lipoplexes and polyplexes - the vehicles of gene delivery
Post on 02-Jul-2015
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Gene Therapy:
Treatment which cure disease By introducing DNA into cells
•Major Challenge in G.T Delivery of gene into target cells
Barriers
ExtracellularIntracellular
Why ?
• immune system•Epithelial cells• Degradative Enzymes in blood
• cell membrane• endosomal membrane• degradative enzymes in cytoplasm• Nuclear membrane
Gene Delivery Systems (vehicles): Characteristics =Specific,Efficient,Safe
Viral Gene Carriers Very Efficient
Problems
Non Viral Gene Carriers
Chemical
Physical
•Microinjection•Electroporation•BiolisticsUses chemicals for
delivering gene
• Immunogenic• Random integration of DNA to genome = can result in Cancer• difficult to reproduce viruses for using them as carriers
Basic Mechanism of chemical delivery System:
Polycationic entities + DNA (-vely charge) = Complexes ( +vely charged)
Plasma Membrane (-vely charged)
Electrostatic Interaction
Endosomes
DNA released in ctyosol
DNA Reaches Nucleus
Main Players of Chemical Delivery System:Lipoplexes
PolyplexesLipoplexes: = Complexes of Liposome +DNA
Cationic lipid + Neutral Lipid
Amphiphatic
Hydrophilic head group is attached to hydrophobic domain via a connector
Should be•Chemical stable•Biodegradable
Examples include•Amino acid•Aromatic rings
•Stabilizes the Complexes•Reduces toxicity•The Other Function
Examples include•DOPE•Cholesterol
Structure of Lipoplexes: Self Assembly!!
1. Multilameller Structure: DNA sandwiched, nearly equal head group and Hydrocarbon cross section
2. Hexagonal and inverted Hexagonal: DNA encapsulated in monolayer tubes, large heard group or small head group w.r.t hydrocarbon cross section
Lipoplexes Mediated Transfection Mechanism:
•Rapid mixing of cationic liposome and anionic lipids of endosomes raptures/ destabilizes the endosomes.
•Neutral lipid promotes rupturing
Polyplexes: Complexes of Cationic polymers + DNA
Consist of polymer,DNA binding proteins with ligands attached to them
Examples•Histones•Synthetic polypeptides
Note: Do not have hydrophobic domain •Poly-L-Lysine
•Polyethylinemine
Polyplexes Structure:
•Spherical•Globular•Rod-like•Toroids
Self Assembly!!
Polyplexes Mediated Transfection Mechanism:
•Proton sponge effect that promotes swelling of endosomes which leads to its rupture.
Problems with Chemical Gene Delivery system:
•New Technology so not that efficient yet as compared to viruses.
Summary:
•What is gene therapy•Barriers for Gene Delivery System and Delivery system Characteristics•Viral Gene Delivery System and their problems•Non Viral Gene Delivery System and their Problems•Lipolplexes, Lipoplexes structure and mechanism of Transfection•Polyplexes , Polyplexes structure and mechanism of Transfection
References:
1. Gene delivery by lipoplexes and polyplexes by Conchita Tros de llarduya and et all ( R.paper)
2. Nonviral gene delivery: Techniques and implications for molecular medicines by Alan L.Parker and et all (R.paper)
3. Understanding gene therapy (book) by N.R.Lemoine
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