Immobilization techniques for dna biosensor lecture 6

Immobilization
Techniques for DNA
biosensor
LECTURE OF SUBJECT:
Dr. sharafaldin Al-musawi
College of Biotecholgy
LECTURE: 6
SUBJECT: Biosensors & Biochips
LEVEL: 4

Immobilization Techniques
for DNA biosensor

 A functional group is a specific group of atoms within a molecule that is responsible
for characteristic chemical reactions of that molecule.
 There are different covalent attachment chemistries involving various functional groups
on the surface of functionalization chip for DNA immobilization.
 Among this factor we can refer to:
 Carboxyl
 Aldehyde
 Epoxy
 Isothiocyanate
 Maleimide
 Mercaptosilane
Functional group for
DNA Immobilization

Carboxyl group
 The carboxyl group is
an organic functional group consisting of
a carbon atom double bonded to
an oxygen atom and single bonded to
a hydroxyl group.
 Another way to view it is as a carbonyl
group (C=O) that has a hydroxyl group
(O-H) attached to the carbon atom.
 The carboxyl group is commonly written
as -C(=O)OH or -COOH.

Reaction of carboxyl group with amine

 The aminated DNA can Interact with immobilized carboxylate via
EDC [1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide] OR Sulfo-
NHS (N-hydroxysulfosuccinimide).

The advantages and disadvantages of the
reaction of carboxy functionalized surface with
aminated DNA
Advantages:
 Simple method of immobilization
 High surface coverage of DNA’s
 Easy coupling reaction
Disadvantages:
 Efficiency of immobilization depends
on:
i. pH
ii. Concentration
iii. Ionic strength
iv. Reaction time.

Aldehyde group
 Aldehyde: any of a class of organic compounds,
in which a carbon atom shares a double bond with
an oxygen atom, a single bond with
a hydrogen atom, and a single bond with another
atom or group of atoms.
 The double bond between carbon and oxygen is
characteristic of all aldehydes and is known as
the carbonyl group.

The aminated DNA can Interact with immobilized
Aldehyde group in bio reception surfaces.
DNADNA
Aminated
DNA
Aldehyde
group
Chemical bonding
with aminated-DNA
+ H2O

Advantages:
 Good stability
 Long hybridization time
 High binding strength
Disadvantages:
 Limits the absolute signal intensity
 Stable enough for long term use
 High hybridization temperature
reaction of aldehyde functionalized surface with
aminated DNA

Epoxy group
 An organic chemical that contains a
group consisting of an oxygen atom
bound to two already connected
atoms, usually carbon.
 A functional group that containing an
oxygen atom joined to two different
groups that are themselves joined to
other groups.

 Double-strand DNA can be immobilized on the epoxy surface Because guanine
bonds easily react with epoxy group.
 Epoxy groups can intract with DNA via chemical (covalent) bonding with
hydroxyl, amine and sulfhydryl groups.

Advantages:
 Easy protocol for immobilization
 Good stability
Disadvantages:
 Reactions between DNA and epoxy
are extremely slow.
 Low Immobilization density
reaction of epoxy functionalized surface with
aminated DNA

Isothiocyanate
Isothiocyanate is the chemical group –N=C=S, formed by
substituting the oxygen in the isocyanate group with a sulfur.

DNADNA
 Isothiocyanate groups can interact with DNA via chemical
(covalent) bonding with its aminated form.
H2

Advantages:
 Well-ordered surface
 Re-usability
 High density DNA/area
Disadvantages:
 High non-specific hybridizations
 Long hybridization time
reaction of Isothiocyanate functionalized
surface with aminated DNA

Maleimide group
 Maleimide is a chemical compound with the formula H2C2(CO)2NH.

 Maleimide group can interact with DNA via chemical (covalent) bonding with its
sulfhydrylated form.
DNA
DNA

 Advantages:
 Faster immobilization reaction
 Re-usability
 Good stability
 Disadvantages:
 High non-specific interaction
 Degradation in aqueous solutions
reaction of maleimide functionalized surface
with sulfated DNA

Mercaptosilane group
• any of a class of odiferous sulfur
containing compounds having the type formula
RSH, where R is any hydrocarbon group.
Also called thiol.
Mercaptan

DNA SH
DNA S S
 Mercaptosilane can perform chemical (covalent) bonding with
DNA-SH.
H2

 Advantages:
 Re-usability
 Good stability
 Disadvantages:
 High non-specific interaction
 High hybridization temperature
reaction of mercaptosilane functionalized
surface with sulfated DNA

Immobilization techniques for dna biosensor lecture 6

More Related Content

What's hot

Viewers also liked

Similar to Immobilization techniques for dna biosensor lecture 6

More from Green University of Al Qasim

Recently uploaded

Immobilization techniques for dna biosensor lecture 6