Nanotechnology, the manipulation of matter at the atomic
and molecular scale to create materials with remarkably varied and new
properties, is a rapidly expanding area of research with huge potential in many
sectors, ranging from healthcare to construction and electronics. In medicine,
it promises to revolutionize drug delivery, gene therapy, diagnostics, and many
areas of research, development and clinical application.
What is
Nanotechnology?
The prefix "nano" stems from the ancient Greek
for "dwarf". In science, it means one-billionth (10 to the minus 9)
of something, thus, a nanometer (nm) is one billionth of a meter, or
0.000000001 meters. A nanometer is about three to five atoms wide, or some
40,000 times smaller than the thickness of human hair. A virus is typically 100
nm in size.
The ability to manipulate structures and properties at
the nanoscale in medicine is like having a sub-microscopic lab bench on which
you can handle cell components, viruses or pieces of DNA, using a range of tiny
tools, robots and tubes.
Manipulating DNA
Manipulating DNA Therapies that involve the manipulation
of individual genes, or the molecular pathways that influence their expression,
are increasingly being investigated as an option for treating diseases. One
highly sought goal in this field is the ability to tailor treatments according
to the genetic make-up of individual patients.
This creates a need for tools that help scientists
experiment and develop such treatments.
Imagine, for example, being able to stretch out a section
of DNA like a strand of spaghetti, so you can examine or operate on it, or
building nanorobots that can "walk" and carry out repairs inside cell
components. Nanotechnology is bringing that scientific dream closer to reality.
For instance, scientists at the Australian National
University have managed to attach coated latex beads to the ends of modified
DNA, and then using an "optical trap" comprising a focused beam of
light to hold the beads in place, they have stretched out the DNA strand in
order to study the interactions of specific binding proteins.
Nanobots and
Nanostars
Meanwhile chemists at New York University (NYU) have
created a nanoscale robot from DNA fragments that walks on two legs just 10 nm
long. In a 2004 paper published in the journal Nano Letters, they describe how
their "nanowalker", with the help of psoralen molecules attached to
the ends of its feet, takes its first baby steps: two forward and two back.
One of the researchers, Ned Seeman, said he envisages it
will be possible to create a molecule-scale production line, where you move a
molecule along until the right location is reached, and a nanobot does a bit
chemisty on it, rather like "spot-welding" on a car assembly line.
Seeman's lab at NYU is also looking to use DNA nanotechnology to make a biochip
computer, and to find out how biological molecules crystallize an area that is
currently fraught with challenges.
The work that Seeman and colleagues are doing is a good
example of "biomimetics", where with nanotechnology they can imitate
some of the biological processes in nature, such as the behavior of DNA, to
engineer new methods and perhaps even improve them.
DNA-based nanobots are also being created to target
cancer cells. For instance, researchers at Harvard Medical School in the US
reported recently in Science how they made an "origami nanorobot" out
of DNA to transport a molecular payload. The barrel-shaped nanobot can carry
molecules containing instructions that make cells behave in a particular way.
In their study, the team successfully demonstrates how it delivered molecules
that trigger cell suicide in leukemia and lymphoma cells.
Nanobots made from other materials are also in
development. For instance, gold is the material scientists at Northwestern
University use to make "nanostars", simple, specialized, star-shaped
nanoparticles that can deliver drugs directly to the nuclei of cancer cells. In
a recent paper in the journal ACS Nano, they describe how drug-loaded nanostars
behave like tiny hitchhikers, that after being attracted to an over-expressed
protein on the surface of human cervical and ovarian cancer cells, deposit
their payload right into the nuclei of those cells.
The researchers found giving their nanobot the shape of a
star helped to overcome one of the challenges of using nanoparticles to deliver
drugs: how to release the drugs precisely. They say the shape helps to concentrate
the light pulses used to release the drugs precisely at the points of the star.
Preventing Heart
Disease
One of the major killers in our time is heart disease. There
are several efforts going on in this area. Researchers at the University of
Santa Barbara have developed a nanoparticle that can deliver drugs to plaque on
the wall of arteries. They attach a protein called a peptide to a nanoparticle
which then binds with the surface of plaque. Studies have verified that the
peptide attaches the nanoparticle to plaque. The researchers plan to use these
nanoparticles to deliver imaging particles and drugs to both diagnosis and
treat the condition.
Researchers at MIT and Harvard Medical School have
attached a different peptide to a drug-carrying nanoparticle. This peptide binds to a membrane that is
exposed in damaged artery walls, allowing the nanoparticle to release a drug at
the site of the damage. The drug helps prevent the growth of scar tissue that
can clog arteries. For more about this, see the article at this link.
To help coordinate this type of research, the U.S.
National Heart Lung and Blood Institute has established four Program of
Excellence in Nanotechnology Centers to focus on diseases of the lung and
cardiovascular system. The scientists are developing methods to detect,
monitor, treat, and eliminate "vulnerable" plaque, the type of plaque
most likely to cause heart attacks.
Diagnostic
Techniques
Researchers at MIT have developed a sensor using carbon
nanotubes embedded in a gel; that can be injected under the skin to monitor the
level of nitric oxide in the bloodstream. The level of nitric oxide is
important because it indicates inflammation, allowing easy monitoring of inflammatory
diseases. In tests with laboratory mice the sensor remained functional for over
a year.
Researchers at the University of Michigan are developing
a sensor that can detect a very low level of cancer cells, as low as 3 to 5
cancer cells in a one milliliter in a blood sample. They grow sheets of
graphene oxide, on which they attach molecules containing an antibody that
attaches to the cancer cells. They then tag the cancer cells with fluorescent
molecules to make the cancer cells stand out in a microscope.
Researchers have demonstrated a way to use nanoparticles
for early diagnosis of infectious disease. The nanoparticles attach to
molecules in the blood stream indicating the start of an infection. When the
sample is scanned for Raman scattering the nanoparticles enhance the Raman
signal, allowing detection of the molecules indicating an infectious disease at
a very early stage.
A test for early detection of kidney damage is being
developed. The method uses gold nanorods functionalized to attach to the type
of protein generated by damaged kidneys. When protein accumulates on the
nanorod the color of the nanorod shifts. The test is designed to be done
quickly and inexpensively for early detection of a problem.
Life Extension and
Nanomedicine
There is no doubt, that the advance in medicine and
overall progress in diagnostics and treatment, can be directly linked to the
expected life extension. Indeed, future advances in nanomedicine could give
rise to life extension through the repair of many processes thought to be
responsible for aging. K. Eric Drexler, one of the founders of nanotechnology,
postulated cell repair machines, including ones operating within cells and
utilizing yet hypothetical molecular computers, in his 1986 book Engines of
Creation. Raymond Kurzweil, a futurist and transhumanist, stated in his book
The Singularity Is Near that he believes that advanced medical nanorobotics
could completely remedy the effects of aging by 2030.
In an interview with Computerworld in 2009, Ray Kurzweil
said that anyone alive come 2040 or 2050 could be close to immortal. The quickening
advance of nanotechnology means that the human condition will shift into more
of a collaboration of man and machine, as nanobots flow through human blood
streams and eventually even replace biological blood, he added.
That may sound like something out of a sci-fi movie, but
Kurzweil, a member of the Inventor's Hall of Fame and a recipient of the
National Medal of Technology, says that research well underway today is leading
to a time when a combination of nanotechnology and biotechnology will wipe out
cancer, Alzheimer's disease, obesity and diabetes.
Cloning and body
part replacement
Some life extensionists suggest that therapeutic cloning
and stem cell research could one day provide a way to generate cells, body
parts, or even entire bodies (generally referred to as reproductive cloning)
that would be genetically identical to a prospective patient. Recently, the US
Department of Defense initiated a program to research the possibility of growing
human body parts on mice. Complex biological structures, such as mammalian
joints and limbs, have not yet been replicated. Dog and primate brain transplantation
experiments were conducted in the mid-20th century but failed due to rejection
and the inability to restore nerve connections. As of 2006, the implantation of
bio-engineered bladders grown from patients' own cells has proven to be a
viable treatment for bladder disease. Proponents of body part replacement and
cloning contend that the required biotechnologies are likely to appear earlier
than other life-extension technologies.
The use of human stem cells, particularly embryonic stem
cells, is controversial. Opponents' objections generally are based on
interpretations of religious teachings or ethical considerations. Proponents of
stem cell research point out that cells are routinely formed and destroyed in a
variety of contexts. Use of stem cells taken from the umbilical cord or parts
of the adult body may not provoke controversy.
The controversies over cloning are similar, except
general public opinion in most countries stands in opposition to reproductive
cloning. Some proponents of therapeutic cloning predict the production of whole
bodies, lacking consciousness, for eventual brain transplantation.
Other Ethical
Issues
Genetic Modification
It is likely that some conditions will be treated most
easily by modifying the body's genetic material. Many people are disturbed by
this idea, especially if the modification is transmissible to offspring.
However, once we have a nanotechnology that can directly manipulate the genes,
transmission of modified genes need not be a cause for concern. Any genetic
manipulation that turns out to be a bad idea will be reversible. Furthermore,
it would be trivial to edit the DNA of any offspring while still in embryo
stage in order to remove the modifications. The idea that a genetic
modification will irreversibly change the whole species becomes incorrect once
genes can easily be directly manipulated.
Overpopulation
A common objection to life extension is that if everyone
lives forever, the earth will become overcrowded. However, a little math will
demonstrate that the earth can become overcrowded much faster due to excess
births than due to reduced death. If everyone killed themselves after 80 years
of life, that act would remove only one person from the population; meanwhile
their children and grandchildren would be reproducing. However, a person who
chose to live a long time and have one fewer child would be reducing the
population by more than one, since a nonexistent person cannot have children.
(Robert J. Bradbury points out that nanotechnology will also give us cheaper
access to space. Using a basic design, it would be feasible for earth's entire
population to leave the earth and live in space.)
Poor Health
Today, people are kept alive for years in terrible
health, sometimes beyond the point where they wish to die. This has given life
extension a bad reputation. Merely extending life without improving health is
often a bad idea. The good news is that if health is improved, life will
naturally be extended. Once we have the technology to eliminate diseases, we
need no longer worry about living on in bad health.
Elitism
It has been argued that it would be selfish for some
people to extend their lives when the technology is not available to everyone.
However, life extension will not be a single technology hoarded by an
elite--instead, it will be a natural consequence of health maintenance. Inequities
in availability of health care are widespread today, and curing more diseases
will not make the problem worse. On the other hand, development of more
effective medical tools will reduce the cost of medical care. If you want to
increase the availability and reduce the cost of a technology, you should
invest in research and development, and buy more technology. The more people
who make use of health maintenance technologies, the faster they will become
cheap and widely available.
Other Risks
Some people have claimed that nanotech itself is
extremely risky, and thus any development or use of it must be constrained.
This argument rests on the idea that tiny self-replicating nanobots appear to
be possible, and that a rogue self-replicator could eat the planet. This
argument does not apply to medical nanotech. There is no reason to use
self-replication for medical nanodevices; it would only make them needlessly
complex and more prone to failure. A medical nanodevice would simply be a
machine like any other, no more capable of running amok than a television. The
factories used to build the nanobots might be self-replicating, but a factory
is equally unlikely to run amok.
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