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A sensor is a device that detects events
that occur in the physical environment (like light, heat, motion, moisture,
pressure …etc.), and responds with an output, typically an electrical,
mechanical or optical signal. Many types of sensors like electrochemical
sensors, immuno-sensors, piezoelectric sensors and more have been used for the
detection of different diseases. All these biosensors face some limitations and
hence require serious efforts to improve the sensitivity, cost, reliability,
and their measurement speed. However, nanotechnology played an important role
in solving some of the problems related to these biosensors. To date, modern
material science has reached a high degree of sophistication. As a result of
continuous progress in synthesizing and domineering materials on the submicron
and nanometer scales, the novel advanced functional materials with modified
properties can be created. When scaled down to a nanoscale, most materials
exhibit novel properties that cannot be extrapolated from their bulk behavior.
The interdisciplinary boundary between materials science and biology has become
a productive ground for new scientific and technological development. For the
fabrication of an efficient biosensor, the choice of substrate for dispersing
the sensing material decides the sensor performance. Various kinds of
nanomaterials, such as gold nanoparticles, carbon nanotubes (CNTs), magnetic
nanoparticles and quantum dots and Graphene are being gradually applied to
biosensors because of their unique physical, chemical, mechanical, optical and
magnetic properties, and markedly enhance the sensitivity and specificity of

In Nanotechnology, we play with the
dimensions, shape, size, and properties of the material. As we go from bulk to
nanomaterial shows a new property. These nanomaterials like Graphene, carbon
nanotubes, Nanofibers, Nanoribbon etc are used in many applications like in
industries, sensors, drug delivery etc. Researchers and Scientists show that
how we can overcome the problems which are faced in traditional biosensors.

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In 2016 Cardiac immune-sensor for early
detection of heart attack (myocardial infarction) was fabricated using amine
functionalized graphene quantum dots (afGQDs) conjugated with antibody
anti-cardiac TroponinI (anti-cTnI) for the detection of cardiac marker antigen
TroponinI(cTnI) using fluorescence resonance energy transfer (FRET) sensor. The
nanomaterials used in this experiment are graphene quantum dots and Graphene.
Here afGQDs has carboxylic groups present on the surface and when it is
functionalized with amine groups this will attach to the ends and increase its
functionalization properties. The graphene acts as a quencher which will show
FRET phenomenon. The anti-cTnI was covalently conjugated with afGQDs through
carbodiimide coupling reaction. The conjugate was categorized by zeta
potential, UV–vis spectroscopy and field emission scanning electron microscopy
(FE-SEM). In FE-SEM different images and changes in the photon count using
confocal microscopy and photoluminescence of GQDs based on interactions of
target cTnI with its specific anti-cTnI antibody shows the sensing phenomenon
of the sensor. The sensor is highly specific and shows a tiny response to
non-specific antigens. The sensor displayed a linear answer to cTnI from 0.001
to 1000 ngmL-1 with a limit of detection of 0.192pgmL-1 1.

In 2016 An impedimetric sensor was
developed which is the label-free and direct detection of C-reactive protein
(CRP).In this sensor, an Indium Tin Oxide (ITO) electrode array was
functionalized with reduced graphene oxide-nanoparticle (rGO-NP) to enhance the
properties of electrodes. When we use the rGO-NP to functionalize the
electrodes then due to the higher surface area of nanomaterials the surface
area of the electrodes will increase. This will lead to the high amount of
immobilization of target molecules on the surface and increase the efficiency
of the sensor. To check the performance of rGO-NP-modified ITO microelectrodes
different characterizations are performed and to find out the influence on the
sensitivity the sensor using nano-structures modified for antibody
immobilization and for appreciation of CRP binding events. In the presence of
the redox couple Fe(CN)6, 3?/4 Impedimetric measurements showed major changes
in charge transfer resistance upon binding of CRP2.




Reference: Bhatnagar, D., et al., Graphene quantum dots FRET based
sensor for early detection of heart attack in human. Biosensors and
Bioelectronics, 2016. 79: p. 495-499.

Reference: Yagati, A.K., et al., Label-free and direct detection of
C-reactive protein using reduced graphene oxide-nanoparticle hybrid
impedimetric sensor. Bioelectrochemistry, 2016. 107: p. 37-44.










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