NANOTECHNOLOGY
AS A DIAGNOSTIC TOOL
BY
OYIKWU
VICTORIA ENE
(MLS/11/161)
A
SEMINAR WORK PRESENTED IN
PARTIAL
FULFILMENT OF the REQUIREMENTS FOR THE
AWARD
OF BACHELOR OF DEGREE IN
MEDICAL
LABORATORY SCIENCE (B.MLS)
IN
DEPARTMENT
OF HAEMATOLOGY/BLOOD TRANSFUSION SCIENCE
(MEDICAL
LABORATORY SCIENCES)
MADONNA
UNIVERSITY, ELELE CAMPUS
RIVERS
STATE, NIGERIA
course
CODE: mls 522
COURSE
TITLE: SEMINAR
SUPERVISOR:
MR. AJUGWO ANSLEM
cordinator:
dr. ADEBAYO .O. ADEGOKE
march, 2015
CERTIFICATION
This
is to certify that this seminar work titled “Nanotechnology as a diagnostic
tool” was done by Oyikwu Victoria Ene with the registration number MLS/11/161
in the Department of Haematology/blood transfusion science, Faculty of Medical
Laboratory Science, Madonna University Elele Campus, River state.
Under
the supervision of Mr. AJUGWO ANSLEM.
------------------------------ ------------------------
Oyikwu
Victoria Ene
Date
(Student)
------------------------------
-----------------------
Mr. Ajugwo Anslem Date
Supervisor
--------------------------------
-----------------------
Dr.
Adebayo. O. Adegoke
Date
Coordinator
--------------------------------
-----------------------
Asso.
Prof. Nnatuanya Isaac .N. Date
H.O.D
DEDICATION
This
piece of work is dedicated to the most sacred of Jesus Christ and immaculate
heart of Mary.
ACKNOWLEDGEMENTS
All thanks and praises be to God for his unending
love, mercy, blessings and grace. I am where I am because He is who He is.
To my beloved parents I
want to say thanks for your love and words of encouragement may the good lord
reward you according to his riches and glory. You are the best parents anyone
could ever have, and I love you.
I am grateful to my supervisor
Ajugwo Anslem for his thorough and constructive criticism which provided me
with challenges to meet the needs of this essay.
I would also like to
acknowledge the seminar coordinator Dr. Adebayo Adegoke, am grateful to you
Sir. And may God reward the rest of my lecturers in my department that
contributed in one way or the other in impacting knowledge and discipline into
me….Amen!
And to my siblings I want
to say I love you all and I appreciate all your support, may your joy know no
bounds.
My course mates and friends
Ada, Lauretta, Isioma, Ambrose, Simony, Mercy and Dorcas may you all experience
joy, peace and Gods unending favour in everything you do. Amen
SUMMARY
Nanotechnology is the manipulation of material
on an atomic and molecular scale; by changing its physical, chemical and
biological properties to produce novel materials, devices, and systems.
Nanomaterials exhibit remarkable characteristics such as high surface to volume
ratio, catalytic activity, and biocompatibility which make them suitable for
various biomedical applications. Nanotechnology have prospective to improve the
whole healthcare process for patient; starts from diagnosis to treatment and
follow-up monitoring. Medical diagnosis based on nanotechnology provides two
major advantages: rapid testing and early diagnosis. The potential
contributions of nanotechnology in the medical diagnosis are extremely broad
and improve traditional diagnostic tools and methods in the field of clinical
diagnosis, imaging and electro- diagnosis. Emerging modalities such as biochip,
microarray, Nano barcode, micro-electromechanical systems, lab on chip and
nanobiosensor have revolutionized the field of medical diagnosis. Nanoscale
materials and Nano-enabled techniques are used for diagnosis of various
diseases such as cardiovascular diseases, cancer, diabetes, infectious disease,
musculoskeletal and neurodegenerative disease etc. Among all medical
applications of nanotechnology, nanobiosensor especially enzyme nanobiosensor
are sensitive, reliable, robust, reproducible and cost effective diagnostic
tool to meet the requirements of healthcare. Nanotechnology also have disadvantages
like making atomic weapons more accessible, more powerful and more destructive.
Because nanotechnology makes use of small particles, It also give problems like
inhalation of those minute particles much like the problems a person gets from
inhaling minute asbestors particles.
TABLE OF CONTENTS
Title
page………………………………………………………………….……i
Certification………………………………………………………………….…ii
Dedication……………………………………………………………………...iii
Acknowledgement………………………………………………………...........iv
Summary……………………………………………………………………….
v
Table of Contents………………………………………………………………vi
CHAPTER ONE
1.0 Introduction………………………………………………………………..1
CHAPTER TWO
LITERATURE REVIEW
2.0 what is nanotechnology……………………………………………………3
2.1 Nanomaterials in medical diagnosis…........................................................3
2.2 Applications of nanotechnology in medical
diagnosis..………….……….7
2.3 Emerging trends in nanotechnology…………………………….……….10
2.4 advantages and disadvantages of
nanotechnology………………………22
CHAPTER THREE
3.0 Conclusion/Recommendation………………………....................................23
References………………………………………………………………….........24
CHAPTER ONE
1.0 INTRODUCTION
According to
the American heritage dictionary of the English language, 4th edition,
Nanotechnology can be seen as the development of engineered devices at the
atomic, molecular and macromolecular level in nanometer range. It can also be
seen as the science and technology of small things in particular, things that
are less than 100nm in size. Nanotechnological devices are being developed for
diagnosis of cancer and infectious diseases which can help in early detection
of the diseases. It also have been beneficial in therapeutic field such as drug
discovery, drug delivery and gene/protein delivery. It can also be seen as the
creation of very small particles, devices and systems: these technology takes
place at a very minute level (Silva, 2004).
Nanotechnology as a diagnostic tool
refers to the use of Nano materials for the early detection, prevention treatment
and follow up of many life threatening diseases including cancer,
cardiovascular diseases, diabetes, Alzheimiers and AIDS as well as infectious
disease (Tallury, 2010).
The
auspicious application of nanotechnology is in Alzheimer’s disease because
patients are diagnosed after they pass away and their brain is examined for
telltate damage, scientists are investigating for test that will make up
diagnosis in living patients (Shinjini et
al., 2008). The use of nanotechnology enables the development of novel
therapies and improves traditional treatment and diagnosis process by
manipulating atom and molecules to produce nanostructures of same size as
biomolecules for interactions with human cells (Fakruddin et al., 2012).
Hexagonal
shape and are few hundred nanometers tall and apart. These Nano structures are
used to enhance the absorption of infra-red light (heat) in in a type of power
source called thermo-voltaic cell to make them more efficient. Nanotechnology makes use of Nano
structures which includes the use of moth’s eye which has a very small bumps on
its surface, they have Nanotechnology can be applied in areas like medicine and
health care, environment, energy, information and communication technologies.
Different nanomaterials are used for diagnostic purposes these include
Different nanomaterials are used for diagnostic purposes these include
·
Magnetic nanoparticles
·
Quantum dots
·
Carbon nanotubes.
·
Graphene oxide.
·
Gold nanoparticles and silver nanoparticles.
·
Porous nanomaterial.
The aim of
clinical diagnosis is the rapid testing and complete diagnosis at an earlier
stage to prove the potential of curing, possibly with less damage to the
patient. It is possible with points of care diagnosis. Which includes
nanobiosensor and nanoscale devices. Bringing the diagnostic technique with
patient point care which reduces disadvantages of conventional diagnosis and
overall cost and time for health care process for patient is reduced
extensively (Richard et al., 2009).
Numerous techniques and assays are
available for diagnosis such as immunoassay, genetic based tests, medical
imaging and bio sensing. Bioassays commonly used in diagnosis are enzyme linked
immunosorbent assay (ELISA), polymerase chain reaction (PCR) based genetic
assay and such as giemsa and Gram for viral and bacterial infections diseases
(Challa, 2007).
Conventional diagnostic methods suffer from few
limitations occurring as a result of low specificity and lack of efficacy. So
nanotechnology enhances assays by accomplishing all requirements to provide a
platform that is more sensitive than the current gold stand in protein
detection and ELISA (Gaster et al., 2011).
CHAPTER TWO
LITERATURE
REVIEW
2.0 WHAT IS NANOTECHNOLOGY
Nanotechnology is the manipulation of
matter at the atomic and molecular scale to create materials with new and
advanced properties. It is applied in diagnosis through the development of
nanoparticles/materials to detect early stage of a disease and also to ensure
rapid diagnosis and treatment of diseases.
Nanotechnology as a diagnostic tool
refers to the use of Nano materials for the early detection, prevention
treatment and follow up of many life threatening diseases including cancer,
cardiovascular diseases, diabetes, Alzheimiers and AIDS as well as infectious
disease (Tallury, 2010).
2.1 NANOMATERIALS FOR MEDICAL DIAGNOSIS
Nanomaterials exhibit higher
chemical reactivity, increased mechanical strength, faster electrical and
magnetic responses owing to its high surface to unit volume ratio.
Nanoparticles can attach to biomolecules allowing detection of disease
biomarkers in a laboratory sample at a very early stage. These materials are
designed to interact with cells and tissues at a molecular (i.e. subcellular)
level with high degree of functional specificity, thereby allowing integration
between the device and biology system not previously attainable (Silva, 2004).
Nanomaterials possess electrical
conductivity catalytic properties, good stability and high loading biomolecules
owing to its high surface to volume ratio. Because of their small size,
nanomaterials can readily interact with biomolecules and gaining access to so
many areas of the human body. Nanomaterials are produced using the top down and
bottom up techniques. The top down start with a bulk material and then breaks
it into smaller pieces using mechanical, chemical or other form of energy. An
additional way is to synthesize the material from atomic or molecular species
through chemical reactions allowing for the precursor particles to grow in size
which is called bottom up technique. Chapter 6 nanomaterials, springer.
Nanomaterials become a platform
fabrication of novel diagnostic tool and revolutionized diagnostic processes by
increasing relative surface area and emergence of quantum effects and
interactions with biological systems present opportunities for scientists. The
effect of increased reactivity and the potential to cross cell membranes have
positive impacts on healthcare (Shao et
al., 2010).
Nanomaterials
include; Magnetic nanoparticles, quantum dots, carbon nanotubes, graphene
oxide, gold nanoparticles and silver nanoparticle, porous nanomaterial.
v MAGNETIC NANOPARTICLES
Magnetic
nanoparticles are employed in multiple disciplines such as biosensors, magnetic
resonance imaging and Nano electronics. It commonly consist of magnetic element
such as iron, nickel and their derivatives. They are versatile diagnostic tool
as they are manipulated using external magnetic field. Its action at a distant
phenomenon, combined with intrinsic penetrability of magnetic field into human
tissue enables their detection in vivo using magnetic resonance imaging (MRI) (Shao
et al., 2010).
Magnetic nanoparticles for biosensors
enhance sensitivity and effectively reduce sample preparation requirements.
Magnetic sensors such as magnetic relaxation switch assay sensors, magneto
resistive sensors and magnetic particle relaxation sensors have been developed (Koh
and Josephson, 2009).
Supra- paramagnetic iron oxide nanoparticles
(SPION) are made of iron oxide core and coated by either inorganic materials
like silica or organic materials such as phospholipids and natural polymers
such as dextran or chitosan are versatile agent for early diagnosis of cancer,
atherosclerosis and other diseases. They are used as contrast agents for
magnetic resonance imaging and as an in-vitro application in bioassay by means
of a vehicle for the detection of biomarker (Hofmann et al., 2010). When supra- paramagnetic iron oxide are used in
biosensors it improves the sensitivity and selectivity of diagnosis (Azzazi et al., 2007).
v QUANTUM DOTS (QD)
They are
spherical fluorescent nanocrystals made of semi conductor materials of
intermediate sizes typically between 2-8nm in diameter. They are widely used as alternative to
conventional fluorophores and for development of biosensors to detect
biomolecules such as proteins, neurotransmitters enzymes and amine acids
(Azzazi et al., 2007).
Bio
conjugated quantum dots have the potential to b used in cancer diagnosis due to
its bright and stable fluorescent light emission and sensitivity of
fluorescence imaging (Smith et al.,
2006). They can also be used in the future for locating cancer tumors in
patients and in the near term for performing diagnostic tests in biological
samples (Xing and Rao, 2008).
v CARBON NANOTUBES (CNT):
These are
extensively used nanomaterials in biosensors and diagnosis. They are long
hollow cylindrical carbon structures composed of one, two or several concentric
graphite layers capped with fullerenes hemisphere which are referred to as
single, double and multi- walled . I.e. they have unique mechanical, optical
and electronic properties with high electrical and thermal conductivity.
Carbon
nanotubes have aspect ratio, unique optical property and small sizes exhibit
potentials for variety of biomedical applications including the diagnosis of
cancer and infectious diseases. These applications are encouraged by their
capability to penetrate biological membranes and relatively low toxicity (Zhang
et al., 2010).
For diagnosis carbon nanotubes can help
to detect a protein biomarkers of disease when fabricated on the surface of a Nano
biosensor. When it binds with a protein, the nanotubes change their electrical
resistance which then be measured to determine the presence of a particular
protein. E.g. serum protein biomarkers that can indicate breast cancer (Leyden et al., 2012). Carbon nanotubes also
have potential to increase the speed of biological sensors by reducing the
biosensor response time. (Vashist et al.,
2011).
v GRAPHENE OXIDE (GO):
Graphene
oxide is a thin layer of sp2 hybridized carbon extensively used for medical
diagnosis due to its exciting properties, turn able band gap, high elasticity,
high mechanical strength, very high temperature quantum hall effect, high
electron mobility and high thermal conductivity (Dresselhaus and Araujo, 2010).
Graphene oxide can also be seen as transparent
material with low productivity cost and minimum environmental impact. The
sheets of graphene oxide on which antibodies attaches binds to cancer cells
which then tag the cancer cells with fluorescent Molecules to make the cancer
cells to make the cancer cells stand out in a microscope. It can also detect a
very low level of cancer cells as low as 3 to 5 cancer cells in a one
milliliter of blood sample (Rajashekhar et
al., 2014).
v GOLD NANOPARTICLES (AUNPS) AND SILVER
NANOPARTICLES (AGNPS):
Nano sized
gold nanoparticles and silver nanoparticles are precious and in great demand by
scientists. Gold nanoparticles are most attractive and extensively studied nanomaterials
in bioanalytical field for medical diagnosis owing to its fascinating features
such as ease of synthesis, high biocompatibility and Nano cytotoxicity. They
have biomedical applications in these areas; labeling and bio sensing. For
labeling, certain properties of the particles are exploited to generate
contrast.
Gold
nanoparticles can also be used in biosensors as their optical properties can
change upon binding to certain molecules permitting the recognition and
quantification of annalites. The silver Nano rods in a diagnostic system are
being used to separate viruses, bacteria and other microscopic components of
blood samples. This method has been demonstrated to allow identification of
viruses and bacteria in less than an hour (Shanmukh et al., 2008).
v PORUS NANOMATERIALS:
The porous
nanomaterials are particularly promising for fabrication of optical biosensors
as it possesses wide range of physical characteristics such as high purity, turn
able porosity, Nanoscale structuring, high photochemical, physical rigidity and
thermal stability. Porous nanomaterials retain native conformations and
reactivity of biomolecules (Satvekar et
al., 2012).
2.2 NANOBASED DIAGNOSTIC
TOOLS
1.
NANOBARCODES
Nano barcodes acts as encoded substrates in multiplexed assays
which are metallic, durable, encode-able and machine readable submicrosized
tags (Griffith et al., 2008). They
are free standing, cylindrical nanoparticles with specific patterns of sub
micro stripes of noble metal ions produced by alternating electrochemical reduction
of the appropriate metals (Zhou et al.,
2001).
Nano barcode is advantageous in coding
multiplexed assays for proteomics, single nucleotide polymorphism (SNP) mapping
and in point of care handheld devices.
Nano barcode assays are
nanotechnological based technique for detecting proteins which extraordinary
sensitivity in detecting certain antigens at extremely low concentrations which
is now devoid of the use of polymerase chain reaction (PCR). These assay uses
disease biomarkers that cannot be used in the conventional assays. ADDLs are
considered neurotoxins in Alzheimer’s disease (AD) pathogenesis clinically
detected by a new diagnostic approach for AD using the Nano barcode assay (David
et al., 2003).
2. NANOBIOSENSORS
Biosensors are widely in medical
diagnosis to scrutinize or detect biomarkers for diagnosis of various diseases
starting from diabetes to cancer. Due to the recent progress in biosensor
fabrication, diagnosis of life threatening diseases more reliably.
Nanotechnology provides great
opportunities to improve the sensitivity, stability and anti-interference
ability of biosensor system. And with the progress in nanotechnology various
novel nanomaterials have been invented and their novel properties are being
gradually revealed which greatly enhances the performance of biosensor. Due to
small sized nanoparticles the limitations of minimization leading to lower
detection limits even getting zepto-molar concentrations are overcome.
Nanoparticles can produce a synergic effect between conductivity, catalytic
activity, and biocompatibility to enhance the signal transduction. Also
nanoscale materials are used in biological sensors in detection of biomolecules.
These nanomaterials based nanobiosensing involves in vivo diagnosis with high
sensitivity, less cytotoxicity and long term stability for early screening of
biomarkers and reliable point of care diagnosis (Huangxianju et al.,
2013).
Nano biosensors have made a great impact
due to their capacity to sense a wide range of biomolecules and incredibly
small concentrations (Turner, 2013).
NANOBIOSENSORS FOR CLINICAL DIAGNOSIS
IUPAC
defines biosensor as a sufficient integrated device which is capable of
providing specific quantitative or semi-quantitative analytical information
using a biological recognition (biomolecules through enzyme, DNA and antibody)
which is retained in direct spatial contact with a transducer element. These biomolecules
include antibodies, enzymes nucleic acids, cell and bio mimic component
employed as bio recognition element which is highly favourable owing to its specificity
and catalytic activity (Thevenot et al.,
2001).
PRINCIPLE OF BIOSENSOR
Biosensor
comprises of a bio recognition element in intimate contact with a proper
transducer. These bio recognition element gives rise to signal as the
biochemical reaction of interested analyte which is detected by transducer to
give electrical signal. This reaction between the biomolecule and the
substrates produces a product in the form of electrochemical heat light or
sound and then a transducer in form of electrochemical semi-conductor or
thermistor which changes the product of the reaction into readable data.
BIOSENSOR
COMPONENT
A biosensor
consist of three components which are;
1. The
biorecognition element e.g. enzymes, antibodies, nucleic acids, cell lysates,
micro organisms, cell receptors etc.
2. The
transducer which acts as an interface, measuring the physical change that
occurs with the reaction at the biorecognition element and then converting that
energy into measuring electrical output. These transducer can be optional,
electrochemical, opto-electronic, piezoelectric, thermal and mass.
3. The
detector element which passed signals from the transducer to a microprocessor
where they are amplified and analyzed (Clark and LYONS, 1962).
TYPES
OF NANOBIOSENSOR BASED ON TRANSDUCER MODE
Biosensors can
be generally classified
into two criteria’s
based on sensing
element and transduction modes. Transduction mode depends on the
physiochemical change resulting from sensing element. Hence
on the basis of
different transducers, biosensors
can be electrochemical (aerometric, conductometric
and potentiometric), optical (absorbance,
fluorescence and chemiluminense),
piezoelectric (acoustic and ultrasonic) and
calorimetric (Habermuller et al.,2000). The major types based on transducer mode are
discussed below:
ELECTROCHEMICAL
BIOSENSOR
AMPHOTERIC NANOBIOSENSOR: Amperometric
biosensor is based on the electrochemical analysis in which the signal of
concern is a current that is linearly dependent upon the concentration of the
biomarker. The signal transduction process is accomplished at a fixed potential
between the working electrode and a reference electrode, and measuring the
current as a function of time which is a direct measure of the rate of electron
transfer. In most cases the biorecognition element is immobilized on the
working electrode. The analyte is oxidized or reduced at the working electrode
and the current flow directly proportional to the concentration of the
electro-active species (Baker, 2004)
POTENTIOMETRIC
NANOBIOSENSOR: In potentiometric sensors, the potential difference between the
reference electrode and the indicator electrode is measured without polarizing
the electrochemical cell. The analytical information is achieved by
transforming the biorecognition process into a potential signal. A permselective
ion-conductive membrane and high impedance voltmeter is normally utilized to
measure the potential signal, which arises when the analyte interacts with the
surface. The electrical potential difference or electromotive force (EMF)
measured between two electrodes at near zero current. The indicator electrode
or an ion-selective electrode (ISE) develops a change in potential as a
function of analyte concentration in sample (zarina et al., 2003).
CONDUCTOMETRIC
NANOBIOSENSORS: These are based on the measurement of electrolyte conductivity,
which varies when the cell is exposed to different environments. Conductivity
measurements are generally accomplished with AC supply which is a linear
function of the ion concentration. Conductometric-based biosensors couple
conductance and a biorecognition event in which mostly reactions involve a
change in the ionic species concentration and this can lead to a change in the
solution electrical conductivity. The major problem with this technique is that
the sensitivity is generally lower compared to other electrochemical methods (Dey
and Goswami, 2011).
OPTICAL BIOSENSORS: Optical biosensors
(optodes), have received considerable attention for diagnosis. The optical
biosensors involve direct detection of the analyte of interest or indirect
detection through optically labeled probes. In general, there are at least four
types of biosensors using the principles of optical technology. These are as
follows: absorption, reflection, chemiluminescence, fluorescence, and phosphorescence.
Optical biosensors are potent
alternative to conventional analytical techniques because these are highly
sensitive, reproducible, rapid, and simple-to-operate. The optical biosensor
design encompass direct detection of the interested analyte or indirect detection through optically
labeled probes, and the optical transducer may detect changes in the
absorbance, luminescence polarization, and refractive index (Kim et al., 2004).
PIEZOELECTRIC
NANOBIOSENSORS: These biosensors are mass sensitive detectors, which has the
principle that an oscillating crystal resonates at the natural resonance
frequency. The piezoelectric materials are able to generate and transmit
acoustic waves. When a piezoelectric biosensor surface is coated with a biomolecule
(antibody) and placed in a solution containing the pathogen, the attachment of
it to the antibody coated surface results in an increase in the crystal mass,
and this shows a corresponding frequency shift. This mechanism is relatively
simple, inexpensive, and offers direct label-free analysis (Cooper, 2003).
CALORIMETRIC NANOBIOSENSOR: Most chemical and
biochemical processes involve the generation of exothermic heat which is used
as a basis for measurement of rate of reaction and ultimately analyte concentration.
The fabrication of the Calorimetric biosensor normally consist a thermistor or
thermopile employed as a temperature transducer to determine heat changes
(CLARK and LYONS, 1962). The device is covered with the enzyme and when this
interacts with the analyte it generates an exothermic reaction, which is
recognized as a heat change. Obvious benefits of this biosensor are that it can
be easily miniaturized, can be used in turbid samples, and it is a label-free
approach (Xie et al.,1999).
TYPES OF
NANOBIOSENSOR BASED ON BIORECOGNITION ELEMENT
Sensing elements include enzymes, antibodies
(Immunosensor), micro-organisms (whole cell biosensors), and DNA. The main
types based on are as follows:
DNA
Nanobiosensor: The DNA nanobiosensor is based on the conversion of the
base-pair recognition event or hybridization event (the complementarities of adenine-thymine
and cytosine-guanosine pairing in DNA) into a measurable electrical signal. DNA
duplex formation or hybridization event forms the basis of electrochemical
detection in which electrochemical signals are generated and enhanced by
covalent binding of nanomaterials to the DNA probe. DNA probe is the known
sequence of bases which can be synthesized and labeled with optically
detectable compounds. DNA biosensors are utilized as suitable candidate for
rapid and reliable diagnosis of genetic diseases, the detection of pathogenic
biological species (Wang, 2002).
IMMUNO-NANOBIOSENSOR:
these are Biosensors which monitor antigen- antibody interactions. Immunosensor
monitor antigen-antibody interaction in which either antigen or antibody is
immobilized on a solid-state surface of electrode and participate in bio
specific interaction with the other component, allowing detection of desired
biomolecule. Antigen-antibody reactions
are very specific
and a very
minute concentration of
target molecule in the body can be detected and easily screened (Stefan et al., 2000). Immunoreactions are
known for their high sensitivity and selectivity so most reliable tool for
clinical diagnosis. Optical and electrochemical detection strategies are mostly
used in immunosensor.
ENZYME
NANOBIOSENSOR: Enzyme nanobiosensor plays a vital role in diagnosis of various
diseases which are composed of enzyme as biorecognition component that uses
their catalytic activity for detection of analyte. The success of any enzyme
sensor depends on enzyme loading, the use suitable pH and type of immobilization
method and how well it retains its enzymatic activity on transducer. The most
important part of a biosensor fabrication is the immobilization of a desired
enzyme (Sassolas et al., 2012).
However, the usefulness of immobilized enzyme on electrodes depends on factors
such as the immobilization method, the chemical and physical conditions (pH,
temperature and contaminants), thickness and stability of the membrane used to
couple the enzyme.
WHOLE CELL
NANOBIOSENSOR: Whole cell biosensors utilizes living cells or Microorganisms
such as bacteria and fungi as the biorecognition element which can detect the
intracellular and extracellular conditions, physiological biomolecules to
produce a response. The detection limit of these biosensors is mainly measured
by the environmental conditions in which the cells can remain alive for long
period. However the major drawback of whole cell biosensor is the stability of
the whole cell, which depends on several conditions such as the lifetime,
sterilization, and biocompatibility etc. Despite these consequences the whole
cell biosensor is still promising among the researcher due to the advantages it
has over the other biosensors. (Belkin and GU 2010).
ENZYME NANOBIOSENSOR
Enzymes are used reliably in the
medical field such as in the diagnosis and treatment of various diseases. For
example, enzymes are used in biosensors for the detection of various biomarkers
such as glucose, cholesterol, uric acid. Enzymes are most favorable candidate
as a biorecognition element in the fabrication of biosensor because of its
selectivity compared to conventional catalyst. However, enzymes are prone to
the microenvironment (PH, temperature) and have a short operational lifetime.
In aqueous solutions, enzymes lose their catalytic activity rapidly due to the
oxidation reaction or their tertiary structure can be destroyed in air-water
interface, these shortcomings can be avoided by immobilization of enzymes.
Immobilized enzymes are more robust and advantageous such as convenient
handling, more resistant to environmental changes and increase the affinity for
the substrate (Rajshri et al., 2014).
The detection limit of enzymatic
biosensors is generally determined by the enzyme’s activity. However, the major
drawback with enzymatic biosensors is the stability of the enzyme, which be
influenced by conditions such as temperature, pH and buffer etc. The capability
to conserve enzyme activity for a long period of time up till now remains a
major obstacle. Regardless of these pitfalls, the enzymatic biosensor is still
the most usually used biosensor, and this is essentially due to the
prerequisite for monitoring glucose, cholesterol, uric acid, lactate for
diagnosis of various diseases in blood.
ENZYME NANOBIOSENSOR FOR CLINICAL DIAGNOSIS
GLUCOSE: The abnormal level of glucose related
to diabetes and the risk for renal, retinal, and neural complications. Thus the
measurement of glucose in human blood is important for diagnosis of diabetes
and other diseases. Glucose biosensors based on glucose oxidase have been
dynamically investigated as the potential biosensor with wide range of
analytical techniques (Scognamiglio, 2013).
CHOLESTEROL: The increasing prevalence of
cardiac arrest and cardiovascular diseases are major reason of death in human
worldwide. The cholesterol level detection in human blood is of great
significance in clinical diagnosis as high cholesterol in blood is associated
with coronary heart disease, hypertension, myocardial infarction, brain
thrombosis, arteriosclerosis, lipid metabolism dysfunction, etc. (Arya et al,2008). In conventional assays,
cholesterol determination is performed by enzymes, such as cholesterol oxidase
and cholesterol esterase which can be used to monitor both free and esterified
cholesterol levels.
URIC ACID:
A major nitrogenous compound of urine is uric acid which is the product
of purine metabolism in the human body. It is correlated to many clinical
disorders; high levels of uric acid in the blood are associated with gout,
hyperuricemia, Lesch-Nyhan syndrome and other conditions including increased
alcohol consumption, obesity, high cholesterol, diabetes, high blood pressure,
kidney disease and heart disease. Lactate: The level of lactic acid in blood is
used in clinical diagnosis of hypoxia, lactic acidosis, some acute heart
diseases.
LACTATE: The
level of lactic acid in blood is used in clinical diagnosis of hypoxia, lactic
acidosis and some acute heart diseases. Trustworthy, blood lactate detection
method would also be of interest in sports medicine.
UREA: Urea is generally monitored in blood
sample to obtain evidence of kidney disease. It is the best biomarker for
evaluating the level of uremic toxins in body. Eggshell membrane is a natural
materials used as a membrane for immobilization of urease enzyme for the
development of a potentiometric urea biosensor and showed good operational and
storage stability (Dsouza et al.,
2013).
FARBRICATION
OF ENZYME NANOBIOSENSOR
The basic requirements for an enzymatic
nanobiosensor are:
(1) an enzyme which
acts on its substrate to produce a molecule which is capable of being reduced
or oxidized at an electrode surface;
(ii) an immobilization technique for the
enzyme to ensure close proximity of enzyme to the electrode which retains the
functionality of the enzyme;
(iii) an electronic system proficient in
controlling the potential of the electrode and measuring the current produced
in the redox reaction. For the immobilization of enzyme chemical and physical
methods such as covalent binding, absorption, cross-linking, entrapment, and
encapsulation have been used. These techniques suffer from some disadvantages
like leaching of biomolecules and loss of activity. Accordingly, choice of the
immobilization materials and methods should be carefully considered to maintain
the enzyme activity for a long time under various conditions. The fabrication
of biosensor is dependent on factors like prerequisite of analysis, techniques
employed and cell configuration. Conventionally, bulky electrodes and
“beaker-type” cells configuration have been utilized. But nowadays,
micro-fabrication permits the replacement of these traditional cells
configuration and bulky electrodes with appropriate sensing devices. The innovative
techniques such as thick and thin film technology, Screen-printing technology
and photolithography are used in fabrication of biosensors for clinical
diagnosis (Gonzalez-Macia et al., 2010).
The fabrication technique which is
well suited for mass production and portable devices allow both in situ and
real time monitoring. Perhaps, disposable screen-printed strips are commonly
used by diabetic patients for self-monitoring of blood glucose levels. Such
fabrication method offers mass production of really inexpensive and hitherto
highly reproducible enzyme biosensor.
2. MICROARRAYS
Microarrays are promising for
competent and personalized approaches to human health care. Microarray offer a
powerful tool for screening thousands of proteins at a time, where variety of
biomolecules such as antibodies and enzymes are immobilized in an array format
on glass slide (Zhu and Synder, 2003).
The surface of the glass slide is then
probed with sample of interest that binds to relevant antibodies on chip which
will be analyzed by detection method on microarray. Profiling proteins on
arrays will be used in distinguishing the proteins of normal cells from early
stage cancer cells and malignant metastatic cancer cells. Likewise, it also
helps to sensing of the vast amount of genomic information and its application
for early detection of genetic diseases. The applications of antibody
microarray to cancer diagnosis are growing in scope and efficiency.
Enhancement in microarrays
miniaturization with the aid of nanotechnology will further contribute to molecular diagnostics and the development
of personalized medicine (Haab, 2005).
3. LAB-ON- A CHIP
Lab-on-a-chip devices are
‘miniaturized integrated laboratories’ that allow separation and analysis of
biological samples. These are composed of micro-fluidic systems including
micro-pumps and micro-valves integrated with microelectronic components
(Griffith et al., 2005).
Nanotechnology allows
miniaturization of these devices which requires high electrical field’s
strengths that can be obtained by using Nano sized electrodes and the membranes
based on Nano pore separation systems. Lab-on-chip devices have rapidly evolved
for applications in a number of clinical analysis operations which is
fabricated on silicon or glass substrates using thin film technology and
photolithography techniques. The advantages of Lab-on-chip devices are the
small sample and reagent volume employed in these systems, rapid response time,
less sample wastage, and prospect of developing disposable devices.
4. DIAGNOSTIC IMAGING
In vivo imaging is most important in
diagnosis of disease which searches for the symptoms of the disease within live
tissue suspected of being infected. Medical diagnostic imaging includes MRI,
PET, CT, OCT, opto-acoustic or photo-acoustic tomography (OAT/PAT) and NIR
imaging (Rosen et al., 2011).
Medical research has exploited the
unique properties of nanomaterials for in vivo imaging where tools and devices
are being developed by using nanomaterials. Nanotechnology is having impact on
this area, particularly by developing molecular imaging agents. A nanoparticle
enhances favorable distribution and improved contrast in MRI and Ultrasound
images. Nanomaterials containing contrast agents can greatly improve
sensitivity of diagnostic imaging techniques. Nanomaterials can improve imaging
techniques even at single cell before any symptoms appear (Wickline et al., 2006).
Super-paramagnetic
nanoparticles are widely used as MRI contrast agent, while liquid perfluorocarbon
nanoparticle and liposome are examples of ultrasound contrast agent. Optically
absorbing gold nanoparticles can be used as contrast agent for opto-acoustic
imaging as well as gold nanoparticles used in NIR imaging due to their
lumiscence properties. Body cannot clear them due to their Nano size, which
prolongs the time span for imaging. Traditional fluorophores such as organic
dyes and fluorescent proteins suffer from several intrinsic problems including
rapid photo-bleaching, spectral cross-talking, narrow excitation profiles, and
limited brightness/signal intensity. These shortcomings can be reverted by iron
oxide nanoparticles (MNP) coated with peptides specifically bind to the tumor
cell which in turn enhances the images of MRI owing to its magnetic properties
(Akhtari et al., 2008). MNP-MRI allowed noninvasive, real-time
quantification of pancreatic inflammation for diagnosis of autoimmune diabetes
(Turvey et al., 2005).
2.3 APPLICATIONS
OF NANOTECHNOLOGY IN MEDICAL DIAGNOSIS
Nanotechnology has multiple
applications which includes; Target identification and validation, animal
experiment, clinical trials, early detection diagnosis and treatment of
diseases, drug delivery and in toxicology which include in vivo and invitro
studies.
NANOTECHNOLOGY AND ITS APPLICATION TO CANCER.
The detection
and diagnosis of cancer usually depends on changes in cells and tissues which
occurs at the nanoscale level inside the cells and are detected either by
physical examination or imaging expertise. Nanotechnology offers a wealth of
tools to provide cancer researchers with new and innovative ways to diagnose
and treat cancer.
DIAGNOSIS
Nano devices
such as nanowires and cantilever can provide rapid and sensitive detection
cancer related molecules by enabling scientists to detect molecular changes
even when they occur only in small percentage of cells.
Cantilever is one tool with potential
aid in cancer diagnosis. Nano cantilevers are tiny bard anchored at one end can
be engineered to bind to molecules associated with cancer. When the cancer
associated molecules binds to the cantilever it changes the surface tension
causing the cantilever to bend. And by monitoring whether the cantilevers are
bent and to what extent enables scientist assess whether the cancer molecules
are present.
THERAPY
Nanoscale
devices have the potential to improve cancer therapy and to discover new
therapeutic agents.
Nano shells
are miniscale beads coated with gold, these beads can be designed to absorb
specific wavelength of light. The absorption of light by the Nano shells
creates an intense heat that is lethal to the cells. These Nano shells can be
linked to antibodies that recognizes cancer cell. Metal Nano shells which are
intense near-infrared (NIR) absorbers are effective both in in vivo and invitro
on human breast carcinoma cells (Hirsch et
al., 2003).
(Ramsey et al., 2005) focused on liposomes which are being investigated
using the lipid based nanotechnology to carry fussed dose anti-cancer drug
combinations.
APPLICATION OF NANOTECHNOLOGY IN
DRUG DELIVERY
According to
(Dubin, 2004), nanotechnology help to improve the solubility and
bioavailability of drugs. They also help to enhance the release rate of drug. This
can be done by targeted drug delivery and controlled drug release system. A
drug delivery system can convey drugs more effectively, increase patient
compliance and extend product life cycle.
Drugs tend to perform more
effectively in Nano particulate form and with fewer side effects. Specific Nano
sized receptors present on the surface of a cell can recognize the drug and
elicit appropriate response by delivering and releasing therapy exactly
wherever needed. So drugs can be loaded through encapsulation, surface
attachment or entrapping.
Nano pores acts as tiny particles for
releasing drugs by making the Nano pores only slightly larger than the
molecules of drugs, they can control the rate of diffusion of the molecules,
keeping it constant regardless of the amount of drugs remaining inside a
capsule.
Also due to poor water solubility of
drugs, therapeutic drugs can be Nano sized in the range of 100-200nm.
Nanoparticles in the range of 50-100nm can easily be used in the treatment of
cancer because they easily move into a tumor.
Nanoparticles can also be used to
monitor conditions, and acts as an artificial means of regulating and
maintaining body own hormonal balance.
2.4 ADVANTAGES AND DISADVANTAGES OF NANOTECHNOLOGY
The use of
nanotechnology led to to so many advantages and disadvantages, by curing
medical issues through the use of nanoparticles/materials.
ADVANTAGES
1. The use of nanotechnology help to protect
drugs from being degraded in the body
before they reach their target.
2. It enhances the absorption of drugs into tumors
and into the cancerous cells themselves.
3.
Nanotechnology allows for better control over the timing and distribution of
drugs to the tissue, making it easier for oncologists to assess how well they
work.
4. It
prevents drugs from interacting with normal cells thus avoiding side effects.
5. Nanotechnology helps in early diagnosis and
rapid testing.
DISADVANTAGES
1. Through the
use of nanotechnology atomic weapons can now be more accessible and made to be
more powerful and more destructive.
2. Since these
particles are very small, problems can actually arise from the inhalation of
these minute particle, much like the problems a person gets from inhaling
minute asbestos particles.
3. Presently,
nanotechnology is very expensive and developing it can cost a lot of money. It
is also difficult to manufacture, which is why products made with
nanotechnology are more expensive.
CHAPTER THREE
3.0 CONCLUSION/RECOMENDATION
Nanotechnology is influencing more deeply on
medical research; new and
safer diagnostic tools are available
which are enabling
us to diagnose diseases very
earlier as it onsets, and to develop
diagnostic strategy against
it. Forthcoming years, nanotechnology will continue to evolve and expand
in many areas of human life and its achievements will be applied in medical
sciences for diagnosis and patient treatment.
Nanotechnology has revolutionary opportunities to fight against many
diseases such as diabetes mellitus, cancer, neurodegenerative diseases;
as well as identifying
the microorganisms and
viruses associated with infections. Existing and conventional
technologies for medical diagnosis may be reaching their confines. Nevertheless,
nanotechnology would provide assistance to make diagnosis of diseases more
sensitive, rapid and create diagnosis tools easier to use, allowing doctors to
identify disease earlier and begin treatment earlier. Nanotechnology for
medical diagnosis is most
innovative and highly specific field, which
will renovate the healthcare in near
future which would enhance
quality of life of patients. The scientific vision carried forward by
nanotechnology is to open up opportunities for developing new diagnostic tools
to provide the ability for people to test themselves and their health to be
constantly monitored. Additionally, medical implants could take advantage of
the improved knowledge on how materials like plastics and metals interact with
the human body, assisting doctors to replace worn out body parts with
artificial ones. Ambitious scientific progress in nanotechnology, medical
diagnosis will move to a phase in which straightforward disease diagnosis;
independent of physician visits and large centralized laboratories. Indeed,
further novel variations and innovation in nanotechnology will continue to
appear and produce new opportunities for medical diagnosis.
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