Joanie July 9th, 2008
DO WE HAVE THE TECHNOLOGY TO BUILD A BIONIC HUMAN?
By Duncan Graham-Rowe
July 4, 2008
More and more of the body is becoming, if not obsolete, then certainly
replaceable. But which of our body parts can be engineered today, and which
will we have to make do with?
Implants that copy the simple structural job of skeletal tissue are the
easiest to build. One UK woman suffering from rheumatoid arthritis was
recently left with only two of her original joints after having the rest
replaced by metal and plastic alternatives.
Hips, teeth and vertebral discs can all be replaced, and customised to match
the patient. A 3D printer can even be used to tailor-make parts within hours
for a perfect fit, useful after accidents. One device prints “bone” using a
new porous polymer that is nearly as strong as the real thing.
But artificial bones are not perfect. One idea that may see them match
natural bone’s strength and lightness is to build implants by zapping
titanium powder with a laser. That can makes pores of different sizes in
different areas of the finished product, controlling strength and stiffness
in the same way as real bone.
Other recently developed ways to improve implants include making them
magnetic to attract drugs or giving them surface textures able to promote
new bone growth.
But growing living bone and cartilage to order is probably the best way to
tackle the problems with getting the body to accept man-made materials.
In the first human trial of this approach, lab-grown cartilage proved able
to fix damaged knees. This type of tissue-engineering cultivates cells over
a scaffold that is usually based on compounds found in connective tissue.
Ligaments can also be grown this way. Placing a scaffold in the body allows
in-situ growth, a technique that can also work with nerves and returned
sight to blind hamsters.
In fact, by culturing normal or stem cells it is now possible to grow pretty
much any type of tissue. Some complete organs have already been grown from
Artificially grown bladders have changed the lives of some spina bifida
patients. Even working penises have been grown, for rabbits, who could
ejaculate and successfully mate using them.
But growing more complex organs with intricate systems of blood vessels is
difficult. One possible solution involves making a plastic cast of an
organ’s blood vessels by filling a donated organ with polymer.
The recovered cast is then seeded with cells that grow into blood vessels,
after which the organs’ new cells are grown over the top. A liver complete
with blood vessels has been made this way, but was not fully functional.
Organs live on
A way to sidestep the problems of growing intricate structures like blood
vessels or alveoli in the lungs is to borrow the structures from donated
A process called “decellularisation” chemically strips away cells, leaving
connective tissue, including blood vessels, behind. This also has the
advantage that, without living cells, the transplant will not be rejected by
First used to replace heart valves, the technique was this year used to
reincarnate a whole rat’s heart. After a few electric shocks, the newly
grown heart was beating regularly.
That technique is still far from reaching human hospitals, but cardiac
patients are already spoilt for choice when it comes to replacements.
The most common are pacemakers, which take over from the clumps of cells
that synchronise heart muscle with pulsing electricity. Scientists have
recently developed a pacemaker powered by the heart itself, saving later
operations to change the battery.
Human heart transplants have been carried out for decades, while artificial
hearts can help people waiting for a transplant.
Other parts of the body¹s plumbing network, such as the lymphatic system,
are becoming replaceable too. Last year, mice were implanted with an
artificial lymph node made from collagen and cells taken from a gland in
This approach could one day be used to rebuild an immune system compromised
by disease like AIDS.
The brain’s complexity makes it doubtful we will ever recreate it. But some
of its functions, and those of other parts of the nervous system can already
be replaced by electronics.
The most successful example is the cochlear implant. More than 100,000
people can hear again thanks to microphone output directly stimulating the
cochlea of the inner ear.
This approach has limitations, though, so a new design stimulates the nerve
connecting the ear to the brain instead, an approach that should offer
better quality hearing and even music to the deaf.
Implants can also help the blind see, by stimulating the retina, optic nerve
or the brain’s visual cortex. However, the quality of results varies. Making
better bionic eyes hinges on better understanding how the retina and brain
Perhaps the most ambitious neural implant yet attempts to replace a whole
section of the brain — the hippocampus — which is involved in spatial and
short-term memory. Researchers are working on an electronic hippocampus that
accepts, processes and produces electrical signals just like a real one.
Out on a limb
Other research seeks to replace entire limbs with robotic replacements.
Electronics and motors must simulate bone, muscle and nerves working in
unison, and integrate smoothly with the real thing.
The Italian CyberHand project aims to let a person control and receive
sensation from an artificial hand just as they would from a real one.
Electrodes will connect the nerves that previously served the missing hand
to the robotic prosthetics motors and force sensors.
Some advanced bionic arms require the nerves that once controlled to a
missing limb be “rewired” to a person’s chest. When they try to move the
prosthetic limb, it causes the chest muscles to twitch, triggering sensors
that control the arm. Rewiring the sensory nerves from a limb in the same
way makes it possible to feel feedback from the arm as if it were real.
US defence agency DARPA has made improved prosthetics a priority, with one
funded project, the “Luke arm”, recently unveiling impressive results.
Despite all these successes and promising leads, the human body is still
more complex than any machine, and we don’t have the advantage of an
All too often, artificial replacements come with a catch. Organ transplants
require lifetime treatment with immunosuppressant drugs to prevent
rejection, while some evidence suggests stem cells treatments can cause
Electronic devices suffer corrosion, wear and tear, and can require repeated
operations to replace batteries. Powering them using movement or other
energy from the body could be the answer.
Electronic implants can also be vulnerable to electromagnetic interference
or even remote attacks. Earlier this year researchers used radio waves to
hack a pacemaker in a way that could cause a heart attack.
Working out how to encourage a body to grow its own replacements avoids most
of these problems. However, superhuman abilities like controlling machines
with your thoughts will always depend on electronics.