This document summarizes non-viral gene delivery systems. It discusses chemical non-viral systems, including cationic liposome/micelle based systems and cationic polymer based systems. Cationic liposome/micelle based systems are effective but heterogeneous and can have stability issues. They have potential for widespread delivery but need to overcome aggregation, cellular entry rate, endosomal escape, and immune response challenges. Cationic polymer systems include simple polymers like poly-L-lysine but require assisting agents. More advanced polymer systems show improved DNA interaction, serum resistance, and gene delivery efficiency. Overall, non-viral systems are promising for gene therapy but require overcoming barriers to stability, delivery efficiency, and safety.

1. NON VIRAL DELIVERY SYSTEMS FOR GENE
THERAPY

2. INTRODUCTION
• Non viral vs viral systems
• Encompass chemical and physical methods of DNA
delivery
• Promising future option for gene therapy

3. CHEMICAL NON VIRAL DELIVERY SYSTEMS:
PRINCIPLES
• Polycationic entities cause compaction of –vely charged
nucleic acids forming nanometric complexes
• Cationic liposome/micelle based: lipoplexes
• Cationic polymer based: polyplexes
• Protect bound NA
• Have a net +ve charge
• Enter cell by endocytosis by non specific interactions
between complex and proteoglycans on adherent cells
• Following entry, DNA can escape endosome and perform its
function

4. • Instability towards aggregation under physiological salt
conditions
• Unstable in the presence of body fluids
• Heterogeneous and polydisperse
• Transfection takes long time
• Inability to escape endosome
• Difficulty to access nucleus
CHEMICAL NON VIRAL DELIVERY SYSTEMS:
PROBLEMS
Efforts to develop many cationic entities
No effort to develop one with all properties

6. CATIONIC LIPOSOME/MICELLE BASED NON
VIRAL DELIVERY SYSTEMS
• Most effective chemical NVDSs
• Formed from
• A single synthetic cationic amphiphile (cytofectin)
• Combination of a cytofection and a neutral lipid (e.g.,
DOPE)
• Currently >30 lipoplex systems
• Cytofectin is the key component
• Induction to unilamellar vesicles (cytofection+lipid)
• Assembly into micellar structures (single cytofection)
• Combining the above with DNA
• Delivery to the cell

7. Unilamellar
Micelle based

8. • Optimum in vivo delivery when the mol ratio of cationic
liposome to DNA is such that the +ve to –ve charge ratio is
1.
• Heterogeneous and polydisperse
• Multilamellar complexes with DNA on the surface
• Thin lipid coated DNA strands
• Free nucleic acids
• Which actually delivers DNA?
CATIONIC LIPOSOME/MICELLE BASED NON
VIRAL DELIVERY SYSTEMS

9. • In vitro transfection efficiency is a poor indicator of in vivo
transfection efficiency
• Less in vivo stability
• Development of poly(ethylene)glycol-lipid conjugates
• Use of cholesterol as lipid part
• Widespread systemic delivery
• Need for direct delivery but susceptibility to aggregation
• Use of ligand modified lipoplex systems
• Limited cell entry rate
• Use of ligand modified lipoplex systems
• Competition between specific natural ligand and non specific
lipoplex
CATIONIC LIPOSOME/MICELLE BASED NON
VIRAL DELIVERY SYSTEMS

10. • Serum inactivation
• Increasing +ve to –ve charge ratio
• Introducing a lipoplex time dependent maturation
• Immune and inflammatory responses
• Use of stabilizing agents
• Low rate of endosome escape
• Use of low pH activated membrane active peptides
• Use of pH sensitive liposomes
• Development of hybrid liposome complexes
CATIONIC LIPOSOME/MICELLE BASED NON
VIRAL DELIVERY SYSTEMS

12. • Less widely used than cationic polymer based non viral
delivery systems
• Developed in the same time period
• Two types
• Simple polymers
• Polymer systems
CATIONIC POLYMER BASED NON VIRAL
DELIVERY SYSTEMS

13. SIMPLE POLYMERS
• Use of poly-L-lysine (pLL), a linear polymer
• Can be produced in different mol.wt (19-1116 aa)
• Conflict between optimal sizes for NA condensation and for gene
delivery
• Need of an assisting agent for efficient gene delivery
• Use of EGF peptide or transferrin for facilitating cellular uptake
• Less endosome escape
• Use of fusogenic peptides or defective viral particles
• Generally prone to aggregation
• Too much additions needed for efficient output

14. • APL polycat-57: glucaramide nonpeptide, nonlipid polymer
• Rapid interaction with plasmid DNA
• Resistant to serum inhibition
• Efficient gene delivery
• Poly(N-ethyl-4-vinylpyridinium bromide, PEVP)
• Copolymers
• Peptoid polymers
• Using DNA as template for polymer generation
POLYMERS SYSTEMS