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TABLE 1: TYPE OF DENDRIMERS
S.NO. Type of dendrimer
Synthesis
Example
Identification
1.
Divergent
Dendritech
These are spheroidal or
Amido
TM
ellipsoidal in shape.[13]
Amine)
(USA)
It has high solubility
PAMAM (Poly
Dendrimer
and
reactivity due to incidence
of a number of functional
end groups and empty
internal cavities.[14,15]
2.
PPI
(Poly
Divergent
Propylene
Asramol by DSM
Its core structure is
(Netherlands)
based on Di amino
Imine ) Dendrimer
butane with primary
amines as end groups and
tertiary propylene amines
as center.
These
are
commercially available
up to G-5 and are
extensively
used in material science
and biology[16]
3.
Chiral Dendrimer
Convergent
chiral dendrimers
The chirality of the
derived from
dendrimers was based
pentaerythritol
upon the building of
constitutionally
different but chemically
alike branches
to chiral core[17]
4.
Multilingual
Dendrimers
Convergent
VivaGel
These are the
dendrimers which hold
multiple copies of a
particular functional
group on their surface[18]
5.
Tecto Dendrimers
Divergent
Mercapto
These were made up of
core dendrimers,
which can be surrounded
by other
dendrimers, which
execute a specific
function leading to a
smart therapeutic
system used for
diagnose the diseased
state and deliver API to
the accepted
diseased cell[18]
6.
Hybrid
Divergent
Dendrimers
Hybrid dendritic
These dendrimers have
linear polymer,
characteristic of
Polysilsesquioxanes both dendritic and linear
polymer[18]
7.
Peptide
Convergent
Dendrimers
Beta Casomorphin
Peptide dendrimers are
(human)
those which hold
amino acid as branching
or interior unit.
These are used for the
diagnostic purpose
and vaccine delivery[19]
8.
Frechet-Type
Dendrimers
Convergent
Frechet type
These were based on
dendron azides,
polybenzyl ether
TM
hyper branched skeleton.
Priostar
Carboxylic
acid group attached on
the surface of
dendrimers that provides
site
for
further functionalization
and also
improve the solubility of
dendrimers[19]
9.
PAMAMOS
Convergent
SARSOX
(Poly Amidoamine
and
containing
Organosilicon)
Divergen
commercial dendrimers
Dendrimers
These
are
silicon
which are
inverted
unimolecular
micelles and
contains exterior
hydrophobic
organosilicon (OS) and
interiorly
hydrophilic, nucleophilic
polyamidoamine[19]
10.
Multiple Antigen
Convergent
vaccine and
These are dendron-like
Peptide
and
diagnostic
molecular assembly
Dendrimers
Divergent
research
based upon a polylysine
frame. Lysine with
its alkyl amino sidechain performed as a
excellent monomer for
the overture of
frequent branching points
[20]
TABLE 2: CHARACTERIZATION OF DENDRIMERS
Spectroscopy
A
spectrometry methods
and Spectroscopy and spectrometry methods of
characterization of dendritic polymer are as
follows[29-34]
Ultra-violet-visible
Provides information for monitoring the synthesis of
spectroscopy
dendrimers. The intensity of the absorption band is
(UV-VIS)
basically
proportional
to
the
number
of
chromophoric units.
Infra red spectroscopy (IR)
Provides information for routine analysis of the
chemical transformations going at the surface of
dendrimers.
Near infra red spectroscopy
Provides information for the characterization of
delocalize π-π stacking interaction between end
groups of modified PAMAM.
Fluorescence
Provides
information
Sensitivity of
for
increasingly
fluorescence
used
high
to
quantify
fast
atom
defects during the
synthesis of dendrimers.
Mass spectroscopy
Chemical
ionization
bombardment
used
for
or
the characterization of
small dendrimers whose mass is below 3000Da.
Electrospray ionization used for dendrimers which
are able to form stable multicharged species.
X-ray diffraction (XRD)
Provides
information
determination
of
the
to
allow
precise
chemical composition,
structure, size and shape of Dendrimer.
B
Scattering techniques
Scattering techniques for characterization of
dendritic polymer are as Follows[35-38]
Small angle X-ray scattering Provides information about their average radius
(SAXS)
of gyration (Rg) in solution. The intensity of the
scattering
also
provides
information
on
the
arrangement of polymer segments.
Small
angle
neutron Provides access to the radius of gyration, but may
scattering (SANS
also disclose more accurate
information
than
SAXS. The location of the ending groups has
also been determined by SANS experiments
conducted
with PAMAM dendrimers and PPI
dendrimers
Laser light scattering (LLS)
It
determines
the
hydrodynamic
radius
of
dendrimers. Dynamic LLS is mostly used for the
detection of aggregates.
C
Microscopy methods
Microscopy methods for characterization of
dendritic polymer are[39-40]
Transmission microscopy
Electron or light produce images that intensify
the original, with a resolution eventually limited
by the wavelength of the source.
Scanning microscopy
It produces an image by touch contact Q at a
few angstroms of a sensitive canilever arm with
sample. Ex. Atomic force microscopy.
D
E
exclusive It allows the partition of molecules according to
Size
chromatography
size.[41]
Electrical techniques
Electrical techniques for characterization of
dendritic polymer are as Follows[42-44]
Electron
paramagnetic Quantitative determination
resonance (EPR)
effectiveness
on
of the substitution
the surface of PANAM
dendrimers
Electrochemistry
It provides information about the possibility of
interaction of electroactive end groups.
Electrophoresis
It provides the information about the assessment
of
purity
and homogeneity of several types of
water soluble dendrimers.
F
Rheology
and
Physical Rheology and physical properties used for
properties
characterization of dendritic polymer are as
follows[45-48]
Intrinsic viscosity
It is as analytical probe of the morphological
structure of dendrimers.
Differential
scanning It used to detect the glass transition temperature
calorimetry (DSC)
depends on the moleculer weight, entangment and
chain composition of polymers.
Dielectric spectroscopy (DS)
Gives
complete
information
about
molecular
dynamic processes (α-, β).
G
Miscellaneous
Other methods used of characterization of
dendritic polymer are as Follows[49-51]
X-ray
Photoelectron It provides detailed information about chemical
Spectroscopy (XPS)
composition of dendrimers such as poly (aryl ether)
dendrons or PAMAM dendrimers which was
obtained using XPS. This technique is most
generally used
for the characterization of layers.
Sedimentation
Technique
used
for
lactosylated
PAMAM
dendrimers, measurements of dipole moments for
PMMH dendrimer.
Titrimetry
It is used for determining number of NH2 end
groups of PAMAM Dendrimers.
TABLE 3: FACTORS AFFECTING DENDRIMER PROPERTIES [52,53,54]
S.NO.
Factor
Level
Effect
1.
Effect of pH
Low
-Structural behaviour of PAMAM dendrimers is
depended upon pH.
-At low pH (< 4) the interior is getting
increasingly hollow.
-Repulsion between the positively charged
amines both at the dendrimer surface
and the tertiary amines in the interior increases
at high generation.
Neutral
-At neutral pH, back-folding occurs which
may be a consequence of hydrogen
bonding between the uncharged tertiary amines
in the interior and the positively
charged surface amines.
High
-At higher pH (pH>10) the dendrimer
contract as the charge of the molecule
becomes neutral, acquiring a more spherical
(globular) structure, where the
repulsive forces between the dendrimer arms
and between the surface groups
reaches minimum
2.
Effect of Salt
High
-High concentration of salt have a strong
effect on charged PPI dendrimers.
Favours a contracted conformation of
dendrimers, with a high degree of
back-folding somewhat similar to what is
observed upon increasing pH or poor
solvation.
Low
The repulsive forces between the charged
dendrimer segments results in an
extended conformation in order to minimize
charge repulsion in the structure
3.
Effect of Solvent
-The solvation power of any solvent to solvate
the dendrimer is a very important
parameter.
-Dendrimers of all generations generally
exhibit a larger extent of back-folding
with decreasing solvent quality.
-The dendrimer arms induce a higher
molecular density on the dendrimer
surface.
-NMR studies performed on PPI dendrimers
concluded that a nonpolar Solvent
like benzene, poorly solvates the dendrimers
favouring intramolecular
interactions between the dendrimer segments
and back-folding
4.
Effect of
-Small angle X-ray scattering (SAXS)
Concentration of
experiments performed on PPI dendrimers
Dendrimer
(G4, G5) in a polar solvent like methanol show
that the molecular conformation
of dendrimers upon increasing concentration
becomes increasingly contracted.
-This molecular contraction may minimize
the repulsive forces between the
dendrimer molecules and increase the ability of
the dendrimers to exhibit a more
tight intermolecular packing.
TABLE 4: DENDRIMERS BASED PRODUCTS[56]
S.NO.
Brand name
Type
of Companey
Application
dendrimer
1.
Vivagel
Multiple
Star Pharma
HIV Prevention
Antigen
2.
Alert ticket
PAMAM
US
army Anthrax
research
Detection
laboratory
3.
Superfect
Ampiphilic
Qiagen
Gene
Transfection
4.
Startus CS
Tecto
Dade Behring
Cardiac Marker
5.
Priofect™,
Tecto
Starpharma
Targeted
Priostar™
diagnostic,
therapeutic
delivery
for cancer cells