Nanobiotechnology involves manipulating structures at the nanoscale (1-100nm) using biological components. Some applications include faster disease diagnostics using biosensors, more targeted drug delivery using nanoparticles, and miniaturizing lab tools. Nanoparticles are typically spherical and composed of functional, protective, and outer layers. They can be used for fluorescent labeling, detecting pathogens, and delivering drugs or genes. Nanowires and nanotubes can also be used as biosensors to detect individual viruses or changes in conductivity when pathogens bind.

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Nanobiotechnology
The word nanotechnology derives from nanometer, which is one-thousandth of a
micrometer (micron), or the approximate size of a single molecule. Nanotechnology, the
study, manipulation and manufacture of ultra-small structures and machines made of as
few as one molecule—was made possible by the development of microscopic tools for
imaging and manipulating single molecules and measuring the electromagnetic forces
between them.
Nanotechnology involves the individual manipulation of single molecules or even atoms.
Building components atom-by-atom or molecule-by-molecule in order to create
materials with novel or vastly improved properties was perhaps the original goal of
nanotechnologists. However, the field has expanded in a rather ill-defined way and
tends to include any structures so tiny that their study or manipulation was impossible or
impractical until recently. At the nanoscale, quantum effects emerge and materials often
behave strangely, compared to their bulk properties. The main practical objectives of
nanobiotechnology are using biological components to achieve nanoscale tasks. Some
of these tasks are nonbiological and have applications in such areas as electronics and
computing, whereas others are applicable to biology or medicine.
Some applications of nanobiotechnology include
• Increasing the speed and power of disease diagnostics.
• Increasing bio-nanostructures for getting functional molecules into cells.
• Improving the specificity and timing of drug delivery.
• Miniaturizing biosensors by integrating the biological and electronic components into a
single, minute component.
Encouraging the development of green manufacturing practices.
Nanoparticles are particles of submicron scale—in practice, from 100 nm down to 5
nm in size. They are usually spherical, but rods, plates, and other shapes are
sometimes used. They may be solid or hollow and are composed of a variety of
materials, often in several discrete layers with separate functions. Typically, there is a
central functional layer, a protective layer, and an outer layer allowing interaction with
the biological world. The central functional layer usually displays some useful optical or
magnetic behavior. Most popular is fluorescence. The protective layer shields the
functional layer from chemical damage by air, water, or cell components and conversely
shields the cell from any toxic properties of the chemicals composing the functional
layer. The outer layer(s) allow nanoparticles to be “biocompatible.” This generally
involves two aspects, water solubility and specific recognition. For biological use,
nanoparticles are often made water soluble by adding a hydrophilic outer layer. In
addition, chemical groups must be present on the exterior to allow specific attachment
to other molecules or structures
Nanoparticles have a variety of uses in the biological arena:
o Fluorescent labeling and optical coding
o Detection of pathogenic microorganisms and/or specific proteins
o Purification and manipulation of biological components
o Delivery of pharmaceuticals and/or genes
o Tumor destruction by chemical or thermal means
o Contrast enhancement in magnetic resonance imaging (MRI)

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Tools of Nanotechnology
• Transmission Electron Microscope (TEM): involves shooting an electron beam through
the sample
• Atomic Force Microscope (AFM): measures the force between the probe tip and the
sample, can detect atoms or molecules by scanning a surface for shape or
electromagnetic properties, can detect and identify individual viruses. Laser monitoring
of the oscillation of a nanoscale cantilever allows single bacteria or viruses to be
individually weighed.
• Scanning Tunneling Microscope (STM): Visualization of individual molecules or even
atoms can be used to detect or move individual atoms on a conducting surface.
• Scanning Electron Microscope (SEM): detects the electrons that are scattered by the
specimen to form a 3-dimensional image.
• Nanomaterials (Carbon Nanotubes , Fullerene , Nanoparticles, Dendrimers )
• Biomaterials (Protein/ enzymes ,Peptides ,Antigens/ antibodies, Neurons ,DNA/RNA
,Cells)
• Electronic elements (Electrodes ,Field-effect, transistors, Piezoelectric crystals, STM
Tip)
• Applications (Biosensor ,Medical devices ,Solar cell ,Biofuel cell)
Hollow nanoparticles may be used to deliver DNA, RNA, or proteins: Because
nanoparticles can be targeted to specific tissues, they can be used to deliver a variety of
biologically active molecules, including both pharmaceuticals and genetic engineering
constructs.
o Large polymeric molecules such as DNA may themselves be compacted to form
nanoparticles of around 50 to 200 nm in size. This involves addition of positively
charged molecules (e.g., cationic lipids, polylysine) to neutralize the negative
charge of the phosphate groups of the nucleic acid backbone. Other molecules
may be added to promote selectivity for certain cells or tissues.
o Hollow nanoparticles (nanoshells) may obviously be used to carry other, smaller
molecules. Such nanoshells must be made from biocompatible materials such as

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chitosan, because it is both naturally derived and biodegradable. It is found in the
cell walls of insects and fungi and among biopolymers is second only in natural
abundance to cellulose. Chitosan is derived from chitin by removing most of the
acetyl groups by alkali treatment. An interesting approach that combines two
trendy technologies is using nanoshells to carry siRNA (short interfering RNA).
Delivery of siRNA triggers RNA interference, which results in the destruction of
target mRNA. The siRNA may be targeted against mRNA from genes expressed
preferentially in cancer cells or genes characteristic of certain viruses.
Nanoparticles may be used to kill cancer cells by localized heating or local
generation of a toxic product: It is possible to destroy tumor cells by a variety of toxic
chemicals or localized heating. In both cases a major issue is delivering the fatal reagent
to the cancer cells and avoiding nearby healthy tissue. Both related objectives may be
achieved by using hollow nanoparticles to carry the reagent. Nanoparticles may be
targeted to tumors by adding specific receptors or reactive groups to the outside of the
nanoparticles. These are chosen to recognize proteins that are solely or predominantly
displayed on the surface of cancer cells. It is hoped that such nanoparticles will be safe to
give by mouth. Diffusion is more difficult to deal with, but may be limited to some extent
by designing nanoparticles for slow release of the reagent.
A clever alternative is to produce the toxic agent inside the nanoparticle after it has
entered the cancer cell. Photodynamic cancer therapy involves generating singlet oxygen
by using a laser to irradiate a photosensitive dye. The singlet oxygen is highly reactive
and in particular destroys biological membranes via oxidation of lipids. After diffusing out
of the nanoparticle, the toxic oxygen reacts so fast that it never leaves the cancer cell.
Nanoparticles may also be used to kill cancer cells by localized heating. In one approach
nanoparticles with a magnetic core are used. An alternating magnetic field is used to
supply energy and heats the nanoparticle to a temperature lethal to mammalian cells.
Another approach uses metal nanoshells. These consist of a core, often silica,
surrounded by a thin metal layer, such as gold. Varying the size of the core and thickness
of the metal layer allows such nanoparticles to be tuned to absorb from any region of the
spectrum from UV through the visible to the IR. Because living tissue absorbs least in the
near infrared, the nanoparticles are designed to absorb radiant energy in this region of
the spectrum.

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Nanocrystals and nanowires may be assembled using unmodified bacteria or
sophisticated phage display techniques. It has been known for many years that
bacteria may accumulate a variety of metallic elements and may modify them chemically,
usually by oxidation or reduction. For example, many bacteria accumulate anions of
selenium or tellurium and reduce them to elemental selenium or tellurium, which is then
deposited as a precipitate either on the cell surface or internally. Certain species of the
bacterium Pseudomonas that live in metal-contaminated areas and the fungus
Verticillium can both generate silver nanocrystals.
It has been found that when Escherichia coli is exposed to cadmium chloride and
sodium sulfide, it precipitates cadmium sulfide as particles in the 2- to 5-nm size range. In
other words, bacteria can “biosynthesize” semiconductor nanocrystals. Rather more
sophisticated is the use of phage display to select peptides capable of organizing
semiconductor nanowires.
Phage display is a technique that allows the selection of peptides that bind any chosen
target molecule. In brief, stretches of DNA encoding a library of peptide sequences are
engineered into the gene for a bacteriophage coat protein. The extra sequences are
attached at either the C terminus or N terminus, where they do not disrupt normal
functioning of the coat protein. When the hybrid protein is assembled into the phage
capsid, the inserted peptides are displayed on the outside of the phage particle. The
library of phages is then screened against a target molecule. Those phages that bind the
target are kept. Phage display libraries have been screened to find peptides capable of
binding ZnS or CdS nanocrystals. Protein VIII of bacteriophage M13 was used for peptide
insertion. For example, ZnS was bound by the peptide VISNHAGSSRRL and CdS on the
peptide SLTPLTTSHLRS. Because the bacteriophage capsid contains many copies of
the coat protein, the displayed peptide is also present in many copies. Consequently an
array of nanocrystals forms on the phage surface. Because M13 is a filamentous phage,
the result is a semiconductor nanowire.

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Nanotubes may be assembled to create surfaces (nanocarpets) that are
antibacterial or act as biosensors. Nanocarpets are formed by stacking a large number
of nanotubes together, with their cylindrical axes aligned vertically. Nanocarpets capable
of changing color and of killing bacteria have been assembled from specially designed
lipids that spontaneously assemble into a variety of nanostructures depending on the
conditions. In water, nanotubes are formed. Partial rehydration of dried nanotubes
generates a side-by-side array—the nanocarpet. The lipid consists of a long hydrocarbon
chain (25 carbons) with a diacetylenic group in the middle of the chain. The individual
nanotubes are about 100 nm in diameter by 1000 nm in length.
The walls of the nanotubes consist of five bilayers of the lipid. Both the separate lipid
molecules and the assembled nanocarpet kill bacteria. Like other long-chain amino
compounds, they act as detergent molecules and disrupt the cell membrane.
Consequently, the nanocarpet provides a surface lethal to bacteria. This property could
be very useful if nanocarpets are used in biomedical applications. Diacetylenic
compounds have the interesting ability to change color. The nanocarpet starts out white,
but if exposed to ultraviolet light, it turns deep blue. UV irradiation causes crosslinks to
form by reaction between acetylenic groups on neighboring molecules. This
polymerization stabilizes the nanocarpet. Blue nanocarpets change color on exposure to
a variety of reagents. Detergents and acids change them from blue to red or yellow, and
the presence of bacteria, such as E. coli , gives red and pink shades. Eventually such
materials may be used both as biosensors and for protection against bacterial
contamination.
Detection of viruses by nanowires: Nanowire sensors are capable of detecting specific
individual viruses. Binding of a virus particle changes the conductance of the nanowire.
Nanowires have nanoscale diameters but may be several microns long.
They may be metallic and act as electrical conductors or they may be made from
semiconductor materials. Biosensors can be made using silicon semiconductor
nanowires. These may be coated with antibodies that bind to a specific virus. Binding of
the virus to the antibody triggers a change in conductance of the nanowire. For a p-type
silicon nanowire, the conductance decreases when the surface charge on the virus
particle is positive and, conversely, increases if the virus surface is negative. Single
viruses may be detected by this approach. It is also possible to attach single-stranded
DNA to the nanowire. In this case, conductance changes are triggered by binding of the
complementary single strand. Possible future applications include both clinical testing and
sensors for monitoring food, water, and air for public health and/or biodefense.