3. process of deliberately introducing nucleic acids into cells.
often used for non-viral methods in eukaryotic cells.
Cells that have incorporated the foreign DNA are called transfectants.
Terminology
Transfection: this term is reserved to describe nonviral gene
delivery method in eukariotic in animal cell.
Transformation: this term is reserved to describe nonviral gene delivery
method in bacteria and nonanimal eukaryotic cell
Transduction or infecion :is a reserved to define gene delivery method using viruses.
4.
Type of transfection
Transient transfection
when DNA is not integrated into host genome but genes are expressed for a limited
time( 24-96 hours(.
the effect on target gene expression is temporary (24-72 hours for RNA probes, 48-
96 hours for DNA probes).
used for studying: gene knockdown or silencing with inhibitory RNAs, or protein
production on a small scale
Stable or permanent transfection
transfected genetic material is integrated into the host cell genome.
used for studying: protein production on a large scale, longer-term pharmacology
studies, gene therapy or research on the mechanisms of long-term genetic regulation.
9. a complex with overall positive charge, allowing it to interact
with negatively charge cell membrane and promote uptake by
endocytosis
as lipophilic complex that fuses with the cell membrane and
deposits the transgene directly into the cytoplasm
10.
Electrostatic interactions between the positive charges of cationic lipid
head groups and the negatively charged phosphates of the DNA backbone
are the main forces that allow DNA to spontaneously associate with
cationic lipids.
the cationic lipid is mixed with a neutral lipid such as
L-dioleoylphosphatidylethanolamine(DOPE)which can enhance the gene
transfer ability of certain synthetic cationic lipids
Cationic Lipids
11.
The successful use of liposome compounds is dependent upon
several factors including lipid formulation, particle size and the
method of liposome preparation.
An overall net positive charge of the complex allows closer
association of the complex with the negatively charged cell
membrane.
Entry of the liposome complex into the cell:
endocytosis or fusion with the plasma membrane via the lipid
moieties of the liposome
When liposomes encounter nucleic acids they re-form into nucleic acid lipid
complexes called lipoplexes which can be actively taken up by
eukaryotic cells by means of endocytosis
13.
Advantages of lipids:
Deliver nucleic acids with high efficiency
Easy to use, minimal steps required.
Works in a wide variety of eukaryotic cells
can be used for in vivo transfer of DNA and RNA to animals and
humans
successful delivery of DNA of all sizes from oligonucleotides to
yeast artificial chromosomes
Disadvantages of lipids:
Not applicable to all cell types.
low efficiencies in most primary cells
Pros and cons
cationic lipid
14.
Principle
DNA is mixed with calcium chloride
Addition to buffered saline/phosphate solution and incubating at room
temperature
Formation of DNA-calcium phosphate coprecipitates which adhere to surface of
cells
Uptake presumably by endocytosis or phagocytosis
Calcium phosphate
15. Advantages:
easily available
Inexpensive
Can be applied to wide range of cell types
Can be used for transient and stable transfection
Calcium phosphate appears to provide protection against intracellular and
serum nucleases.
Disadvantages:
low efficiency
is not suited for in vivo gene transfer to whole animals
Size and quality of the precipitate are crucial to the success of transfection
toxicity, especially to primary cells
its sensitivity to slight changes in pH, temperature and buffer salt
concentrations.
Pros and Cons
Calcium phosphate
16.
Cationic polymer differ from cationic lipid in that they do
not contain a hydrophobic moiety and are completely
soluble in water.
Cationic polymer
cationic polymer include: polybrene, polyethyleneimine(PEI) and
dendrimers.
ability of cationic polymer more efficiently condense DNA.
cationic polymer cannot release their DNA load into the cytoplasm
Cationic polymer
synthesized (lengths , geomrtry)
19. Dendrimers are highly branched, globular macromolecules that
are capable of interacting with DNA to form small complexes.
Positively charged amino groups (termini) on the surface of the
dendrimer molecule interact with the negatively charged
phosphate groups of the DNA molecule to form a DNA-
dendrimer complex.
Complexes bound to the cell surface are taken into the cell by
nonspecific endocytosis.
Dendrimers
20. Amino groups on the dendrimers that are unprotonated at
neutral pH can become protonated in the acidic environment of
the endosome.
This leads to buffering of the endosome, which inhibits pH-
dependent endosomal nucleases.
Dendrimers are stable in biological liquids and are not sensitive
to temperature.
highly efficient tools for tissue culture transfections.
However, dendrimers are also The downside of dendrimers non-
biodegradable and may cause significant cytotoxicity.
21. DEAE-dextran was the first non-viral transfection method
verified by Vaheri and Pagano in 1965.
DEAE-Dextran is a cationic polymer that tightly associates with
the negatively charges nucleic acids.
principle
DNA is mixed with DEAE-dextran
DNA/polymer complex comes into contact with negatively
charged membrane due to excess of positive charge contributed
by polymer entry in to the cytoplasm via endocytosis or osmotic
shock induced by DMSO or glycerol.
Uptake presumably by endocytosis
DEAE-Dextran
chemical method
22.
Advantages:
Inexpensive
Easy to perform and quick
Can be applied to a wide range of cell types.
Low cost
Disadvantages:
High concentration of DEAE-Dextran can be toxic to the cell
Transfection efficiency will vary with cell type
Can be used only for transient transfection
Typically produces less than 10% delivery in primery cells
Pros and Cons
DEAE-Dextran
24.
Magnet-mediated transfection
(Magnetofection)
Magnet-mediated method
uses magnetic force to deliver
DNA into the target cells.
Nucleic acids are first
associated with magnetic
nanoparticles.
DNA are bound to MNPs,
which then move from the
media to the cell surface by
applying a magnetic force.
25.
Plasmid DNA or siRNA is attached to magnet nanoparticles and incubated
with cells in culture.
(i) An oscillating magnet array below the surface of the cell culture plate pulls
the particle into contact with the cell membrane
(ii) and drags the particles from side-to-side across the cells
(iii)mechanically stimulating endocytosis
(iv) Once the particle/DNA complex is endocytosed, proton sponge effects
rupture the endosome
(v) releasing the DNA
(vi) which then transcribes the target protein.
26.
Advantages
Rapid
Increased transfection efficiency by direct transport, especially
for low amount of nucleic acid
High transfection rates for adherent mammalian cell lines and
primary cell cultures
Can also be performed in the presence of serum
Disadvantages
Require adherent cells; suspension cells need to be immobilized
or centrifuged.
Pros and cons
Magnet-mediated transfection
27.
in this method, naked DNA is deposited directly into the cell by
exploiting a physical force
Instrument(Physical )-based
method
28. Electroporation was first reported for gene transfer studies in
mouse cells .
This technique is often used for cell types such as plant
protoplasts.
Electroporation uses an electrical pulse to create temporary
pores in cell membranes through which substances like nucleic
acids can pass into cells.
More modern instrumentation successful transfer of DNA and
RNA to primary and stem cells.
Electroporation
29. ectroporation
1)Electroporation exposes a cell to a
high-intensity electric field that
temporarily destabilizes the membrane
2)During this time the membrane is
highly permeable to exogenous molecules
present in the surrounding media
3) DNA then moves into the cell through
these holes
4)When the field is turned off, the pores
in the membrane reseal, enclosing the
DNA inside
30.
Advantages
fast
doesn't seem to alter the biological structure or function of the
target cells
Easy to perform
High efficiency
Can be applied to transient and stable transfection a wide range of
cell types
Disadvantages
Cell mortality
low efficiency in primary cells and high mortality rates, caused by
the high voltage pulses or only partially successful membrane
repair.
Pros and cons
electroporation
31.
Cell squeezing is a method invented in 2012 by
Armon Sharei, Robert Langer and Klavs Jensen.
Cell squeezing
32.
It eliminates the possibility of toxicity or off-target effects as it does not
rely on exogenous materials or electrical fields.
describe a microfluidic approach to delivery in which cells are
mechanically deformed as they pass through a constriction 30–80%
smaller than the cell diameter.
transient holes that enable the diffusion of material from the
surrounding buffer into the cytosol.
The method has demonstrated the ability to deliver a range of material,
such as carbon nanotubes, proteins, and siRNA, to 11 cell types,
including embryonic stem cells and immune cells.
33.
34.
involves projecting microscopic heavy-metal particles
(often gold or tungsten) coated with nucleic acids into
recipient cells at high velocity using a biolistic device
(i.e., “gene gun”).
Biolistic particle delivery can be used to transiently
transfect dividing and non-dividing cells in culture as
well as cells in vivo, and it is often used for genetic
vaccination and agriculture applications.
particle bombardment))Biolistic Particle
Delivery
Delivery of nucleic acids into cells via high-velocity nucleic acid-
coated microparticles
37.
Pros and cons
Biolistic particle delivery
Advantages
Simple, rapid technique
Cell type independent
Uses small amounts of DNA
Can deliver large DNA fragments
Requires little manipulation of
cells
High reproducibility
Dis advantages
Generally lower efficiency
compared to electroporation or
viral or lipid mediated transfection
Requires the preparation of
microparticles
Instrument cost
causes physical damage to the
samples, and necessitates high cell
numbers due to high mortality.
38. delivers nucleic acids into the cytoplasm or the nucleus one cell
at a time by means of a fine needle;
therefore, this method is limited to ex vivo applications such as
the transfer of genes into oocytes to engineer transgenic
animals or the delivery of artificial chromosomes.
Microinjection
39. Advantage:
Frequency of stable integration of DNA is far better as compare to other
methods.
Method is effective in transforming primary cells
The DNA injected in this process is subjected to less extensive modifications.
used to transfer DNA into embryonic stem cells that are used to produce
transgenic organisms
Disadvantage:
Costly.
Skilled personal required.
Method is useful for protoplasts and not for the walled cells.
Pros and cons
40. This procedure uses laser light to transiently permeabilize a
large number of cells in a very short time.
Various substances, including ions, small molecules, (siRNAs),
plasmids, proteins, can be efficiently optoinjected into
numerous cell types.
When the laser induces a pore in the membrane, the osmotic
difference between the medium and the cytosol facilitates the
entry of nucleic acids or other desired substances in the
medium into the cell.
Laserfection/Optoinjection
41.
Pros and cons
Advantage
high transfection efficiency and the ability to make
pores at any location on the cell.
Work with many cell type
Fewer cell maniupullation needed
Disadvantage
requires an expensive laser-microscope system and
the cells to be attached to a substrate.
i.e., introduction of DNA (or RNA) from a prokaryote-infecting virus or bacteriophage into cells, resulting in an infection
Transfection is a method that neutralizes or obviates the issue of introducing negatively charged molecules (e.g., phosphate backbones of DNA and RNA) into cells with a negatively charged membrane
Thus. Transient transfection with mRNA can deliver even more rapid results than with conventional plasmid DNA, because mRNA can be expressed outside of the nucleus; in some systems, it is possible for transfected mRNA to be expressed only minutes after transfection.
Although the production of large amounts of recombinant proteins with proper folding and post-translational modifications (which is not available when expressing recombinant proteins in bacterial cells) traditionally has been limited to stably transfected cells, recent advances in transient transfection and cell culture methods are changing this. Ubiquitous cell culture lines such as HEK293 and CHO cells, modified to grow in suspension rather than in plated culture conditions, can now be transiently transfected to produce large amounts of recombinant proteins, as well.
Frequently used selectable markers are the genes encoding aminoglycoside phosphotransferase (APH; neoR gene) or hygromycin B phosphotransferase (HPH). Other selectable markers are the genes encoding adenosine deaminase (ADA), dihydrofolate reductase (DHFR), hymidine kinase (TK), or xanthine-guanine phosphoribosyl transferase (XGPRT; gpt gene).
Every cell line has optimal culture conditions. Refer to the American Type Culture Collection [ATCC] web site.
For example, one reagent may work
well with HEK-293 cells, but a second reagent is a better
choice when using HepG2 cells. Promega offers several
online resources to help identify a transfection reagent and
protocol for your cell line, including the Transfection
Assistant (www.promega.com/transfectionasst/) and
FuGENE
®
HD Protocol Database (www.promega.com
/techserv/tools/FugeneHD/). A drop-down menu allows
you to search the databases by cell line, transfection type
and transfection reagent.
TISSUE CULTURE
Most mammalian cells are adherent
Cultured in plates or flasks
Grow in monolayer on specially treated surfaces
Medium supplemented with 5-10% Fetal Calf Serum
Laminar flow cabinet
CO2 incubator
; DNA will be taken from the surroundings when the DNA is presented as a synthetic complex either as;
Such lipids form liposomes that associate with DNA and merge with the cell membrane to enable the intracellular transfer of DNA3.
Cationic transfection lipids consist of a positively charged head group, such as an amine, a flexible linker group such as an ester or ether, and two or more hydrophobic tail groups.
The ability of a lipid to destroy endosomes is one of the main characteristics of a transfection reagent.
. For cultured cells, an
overall net positive charge of the liposome/nucleic acid
complex generally results in higher transfer efficiencies,
presumably because this allows closer association of the
complex with the negatively charged cell membrane. Entry
of the liposome complex into the cell may occur by
endocytosis or fusion with the plasma membrane via the
lipid moieties of the liposome
Following cellular internalization, the complexes appear
in the endosomes and later in the nucleus. It is unclear how
the nucleic acids are released from the endosomes and
lysosomes and traverse the nuclear membrane \
DOPE is
considered a “fusogenic” lipid (Farhood et al. 1995), and
its role may be to release these complexes from endosomes
as well as to facilitate fusion of the outer cell membrane
with liposome/nucleic acid complexes. While DNA will
need to enter the nucleus, the cytoplasm is the site of action
for RNA, protein or antisense oligonucleotides delivered
via liposomes.
The endosomal structure is destroyed by increasing the osmotic pressure created by the lipids' buffering action within the endosomes and by the fusion of the lipid with the endosomal membrane.
The successful use of liposome compounds to deliver exogenous nucleic acids to specific biological system is dependent upon several factors including lipid formulation, charge ratio, particle size and the method of liposome preparation.
Neutral “helper” lipids, such as DOPE, allow entrapped DNA to escape the endosomes by fusion of the liposome with the membrane.
The cells will be treated with lysozyme to remove cell wall, resulting in protoplasts that will be centrifuged gently onto a monolayer of mammalian cells to promote fusion among them using polyethylene glycol.
Using lyposomes is more commonly used for this type of transfection. This method is commonly known as lipofection. This method is far more efficient than chemical transfection method. With this method up to 90% of cells in culture dish can be transected.
The process of transfection involves the admixture of isolated DNA (10-100ug) with solution of calcium chloride and potassium phosphate under condition which allow the precipitate of CaPO4 to be formed.
In general, the following two protocols are used by the majority as a starting point.
The first one relies on the calcium phosphate–DNA complex formed before the addition to the cells,
and the second one relies on the slow formation of calcium phosphate–DNA complex while present in the cell culture.
4Additional modifications to the calcium phosphate method that can achieve higher efficiencies include glycerol shock and/or chloroquine treatmen
this method gives only 1-2% transfection efficiency
enclose محصور کردن
When used for the delivery of transcription factors, the microfluidic devices produced a 10-fold improvement in colony formation relative to electroporation and cell-penetrating peptides.
Indeed, its ability to deliver structurally diverse materials and its applicability to difficult-to-transfect primary cells indicate that this method could potentially enable many research and clinical applications
واحد فشار هوا بوده و مخفف پوند بر اینچ مربع میباشد و هر 14.5psi آن 1 بار میباشد . (برای تبدیل کلیه واحدهای فشار میتوانید از جدول تبدیل فشارها در بخش مقالات استفاده کنید)
For in vitro, ex vivo (and in vivo for some plants and microbes)
Applications for animal cell and organ culture, plant cell culture and explants, pollen, insects, algae, fungi and bacteria
Pressure range 450–2200 psi gives flexibility and penetration — ideal for plant applications
Large target area — more cells can be transformed
First - you need the gene of interest in the proper form. A linear transgene construct is made, which contains:
the structural gene of interest, with introns
a strong mouse gene promoter and enhancer to allow the gene to be expressed