PEI/DNA formation affects transient gene expression in suspension Chinese hamster ovary cells via a one-step transfection process.

Polyethylenimine (PEI) has been used widely in transient gene expression studies of mammalian cells. We performed transient gene expression in suspension Chinese hamster ovary cells using a one-step transfection procedure in which DNA and PEI were simultaneously added to a cell culture in suspension without prior PEI/DNA complex incubation. To further understand the effect of PEI/DNA formation on the transfection and expression of exogenous gene in shaking state, we investigated the diameter and overcharge of the PEI/DNA complex. The results showed that the diameter of the complex was smaller with more positive charge when the PEI/DNA ratio was higher. Moreover, DNA more easily penetrated cells and nuclei at higher PEI concentrations. The highest transcription level, transfection efficiency, and GFP expression were obtained when the PEI/DNA ratio was 5:1.