function in vitro. NPs, loaded with or without marker genes, can also be used for
isolation, purification and enrichment of adult stem cells such as MSCs, and germline stem cells. One such approach is to load the NPs with a cell-type-specific cell
surface marker, which can then be used to label the stem cells in a mixed
population of cells and to purify,isolate and enrich by fluorescence-activated cell
sorting (FACS) or magnetic-activated cell sorting (MACS). MNPs loaded with
anti-CD34 antibody have been used to label CD34-positive stem cells, which were
then enriched by magnetic sorting [94]. A similar approach has been used
extensively for isolation and enrichment of male germ-line stem cells, which
have otherwise been very difficult to isolate and purify by conventional means
[95].
NPs, loaded with or without genes, can also be used to create a nanostructured
3D scaffold or cell culture substrate to mimic the in vivo stem cell niche or nanoenvironment for stem cell self-renewal, proliferation and/or targeted differentiation.
Several nanostructured NPs based on chitosan, PLGA, gelatin, etc. have been
shown to be safe and of potential application in stem-cell-based tissue engineering
applications. Carbon nanotubes have recently been gaining potential interest as a
promising nanomaterial because they have dimensions similar to the 3D structure
of proteins found in extracellular matrices [96, 97]. Mooney et al. [97] found that
small carbon nanotubes promoted the adhesion of human MSCs without noticeable
differentiation, whereas large carbon nanotubes led to a dramatic stem cell elongation, inducing cytoskeletal stress and selective differentiation into osteoblast-like
cells. Unfortunately, carbon nanotubes have also been reported to be genotoxic and,
therefore, further improvement is required prior to their safe and effective use [98].
A biocompatible, self-assembling peptide nanofiber scaffold (SAPNS) that mimics
the structure of extracellular matrix has also been developed and has been
demonstrated to mimic a 3D nano-environment for the migration and differentiation of neural stem cells and the growth of blood vessels and axons in the scaffolds
[99–101]. Another recent study has established a culture system to expand and
maintain mouse ES cells using MNPs, creating the magnetic field-MNP culture
system without affecting the pluripotency [102].
4.1 NP-Based Gene Delivery for Stem Cell Isolation and Culture
NP-based gene delivery is a relatively recent concept in stem cell engineering.
Among non-viral methods, lipofection and electroporation have been optimized
for several stem cell types and were shown to give an acceptable level of
transfection. A need for improvement was felt for stem cell types that are
resistant to gene introduction (e.g. germ-line stem cells) or grow as clump
(e.g. ES cells) or when multiple genes need to be introduced simultaneously
(e.g. iPS cells). Subsequently, with advancements in the nanotechnology, several
NP-based gene delivery options have been explored, tested and commercialized
Nanoparticles for Gene Delivery into Stem Cells and Embryos
65
isolation, purification and enrichment of adult stem cells such as MSCs, and germline stem cells. One such approach is to load the NPs with a cell-type-specific cell
surface marker, which can then be used to label the stem cells in a mixed
population of cells and to purify,isolate and enrich by fluorescence-activated cell
sorting (FACS) or magnetic-activated cell sorting (MACS). MNPs loaded with
anti-CD34 antibody have been used to label CD34-positive stem cells, which were
then enriched by magnetic sorting [94]. A similar approach has been used
extensively for isolation and enrichment of male germ-line stem cells, which
have otherwise been very difficult to isolate and purify by conventional means
[95].
NPs, loaded with or without genes, can also be used to create a nanostructured
3D scaffold or cell culture substrate to mimic the in vivo stem cell niche or nanoenvironment for stem cell self-renewal, proliferation and/or targeted differentiation.
Several nanostructured NPs based on chitosan, PLGA, gelatin, etc. have been
shown to be safe and of potential application in stem-cell-based tissue engineering
applications. Carbon nanotubes have recently been gaining potential interest as a
promising nanomaterial because they have dimensions similar to the 3D structure
of proteins found in extracellular matrices [96, 97]. Mooney et al. [97] found that
small carbon nanotubes promoted the adhesion of human MSCs without noticeable
differentiation, whereas large carbon nanotubes led to a dramatic stem cell elongation, inducing cytoskeletal stress and selective differentiation into osteoblast-like
cells. Unfortunately, carbon nanotubes have also been reported to be genotoxic and,
therefore, further improvement is required prior to their safe and effective use [98].
A biocompatible, self-assembling peptide nanofiber scaffold (SAPNS) that mimics
the structure of extracellular matrix has also been developed and has been
demonstrated to mimic a 3D nano-environment for the migration and differentiation of neural stem cells and the growth of blood vessels and axons in the scaffolds
[99–101]. Another recent study has established a culture system to expand and
maintain mouse ES cells using MNPs, creating the magnetic field-MNP culture
system without affecting the pluripotency [102].
4.1 NP-Based Gene Delivery for Stem Cell Isolation and Culture
NP-based gene delivery is a relatively recent concept in stem cell engineering.
Among non-viral methods, lipofection and electroporation have been optimized
for several stem cell types and were shown to give an acceptable level of
transfection. A need for improvement was felt for stem cell types that are
resistant to gene introduction (e.g. germ-line stem cells) or grow as clump
(e.g. ES cells) or when multiple genes need to be introduced simultaneously
(e.g. iPS cells). Subsequently, with advancements in the nanotechnology, several
NP-based gene delivery options have been explored, tested and commercialized
Nanoparticles for Gene Delivery into Stem Cells and Embryos
65