorods of Ni with Au edges were successfully used to remove His-tagged
proteins with 90% recovery (Lee 2004 Angewandte).
c. Cell separation
Similar to protein purifications, magnetic separations offer rapid quantification, high
cell recovery when compared to the conventional methods, i.e. centrifugation (Chang
2005 J Ind Microbiol). As early as 1977, 99% recovery of neuroblasioma cells was
obtained in a matter of minutes (Kronick 1977 Science). Same year, magnetic separation
of red blood cells and lymphoid cells were also introduced (Molday 1977 Nature).
Magnetic separation of cells is advantageous over the conventional methods mainly
because it lets target cells to be isolated directly from the medium, i.e. blood, bone
marrow, tissue homogenates, stool, cultivation, media, food, water, soil etc (Safarik
1999 JChromB).

Labeled cells, i.e. neural progenitor cells (Lewin 2000 Nature Biotech), red blood cells
(Haukanes 1993 Nature Biotech, Takayasu 2000, Zborowski 2003 BiophysicalJ, Seesod
1997 Am J Trop Med Hyg), tumor cells (Wang 2004 NanoLett), malarial parasites
(Melville 1981 IEEE), baker’s yeast (Azevedo 2003 IEEE), can be targeted to magnetic
beads which can therefore be separated (Pankhurst 2003). Magnetic moment or giant
magnetoresistance of the magnetic particle-cell assembly can tell us about the location
and even the count of the cells that are present (Pankhurst 2003).
With efforts to take magnetic cell separation to industrial level, Berger and coworkers
were able to develop a micro cell separator (Berger 2001 Electrophoresis), Haik
introduced a magnetic device for continuous separation of red blood cells (Haik 1999
JMMM) and Zborowski applied a magnetic quadrupole flow sorter on a model cell
system of human peripheral lymphocytes targeted with commercial monoclonal
antibodies and iron-dextran colloid (Zborowski 1999 JMMM). Figure 14 and 15 shows
two examples of magnetic devices for cell separations.
Recently, magnetic nanowires were experimented with cell separation techniques and
found to be four times better in purity (80 %) and recovery (85%) yields (Hultgren 2004
IEEE).

Figure 14. Magnetically labeled cells can be separated on a gravity feed through a high
gradient magnetic separator (HGMS). From ref (Berger 2001 Electrophoresis)

Figure 15. A magnetic device for separation of red blood cells. (from ref [Haik 1999
JMMM])
d. Drug Delivery

Bio-distribution of pharmaceuticals always faces a big challenge: Unspecific, evenly
distribution of the drugs all over the body. This requires a large amount of the dose
to get enough of it to the target which also brings a side effect of the non-specific
toxicity in healthy sectors. Among other drug targeting methods, magnetic targeting
offers one of the most viable solutions to the targeting problem (Torchilin 2000
Europ J Pharm). To our knowledge, first applications in magnetic drug targeting
date back to late 1970s (Mosbach 1979 and Senyei 1978, Widder 1978).
For a successful delivery, a carrier must also be fully controllable. Aggregation,
clogging or intrinsic, permanent magnetic behavior is completely unacceptable.
Superparamagnetic iron oxides, therefore, offer both requirements for being an
excellent shuttle for a successful drug delivery. Figure 12 explains how a
magnetically targeted carrier would work.

Figure 16. Magnetic Targeted Carriers (MTC) offer a target oriented drug delivery.
(Courtesy of FeRx Inc. from Saiyed 2003)
Researchers at FeRx Inc. were able to craft iron particles with activated carbon (1-2
μm) and attach Doxorubicin, an anti-cancer drug (Wilson 2004 Radiology). They
used the magnetic particle – drug assembly to cure cancer tumor in a reversible drug
release fashion (Saiyed 2003, http://www.magneticsmagazine.com/e-
prints/ReRx.pdf). Sadly, FeRx, Inc. is now out of business and laid off most of its
employees (For more information visit
http://www.biotechcareercenter.com/FeRx.html,
http://www.9news.com/acm_news.aspx?OSGNAME=KUSA&IKOBJECTID=c17c
7125-0abe-421a-00b3-c79476c2f9f1&TEMPLATEID=0c76dce6-ac1f-02d8-0047-
c589c01ca7bf).
As can be clearly seen in FeRx example, physical (magnetic properties to drug
binding capacity) and physiological (target position to body weight) limitations for
the in vivo studies resulted unsuccessful clinical trials which only encouraged more
in depth research (Dobson 2006 DDT). For this reason, using epirubicin, an
anticancer drug, Lubbe and coworkers identified the potential of ferrofluids (Lubbe
1999 JMMM). More theoretical studies followed: a mathematical model for
magnetic targeted drug delivery (Grief 2005 JMMM), a hypothetical magnetic drug
targeting system using FEMLAB simulations with the high gradient magnetic
separation (HGMS) principles (Ritter 2004 JMMM), a two-step targeted drug

delivery system (Rosengart 2005 JMMM), and a new method for locally targeted
drug delivery with magnetic implants in the cardiovascular system (Yellen 2005
JMMM). Regardless, anti-cancer drug delivery via magnetic carriers increases drug
concentration at the tumor site and limits the systemic drug concentration, by which
it enhances the drug activity to multiples of magnitude (Neuberger 2005 JMMM).
Recent treatments with magnetic drug targeting involved using of MTCs (Magnetic
Targeted Carriers) in liver and lung (Goodwin 1999 JMMM), treatment of squamous
cell carcinoma in rabbits with FFs (ferrofluids) bound to mitoxantrone (FF-MTX)
that was concentrated with a magnetic field (Alexiou 2000 Cancer Res, Alexiou
2005 JMMM), preparation of magnetic liposomes containing submicron-sized
ferromagnetic particles encapsulating the muscle relaxant drugs, diadony or
diperony, for local anesthesia (Kuznetsov 2001 JMMM), an improved method for
the physical delivery of rAAV vectors in vivo in which virion particles are
conjugated to microsphere supports (Mah 2002 Mol Therapy), thrombosis treatment
using a composition of ferrofluid with fibrinolytic enzyme (Rusetski 1990 JMMM),
nucleic acid delivery with magnetically labeled non-viral vectors (Schillinger 2005
JMMM)
e. Biocatalysis
This newly developing field is strictly bound to the control of the magnetic beads
that can immobilize several bio-catalysts, mainly enzymes, such as β-lactamase

(Gao 2003 ChemComm) and peroxidase (Yang 2004 Anal Chem). Figure 17 shows
how an enzyme can be immobilized on a nano iron oxide.
Figure 17. Preparation of enzyme immobilized, silica coated nano iron oxide.
(courtesy of Gao 2003 CC)
E. Acknowledgements
The authors would like to thank the NSF (EEC-0118007) Center of Biological and
Environmental Nanotechnology and the Robert A. Welch Foundation (C-1349) for
funding and XYZ for their invaluable help.

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