Gene Delivery Using Physical Methods - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 100

Figure 3.3 Microinjection of DNA into the nucleus of a single cell.
half-life of 50-90 min. Hence, microinjecting naked DNA directly into the nucleus
has shown to avoid cytoplasmic degradation and has shown much higher levels of
gene expression than injection into the cytoplasm [205,206] .
Microinjection has shown to deliver adenoviral vectors effectively in a controlled
manner to tumors (xenotransplants) in nude mice and also provides reproducible
transfection results [207] . Microinjection has been very useful for producing recom-
binant cell lines; for example, green fluorescent protein (GFP) as a reporter gene
effectively transferred to different cell lines like CHO DG44 and BHK-21 with satis-
factory outcomes [208] .
Even with the direct nuclear approach, microinjection is a laborious procedure.
Only one cell can be injected at a time, and many injections are required before get-
ting a successful transgene expression. Microinjection imposes a limitation on cell
injections per experiment; so, with the current technology, microinjection has very
limited applications for in vivo gene therapy.
3.7 Sonoporation-Ultrasound-Mediated Gene Delivery
In vivo EP and hydrodynamic and gene gun-mediated DNA delivery all have been
shown to be very efficient techniques of DNA transfection. However, these techniques
have been less preferred because of their invasiveness. Hence, other noninvasive