By far one of the most challenging and limiting features of current insect genetic modification technologies it that they must be delivered to the appropriate cells by direct microinjection of embryos.
Various efforts over the years have been made to devise microinjection-free strategies including biolistics and electroporation. Some positive evidence has been reported but neither of these systems have been adopted by insect scientists.
The delivery problem is severe because not all insect embryos will be accessible for injection or amenable for injection for other reasons.
Joo et al. (2014) report on the use of a particular transfection agent to introduce nucleic acids into the embryos of Drosophila melanogaster. The eggs were dechorionated and essentially soaked in the transfection compound. The authors show images of Drosophila embryos at 6 hr and 12 hr of development with evidence of internalized transfection agent.
A typical problem with these microinjection-free delivery systems is the low delivery rates. Yes you might be able to get some nucleic acid into cells but will there be enough to affect gene expression or phenotype or transformation. Joo et al. (2014) do not address this issue directly. For example, they did not use this method to create transgenic flies. If they had then this would have been a particularly impressive result.
As it is, this is a report of using a delivery approach that might be considered by some insect biologists since some interesting observations were made. Evidence that delivery rates are practical is needed.
Microinjection free delivery of miRNA inhibitor into zygotes
Jin Young Joo, Jonghwan Lee, Hae Young Ko, Yong Seung Lee, Do-Hwan Lim, Eun-Young Kim, Sujeong Cho, Ki-Sung Hong, Jung Jae Ko, Suman Lee, Young Sik Lee, Youngsok Choi, Kyung-Ah Lee & Soonhag Kim
Scientific Reports 4, Article number:5417