dendrimers,anuradha patel

Views:
 
Category: Entertainment
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

Prepared By:Mrs Anuradha G. Patel Smt BNB Swaminarayan Pharmacy college ,Salvav, Vapi. :

Prepared By:Mrs Anuradha G. Patel Smt BNB Swaminarayan Pharmacy college ,Salvav, Vapi. 5/31/2016 1 Dendrimers: properties and applications in Drug Delivery

Slide 2:

Definition: In the recent past it has been found that the properties of highly branched macromolecules can be very different from conventional polymers. The structure of these materials has also a great impact on their applications. First discovered in the early 1980’s by Donald Tomalia and co-workers , these hyperbranched molecules were called dendrimers. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 2

Slide 3:

Dendrimers are generally prepared using either a divergent method or a convergent one. In the divergent methods, dendrimer grows outwards from a multifunctional core molecule. The core molecule reacts with monomer molecules containing one reactive and two dormant groups giving the first generation dendrimer. Then the new periphery of the molecule is activated for reactions with more monomers. The pro- cess is repeated for several generations and a dendrimer is built layer after layer. Problems:occur from side reactions and incomplete reactions of the end groups that lead to structure defects. To prevent side reactions and to force reactions to completion large excess of reagents is required. It causes some difficulties in the purification of the final product. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 3 SYNTHESIS

Slide 4:

A. The divergent growth method 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 4

Slide 5:

The convergent methods were developed as a response to the weaknesses of the divergent synthesis . In the convergent approach, the dendrimer is constructed stepwise, starting from the end groups and progressing inwards. When the growing branched polymeric arms, called dendrons, are large enough, they are attached to a multifunctional core molecule (Fig. 1B). The convergent growth method has several advantages. It is relatively easy to purify the desired product and the occurrence of defects in the final structure is minimised. It becomes possible to introduce subtle engineering into the dendritic structure by precise placement of functional groups at the periphery of the macromolecule. The convergent approach does not allow the formation of high generations because steric problems occur in the reactions of the dendrons and the core molecule. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 5

Slide 6:

B. The convergent growth method 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 6

Slide 7:

Dendrimers are monodisperse macromolecules, unlike linear polymers. The classical polymerization process which results in linear polymers is usually random in nature and produces molecules of different sizes, whereas size and molecular mass of dendrimers can be specifically controlled during synthesis. Because of their molecular architecture, dendrimers show some significantly improved physical and chemical properties when compared to traditional linear polymers. In solution, linear chains exist as flexible coils; in contrast, dendrimers form a tightly packed ball. This has a great impact on their rheological properties. Dendrimer solutions have significantly lower viscosity than linear polymers . When the molecular mass of dendrimers increases, their intrinsic viscosity goes through a maximum at the fourth generation and then begins to decline . Such behaviour is unlike that of linear polymers. For classical polymers the intrinsic viscosity increases continuously with molecular mass. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 7 PROPERTIES

Slide 8:

The presence of many chain-ends is responsible for high solubility and miscibility and for high reactivity . Dendrimers’ solubility is strongly influenced by the nature of surface groups. Dendrimers terminated in hydrophilic groups are soluble in polar solvents, while dendrimers having hydrophobic end groups are soluble in nonpolar solvents. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 8

Slide 9:

Dendrimers can be used as coating agents to protect or deliver drugs to specific sites in the body or as time-release vehicles for biologically active agents. 5-Fluorouracil (5FU) is known to have remarkable antitumour activity, but it has high toxic side effects. The dendrimers are water soluble and hydrolysis of the conjugates releases free 5FU. The slow release reduces 5FU toxicity. Such dendrimers seem to be potentially useful carriers for antitumour drugs. Therapeutic agents can also be attached to a dendrimer to direct the delivery. A good example of such application is using dendrimers in boron neutron capture therapy (BNCT). Boron neutron capture therapy is an experimental approach to cancer treatment which uses a two-step process. First, a patient is injected with a non-radioactive pharmaceutical which selectively migrates to cancer cells. This component contains a stable isotope of boron ( 10 B). Next, the patient is irradiated by a neutral beam of low-energy or thermal neutrons. The neutrons react with the boron in the tumour to generate alpha particles, which destroy the tumour leaving normal cells unaffected 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 9 Applications

Slide 10:

Dendrimers can act as carriers, called vectors, in gene therapy. Vectors transfer genes through the cell mem Currentlyliposomes and genetically engineered viruses have been mainly used for this. brane into the nucleus. PAMAM dendrimers have also been tested as genetic material carriers . They are terminated in amino groups which interact with phosphate groups of nucleic acids. This ensures consistent formation of transfection complexes. A transfection reagent called SuperFect TM consisting of activated dendrimers is commercially available. SuperFect–DNA complexes are characterised by high stability and provide more efficient transport of DNA into the nucleus than liposomes. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 10

Slide 11:

Besides biomedical applications dendrimers can be used to improve many industrial processes. The combination of high surface area and high solubility makes dendrimers useful as nanoscale catalysts . They combine the advantages of homogenous and heterogeneous catalysts. Homogenous catalysts are effective due to a good accessibility of active sites but they are often difficult to separate from the reaction stream. Heterogeneous catalysts are easy to separate from the reaction mixture but the kinetics of the reaction is limited by mass transport. Dendrimers can encapsulate insoluble materials, such as metals, and transport them into a solvent within their interior. synthesised fluorinated dendrimers which are soluble in supercritical CO2 and can be used to extract strongly hydrophilic compounds from water into liquid CO2. This may help develop technologies in which hazardous organic solvents are replaced by liquid CO2. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 11

Slide 12:

Newkome, G.R., Yao, Z.Q., Baker, G.R. & Gupta, V.K. (1985) Cascade molecules: A new approach to micelles, A[27]-arborol. J. Org. Chem. 50 2003–2006. Hodge, P. (1993) Polymer science branches out. Nature 362, 18–19. Hawker, C.J. & Fréchet, J.M.J. (1990) Preparation of polymers with controlled molecular architecture. A new convergent approach to dendritic macromolecules. J. Am. Chem. Soc. 112, 7638– 7647. Alper, J. (1991) Rising chemical “stars” could play many roles. Science 251, 1562–1564. Tomalia, D.A., Naylor, A.M. & Goddard III, W.A. (1990) Starburst dendrimers: Molecular-level control of size, shape, surface chemistry, topology, and flexibility from atoms to macroscopic matter. Angew. Chem., Int. Edn. 29, 138–175. Jansen, J.F.G.A. & Meijer, E.W. (1995) The dendritic box: Shape-selective liberation of encapsulated guests. J. Am. Chem. Soc. 117, 4417–4418. Archut, A., Azzellini, G.C., Balzani, V., Cola, L.D. & Vögtle, F. (1998) Toward photoswitchable dendritic hosts. Interaction between azobenzene-functionalized dendrimers and eosin. J. Am. Chem. Soc. 120, 12187–12191. Gilat, S.L., Adronov, A. & Fréchet, J.M.J. (1999) Light harvesting and energy transfer in novel convergently constructed dendrimers. Angew. Chem., Int. Edn. 38, 1422–1427. Adronov, A., Gilat, S.L., Fréchet, J.M.J., Ohta, K.,,Neuwahl, F.V.R. & Fleming, G.R. (2000) Light harvesting and energy transfer in laser-dye-labelled poly(aryl ether) dendrimers. J. Am. Chem. Soc. 122, 1175–1185. 5/31/2016 Smt BNB Swaminarayan Pharmacy college,Salvav,Vapi. Prepared by:Anuradha G Patel 12 References

authorStream Live Help