Effective delivery of siRNA to transgenic rice cells for enhanced transfection using PEI-based polyplexes

Various polymers were used as transfection factors for small interfering RNA (siRNA) to effectively suppress human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig) gene in transgenic rice cells. Five kinds of polymers (PEI, PVA, PVP, and 8 and 20 kDa PEGs) were applied for delivery of siRNA with lipofectamine used as a control. In the cytotoxicity test, all polymers except 8 kDa PEG showed nontoxicity in relation to cell viability. For transfection efficiency, polyplexes composed of siRNA and PEG (20 kDa) did not significantly reduce production of intracellular hCTLA4Ig. On the other hand, siRNA + PEI polyplexes showed the most effective suppression efficiency with regards to production of intracellular hCTLA4Ig among all other polyplexes (PVA, PVP, and PEG (8 kDa)). Effects of molecular weight ratios of siRNA:PEI were investigated to obtain optimal transfection efficiency and avoid excessive damage to cells. PEI-based polyplexes with a 1:10 ratio of siRNA:PEI reduced production of intracellular hCTLA4Ig up to 70.6% without alteration of cell viability. These results demonstrate that PEI-based polyplexes are easy to prepare, inexpensive, non-toxic, and effective to deliver siRNA to transgenic plant cell cultures.