Shiv SharmaGaro YessayanZachary Nicoll

George ChahwanJason Tarantino

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AbstractThe objective of this review is to track the on-going progress and evolution of the

biotechnological field through the experimentation with magnetic bead technology and its

applications to modern society. The review will look at the history of magnetic bead technology,

from its development to its current applications, its effect on the scientific community, and its

marketability.

IntroductionBackground

Magnetic Bead Technology became popular in the 1980’s with the discovery that

magnets can be used to more accurately perform already present technology. The technology is

based around the use of para-magnetic materials that act as magnets in the presence of a

magnetic field but are no longer magnetic when the field is gone. This allows scientists to study

the materials effects in a magnetic field and then separate the proteins and peptides to get

physical results. Major companies have become interested in the development and application of

the technology so it has been able to grow rapidly. The major upsides of this technology are that

it is significantly cheaper, requires less labor and is widely applicable. These advantages are the

driving forces behind the conception and development of the magnetic bead technology. Some of

the applications are highly interesting and can be productive in the medical field. Bar-coded

magnetic bead (BMB) technology is new, upcoming and is currently being introduced to society.

This technology can help us in the medical field by assisting doctors in the bacteria testing

department. Bacteria can be quickly identified and can also get accurately matched up with the

best possible antibody. This can cut days off the old methods of testing which can not only

improve a patient’s health faster, but can also hinder anti-body resistance by picking the

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strongest medication for the job. In addition, these advancements will offer new opportunities for

automated, low-cost and fast cancer diagnosis.

The Needs and Opportunities Lately, there has been a seemingly eternal quest for improved medical care at lower costs.

With an aging US population In Vitro Diagnostic (IVD) companies are scrambling to find

biological solutions that will bring down the price of improved medical care. Due to this urge,

the IVD industry is rapidly evolving. In a nutshell, the need for improved care at a low cost

entails improved diagnostic methods. Therefore, a lot of recent research is focused in figuring

out more efficient and precise

diagnostic methods. An example

would include improved testing

sensitivity. Improvements in this

phase of the diagnostic method will lead to better diagnosis, a better clinical management, and

inevitably reduced costs of clinical care. Thus, IVD companies have been looking at numerous

technologies such as magnetic beads to help if finding a solution to the needs of consumers.

Magnetic beads, in the last twenty years have exponentially progressed to now be

considered the “golden standard” in the magnetic microspheres and magnetic nanospheres field.

Magnetic beads are an essential component of immunoassay diagnostic kits for analyzers in

clinical labs. These microspheres are actually polymer shells with a magnetic pigment; here, the

magnetic material is mainly iron oxide. Functional groups of the polymer surface permit

chemical derivatization of magnetic particles. This process allows the conversion of magnetic

particles into a binding agent for tests using immunoassays.

In the biomedical field, magnetic beads range in size anywhere between 1um-100um,

being 1um-2um in size on average. The iron content of these beads also varies between 15%-

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60%; this amount determines the response to an applied magnetic field, facilitating the

manipulation of any phase in any biomedical test.

InstrumentationTurbo Beads

Turbo Beads are the next generation of magnetic beads; they are magnetic nanobeads that

have a core and shell structure. The beads core is constructed of metal, and its shell is made out

of carbon. The metal core is used because of its highly

magnetic properties, and the carbon is used to provide

a chemical stability. This new technology provides a

fast and efficient way to separate various compound

from one another.

This technology began by taking highly

reactive metal nanomagnetics and coating them in graphene- carbon. The binding of the beads is

a carbon to carbon bond. This covalent bond allows for no ligands to be lost. A ligand is an atom

that is bonded to the central metal atom. The graphene-carbon allows the beads to have high

thermal stability. This means that the beads can be used in areas that had low pH levels (Acids)

and high temperatures without oxidation of the core.

That is not the only positive property of the turbo

bead. Due to the combination of the metal core and

carbon shell these beads display a large increase in

their magnetic properties. Below is an image that

demonstrates how much more reactive the turbo

bead is compared to a ferrite based bead.

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In the image on the left we can see that the ferrite based bead is located to the left and is in a red

color; whereas the turbo bead is located to the right and is in a black

color. In the middle of the two tubes is a standard magnet. It is clear that

after forty seconds the turbo bead concentration is comparatively much

greater than the ferrite bead concentration.

The picture on the side is another example demonstrating how

quickly the turbo beads can separate from a substance. In this image

there is a substance that contains the turbo beads. It can be seen that

once a magnet is applied to the vessel (bottom left corner) it only takes five minutes for the turbo

beads to completely separate from the substance.

The chemical properties of the turbo beads allow them to have a selective separation of

precious metals at low concentrations. Also, their highly magnetic properties allow for high

recyclability of magnetic chemicals, which permits them to be reused.

Today these turbo beads are being used for toxin management in water streams. Given

that the beads are highly reactive and chemically stable, they can be used for the selective

separation of heavy metals. The compounds that create the magnetic bead result in reagents for

swift removal of toxins that can be found in

contaminated water.

The picture on the left is a graph that shows

the amount of cadmium that is in water before

and after the use of turbo beads. It can be seen

that using the turbo beads significantly

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decrease the amount of cadmium found in contaminated water. This means that turbo beads

allow the purification to go down to drinking water standards.

CardioGenics Magnetic BeadsCardioGenics’ bead is a type of magnetic bead that was developed to improve testing

sensitivity. Most commercial magnetic beads have a dark color to them, and approximately 80%

of the light they generate is lost, causing them to have a low testing sensitivity.

The CardioGenics magnetic bead is a lighter colored bead that is used to optimize and

collect light signals in binding tests. These beads are a lighter color than the generic bead

because they are coated with a thin layer of silver before they are covered with a polymer shell.

Since these beads are lighter they become more sensitive to light; which in turn maximizes light

collection. The CardioGenics can vary in size from 1 to 50 microns, and have seven times more

light sensitivity than a generic magnetic bead. Due to the increase in light sensitivity these beads

improve the testing sensitivity.

Below are two images that show the different amounts of silver coating that can be added

in order to change the color of the beads. The lighter the beads are the more sensitive they are to

light.

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Asynchronous Magnetic BeadsA new promising technology is the asynchronous magnetic bead rotation (AMBR). In

order for this technology to be useful in the field of pharmaceuticals and medicine, the beads

need to be extremely sensitive as the beads

are to examine various biomolecules on the

micro even nano scale.

This breakthrough technology was

elucidated through the monitoring of the

continuous growth of individual bacteria by

direct observation using optical imaging.

Unfortunately, direct observation has

numerous limitations such as optical diffraction and a limit to the number of cells that could be

continuously monitored. On the brighter side, advances have been made to increase the rotational

speed of the AMBR to 145 Hz which allows the bead to have a detection limit of 59nm. Such

precision could be used to measure nanoscale growth dynamics of individual bacterial cells.

AMBR sensors operating at high frequencies of 145 Hz allow for higher resolution

candid; this is important while dealing with molecules on a very small scale. Even though other

technologies like electron microscopy and

cantilevers already offer high resolution

monitoring, the drawback of using electron

microscopy and cantilevers is that they give

optimal results in vacuum or air. AMBR sensors

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will make real time single bacterium growth monitoring and single virus detection possible in

their given fluid environment.

Ωc= mBk ɳ V

A rotating magnetic field controls the rotation of a ferromagnetic bead. The bead rotation

becomes asynchronous with the magnetic field at a critical frequency Ωc. The critical frequency

depends on the magnetic momentum of the bead m, the magnetic field strength B, the kinetic

viscosity ɳ, the volume of the bead V, and the shape factor k (for a sphere, the shape factor is 6)

ApplicationsTurbo Beads/ CardioGenics Magnetic Beads Applications

With magnetic beads being such a new but fast growing technology, there is no doubt

that this technology can be applied to numerous fields shown in the figure below. A few fields

include clinical diagnostics, drug targeting, cell isolation, purification, nucleic acid purification

and detection.

A very popular application of magnetic beads would be providing more efficient assay

platforms compared to suspension bead based assay platforms. Immunoassays are used to

investigate the roles of biomolecules. Immunoassays help with trying to stop the progression of

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diseases such as HIV, Alzheimer’s

disease, and numerous cancers.

Immunoassays can use both magnetic

bead platforms or suspension

platforms but there are numerous

reasons as to why magnetic beads are

a better choice.

At a glance, there are various

drawbacks to suspension beads.

Though these beads offer numerous

advantages in the areas of sensitivity

and cost, there are many unintended

consequences that are elucidated

during the process of use. Examples

include the vacuum that is used to

wash and remove liquid from the

microscopic beads cause pressure that

can fluctuate between wells and

plates. This can ultimately skew data results. Also, human error is a major influence on the

results in suspension bead tests are a lot of manual care-take is involved.

On the contrary, magnetic beads just make the whole testing process more efficient and

precise. The magnetic bead based assay platforms use a series of magnetic beads that have

different dyes and emit at varied wavelengths. This is done to create a unique spectral address for

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each bead. These beads then serve as solid phases to capture analytes. The figure on the side

describes the process of the magnetic beads in the assay platform.

Using magnetic beads to carry out the process of magnetic separation in an automated

wash eliminates the variables that cause skewed answers with suspension bead use. Additionally,

with magnetic bead technology, assays can be completed in 3-4 minutes and do not require

additional user training. Conclusively, the benefits of using magnetic beads outweigh those of

suspension beads.

Magtration TechnologyMagtration technology in simple terms is the filtration for a nucleic solution by means of

a magnetic force. When studying these nucleic acids, one can learn much about how cells

function, research diseases, discover new medicines, and countless more applications. Nucleic

acids are known as the building blocks of life and contain different types of DNA and RNA.

These are found inside every animal cell and we can now separate nucleic acids by implementing

magtration technology.

Every cell is surrounded by a cell membrane which must be broken down first in order to

get to the inside of the cell where nucleic acids are found. To do this, there are certain toxins and

detergents that will break down a cell membrane but not harm the internal parts of the cell. A

separate solution containing these paramagnetic beads is added to the lysis solution. These

paramagnetic beads are coated with silica with is a natural attraction for the nucleic acid. This

new mixture is shot up and down a pipette in which the magnetic beads are trapped up against

the wall where a magnet is placed. Now that the magnetic beads and the nucleic acid trapped in

the pipette, it must go through separate washing solutions. Several wash cycles should be

preformed to maximize the purification process. From here, the beads are moved into a new

container containing a low ionic strength solution. When this solution is warmed up, it separates

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the beads from the nucleic acid. Then the final step is to remove the beads from the solution by

use of a magnet and aspirating the solution up and down to collect the beads as done earlier and

what remains is the purified nucleic acid.

Asynchronous Magnetic Bead ApplicationsAs mentioned earlier, researchers are looking to operate AMB’s at a high frequency

because that would mean a higher resolution and a higher sensitivity caused by changes in

diameter. Many current applications would benefit from a higher critical frequency; examples

include micro-mixing and growth studies. Using a ferromagnetic bead to reach a bead frequency

of 145 Hz (shown in graph 1) that allows a detection limit of 59 nm; this is sensitive enough to

study single bacterial growth.

Graph 1 (1)

The rotational frequency of the bead is calculated using the following formula:

¿θ>¿Ω−√(Ω2−Ωc¿¿2¿)¿¿

Many applications use the sensors to monitor the growth of individual bacteria. In a

recent experiment the sensors were used to monitor the growth of bacteria and its susceptibility

to a particular drug. The Escherichia coli also known as E coli bacteria along with the

antibacterial ampicillin were used for the experiment (2).

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The experiment showed that the AMBR sensor was able to detect changes at even 80nm

in a single E coli cell. The sensor was also able to detect the response of the E coli cell to the

antibacterial used. What is also worth mentioning is the fact that the experiment was done in

water; this shows that the sensor is able to work in an aqueous environment unlike previous

technologies like electron microscopy that would work best in a vacuum environment. The

success of this experiment has extended the method to similar single cell studies like cancer

cells.

Finally, we can conclude that asynchronous magnetic bead rotation technology has a lot

of potential. It has the ability to speed up treatment of bacterial infections by allowing us to find

antimicrobials for infections in minutes instead of days. Another field where the technology

could be of vital use would be for studying the response of individual cancer cells; such tests

could equal huge advances in drug development and treatment. The AMBR technology will help

get faster results at a cheaper price hence saving more lives.

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Radiation Checking Magnetic BeadsProfessor Lawrie Challis, chairman of Mobile telecommunications and health and

research programme, has been looking into the affects of mobile phone radiation and

alternatives. Mobile phones output electromagnetic

radiation which, at 10^(-8) Hertz resemble the

frequency of microwaves. Cell phones are not the only

technology to emit such radiation; in fact any type of

wireless communication device will use the same

technology. Excessive use of these devices can lead to

many health risks. Two of the leading problems are developing brain tumors, and break down of

the blood brain barrier. The blood brain barrier protects the brain from incurring harmful

substances that are within the body. When it breaks down it makes your brain susceptible to

many health dangers. Two leading diseases that are related to the BBB breakdown include

Alzheimer’s disease and Parkinson’s disease. Other smaller risks include constant headaches,

sleep disturbances, memory loss, learning disabilities, and infertility.

Every device has a specific absorption rate which is the measure of the amount of radio

frequency energy is absorbed by one’s body when

using these device headsets which determine the

danger of the device. All these risks decrease

vastly with increased distance from the device to

your body. This is why hands free devices are

very good based on the fact that they cut down

immensely the amount of radiation that is absorbed into your body. Unfortunately, they do not

eliminate these harmful risks.

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Professor Challis has done much research and found that attaching a magnetic bead to the

wire or antenna of the phone. This type of bead is called a ferrite bead because it acts as a

suppressant to the high frequency noise in the device; it stops any current from passing it on the

outside of the wire. In simple terms it means that no radiation is pulsing out of the phone and is

unable to reach the head. This technology can be used as a marketing technique that will

promote certain phones that contain the beads as “health safe phones”.

There is ongoing debate on whether these magnetic beads are a necessity within the cell phone

unit. There are two main arguments against the use of magnetic beads in cell phones: one is that

the cell phones pass a government safety test which regulates the amount of radiation a phone

can legally have; the United States requires a 1.6 watt per kilogram SAR rating (specific

absorption rate). The other argument against the use of magnetic beads in cell phones is that

since the effect of the radiation takes a very long time to develop, not all scientists are convinced

that there is a link between the radiation and any illnesses. The scientists argue that these

illnesses can be caused by many effects and not just radiation poisoning.

Illness Detection

Magnetic bead technology has also been linked with the purification and detection of

timorous cells. Mixing magnetic bead technology and micro-electro-mechanicals-systems

(MEMS) has resulted in the ability to detect tumor cells rapidly and it also has the capability of

collecting and purifying them. The magnetic beads allow specific antibodies to be incorporated

onto their surface to target and recognize the desired tumor cells in the clinical body fluids. The

whole idea is based around the technology developed called a 3D micro-incubator. The machine

itself was developed for the incubation and mixing process, and it has the ability, using the

vortex effect, to mix large amounts of bio-samples efficiently and rapidly. It has also

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successfully detected ovarian and lung cancer cells by performing on-chip identification. The

resulting mixture of magnetic beads and the 3D micro-incubator leads to a new ability for rapid

purification and detection of cancer cells.

The need for a means of detecting cancerous

cells has long been a top priority in the scientific

field since there exists no known guaranteed cure.

Currently we are capable of detecting cancerous

cells using biomarkers of tumor cells, cell biopsy

and magnetic resonance imaging (MRI), but these methods of detection take a long time and

require complicated machinery and procedures.

Therefore the need for a rapid means of detection

exists. It is known that an early detection of

cancerous cells is crucial to the prevention of the

cells metastasizing, so a technology enabling very

early detection is highly sought after. With the

emergence of MEMS technology we have been able

to miniaturize biomedical devices and systems. The combination of MEMS technology and its

use in Biology has led to the emergence of a new field called lab-on-a-chip technology (LOC).

This technology means that a whole host of procedures and devices can be placed onto a single

microchip, and it also reduces the amount of time it takes to diagnose because the process of

analysis and preparation have been reduced to an automatic function. Using these LOC devices,

scientists have been able to perform cancer analysis using cell sorting, separation and

spectroscopy techniques. This technology may possibly lead to the ability to specify treatments

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to individuals, however the process still requires lots of bulk equipment that are needed to

perform the identification of the cancer cells. This is where the implementation of magnetic

beads comes in to play. We are able to surface-modify magnetic beads, which allows for a

specific type of cell to be detected rapidly, and when combined with the previous technologies

the overall process becomes much quicker.

An actual experiment for the purification and detection of tumor cells was performed to

accurately test the hypothesized outcomes. First they extracted body fluid in large amounts,

around 20mL. The body fluids were then pre-centrifuged and collected. The next step involved

re-suspending them with phosphate buffered saline into a 1 mL volume in an eppendorf tube.

The samples were then incubated with magnetic beads specifically coded to recognize the tumor

cells which could then be purified by using a magnetic field. The actual purification process is

performed by using a vacuum pump to suck out all of the interference substances, leaving only

the magnetized beads behind. The target mRNA can then be reverse transcripted and amplified

using a built-in-self-compensated temperature control module.

The overall layout of the system is comprised of three main units; the 3D micro-

incubator, a microfluidic control module and a nucleic acid amplification module. The 3D micro-

incubator has three layers of PDMS structures which allow large quantities of fluids to be mixed

quickly. Each layer has a thick PDMS structure and a thin pneumatically-driven PDMS

membrane which generates the mixing effect. The thick PDMS structure is made up of two air

chambers with a connecting chamber. It has a built in electromagnetic valve capable of driving it

via a digital controller and a vacuum pump. The vacuum pump generates the vortex flow in the

mixing chamber, which is what is needed for the incubation process. For final proof, two kinds

of cancer cells were incubated with magnetic beads, ovarian cancer and lung cancer. The

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magnetic beads were conjugated with the correct antibodies and placed in the incubator. Using a

magnetic the beads were attracted and the unwanted substances were sucked out with a vacuum.

It was recorded that almost all of the cancer cells were captured and purified by the experiment.

On average about 92% of tumor cells are capable of being specifically targeted by this

technology. The use of this technology will hopefully bring about the ability to detect and

prevent cancer, that way we can avoid the need to cure it.

Marketability

Magnetic beads are the most

widely used solid phase for

automated methods for isolation and

detection of biomolecules. In fact,

9/10 top IVD companies use

magnetic beads in their automated

analyzers. Additionally, binding tests (such as immunoassays and molecular tests) combine for

1/3 of the clinical tests done in the market. These tests use magnetic beads as the primary

component. This market is also valued at USD $42 billion as of 2008. Magnetic beads

themselves have a market of $1 billion for immunoassay and molecular diagnosis.

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Furthermore, Dynal, a leading

magnetic bead manufacturer claims that

while the IVD market is fast growing,

the magnetic beads market is growing

exponentially faster. In the same report,

Dynal explains that immunoassays make

up $4 billion if the IVD market where magnetic beads are once again the golden standard.

Moreover, nucleic acid testing makes a smaller portion, roughly $2 billion of the IVD market;

here, magnetic beads are the most common solid phase employed. Even areas such as genomics

that include DNA and RNA extraction and purification (a $2.3 billion market) have started using

magnetic beads at a growing pace.

ConclusionThere is no doubt that magnetic bead technology is the most modern and progressive

technology available in the market today. Being in the market for only a few years, magnetic

beads have gone from niche experimentation to a staple in the biomedical field. With its

numerous practical applications such as asynchronous bead rotation, radiation sensing abilities

and biomolecules separating abilities, magnetic beads are a technology that will be implemented

for numerous years to come. Even from a marketing point of view, the technology has a lot of

room to grow in the market; based on a simple cost analysis it can be seen that this technology

will only rise monetarily for the fore coming future.

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