Abstract:  The cultured Plasmodium falciparum parasites were synchronized twice by 5% sorbitol treatment twice（8-hour window）, and then incubated at 37 ℃ for 16 h. Parasites were transfected with fluorescein-labelled oligonucleotides （group A） or fluorescein-labelled oligonucleotides+Entranster-R siRNA transfection reagent （group B）. After 5 h a part of parasites was evaluated by fluorescence microscopy and flow cytometry. The rest of parasites were washed with RPMI 1640 medium, and then incubated with 500 μl new medium containing 2% fresh erythrocytes for another 12 h, and detected by flow cytometry. The fluorescein-labelled oligonucleotides were localized in erythrocytes in group B, but nearly no fluorescence was observed for group A. Flow cytometry analysis indicated that the transfection efficiency of group B [（47.40±3.39）%] was higher than that of group A [（0.60±0.27）%]. In the second cell cycle, the transfection efficiency in group B was （26.85±2.90）%, while that of group A was nearly zero. The results indicated that Entranster-R siRNA transfection reagent may increase the oligonucleotides transfection efficiciency.

Key words: Plasmodium falciparum, Transfection, Oligonucleotides