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Liposome-Mediated DNA Delivery (Lipofection)


Liposome-Mediated DNA Delivery (Lipofection)


Definition


Liposome-mediated DNA delivery, also known as lipofection, is a chemical method of gene transfer in which DNA is encapsulated or complexed with liposomes (artificial lipid vesicles) and delivered into cells through membrane fusion or endocytosis.

Principle

Liposomes are spherical vesicles made of phospholipid bilayers, similar to the cell membrane.
Negatively charged DNA binds to positively charged (cationic) liposomes, forming DNA–liposome complexes (lipoplexes).
These complexes interact with the cell membrane, leading to:
Membrane fusion, or
Endocytosis followed by DNA release into cytoplasm and nucleus.
The delivered DNA may be transiently expressed or stably integrated into the host genome.

Types of Liposomes

Cationic liposomes
Most commonly used
Bind DNA efficiently
Example: DOTAP, DOTMA
Neutral liposomes
Lower toxicity
Lower transfection efficiency
Anionic liposomes
Rarely used for DNA delivery
Materials Required
Plasmid DNA (gene of interest + selectable marker)
Lipids (cationic lipids + helper lipids like DOPE)
Buffer (serum-free medium)
Target cells (animal cells, plant protoplasts, cultured cells)
Cell culture medium and incubator
Procedure / Steps

1. Preparation of Liposomes

Lipids are dissolved in organic solvent.
Solvent is evaporated to form a thin lipid film.
Hydration produces liposomes.

2. Formation of DNA–Liposome Complex

DNA is mixed with cationic liposomes.
Electrostatic interaction forms lipoplexes.

3. Transfection

Lipoplexes are added to cultured cells.
Complexes attach to cell membrane.
DNA enters the cell by endocytosis or membrane fusion.

4. Expression and Selection

DNA is released into cytoplasm and nucleus.
Gene expression is analyzed.
Selection is done using antibiotic or reporter genes.
Mechanism of DNA Uptake

Binding of lipoplex to cell membrane
Endocytosis into vesicles
Escape from endosomes
Transport of DNA to nucleus
Transcription and translation

Advantages

Simple and easy to perform
Does not require specialized equipment
Suitable for animal cells and plant protoplasts
Can deliver DNA, RNA, and oligonucleotides
Low immunogenicity
Useful for transient gene expression studies

Limitations
Low efficiency in cells with rigid cell walls
DNA degradation in endosomes
Possible cytotoxicity of cationic lipids
Limited in vivo application
Random integration of DNA

Applications

Gene expression studies
Transient transfection in mammalian cells
Delivery of siRNA and mRNA
Functional genomics
Gene therapy research (experimental level)
Protein production in cultured cells

Conclusion

Liposome-mediated DNA delivery is a widely used chemical gene transfer method due to its simplicity, versatility, and effectiveness in animal cell systems. Despite limitations like cytotoxicity and lower efficiency in plant cells, it remains a standard technique for transient transfection and molecular biology research.


50 MCQs on Liposome-Mediated DNA Delivery with Answers


Basics & Principle
Liposome-mediated DNA delivery is also known as:
A) Electroporation
B) Lipofection
C) Biolistics
D) Microinjection
Answer: B
Lipofection is classified as a:
A) Physical method
B) Biological method
C) Chemical method
D) Viral method
Answer: C
Liposomes are composed mainly of:
A) Proteins
B) Phospholipids
C) Carbohydrates
D) Nucleic acids
Answer: B
DNA binds to liposomes through:
A) Covalent bonding
B) Hydrogen bonding
C) Electrostatic interaction
D) Enzymatic reaction
Answer: C
DNA-liposome complexes are called:
A) Proteosomes
B) Lipoplexes
C) Endosomes
D) Micelles
Answer: B
Types of Liposomes
Most commonly used liposomes for gene delivery are:
A) Neutral liposomes
B) Anionic liposomes
C) Cationic liposomes
D) Zwitterionic liposomes
Answer: C
Positive charge on liposomes helps in:
A) DNA degradation
B) Binding negatively charged DNA
C) Protein synthesis
D) Cell division
Answer: B
Anionic liposomes are:
A) Highly efficient
B) Rarely used for DNA delivery
C) More toxic
D) Used only in plants
Answer: B
Helper lipid commonly used with cationic liposomes is:
A) PEG
B) DOPE
C) SDS
D) EDTA
Answer: B
Example of cationic lipid used in lipofection:
A) DOTAP
B) Agarose
C) Cellulose
D) Chitosan
Answer: A
Procedure
First step in lipofection is:
A) DNA selection
B) Liposome preparation
C) Cell harvesting
D) Antibiotic selection
Answer: B
DNA and liposomes are usually mixed in:
A) Distilled water
B) Serum-free medium
C) Antibiotic solution
D) Buffer with enzymes
Answer: B
Lipoplexes enter cells mainly by:
A) Passive diffusion
B) Endocytosis
C) Osmosis
D) Active transport only
Answer: B
After entry, DNA must escape from:
A) Nucleus
B) Ribosome
C) Endosome
D) Lysosome
Answer: C
For gene expression, DNA must reach the:
A) Cytoplasm
B) Cell membrane
C) Nucleus
D) Mitochondria
Answer: C
Mechanism
Liposomes mimic:
A) Nuclear membrane
B) Cell membrane
C) Mitochondrial membrane
D) Lysosomal membrane
Answer: B
Entry of lipoplex may also occur by:
A) Membrane fusion
B) Heat shock
C) Centrifugation
D) Sonication
Answer: A
DNA released into cytoplasm is transported to nucleus during:
A) Mitosis
B) Meiosis
C) Apoptosis
D) Necrosis
Answer: A
Expression without integration is called:
A) Stable expression
B) Transient expression
C) Mutational expression
D) Constitutive expression
Answer: B
Stable gene expression requires:
A) Cytoplasmic localization
B) Nuclear degradation
C) Genomic integration
D) Protein secretion
Answer: C
Efficiency & Factors
Transfection efficiency depends on:
A) DNA concentration
B) Lipid-to-DNA ratio
C) Cell type
D) All of the above
Answer: D
Presence of serum during complex formation may:
A) Increase efficiency
B) Decrease efficiency
C) Have no effect
D) Destroy cells
Answer: B
Lipofection is most efficient in:
A) Bacteria
B) Plant cells with cell walls
C) Mammalian cells
D) Fungal spores
Answer: C
Cell wall is a major barrier for lipofection in:
A) Animal cells
B) Plant cells
C) Human cells
D) Cancer cells
Answer: B
High lipid concentration may cause:
A) Increased efficiency only
B) Cytotoxicity
C) No effect
D) Cell wall formation
Answer: B
Advantages
Lipofection does not require:
A) Viral vectors
B) Lipids
C) DNA
D) Cell culture
Answer: A
Specialized equipment is:
A) Essential
B) Not required
C) Always expensive
D) Mandatory for plants only
Answer: B
Lipofection is commonly used for:
A) Stable plant transformation
B) Transient gene expression
C) Bacterial cloning
D) Chromosome transfer
Answer: B
Liposomes can deliver:
A) DNA only
B) RNA only
C) Proteins only
D) DNA, RNA, and oligonucleotides
Answer: D
Lipofection has low:
A) Flexibility
B) Efficiency in animal cells
C) Immunogenicity
D) Simplicity
Answer: C
Limitations
Major limitation of lipofection is:
A) Need for enzymes
B) Low efficiency in plant cells
C) High cost
D) Use of radiation
Answer: B
Cationic lipids may cause:
A) Cell proliferation
B) Cytotoxic effects
C) DNA replication
D) Cell wall synthesis
Answer: B
DNA degradation may occur in:
A) Ribosomes
B) Endosomes
C) Golgi bodies
D) Chloroplasts
Answer: B
Integration of DNA after lipofection is:
A) Site-specific
B) Random
C) Controlled
D) Absent always
Answer: B
Lipofection is less suitable for:
A) In vitro studies
B) In vivo delivery
C) Mammalian cells
D) siRNA delivery
Answer: B
Applications
Lipofection is widely used in:
A) Gene therapy research
B) DNA sequencing
C) Protein crystallization
D) Chromosome walking
Answer: A
siRNA delivery commonly uses:
A) Biolistics
B) Lipofection
C) Microinjection
D) PEG fusion
Answer: B
Reporter genes delivered by lipofection include:
A) GFP
B) GUS
C) Luciferase
D) All of the above
Answer: D
Lipofection is mainly an:
A) In vivo technique
B) In vitro technique
C) Field technique
D) Agricultural method
Answer: B
Liposome-mediated delivery is useful for:
A) Functional genomics
B) Protein expression studies
C) Gene regulation analysis
D) All of the above
Answer: D
Comparison & General
Compared to electroporation, lipofection is:
A) More damaging
B) Less damaging
C) Same efficiency in all cells
D) More expensive
Answer: B
Lipofection bypasses use of:
A) Cell membrane
B) Viral vectors
C) Nucleus
D) Ribosomes
Answer: B
Liposomes are artificial versions of:
A) Ribosomes
B) Cell membranes
C) Chromosomes
D) Enzymes
Answer: B
Liposome size is usually in the:
A) Millimeter range
B) Micrometer range
C) Nanometer range
D) Centimeter range
Answer: C
Lipoplex formation is based on:
A) Hydrophobic forces only
B) Electrostatic attraction
C) Covalent bonding
D) Hydrogen bonding
Answer: B
Final
Lipofection was first developed mainly for:
A) Plant cells
B) Bacterial cells
C) Animal cells
D) Viral packaging
Answer: C
DNA delivery without cell wall removal is possible in:
A) Plant cells
B) Protoplasts
C) Animal cells
D) Fungal cells
Answer: C
Liposome-mediated transfer avoids use of:
A) High voltage
B) Lipids
C) DNA
D) Culture medium
Answer: A
Lipofection is best suited for:
A) Large-scale stable transformation
B) Transient expression studies
C) Chromosome transfer
D) Bacterial cloning
Answer: B
Liposome-mediated DNA delivery is mainly used in:
A) Agriculture
B) Molecular and cell biology laboratories
C) Field trials
D) Industrial fermentation
Answer: B


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