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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