Biolistic techniques for transfection of mosquito embryos (Anopheles gambiae)

To compensate for the extremely low rates of transformation by DNA microinjection into mosquito embryos of Anopheles gambiae, biolistic techniques were evaluated for introduction of DNA into large numbers of mosquito embryos. Biolistic experiments were first performed with a commercially available instrument intended for this purpose, according to the recommended procedure. The amount of DNA delivered was measured by the expression of luciferase under the control of the Drosophila heat shock protein (hsp) 70 promoter. Despite attempts to optimize biolistic parameters, the level of luciferase activity was low and highly variable. Two other methods of biolistic delivery of DNA-coated particles in aqueous suspension were then evaluated. One method used the gas explosion of the commercially available instrument (mentioned above) to drive an aqueous suspension of DNA-coated particles at high pressure. This method reproducibly increased the level of expression about 100-fold without greatly reducing embryo viability. Another method, which was recently described for plant transfection, uses lower pressure to deliver the aqueous suspension of DNA-coated particles. The level of expression of luciferase and the survival of embryos were equivalent to that obtained with the instrument modified for aqueous delivery of particles. Thus, both aqueous methods offer the advantages of reproducibly delivering more DNA to the embryos. Moreover, these methods could be suitable for delivering DNA mixed with proteins, such as restriction endonucleases and integrases, that may be destroyed by ethanol precipitation used in the standard PDS-1000/He method.