Richard Bernache December 17th, 2011 Chemistry II Nanotechnology Project: Briefing In the current age people are always looking for the most compact device. As we gain speeds never before reached with our technology, we are now looking to downsize,

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Richard Bernache

December 17th, 2011

Chemistry II

Nanotechnology Project: Briefing




In the current age people are always looking for the most compact device.

As we
gain speeds never before reached with our technology, we are now looking to down
size,
creating objects of smaller size, with the same outstanding performance.

However,
modern science is fast approaching a road block.

Our current macro
-
sized technologies
just aren’t small enough.

Now the world is looking towards nanotechnologies, or

machines smaller than 1,000 nanometers.

The uses of these machines are almost
limitless, from

making technologies even smaller, to creating disease fighting robots that
can be injected directly into a patient

s bloodstream.

The only problem is creating
sustainable nano
-
devices through conventional methods. The size of these objects
presents an obvious problem, how are we to create parts an
d

assemble working
machinery on such a tiny scale.

It is this problem that is currently stalling scientists.

Today’
s nanotechnologies are extremely difficult to construct, and assembling them is
harder still.

The result is unstable technologies that are for the most part unreliable.

So
how do we confront this problem? The answer may lie in biology.


While man made na
nostructures are unstable, those that occur naturally are
uniformed, stable, and surprisingly strong. The secret to the assembly of nanostructures
is the protein. Protein’s are nature’s builders, and are responsible for the construction of
naturally occu
rring nanostructures. Knowing this, scientists are beginning to look for
ways to harness these proteins and use them to construct nanotechnologies of there own.
Proteins offer three solutions to the current problems of nano
-
assembly. Through
utilizing g
enetic engineering, it is possible to create a protein template that will allow for
total control of what materials are used to construct the final product. The second is that
proteins can act as the binding agent between nano
-
particles, create larger str
uctures.
Finally, by harnessing proteins we gain control over biological molecules to self
-
assemble into organized nanostructures, effectively building themselves.

It is from this that the field of Biomimetics is born. Biomimetics is the production of
te
chnology using genetically engineered proteins and nanotechnologies. Proteins build
by binding to substances, and so the first step to harnessing them, is getting them to bind
to the scientist’s desired compound.


There are several possible ways to gain c
ontrol of a protein’s binding and using it
to our advantage. One possibility utilizes the fact that every protein binds to a specific
group of substances naturally. It is entirely possible that these proteins would also bind
to inorganic compounds used t
o create nanotechnologies. Because little testing has been
done on this the result would be a very lengthy and expensive process of determining
which proteins naturally bind to what compounds. Obviously the result would be an
incredibly long research pha
se (prior to any type of research on actually constructing
these technologies) that would take a great number of years to complete. For this reason,
the possibility is generally disregarded.

The second option involves extracting proteins
from hard tissue,

purifying, and cloning them. However, many extremely complex
proteins exist together in hard tissue, making it difficult to isolate and utilize specific
strands. Furthermore, it is possible that these proteins would only be capable of
regenerating the i
norganic compounds they naturally bind to, and would little to no use in
the construction of nanotechnologies.

Clearly, this route is not highly regarded either.


The method that has been deemed most practical and that is being given the most
research is c
ombinatorial biology techniques.

This involves the use of massive libraries
of randomly created amino acids, all of the same length, but of different structure. These
libraries can be “scanned” for proteins that bind to a certain inorganic compound,
engi
neered, and then cloned for future use.

This is done by inserting the randomized
amino acid strands into certain genes. Then these random sequences are incorporated into
the protein, resting on its surface. This causes each of the cells to display a diffe
rent
random peptide on its surface. Next, the inorganic substance is introduced and sequences
that bind to it proceed to do so. The process then undergoes several wash cycles, which
break free any weak or non connected sequences. The cells that do bind
are then
removed and amplified by being reintroduced into the host gene, creating only cells with
the specifically needed sequence. This process is repeated multiple times in order to
strengthen the binding capabilities of the amino acid sequence. Once t
he sequence is
deemed strong enough it is cloned, and the amino acid sequence needed for a particular
inorganic is engineered.


While this process is favored, it is not without its drawbacks. Removing the
created sequences from the compound may weaken the
m, leading to a lack of good
binding agents. This can be combated through the strengthening processes, but the
problem of the created amino acid binding to other compounds that is what not intended
for still remains. Carefully using buffers to avoid cont
act with other substances may
help, but the problem is a large one.

There is always the possibility of a mis
-
screen so it
is important to use parallel screens in order to create the most powerful binder. It appears
that with this process current methods
may not be enough, and so new ones will have to
be discovered.


These genetically engineered proteins are called GEPI (Genetically engineered
polypeptide for inorganics). Previously, research with GEPIs’ were done with powders,
rough substances that aren’
t very strong or good for construction. Today’s research is
being done with more stable materials such as noble metals. It is believed that both
chemical and structural properties contribute to the binding strength and capability of a
certain amino acid c
hain. Research is currently being conducted on already identified
amino acids and their corresponding inorganics in order to decipher the true source of the
bond. One study done with gold suggested that while gold was binded to the
polypeptide, it retain
ed it own characteristics
, m
eaning that it acted dependently from the
protein and could later be removed.
Also, studies using noble metals found that the
metals were bound by an interaction between hydrogen and nitrogen atoms. By repeating
this study wit
h multiple metals this characteristic was found to be the same throughout.
Another success of the study was that it determined at least three cycles of genetically
altering and strengthening of the polypeptide were needed before a strong enough binding
ca
pability was achieved. Studies are also being performed on metal oxides and ionic
crystals, finding that the binders for both are usually strong basic compounds with
relatively high positive charges. Meanwhile, non
-
oxide semiconductors have been found
to

bind with slightly basic binders with no charge at all. With these differences already
discovered between the chemical binding possibilities of different types of substances, it
becomes easier to narrow the search for the correct binder. This, along wit
h physical
traits, narrows the list even further, allowing scientists to more easily create the needed
amino acid sequence.


As previously stated both chemical and physical properties contribute to
determining which binders will attach to a desired inorgan
ic. Ideally, a specific structure
should be used when determining a binder for a substance. However, more often than
not, powders are used. This presents two issues: 1) The GEPI may bind to a particular
size or structure of substance more than another.
2) A GEPI may also bind to another
substance that has similar structure, but different composition, which poses an obvious
threat to the desired result. The best approach to solving this problem is by using the
powder trials as a preliminary, and then sea
rching for a specific structure of the material
desired. Studies done with gold found that certain binders bound strongest do the lattices
of gold. Some binders left noticeable gaps, allowing for molecules to fill the space and
weakening the connection.


In order to create functioning devices using nanotechnology, certain problems
must be addressed. Problems such as creating nanostructures (rods and tubes) with a
uniform size and shape, as well as controlling their surface structure and chemical make
up.

We also have to be able to predict the spatial distribution of the structure.
Biomimetics offers a solution to these problems
. Because a GEPI can be inserted into a
protein, designer builders can be created with the ability to bind to specific substanc
es.
They can also be combined with man made polymers, giving them the dual purpose of
their original capabilities as well as specific binding properties. As binders are bein
g
identified the reality of using Biomimetics becomes more likely.


So what exac
tly is the future use of a process like Biomimetics? The possibilities
are extremely broad. Controlling the assembly of proteins has been a major goal of
modern engineering. With better control we can create better functioning implants
,
making them longe
r lasting, more efficient and safer. Also, Biomimetics plays a large
role in the production of hard tissues. As the process of developing GEPIs improves,
they can also be fused to human proteins, and be genetically designed to create a better
biocompatib
ility of devices such as artificial implants, or donated organs. They can also
be used to more effectively deliver drugs. The obvious possibility is that GEPIs may
constitute the first step towards creating dynamic nanostructures. While the prospects
see
m promising, it is important to remember that there are still many problems with this
system to work out before it can begin to be used.