memberane used in biosensor
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Membranes used in Biosensor
Presented by:
Arushe Tickoo
DTU, Delhi
A biosensor is an analytical device, used for the detection of an analyte, that combines a biological component with a detector.
A membrane is a layer of material
that serves as a selective barrier
between two phases & remains
impermeable to specific particles,
molecules
MEMBRANE
A mechanical, thin, flat flexible part
that can deform or vibrate when
excited by an external force
Characteristics of a Membrane
Physically rigid
Chemically inert
Photochemical & Thermal stability
Good Optical Transparency
Enhanced Charge Transport
Membranes for Biosensor
Conducting Polymers
Langmuir-Blodgett Films
Sol Gels
Self Assembled Monolayer
Nano Structured Materials
Conducting Polymers Polymers
Insulators
Orbitals to be partiallyfilled to allow freemovement of electrons
Conductors byoverlapping of molecularorbitals to allow theformation of delocalizedmolecular wave function.
They are made of conjugate Pi (П)
and sigma (σ) bonds
It began with the discovery of Poly (sulphur nitride) in 1975 which
became superconducting at low temperature.
Poly- paraphenylene was synthesized in 1979. It forms highly conducting
charge transfer complexes with both n and p type dopants. Doping with
AsF5 increases its conductivity
Examples : polyfuran, polyindole, polycarbazole, polyaniline etc
HISTORY
Polyaniline, in particular, has been studied thoroughly because of its stability in
fluid form, conductive properties, and strong bio-molecular interactions.
Electrophoretic Deposition
In electrophoretic deposition, charged molecules,
dispersed or suspended in a liquid medium are
attracted & deposited onto a conductive substrate of
opposite charge on application of a DC electric
field.
Colloidal suspension
ITO-coated glass
Platinum electrode
Colloidal suspension
ITO-coated glass
Platinum electrode
Colloidal suspension
ITO-coated glass
Platinum electrode
Electrophoretic technique is known to yield uniform,
dense and nanoporous conducting polymer films.
Electrophoretic deposition from a colloidal
suspension of a conducting polymer results in nano-
structured conjugated polymer films
Immobilization of enzyme (GOx) on the Polyaniline Matrix
Adduct-II
Adduct-I
NHS
Polyaniline
EDC Enzyme
O
OH
Enz CH3CH
2-N=C=N-(CH
2)3N(CH
3)2
O
O
O
O
P NH2
P NH
O
Amide bond formation
NEnzEnz
O
O N
NH
N-(CH2)3N(CH
3)2
-CH2CH
3
O O
OH
N
Enz
Electrophoretic deposition from a colloidal suspension of a conducting polymer results in
nano-structured conjugated polymer films
NH2n (NH4)2 S2O8, HCl/H2SO4
-5oC to 0oC, 4-5 hrN
H
n
Oxidative polymerization of aniline leads to polyaniline in
emralidine base form
Formation of polyaniline colloidal suspension
Electrophoretic deposition of
polyaniline from its colloidal
suspension at 80V
Langmuir Film:
The two dimensional crystalline arrangement of molecules at the air- water interface
is known as Langmuir film.
Langmuir-Blodgett (LB) Film(1932):
When the mono- or multilayer's of Langmuir films were transferred onto a solid
substrate it is called Langmuir-Blodgett (LB) film. Langmuir–Blodgett films are
named after Irving Langmuir and Katharine B. Blodgett, who invented this
technique.
Deposition of Langmuir film onto solid substrate:
There are three deposition schemes commonly used to transfer Langmuir film onto
solid substrate to form Langmuir-Blodgett (LB) film.
These are:
Y-Type deposition
X-Type deposition
Z-Type deposition
Langmuir-Blodgett
LB films are formed when amphiphilic molecules like surfactants interact with air
at an air–water interface. Surfactants (or surface-acting agents) are molecules with
hydrophobic 'tails' and hydrophilic 'heads'.
When surfactant concentration is less than critical micellar concentration (CMC),
the surfactant molecules arrange themselves as shown.
The overall effect is reduction in the surface energy (or equivalently, surface
tension of water).
A self assembled monolayer (SAM) is an organized layer of amphiphilic
molecules in which one end of the molecule, the “head group” shows a special
affinity for a substrate. SAMs also consist of a tail with a functional group at the
terminal end.
Self Assembled Monolayer (SAM)
Characteristics of SAM
The word SAM generally denotes a monomolecular thick film of organic compounds
on flat (i.e., two-dimensional) metal or semiconductor surfaces.
SAM formation provides one of the easiest ways to obtain ordered monolayers
through strong chemisorption between the head group of a desired compound and
the metal surface leading to the preparation of thermodynamically stable monolayers.
Long-chain alkane thiols (containing more than six to seven methylene units) form
more well-ordered defect-free monolayers than short-chain alkane thiols, disulphides
or sulphides.
A famous example involves thiols (RS-H) adsorbing onto the surface of gold (Au).
Alkanethiols (RS-H) onto the surface of gold
Substrate
Hydration
H
O
H
O
H
OH
O
H
O RSiX3
H2OXH
H
O
H
O
H
OH
O
H
O
Si
X XX
R
Si
X XX
R
H
O
H
O
H
OH
O
H
O
Si
X XX
R
Si
X XX
R
Si O Si O Si
R R R
OHOH
OO O
HH H H HH
O O O
Si O Si O Si
R R R
OHOH
OO O
where X = Cl, OCH3, OC2H5 etc.
Schematic of Silane SAM Formation
• The sol-gel process is a method for producing solid materials from small molecules.
• The process involves conversion of monomers into a colloidal solution (sol) that
acts as a precursor for an integrated network (or gel) of either discrete particles or
network polymers.
•
Sol-gel
Chemical Reaction
1. Hydrolysis
2. Condensation
Properties
Rigid
Transparent
Negligible
swelling
Stable
1. Metal & Metal Oxide Nanoparticles
Gold Nanoparticles (GNPs)
Zinc Oxide Nanoparticles (ZnO)
Cerium Oxide Nanoparticles (CeO)
TiO2/CeO2 Nanoparticles
Nano-materials Based membranes
2. Carbon Nanotubes
3. Carbon Nanowires
Nanostructured Metal oxides have Unique
Properties
High specific surface area,
Non-toxicity,
High chemical stability,
Electrochemical activity,
High adsorption capability,
High electron communication
Nano-ZnO/ Chitosan films for Cholesterol Sensor
O
OH
H NH2
H
H
CH2OH
O
O
OH
H NH2
H
H
CH2OH
O O
n
ITO
ZnO NanoCrystal
(acetate buffer)
Chitosan beckbone
O
OH
H NH2
H
H
CH2OH
O
OH
H NH2
H
H
CH2OH
O O
O
OH
H NH2
H
H
CH2OH
O
OH
H NH2
H
H
CH2OH
O O
n
O
OH
H NH2
H
H
CH2OH
O
OH
H NH2
H
H
CH2OH
O O
O
OH
H NH2
H
H
CH2OH
O
OH
H NH2
H
H
CH2OH
O O
n
(ChOx)
ChOx/NanoZnO/CHIT/ITONanoZnO/CHIT/ITO
ZnO nano crystal
ChOx
Many CNTs based nanohybrids, such as MWCNT/AuNPs/ionic liquid
(F. Jia, Shan, Li, & Niu, 2008), SWCNT/GOD/Nafion (Lyons & Keeley,
2008), polyaniline (PANI)-coated Fe3O4 nanoparticle/MWCNT (Zhun Liu,
Wang, Xie, & Chen, 2008), and palladium/SWCNT (Meng, Jin, Yang, Lu,
Zhang, & Cai, 2009), have been explored to immobilize GOD for glucose
biosensing
CNT also used for cholesterol sensing and therapeutics.
Carbon Nanotubes
A strategy for using SWNTs as
intracellular vectors for delivery of
ASODNs modified with gold
nanoparticles. This strategy allows
intracellular delivery and localization to
enhance the therapeutic efficiency of
the ASODNs by the conjugations of
SWNTs and GNPs
OO
-
O-
O
OO
-
O-
O
N+
NH
NH
N+
..
H
H
n
N+
NH
NH
N+.
.
H
H n
NH
N+
N+
NH
.
.
H
H
H
N+
N+
NH NH ..H H
(a)
(b)O
O
O
O- O
-
OH
OH
O
O-
(c)
n
n
MWCNT-c wrapping by ES
+
MWCNT-c
Emeraldine salt (ES)
ES/MWCNT-c composite
MWCNT-Polyaniline composite for free Cholesterol Sensing
preparation procedure of glucose oxidase (GOD)–Au Nps/carbon nanotubes (CNTs)- Ab2 tracer
GOD have been immobilized on CNTs for enhancing the enzymatic signal. Typically, a novel
immunosensor array was constructed by coating layer-by-layer colloidal Prussian blue (PB), gold
nanoparticles (AuNPs), and capturing antibodies on screen-printed carbon electrodes (Figure 7) and
coupling with a new tracer nanoparticle probe labeled antibody (Ab2) that was prepared by one-pot
assembly of GOD and the antibodies on AuNPs attached CNTs
• DETECTION OF SINGLE VIRUS
NANOWIRES CONFIGURED AS A FET
DETECTION OF SINGLE VIRUS ON RECEPTORS CHANGES CONDUCTANCE
• DETECTION OF
BIOMOLECULE
NANOWIRE
CANTILEVER ARRAY SENSOR
FOR CANCER DIAGNOSIS
When the cancer-associated molecules bind to the cantilevers, changes in surface
tension cause the cantilever to bend
The mass detection limitation of NEMS cantilevers is improved to the
enumeration of a single DNA molecule consisting of ~1600 base pairs and
weighing ~1 ag (atto = 10^18)
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