Nanoparticles for Stem-Cell Engineering - Stem-Cell Nanoengineering - page 144

transfected genes but the level was sufficient for osteogenic differentiation of MSCs
[206, 207, 231]. Their work indicated that transient gene transfection with nonviral vectors
may be sufficient in regulating differentiation and lineage commitment of stem cells in regen-
erative medicine. In a related study, Santos et al . were able to improve transfection efficiency
to MSCs by functionalizing the dendrimers with high-affinity MSC peptides [206].
To reduce cytotoxicity of PEI-based vectors, Song et al . used core-shell vectors with a core
of PEI-DNA complex and a shell made of cationic lisinylated or histidylated cholesterol for
transfection of MSCs with hVEGF 165 DNA [231] (Figure 9.4C). The core-shell lipopoly-
plexes, due to accelerated DNA nuclear localization, had higher transfection efficiency than
the optimized PEI/DNA polyplexes with no cytotoxicity. Cyclodextrin is a cup-shaped mol-
ecule with high inclusion capacity, which is able to disrupt the cell membrane by complexation
with phospholipids and cholesterol [232]. Tong et al . reported that the quantum dot labeled
PEI-β-cyclodextrin nanopolymers had higher capacity for delivery of pDNA to the lyso-
zyme and nucleus of MSCs than PEI alone [209], which was consistent with the higher ALP
activity of MSCs transfected with BMP-2 or BMP-7 DNA [233]. Zhu et al ., reported high
transfection efficiency and low toxicity for a hyperbranched poly(amidoamine) (hPAMAM)
polyplex as a delivery system for hypoxia-regulated VEGF 165 pDNA, which promoted endo-
thelial cell proliferation in vitro , increased neovascularization, and preserved cardiac function
to a greater extent than the nontransfected MSC transplantation [212].
An alternative strategy to increase transfection efficiency is to immobilize the DNA plasmid
on magnetic NPs and use an external magnetic field to concentrate them around the targeted
cells (Figure 9.4D). Song et al . investigated the combined use of magnetofection and cationic
cell-penetrating peptides (CPP) to enhance transfection efficiency [234] (Figure 9.4E). In
that approach, magnetic NPs and pDNA were mixed in aqueous solution at ambient condi-
tions to form a binary complex. Next, the cationic histidine-rich cysteine-functionalized
bis(cysteinyl) Tat peptide was added to the aqueous solution and allowed to form a ternary
complex with the Tat peptide covering the surface of NPs. Then, oxygen gas was bubbled
through the aqueous solution to form disulfide bonds to reduce desorption of the peptide
from the surface of the NPs. Song et al . reported that the ternary complexes increased trans-
gene expression of pDNA by fourfold in human neural stem cells over the binary complexes
without the Tat peptide, and transfected up to 60% of the cells [235]. The lumbar intrathecal
injection of the ternary complex in the rat spinal cord fluid responded to a moving magnetic
field by mediating gene expression in a region outside of the injected site [236]. In a related
approach, an external magnetic field was used to enhance endocytosis of binary complexes
of magnetic NPs and pDNA [68] (Figure 9.4D). In that technology, an externally applied
oscillating magnetic field was applied to the seeded cells in a suspension of DNA-magnetic
NP complex [68]. Adams et al . reported that the magnetotransfection technique has no effect
on cell viability, cell marker expression, and differentiation of neurospheres [68]. The authors
postulated that the oscillating magnetic field formed ruffles on the cell membrane to enhance
endocytosis and intracellular uptake of the NPs (Figure 9.4D) [68].
Magnetic NPs can also be used for dark-field imaging and monitoring the distribution of
the cargo genes after in vivo delivery. In that approach, Shah et al . developed NPs with a
magnetic core and a gold shell (MCNPs) coated with a cationic polyamine dendrimer for
complexation with the negatively charged pDNA or siRNA [123]. The gold shell of the NPs
provided a large surface area for functionalization and complexation with anionic nucleic
acids. The cationic dendrimers on the surface of the NPs acted as a proton sponge in the
endosomes, thus aiding endosomal escape of the complex and protecting the cargo from the
acidic microenvironment [123]. Further, the MCNPs, due to their magnetic susceptibility,
can be concentrated to the targeted site using an external magnetic field. When NSCs were
incubated with MCNPs carrying CAVEOLIN-1 (siCAV) and SOX9 (siSOX9), neural switch