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)