period of time. Consequently, long-term expression of the desired protein can be
achieved with a smaller amount of required DNA, as compared with bolus delivery.
6.9 Cytotoxicity
Several NPs have been reported to have inherent cytotoxicity, which might be
augmented by excessive exposure and/or high concentrations of NP–DNA
complexes and by stress due to temperature shifts or long periods without medium,
etc. Full attention, therefore, must be given to minimize the cytoxicity. Interestingly, although most NPs are reported to cause oxidative stress by increasing the
levels of reactive oxygen species (ROS) and reducing the glutathione levels [34],
some NPs were demonstrated to have antioxidants action by blocking ROS production or scavenging the ROS [151, 152]. NPs can also cause mitochondrial damage.
Thus, a biodegradable, biocompatible NP with minimal cytotoxicity should be
chosen and properly exposed to cells to achieve the maximal number of transfected
cells. Several approaches such as use of biodegradable polymers and/or surface
coating of NPs with biodegradable polymers have, therefore, been used.
6.10 Stability, Storage and Shelf-Life of NPs
In order to maintain the structural and functional integrity of the entrapped DNA,
the NP preparation process needs to be optimized for molecular weight, crosslinking method, crosslinking time and N:P ratio. Tzeng et al. [153] developed
polymer-DNA NPs that remained stable in normal serum and could also be stored
for at least 3 months in ready-to-use form with no measurable decrease in efficacy,
thus expanding their potential in a practical setting.
7 Conclusions
NP-based gene delivery into stem cells provides an unprecedented opportunity for
isolation, in vitro culture, differentiation and post-transplantation tracking of stem
cells. It has also enabled the fabrication of controlled and high-throughput in vitro
culture methods for culturing stem cells that were otherwise difficult to grow and
differentiate in vitro. However, a variety of factors influence the application of NPs
in stem cells and must be suitably addressed. Despite tremendous improvements,
most NP-mediated gene delivery systems still suffer from low transfection efficiency and further research is needed on tailoring the size, content and surface
electronic properties through chemical and physical methods. Furthermore, before
NP technology can be used to deliver genes, several issues regarding the fate,
Nanoparticles for Gene Delivery into Stem Cells and Embryos
77
achieved with a smaller amount of required DNA, as compared with bolus delivery.
6.9 Cytotoxicity
Several NPs have been reported to have inherent cytotoxicity, which might be
augmented by excessive exposure and/or high concentrations of NP–DNA
complexes and by stress due to temperature shifts or long periods without medium,
etc. Full attention, therefore, must be given to minimize the cytoxicity. Interestingly, although most NPs are reported to cause oxidative stress by increasing the
levels of reactive oxygen species (ROS) and reducing the glutathione levels [34],
some NPs were demonstrated to have antioxidants action by blocking ROS production or scavenging the ROS [151, 152]. NPs can also cause mitochondrial damage.
Thus, a biodegradable, biocompatible NP with minimal cytotoxicity should be
chosen and properly exposed to cells to achieve the maximal number of transfected
cells. Several approaches such as use of biodegradable polymers and/or surface
coating of NPs with biodegradable polymers have, therefore, been used.
6.10 Stability, Storage and Shelf-Life of NPs
In order to maintain the structural and functional integrity of the entrapped DNA,
the NP preparation process needs to be optimized for molecular weight, crosslinking method, crosslinking time and N:P ratio. Tzeng et al. [153] developed
polymer-DNA NPs that remained stable in normal serum and could also be stored
for at least 3 months in ready-to-use form with no measurable decrease in efficacy,
thus expanding their potential in a practical setting.
7 Conclusions
NP-based gene delivery into stem cells provides an unprecedented opportunity for
isolation, in vitro culture, differentiation and post-transplantation tracking of stem
cells. It has also enabled the fabrication of controlled and high-throughput in vitro
culture methods for culturing stem cells that were otherwise difficult to grow and
differentiate in vitro. However, a variety of factors influence the application of NPs
in stem cells and must be suitably addressed. Despite tremendous improvements,
most NP-mediated gene delivery systems still suffer from low transfection efficiency and further research is needed on tailoring the size, content and surface
electronic properties through chemical and physical methods. Furthermore, before
NP technology can be used to deliver genes, several issues regarding the fate,
Nanoparticles for Gene Delivery into Stem Cells and Embryos
77