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Smart Bionanotubes Developed
"Smart" bionanotubes: Lipid
protein nanotubes made of microtuble protein
(made of tubulin protein subunits shown
as red-blue-yellow-green objects) that
is coated by a lipid bilayer (drawn with yellow
tails and green and white spherical heads)
which in turn is coated by tubulin protein
rings or spirals. By controlling the relative
amount of lipid and protein it is possible
to switch between two states of nanotubes
with either open ends (shown in the center) or closed
ends with lipid caps (shown on the left),
a process which forms the basis for controlled
chemical and drug encapsulation and release.
A top view of the nanotubes and a magnified
region is shown on the right. The image was created by Peter Allen.
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Smart Bionanotubes Developed; Can help in Drug Delivery Applications
Material Scientists and Biologists
from university of california, santa barbara have
developed a smart BioNanotube from a Protein filament
(Microtubule) and a lipid bilayer membrane, which
can be developed further for drug / gene delivery
applications.
The news is reported
in an article to be published August 9 issue of the
Proceedings of the National Academy of Sciences. It
is currently available on-line in the PNAS Early Edition.
See: http://www.pnas.org/cgi/content/abstract/0502183102v1.
These Bionanotubes are smart because in future they
can also be designed to encapsulate and then open
to deliver a drug at a particular location in the
body. Scientist at University of california found
that manipulating the electrical charges of lipid
bilayer membranes and protein filaments (microtubule)
from cell.
The findings resulted
from a collaboration between the laboratories of Cyrus
R. Safinya, professor of materials and physics and
faculty member of the Molecular, Cellular, and Developmental
Biology Department, and Leslie Wilson, professor of
biochemistry in the Department of Molecular, Cellular
and Developmental Biology and the Biomolecular Science
and Engineering Program. The first author of the article
is Uri Raviv, a post-doctoral researcher in Safinya's
lab and a fellow of the International Human Frontier
Science Program Organization. The other co-authors
are: Daniel J. Needleman, formerly Safinya's graduate
student who is now a postdoctoral fellow at Harvard
Medical School; Youli Li, researcher in the Materials
Research Laboratory; and Herbert P. Miller, staff
research associate in the Department of Molecular,
Cellular and Developmental Biology.
For the experiments,
Scientists used Microtubes purified from brain tissue
of a cow. Microtubules are nano-objects hollow cylindrical
in shape derived from cell cytoskeleton (Protien filament
from the cell). In living tissues microtubles along
with their assembled structures serves a function
of Providing tracks for the transport of cells, forming
spindle structure in the cell division and transport
of neurotransmitter precursors in neurons.
Safinya, Professor of
Material said, "In our paper, we report on a
new paradigm for lipid self-assembly leading to nanotubule
formation in mixed charged systems"
Uri Raviv explained,
"We looked at the interaction between microtubules,
negatively charged nanometer-scale hollow cylinders
derived from cell cytoskeleton and cationic (positively
charged) lipid membranes. We discovered that, under
the right conditions, spontaneous lipid protein nanotubules
will form."
In their research paper,
they used the example of car coating, depending on
whether car has been waxed or not. Similarly the lipid
membrane will either mould up on the surface of the
microtubule or flatten out and the coat the hollow
cylindrical surface of the microtubule. Behaviour
of the lipid membrane will depend on the charge saturation.
The new type of self-assembly
arises because of an extreme mismatch between the
charge densities of microtubules and cationic lipid,
explained Raviv. "This is a novel finding in
equilibrium self-assembly," he said.
"Very interestingly,
we have found that controlling the degree of overcharging
of the lipid-protein nanotube enables us to switch
between two states of nanotubes," said Safinya.
"With either open ends (negative overcharged),
or closed ends (positive overcharged with lipid caps),
these nanotubes could form the basis for controlled
chemical and drug encapsulation and release."
Bionanotubes used in
the experiments are about 19 nanometers in diameter
and the whole capsule of bionanotubes is about 40
nanometers in diameter.
Chemotherapy drug TAXOL
is one of the types of drug which can be delivered
with these bionanotubes. The Material scientists and
biologists already using TAXOL in their experiments
to stabilize lipid-microtubule bionanotubes.
The experiment
was performed using "state of the art" synchrotron
X-ray scattering techniques at SSRL (standford synchrotron
radiation laboratory), along with sophisticated electron
microscopy from University of California, Santa Barbara.
The work was funded by the National Institutes of
Health and the National Science Foundation. SSRL is
supported by the U.S. Department of Energy. Raviv
was also supported by the International Human Frontier
Science Program and the European Molecular Biology
Organization.
The original news release can be found at
http://www.ia.ucsb.edu/pa/display.aspx?pkey=1325
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