Background We have developed a gene transfection system using laser beams. The principle of this procedure is that a small hole is made in a cell membrane by pulse laser irradiation, and a gene contained in a medium is transferred into the cytoplasm through the hole. This hole disappears immediately with the application of laser irradiation of the appropriate power.
Methods A pulse-wave Nd:YAG laser with a wavelength of 355 nm was used to make a hole in a cell membrane. To trap a cell, a continuous-wave Nd:YAG laser with a wavelength of 1015 nm was used. Plasmids that encode the enhanced green fluorescent protein (EGFP) gene were contained in a medium and transferred to HuH-7 and NIH/3T3 cells with pulse laser irradiation. We evaluated transfection efficiency on the basis of the number of cells that expressed EGFP. Stimulatory protein 2 cells in suspension were fixed using a trapping laser and the neomycin-resistance gene was transfected by pulse laser irradiation. We examined cell proliferation in the selection medium.
Results Cells that expressed EGFP were recognized in the group that was irradiated by pulse laser. No cells expressed EGFP without irradiation. Transfection efficiency was ≈10% at a plasmid concentration of 10.0 μg/mL. At concentrations greater than 20 μg/mL, the transfection rate reached a plateau. We also successfully transfected neomycin-resistance genes to cells floating in suspension after fixation that was achieved with trapping laser irradiation.
Conclusions This method enables us to transfect targeted cells, ie, cells in suspension as well as attached cells, with a simple technique that does not involve harmful vectors. The present method is very useful for gene transfection in cellular biotechnology.