Biomedical Engineering Reference
In-Depth Information
a new device was invented for combined injection delivery, followed by EP [37] . The
device injects DNA into the muscles through two needles and distributes the injection
volume along the needles, which also serve as electrodes. The transfection efficacy
after injecting DNA along the needle was found to be higher than transfection after
injecting DNA between the electrodes. This device was used successfully for efficient
immunization after electroporating therapeutic DNA, such as IgG2b anti-NIP [37] .
Another novel EP system, which includes a microchip and a logic circuit, combined
with the function of electrophoresis, was developed for site-specific in vitro gene
transfection in cell lines by enhancing the gene concentration at the target site. In
this microdevice, the outer electrode provided the electrophoresis function for DNA
attraction, and the inner electrode provided appropriate electric fields for cell EP on
the chip surface. The electrostatic force can be designed into specific regions, where
the DNA plasmids are attracted to provide the region-targeting function. The study
demonstrated significantly enhanced transgene expression with increasing electric
field. This microchip system is portable, cost-effective, and easy to operate; it has
high transfection efficiency and is easily manipulated for in situ transfection, even for
adherent cells without detachment [38] .
In vivo EP of the DNA for preclinical studies has been based on earlier successful
in vitro EP studies and successful clinical trials of in vivo delivery of macromole-
cules such as bleomycin to local tumors [39] . In vivo EP of plasmid DNA was stud-
ied in the skin, kidney, lung, liver, skeletal and cardiac muscle, joints, spinal cord,
brain, retina, cornea, vasculature, and in local melanoma [40-43] . In most of these
studies, EP demonstrated enhanced transgene expression by 100- to 1000-fold when
compared with naked plasmid DNA injection.
EP in the skeletal muscles has been studied extensively to treat malignancies,
renal disease, and anemia and to prevent drug toxicity to sensory nerves, by gene
therapy [44] , with significantly higher transfection efficiency when compared with
DNA alone or DNA-polymer complex. However, the local tissue damage observed
alongside EP and the subsequent repair processes may also interfere with the mea-
surement of physiological, biochemical, and molecular properties for a given experi-
ment, especially in the treatment of myopathies and muscle-wasting conditions [45] .
An optimization study of the various electric pulse parameters was proposed, to
reduce muscle toxicity while maintaining significant transgene expression, and less
damaging EP parameters for intramuscular gene delivery and therapeutic protein pro-
duction were further studied [46] . In addition, the level of protein detected in serum
and the total gene expression level detected in muscles were compared to determine
the correlation between them [46] . The expression of green fluorescence protein
plasmid (pGFP) and luciferase plasmid DNA in satellite cells of skeletal muscles
after EP has also been studied and confirmed by RT-PCR and immunohistochemistry
analysis showing sustained transgene expression to form regenerated myocytes and
muscle fibers [47] . Skeletal muscle gene therapy was also employed for angiogenic
gene therapy in the treatment of ischemic limb diseases. The angiogenesis assay was
performed to determine the efficiency of gene transfer. A naked plasmid DNA vector
encoding vascular endothelial growth factor cDNA (pJDK-VEGF165) combined with
an EP procedure was used for gene transfer into the tibialis anterior muscle of Balb/c
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