Smell is one of the most evocative senses. Odours can dredge up long-forgotten
memories, inspire changes of mood, even elicit a physical response. A whiff
of sizzling bacon cheers up a gloomy morning and can set your mouth
watering, while the stench of sewage is enough to turn even the hardiest of
stomachs.
Scientists are beginning to harness the power of smell for medical purposes
and researchers will gather this week in London, at the Science Museum’s
Dana Centre, to showcase their best work in the field. One of their most
exciting inventions is a type of electronic nose that could be used as a
diagnostic tool to “smell” disease, though one researcher is particularly
proud of a perfume he has developed that taps into our brain’s pleasure
circuits and increases women’s libido (see panel, right).
Professor Julian Gardner, a scientist at the University of Warwick, has been
thinking deeply about fake mucus. Along with his team, one of whom will be
speaking at the event this week, he is developing an electronic nose (or
e-nose) complete with a plastic coating that acts as artificial nasal mucus.
E-noses could soon be used to sniff out diseases such as lung and breast
cancer, TB and pneumonia, and to detect super-bugs such as MRSA. The hope is
that these inventions will speed up diagnosis times and enable patients to
be treated sooner.
Professor Gardner’s e-nose works in a similar way to human noses. Like our own
nasal cavity, the e-nose contains thousands of molecule-catchers, called
receptors. Each of these catchers can collect only a molecule of a certain
size and shape, like fitting a piece in a puzzle. In your nose, once a
receptor has caught a molecule, it sends off a signal to your brain, which
is interpreted as a smell. In the case of the electronic nose, the
molecule-catchers are designed to catch molecules that are characteristic of
a particular disease, so the device “smells” illness.
The electronic nose may work like a human version, but it looks more like a
computer chip (see main picture). It is made of an array of
molecule-catching sensors positioned beneath a special layer of plastic
coating that acts as artificial mucus. As in the nose, the “mucus” layer
traps molecules and allows them to be caught by the receptors underneath.
Professor Gardner deliberately modelled his e-nose as closely as possible to
the real thing. He says: “I have always been inspired by the fantastic
capability of the human olfactory system.”
E-nose that knows cancer
Professor Gardner and his group are working on an e-nose that will detect
molecules in a patient’s breath that are characteristic of lung and breast
cancer. But how does cancer show up in breath? In the case of breast cancer,
cancerous cells produce specific molecules that are released into the
bloodstream. These molecules then migrate from the blood capillaries in the
lungs into the air space. Then they are breathed out with exhaled air. The
e-nose would then detect them in the exhaled breath. In the case of lung
cancer, molecules from the cancerous lung cells are simply released into the
air space in the lungs and then exhaled.
However, although this cancer-fighting technology is promising, Professor
Gardner says that it is unlikely to be available for about five years. But
something that may hit the clinic sooner is an electronic nose that will
diagnose respiratory diseases caused by bacteria such as MRSA.
These gadgets, which will cost less than £5 each, should be in widespread use
in hospital clinics within three years, providing a quick, simple and
accurate diagnosis. The MRSA e-nose will work in a slightly different way
from the cancer-detecting device. Instead of a patient blowing over the
device, a swab is taken from the area on the patient where doctors suspect
MRSA dwells. Then the swab and e-nose are held in an airstream, so that the
air first blows over the swab, then blows any MRSA molecules from the swab
on to the e-nose.
Prototype e-noses that detect TB are also being developed at Cranfield
University, in Bedfordshire, and devices to detect bacterial vaginosis are
being developed by the British bio-tech company, Osmetech. And scientists at
the University of Pennsylvania in the US are working on e-noses that can
diagnose pneumonia.
Smell takes place at the Dana Centre at the Science Museum, London (danacentre.org.uk
) on Tuesday. Tickets are free but places should be booked by calling
020-7942 4040 or e-mailing tickets@danacentre.org.uk.
Noses and numbers
75% the proportion of taste that is determined by smell
80% of the population will have some kind of smell loss by age 80
90% of new mums will be able to recognise their newborn baby’s smell
within an hour of giving birth
10,000 the number of smells that your brain can distinguish
10million the number of smell-catching receptor cells in your nose
Scent of a sexy woman
Dr George Dodd, a scientist and perfumer, discovered his talent for
distinguishing scents at the age of 5, when he realised that he could smell
things that other people couldn’t. Now 65, he has been passionate
about smell ever since and has spent his career delving into the science
behind aromas, after gaining a PhD in biochemistry.
At his company, AromaSciences (www.aromasciences.com), based in the Highlands,
Dr Dodd studies both perfumery and science in equal measure, and has used
his expertise to design a perfume – called Scentuelle (www.scentuelle.net) –
that he claims can increase libido in women. The molecules in the
perfume have been designed, he says, to mimic the feel-good hormone
dopamine. The theory is that these molecules excite specific receptors in
the brain, stimulating a woman’s pleasure centre and heightening libido. So
far, customer feedback for the perfume, which costs £17, has been positive.
In a recent survey, carried out by Dr Dodd, 60 per cent of the perfume users
reported an increase in sexual activity.
Picking up the smell Sense of smell and sickness
Loss of smell may be an early symptom of Alzheimer’s or Parkinson’s disease.
Scientists believe that smell is lost in Alzheimer’s because the olfactory
bulb, the area of the brain at the top of the nose that processes smell, is
one of the first parts of the brain to be affected by the disease. Doctors
are unsure why Parkinson’s sufferers lose their sense of smell.
Smell loss or disruption is also associated with other diseases such as motor
neurone disease, Huntingdon’s, brain tumours and leprosy.
Bad breath and disease
If your breath smells of acetone (like peardrops), this may be a sign of
diabetes; fishy breath could be a sign of kidney problems. If you want to
smell your own breath, lick your wrist, wait a few seconds for it to dry,
and then give it a sniff.
Healing scents
Some smells are believed to have healing powers – aromatherapy in modern times
stems from medieval medical practices. And one study this year indicated
that sniffing lavender and rosemary oils may reduce stress levels.
Whiffy diagnosis
In medieval times, diagnosis of disease was often based on the smell of blood,
urine, phlegm and faeces. This sometimes still occurs today, as some doctors
believe that the smell of faeces can be used as a diagnostic tool for gut
complaints, and have found that the stools of someone with ulcerative
colitis smell differently from those of healthy people. Unpleasant-smelling
urine may be a sign of a urinary infection.
Dogs can sniff out disease
Dogs can smell cancer on people’s breath. After training they can tell the
difference between healthy patients and those who have lung or breast
cancer.
