Did you
know?
Alignate is extracted from
the cell walls of brown
algae. It is a flavourless
gum, added to thicken
and emulsify foods
such as ice cream.
Alginate is also
used for
waterproofing
fabric, in the
manufacture
of paper and
as an appetite
suppressant.
Cutting-edge chemistry
Helping good bacteria reach their target
Most probiotic bacteria that are added to foods, such
as yoghurt, to aid the digestive system are not reaching
their intended target in the intestine. Instead, the
majority are destroyed in the stomach before they can
do any good. Now, UK scientists have come up with a
coating to overcome this problem.
Probiotics are bacteria that naturally live in the small
and large intestine. They provide health benefits by
producing nutrients, compete with infectious bacteria
for binding sites and stimulate the immune system.
Protecting bacteria
Find out more
out foods with
Learn more ab
benefits –
specific health
s – with this
od
fo
functional
emistr y World
ar ticle from Ch
iyfAf
http://rsc.li/Q
Probiotic bacteria are
added to food such
as yoghurt to aid the
digestive system
Materials scientist Vitaliy Khutoryanskiy and
microbiologist Dimitris Charalampopoulos and their
colleagues at the University of Reading overcame the
problem of the bacteria dying before they could enter
the intestines by building them a coat of alginate and
chitosan layer-by-layer. This coat protects the bacteria
as it travels through the stomach to the intestine.
‘Delivering probiotics via the oral route is considered
to be beneficial for treating disorders of the
gastrointestinal tract including irritable bowel
syndrome, bacterial infections and diarrhoea caused
by antibiotics,' says Khutoryanskiy. 'However, the
majority of probiotic bacteria taken orally cannot
pass through the acidic environment in the stomach
and remain viable. So our idea was to protect these
bacteria via encapsulation.'
Building the coat
The team dispersed live bacteria in an aqueous sodium
alginate solution and extruded it into a solution of
calcium chloride to form calcium alginate beads
(alginate forms a gel in the presence of calcium ions).
Then, they formed a coating around the beads by
depositing alternating layers of alginate, a negativelycharged polysaccharide, and chitosan, a positivelycharged polysaccharide, on their surface.
‘We have established that the formation of a multilayered coating can result in efficient protection of
live bacteria within these capsules, but the levels
of protection and the viability of bacteria
are dependent on the number of multilayers
deposited,’ says Khutoryanskiy. ‘Encapsulation
in the alginate matrixes coated with three layers
gave us the highest levels of viable cells.’ They
also demonstrated that the capsules release
viable bacteria in vitro under the pH conditions of
the intestinal tract.
A worthy goal
In the future, the team hopes to study the
delivery of viable bacteria using their capsules in
experimental animals. ‘We also need to evaluate
the shelf life and long-term stability of these
capsules under various storage conditions,’ adds
Khutoryanskiy.
Shutterstock
‘Encapsulating probiotic bacteria for their
protection and targeted release is important,
as probiotics are apparently important for our
health,' says Yoav Livney, from the Israel Institute
of Technology, in Haifa, Israel. 'Increasing their
survival through the stomach is a worthy goal.'
Elinor Hughes
8 | The Mole | January 2013
www.rsc.org/TheMole
Did you
know?
Cotton thread to monitor athletes’
dehydration
It's possible to determine
a person’s sex through the
compounds present in
their sweat and deposited
in their fingerprints:
http://rsc.li/VsU5yd
Scientists in Italy have integrated a device to monitor
the salt concentration of sweat into a cotton fibre.
The fibre can then be embedded into cloth and could
be used to monitor hydration levels in athletes by
measuring how much they are sweating.
shutterstock
Functionalised fibres have been proposed as electronic
sensors before but they only work with gel or solid
electrolytes. As a result, they require complex fabrication
techniques, are cumbersome when integrated into
fabrics and are unable to detect liquids.
To overcome these challenges, Nicola Coppedè and
colleagues from the Institute of Materials for Electronics
and Magnetism in Parma made a device that can use a
liquid as an electrolyte – in this case sweat – so that it
can be used as a liquid sensor.
The team functionalised a cotton fibre with a conductive
polymer (poly(3,4-ethylenedioxythiophene:poly(styrene
sulfonate)) and a silver wire. It is fully compatible
with standard clothing, says Coppedè. Even when
impregnated with the conductive polymer, the thread
again after 40 minutes to compare results. They found
keeps its mechanical characteristics and thin silver wires
that the salt concentration decreased significantly for
are already commonly used in textile manufacturing.
all athletes. ‘By a simple electric measurement we could
Saline ions
detect, in real time, the hydration condition of an athlete
The functionalised fibre can measure the current
using a low cost device, which could easily be integrated
passing through it when it makes contact with the silver into cloth,’ he adds.
wire thanks to the sweat from the athlete. A voltage
Not just for athletes
applied to the wire moves the ionic species in the liquid
As well as monitoring athletes, Coppedè also wants
to the cotton thread, changing its conductivity. The
to use the device to monitor the clinical condition of
change depends on the concentration of the saline ions
unconscious patients. ‘We could evaluate dehydration
diluted in the liquid.
or other clinical problems, which represent a possible
‘We applied the sensor to detect the concentration of
risk if not detected in time, through changes in sweat
salt in human sweat, to monitor stress conditions when characteristics and reveal them by the simple device in
doing sport,’ explains Coppedè. The team used the
the textile,’ he says.
device on athletes after 10 minutes of jogging and then Elinor Hughes
Diego Barbieri/Shutterstock
Conductive polymer
A cotton fibre
functionalised with a
conductive polymer
can detect salt levels in
human sweat
Find out more
ucting
What are cond
can we use
ow
H
s?
er
polym
ws to capture
them in windo
e sun? Find
th
energy from
ticle from the
ar
is
th
out with
12 issue of The
September 20
c.li/UWJ1cg
Mole: http://rs
A drop of a liquid
electrolyte placed in
contact with the thread
and the silver wires
www.rsc.org/TheMole
January 2013 | The Mole | 9