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Nanotechnology

Nanotechnology is the engineering of functional systems at the molecular scale. In its original

sense, 'nanotechnology' refers to the projected ability to construct items from the bottom up,

using techniques and tools being developed today to make complete, high performance products.

Nanotechnology, or, as it is sometimes called, molecular manufacturing , is a branch of

engineering that deals with the design and manufacture of extremely small electronic circuits and

mechanical devices built at the molecular level of matter. The Institute of Nanotechnology in the

U.K. expresses it as "science and technology where dimensions and tolerances in the range of 0.1

nanometer (nm) to 100 nm play a critical role." Nanotechnology is often discussed together with

micro-electromechanical systems (MEMS), a subject that usually includes nanotechnology but

may also include technologies higher than the molecular level.

“Nanotechnology is the understanding and control of matter at dimensions between

approximately 1 and 100 nanometers, where unique phenomena enable novel

applications. Encompassing nanoscale science, engineering, and technology,

nanotechnology involves imaging, measuring, modeling, and manipulating matter at

this length scale.”

“Nanotechnology is science, engineering, and technology conducted at the

nanoscale, which is about 1 to 100 nanometers”

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Nano-Biosystems

Nano-biosystems is a field that includes both the use of nanotechnology in biological systems

and utilization of biological or bio-mimetic techniques in nanotechnology. Nano-biotechnology

shows a tremendous promise of improving the quality of life. For example, nano-vehicles might

deliver drugs directly to targeted cells, nano-membranes may be used for development of cheap,

effective water purification systems, or nano-chips that interface neurons with electronics may

become common place. Additionally, Nano-Electro­ Mechanical Systems (NEMS) might use

sensors and physical controls to stabilize individuals with heart, kidney or liver disease.

Nano-network

A nanonetwork or nanoscale network is a set of interconnected nanomachines, (devices a few

hundred nanometers or a few micrometers at most in size), which are able to perform only very

simple tasks such as computing, data storing, sensing and actuation. Nanonetworks are expected

to expand the capabilities of single nanomachines both in terms of complexity and range of

operation by allowing them to coordinate, share and fuse information. Nanonetworks enable new

applications of nanotechnology in the biomedical field, environmental research, military

technology and industrial and consumer goods applications.

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Nanocomposites

A nanocomposite is a manmade material designed for enhanced performance in any number of

unique applications: structural, functional or cosmetic. As with other composites, the

nanocomposite includes a base medium, or matrix, composed of plastic, metal or ceramic

combined with nanoparticles in suspension. The filler particles are much smaller than those in

regular composites and are the size of large molecules, at least one hundred times smaller than

the nucleus of a human egg cell.

The solid base medium of a nanocomposite starts as a liquid that can be sprayed onto a surface,

extruded or injected into a mold. The filler particles function depending on their shape: round,

like a ball, or long and thin, like a tube. Fullerenes, nanoparticles composed entirely of carbon

atoms such as buckyballs or nanotubes, are orders of magnitude smaller than the carbon fibers or

bead fillers found in regular composites. These fullerenes can carry any number of reactive

molecules used in medicinal applications.

The smaller the size of the filler particles in suspension within the base medium, the greater the

surface area available for interaction and the greater the potential to affect material properties. In

the forming stages of nanocomposites, the base medium must flow easily into molds. With some

applications, the filler must align with, and not disrupt, the flow in specific directions where

strength or conductivity is required. Fillers with high length-to-width ratios align well in the flow

of a liquid base that has yet to become solid.Nanocomposites are materials that incorporate

nanosized particles into a matrix of standard material. The result of the addition of nanoparticles

is a drastic improvement in properties that can include mechanical strength, toughness and

electrical or thermal conductivity. The effectiveness of the nanoparticles is such that the amount

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of material added is normally only between 0.5 and 5% by weight. Nanocomposites can

dramatically improve properties like:

Mechanical properties including strength, modulus and dimensional stability

Electrical conductivity

Decreased gas, water and hydrocarbon permeability

Flame retardancy

Thermal stability

Chemical resistance

Surface appearance

Optical clarity

Nanoparticles have an extremely high surface to volume ratio which dramatically changes

their properties when compared with their bulk sized equivalents. It also changes the way in

which the nanoparticles bond with the bulk material. The result is that the composite can be

many times improved with respect to the component parts. Some nanocomposite materials

have been shown to be 1000 times tougher than the bulk component materials.

Nanocomposites are currently being used in a number of fields and new applications are

being continuously developed. Applications for nanocomposites include:

• Thin-film capacitors for computer chips

• Solid polymer electrolyes for batteries.

• Automotive engine parts and fuel tanks

• Impellers and blades

• Oxygen and gas barriers

• Food packaging

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Nanoparticles

Nanoparticles are particles between 1 and 100 nanometers in size. In nanotechnology, a

particle is defined as a small object that behaves as a whole unit with respect to its transport

and properties. Particles are further classified according to diameter. Ultrafine particles are

the same as nanoparticles and between 1 and 100 nanometers in size, fine particles are sized

between 100 and 2,500 nanometers, and coarse particles cover a range between 2,500 and

10,000 nanometers. Nanoparticle research is currently an area of intense scientific interest

due to a wide variety of potential applications in biomedical, optical and electronic fields.

The National Nanotechnology Initiative has led to generous public funding for nanoparticle

research in the United States.

Uses and advantages of nanoparticles in biology and medicine include:

Creating fluorescent biological labels for important biological markers and molecules

in research and diagnosis of diseases

Drug delivery systems

Gene delivery systems in gene therapy

For biological detection of disease causing organisms and diagnosis

Detection of proteins

Isolation and purification of biological molecules and cells in research

Probing of DNA structure

Genetic and tissue engineering

Destruction of tumours with drugs or heat

In MRI studies

In pharmacokinetic studies.

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Nanoparticles are being increasingly used in drug delivery systems. The advantages of using

nanoparticles as a drug delivery system include:

The size and surface characteristics of nanoparticles can be easily manipulated. This

could be used for both passive and active drug targeting

Nanoparticles can be made to control and sustain release of the drug during the

transportation as well as the location of the release. Since distribution and subsequent

clearance of the drug from the body can be altered, an increase in drug therapeutic

efficacy and reduction in side effects can be achieved.

Choosing an appropriate matrix also helps in increasing the efficacy and reducing

side effects

Targeted drugs may be developed

Various routes of administration including oral, nasal, injection, intra-ocular (within

the eyes) etc. can be used.

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Biological networks

Biological processes are often represented in the form of networks such as protein-protein

interaction networks and metabolic pathways. The study of biological networks, their modeling,

analysis, and visualization are important tasks in life science today. An understanding of these

networks is essential to make biological sense of much of the complex data that is now being

generated.

Biological Neural Networks

The neural system of the human body consists of three stages: receptors, a neural network, and

effectors. The receptors receive the stimuli either internally or from the external world, then pass

the information into the neurons in a form of electrical impulses. The neural network then

processes the inputs then makes proper decision of outputs. Finally, the effectors translate

electrical impulses from the neural network into responses to the outside environment.

Three Stages of Biological Neural System

The fundamental element of the neural network is called a neuron. As shown in figure 2.2, a

neuron mainly consists of three parts: dendrites, soma, and axon. Dentrites are the tree-like

structure that receives the signal from surrounding neurons, where each line is connected to one

neuron. Axon is a thin cylinder that transmits the signal from one neuron to others. At the end of

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axon, the contact to the dendrites is made through a synapse. The inter-neuronal signal at the

synapse is usually chemical diffusion but sometimes electrical impulses.

A Biological Neuron

The incoming impulse signal from each synapse to the neuron is either excitatory or inhibitory,

which means helping or hindering firing. The condition of causing firing is that the excitatory

signal should exceed the inhibitory signal by a certain amount in a short period of time, called

the period of latent summation. As we assign a weight to each incoming impulse signal, the

excitatory signal has positive weight and the inhibitory signal has negative weight. This way, we

can say, ``A neuron fires only if the total weight of the synapses that receive impulses in the

period of latent summation exceeds the threshold.

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Molecular motors

Molecular motors are biological molecular machines that are the essential agents of movement in

living organisms. In general terms, a motor may be defined as a device that consumes energy in

one form and converts it into motion or mechanical work; for example, many protein-based

molecular motors harness the chemical free energy released by the hydrolysis of ATP in order to

perform mechanical work. One important difference between molecular motors and macroscopic

motors is that molecular motors operate in the thermal bath, an environment in which the

fluctuations due to thermal noise are significant.

Cellular functions

The best prominent example of a motor protein is the muscle protein myosin which "motors" the

contraction of muscle fibers in animals. Motor proteins are the driving force behind most active

transport of proteins and vesicles in the cytoplasm. Kinesins and cytoplasmic dyneins play

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essential roles in intracellular transport such as axonal transport and in the formation of

the spindle apparatus and the separation of the chromosomes during mitosis and meiosis.

Axonemal dynein, found in cilia and flagella, is crucial to cell motility, for example

in spermatozoa, and fluid transport, for example in trachea.

Diseases associated with motor protein defects

The importance of motor proteins in cells becomes evident when they fail to fulfill their function.

For example, kinesin deficiencies have been identified as cause for Charcot-Marie-Tooth

disease and some kidney diseases. Dynein deficiencies can lead to chronic infections of

the respiratory tract as cilia fail to function without dynein. Defects in muscular myosin

predictably cause myopathies, whereas defects in unconventional myosin are the cause for Usher

syndrome and deafness.

Cytoskeletal motor proteins

Motor proteins utilizing the cytoskeleton for movement fall into two categories based on their

substrates: Actin motors such as myosin move along microfilaments through interaction

with actin. Microtubule motors such as dynein and kinesin move along microtubules through

interaction with tubulin. There are two basic types of microtubule motors: plus-end motors and

minus-end motors, depending on the direction in which they "walk" along the microtubule cables

within the cell.

Actin - Myosin motors

Myosins are actin motors and form myosin complexes consisting of two heavy chains with motor

heads and two light chains. Derived from the Greek word for muscle, myosin is the protein

responsible for generating muscle contraction. By non-processively walking

along actin filaments, many molecules of myosin generate enough force to contract muscle

tissue. Myosins are also vital in the process of cell division. They are also involved

in cytoplasmic streaming, wherein movement along microfilament networks in the cell

allows organelles and cytoplasm to stream in a particular direction. Eighteen different classes of

myosins are known.

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Aa | Myosin V works as a dimer to 'processively' transport intracellular cargo along actin filaments. Its

functional segments are labelled. Ab | 'Non-processive' dimeric myosin II has similar functional domains

to myosin V but assembles in a different manner. Several proteins associate through their tail domains

into bipolar filaments that can exert tension between actin filaments. Ac | Kinesins and dyneins move

along microtubules. Kinesin-1 and cytoplasmic dynein (shown in the figure) are processive and move

intracellular cargo. Kinesins have a similar domain structure to myosins (functional segments are

labelled). Dynein also acts as a dimer, but it is structurally different from other cytoskeletal motors. B |

Structural changes of a myosin II head during its power stroke. The respective nucleotide state is

indicated. The motor head starts in an unbound state (step 1), then binds to actin with the products of ATP

hydrolysis, ADP and inorganic phosphate (Pi), bound to the catalytic site (step 2). The release of Pi is

coupled to a first lever-arm rotation, which causes actin to move (step 3; actin movement is indicated by

the white arrow). Release of ADP causes a second, smaller rotation of the lever arm and additional actin

movement (step 4). ATP binding induces detachment of the motor (step 5). C | Structural changes of a

dimeric Kinesin-1 during a processive step, with nucleotide states indicated. ATP binding to the bound

head (step 1) causes neck-linker docking, which directs the unbound head forward to the next binding site

along the microtubule (step 2). Binding at this site causes ADP release (step 3). ATP hydrolysis followed

by Pi release causes the now trailing head to detach (step 4). ATP binding to the leading head again

causes neck-linker docking, and the cycle repeats (step 5).

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Microtubule motors

Kinesin

Kinesins are a group of related motor proteins that use a microtubule track

in antegrade movement. They are vital to the movement of chromosomes during mitosis and are

also responsible for shuttling mitochondria, Golgi bodies, and vesicles within eukaryotic cells.

Kinesins typically contain two heavy chains with motor heads which move along microtubules

via a pseudo-processive asymmetric walking motion that can be towards the plus-end or the

minus-end, depending on the type of kinesin. Fourteen distinct kinesin families are known, with

some additional kinesin-like proteins that cannot be classified into these families.

Dynein

Dyneins are microtubule motors capable of a retrograde sliding movement. Dynein complexes

are much larger and more complex than kinesin and myosin motors. Axonemal dynein facilitates

the movement of cilia and flagella, and cytoplasmic dynein facilitates transport of intracellular

cargos. Compared to 15 types of axonemal dynein, only two cytoplasmic forms are known.

Plant-specific motors

In contrast to animals, fungi and non-vascular plants, the cells of flowering plants lack dynein

motors. However, they contain a larger number of different kinesins. Many of these plant-

specific kinesin groups are specialized for functions during plant cell mitosis. Plant cells differ

from animal cells in that they have a cell wall. During mitosis, the new cell wall is built by the

formation of a cell plate starting in the center of the cell. This process is facilitated by

a phragmoplast, a microtubule array unique to plant cell mitosis. The building of cell plate and

ultimately the new cell wall requires kinesin-like motor proteins.

Another motor protein essential for plant cell division is kinesin-like calmodulin-binding

protein (KCBP), which is unique to plants and part kinesin and part myosin.