introduction have not been successful. In particular, transgenic chicken has proven
to be difficult to produce by conventional transgenesis owing to their unique
reproductive system and hard shell around the egg. Consequently, retroviral or
lentiviral injection into the blastoderm layer of Stage X embryos are generally used.
We and others have shown that Polybrene (hexadimethrine bromide) can increase
the infection rate of viral vectors to increase the transgenesis rate [133–136]. Thus,
other polycations might be of use in improving the success of transgenesis and need
to be explored.
In a recent study, Tseng et al. [87] used gelatin as a nanocarrier of plasmid DNA
for transfecting chicken embryos. The plasmid DNA was encapsulated in gelatin to
produce NPs (~300 nm) by a water–ethanol solvent displacement method. The NPs
were nontoxic to cells, and its direct injection in the area opaca of the egg resulted
in the highest hatching rate without affecting embryo development. Gene expression in embryo sections was observed 4 days after injection.
6 Factors Affecting Gene Delivery Efficiency of NPs
6.1 Cell Type
The gene delivery efficacy of several NPs are known to be cell-type-dependent and
they preferentially transfect certain cell types over the others [77]. In certain cases,
NPs are intentionally modified to allow the transfection of specific cell types by
attaching a ligand that specifically identifies a particular cell surface property of
the target cell. Some cell types are also relatively resistant to gene transfection
(e.g. germ cells).
6.2 Cell Cycle Stage
The nuclear envelope is one of the major cellular barriers in the intranuclear
delivery of DNA [137]. In a non-dividing cell, the nuclear enclosure of NPs is
dependent on size (with 100 and 200 nm particles being better included than 500 nm
particles) and charge (with positively charged particles being better included than
negatively charged particles) on the NPs [138]. However, nuclear membrane
breakdown during mitosis and meiosis facilitates the access of NPs to the chromatin
and it is highly plausible that at least few of them are included by chance in the
nuclei of the daughter cells. Thus, cell division has a positive influence on the
efficiency of gene delivery. Conversely, transfection efficiency of NPs is higher in
dividing (mitotic) cells than in non-dividing (non-mitotic) cells.
Nanoparticles for Gene Delivery into Stem Cells and Embryos
73
to be difficult to produce by conventional transgenesis owing to their unique
reproductive system and hard shell around the egg. Consequently, retroviral or
lentiviral injection into the blastoderm layer of Stage X embryos are generally used.
We and others have shown that Polybrene (hexadimethrine bromide) can increase
the infection rate of viral vectors to increase the transgenesis rate [133–136]. Thus,
other polycations might be of use in improving the success of transgenesis and need
to be explored.
In a recent study, Tseng et al. [87] used gelatin as a nanocarrier of plasmid DNA
for transfecting chicken embryos. The plasmid DNA was encapsulated in gelatin to
produce NPs (~300 nm) by a water–ethanol solvent displacement method. The NPs
were nontoxic to cells, and its direct injection in the area opaca of the egg resulted
in the highest hatching rate without affecting embryo development. Gene expression in embryo sections was observed 4 days after injection.
6 Factors Affecting Gene Delivery Efficiency of NPs
6.1 Cell Type
The gene delivery efficacy of several NPs are known to be cell-type-dependent and
they preferentially transfect certain cell types over the others [77]. In certain cases,
NPs are intentionally modified to allow the transfection of specific cell types by
attaching a ligand that specifically identifies a particular cell surface property of
the target cell. Some cell types are also relatively resistant to gene transfection
(e.g. germ cells).
6.2 Cell Cycle Stage
The nuclear envelope is one of the major cellular barriers in the intranuclear
delivery of DNA [137]. In a non-dividing cell, the nuclear enclosure of NPs is
dependent on size (with 100 and 200 nm particles being better included than 500 nm
particles) and charge (with positively charged particles being better included than
negatively charged particles) on the NPs [138]. However, nuclear membrane
breakdown during mitosis and meiosis facilitates the access of NPs to the chromatin
and it is highly plausible that at least few of them are included by chance in the
nuclei of the daughter cells. Thus, cell division has a positive influence on the
efficiency of gene delivery. Conversely, transfection efficiency of NPs is higher in
dividing (mitotic) cells than in non-dividing (non-mitotic) cells.
Nanoparticles for Gene Delivery into Stem Cells and Embryos
73