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0:00
Hello, my name is
Szczepan Zapotoczny,
I work as a professor heading
the Group of Nanotechnology
of Polymers and
Biomaterials at
the Agilonian University
Faculty of Chemistry
in Krakow, Poland.
I'm going to talk about
the formation of layer
by layer assemblies,
such as films, capsules,
and their applications
in drug delivery.
0:25
I'm going to start
with the introduction
to the layer by
layer assembly as
the position technique enabling
fabrication of multi
layer films and capsules.
I will particularly focus on
capsules that can
be formed using
solid micro particles as well as
liquid nano droplets
serving as templates.
Then encapsulation of drugs and
their release from the capsules
and films will be addressed,
I will complete the talk
with some examples of
drug delivery systems
based on LbL assemblies.
1:03
LbL assembly based on
sequential absorption
of oppositely charged polymers
was introduced by
Professor Decher
in the 90s, but
some first attempts
with application of
charge microparticles
were already reported
30 years earlier.
In a classical approach,
polyelectrolytes are absorbed on
oppositely charged surfaces by
simple immersion
of a substrate in
an aqueous solution
of polyelectrolyte,
for example, poly-anion,
followed by washing
the coating to
remove loosely bound
macro-molecules,
and subsequent deposition
of another
polyelectrolyte layer,
in this case, polyketile.
By repeating this procedure,
a number of times
multi layer films of desired
thickness are formed,
such a sequential absorption
of thin layers of
oppositely charged
polyelectrolytes relies
mainly on electrostatic
forces acting
cooperatively for high
molecular weight compounds.
This technique has a
number of advantages
with respect to other
film fabrication methods.
It is relatively simple
and inexpensive,
it can be applied on
various charged substrates,
both flat and curved,
such as micro or nano particles.
Importantly, various
synthetic and natural
polyelectrolytes
can be used in LbL
approach that is
crucial for their potential
biomedical applications.
Thus typical synthetic
polyelectrolytes such as
poly(sodium-4-styrenesulfonate)
abbreviated PSS,
or poly(allylamine
hydrochloride) PAH,
but also biocompatible
polysaccharides
such as hyaluronic
acid, chitosan,
as well as charged
polypeptides can be
used in preparation
of LbL coatings.
LbL offers also
high control over
film thickness down to about
one nanometer per layer,
as well as its related
properties such
as permeability and
density of the coating.
Such coatings are pretty
robust also in aqueous media,
but can be further strengthened
by cross linking of
the polymer layers.
The methodology
is not limited to
polyelectrolytes only since
other charged objects,
such as nanoparticles,
nanotubes,
or nanoplates can be applied.
LbL can also be driven by
other types of interactions,
such as hydrogen bondings,
host gas interactions
that significantly
broaden application of this
film fabrication method.
