(Fig. 1). Many of these NP-based gene delivery systems have been shown to be
superior to commercially available lipofection systems [53, 93]. Qiagen has
developed NanoFect Transfection Reagent, based on a chemically synthesized,
lipid-free reagent that has now been shown to be efficient in DNA delivery in a
broad range of cell types. However, it is MNPs that have grabbed maximum
acceptance. System Biosciences has developed a MNP suspension, LentiMag,
that effectively binds DNA (and viral) vectors and very quickly concentrates
them onto target cells by use of a magnetic plate. Using LentiMag, higher
transduction efficiencies have been achieved compared with transductions
performed with Polybrene (hexadimethrine bromide). Commercially available
or in-house produced MNPs have now been used for several cell types, including
both embryonic and adult stem cells [103–105].
NP-based gene delivery systems have gained fresh impetus with the identification of iPS cells. The iPS cells offer several advantages over other existing cell
types such as ES cells (see [106, 107] for a detailed review on iPS cells). iPS cells
are derived by cellular reprogramming of patient-derived somatic cells through
introduction of one or more pluripotency genes (Oct4, Sox2, Klf4 and cMyc OR
Oct4, Sox2, Nanog and Lin14) [108]. Introduction of multiple genes necessitates
the use of retroviral or lentiviral vectors, which raises safety issues. Furthermore,
despite using viral vectors, the efficiency of cellular reprogramming has been very
low (in the range of 0.001–0.01%). Accordingly, intense research has been focused
on either reducing the number of genes required for cellular reprogramming [109],
and/or using non-viral vectors [110], non-integrating episomal vectors [111],
mRNAs [112], proteins [113], novel culture methods [114–116], pluripotencyinducing proteins [117], etc. Furthermore, Lee et al. [104] demonstrated that
MNPs were efficient in simultaneous delivery of four genes (Oct4, Sox2, Klf4
and cMyc) into somatic cells to reprogram them into iPS cells at an improved
efficiency. Similarly, Ruan et al. [118] obtained efficient generation of iPS cells by
introduction of four genes (Oct4, Sox2, LIN28, and Nanog) into somatic cells using
polyamidoamine dendrimer-modified MNPs as the delivery system. Thus,
magnetofection provided safe, virus-free and exogenous DNA-free iPS cells.
Because stem cells can be grown long-term in vitro, their genetic modification
prior to transplantation provides a unique opportunity for correcting genetic defects
such as ADA severe combined immunodeficiency (ADA-SCID), Shwachman–
Bodian–Diamond syndrome (SBDS), Gaucher disease (GD), Duchenne muscular
dystrophy (DMD), Becker muscular dystrophy (BMD), Parkinson disease (PD),
Huntington disease (HD), Lesch–Nyhan syndrome (HPRT), Diabetes mellitus
(JDM) and Down syndrome [119]. Indeed, several genetic diseases were shown
to be curable using stem-cell-based genetic engineering in animal models [119].
Considering the several advantages of NP-based gene delivery systems over the
viral vector methods, it can be envisioned that NPs will find potential application in
stem-cell-based genetic correction of diseases.
66
P. Pushp et al.
superior to commercially available lipofection systems [53, 93]. Qiagen has
developed NanoFect Transfection Reagent, based on a chemically synthesized,
lipid-free reagent that has now been shown to be efficient in DNA delivery in a
broad range of cell types. However, it is MNPs that have grabbed maximum
acceptance. System Biosciences has developed a MNP suspension, LentiMag,
that effectively binds DNA (and viral) vectors and very quickly concentrates
them onto target cells by use of a magnetic plate. Using LentiMag, higher
transduction efficiencies have been achieved compared with transductions
performed with Polybrene (hexadimethrine bromide). Commercially available
or in-house produced MNPs have now been used for several cell types, including
both embryonic and adult stem cells [103–105].
NP-based gene delivery systems have gained fresh impetus with the identification of iPS cells. The iPS cells offer several advantages over other existing cell
types such as ES cells (see [106, 107] for a detailed review on iPS cells). iPS cells
are derived by cellular reprogramming of patient-derived somatic cells through
introduction of one or more pluripotency genes (Oct4, Sox2, Klf4 and cMyc OR
Oct4, Sox2, Nanog and Lin14) [108]. Introduction of multiple genes necessitates
the use of retroviral or lentiviral vectors, which raises safety issues. Furthermore,
despite using viral vectors, the efficiency of cellular reprogramming has been very
low (in the range of 0.001–0.01%). Accordingly, intense research has been focused
on either reducing the number of genes required for cellular reprogramming [109],
and/or using non-viral vectors [110], non-integrating episomal vectors [111],
mRNAs [112], proteins [113], novel culture methods [114–116], pluripotencyinducing proteins [117], etc. Furthermore, Lee et al. [104] demonstrated that
MNPs were efficient in simultaneous delivery of four genes (Oct4, Sox2, Klf4
and cMyc) into somatic cells to reprogram them into iPS cells at an improved
efficiency. Similarly, Ruan et al. [118] obtained efficient generation of iPS cells by
introduction of four genes (Oct4, Sox2, LIN28, and Nanog) into somatic cells using
polyamidoamine dendrimer-modified MNPs as the delivery system. Thus,
magnetofection provided safe, virus-free and exogenous DNA-free iPS cells.
Because stem cells can be grown long-term in vitro, their genetic modification
prior to transplantation provides a unique opportunity for correcting genetic defects
such as ADA severe combined immunodeficiency (ADA-SCID), Shwachman–
Bodian–Diamond syndrome (SBDS), Gaucher disease (GD), Duchenne muscular
dystrophy (DMD), Becker muscular dystrophy (BMD), Parkinson disease (PD),
Huntington disease (HD), Lesch–Nyhan syndrome (HPRT), Diabetes mellitus
(JDM) and Down syndrome [119]. Indeed, several genetic diseases were shown
to be curable using stem-cell-based genetic engineering in animal models [119].
Considering the several advantages of NP-based gene delivery systems over the
viral vector methods, it can be envisioned that NPs will find potential application in
stem-cell-based genetic correction of diseases.
66
P. Pushp et al.