Streptavidin-modified quantum dots combined with biotinylated folic acid in diagnostic imaging of ovarian cancer SKOV3 cells in vitro

Objective: To evaluate the value of streptavidin (SA)-modified quantum dots (QDs) combined with biotinylated folic acid (FA) in diagnostic imaging of ovarian cancer SKOV3 cells in vitro.Methods: SA was covalently conjugated to QDs by active ester method, and biotinylated FA was synthesized using the carrier polyamidoamine (PAMAM) (FA-PAMAM-biotin) by the same method. The fluorescent probe of SA-QDs combined with FA-PAMAM-biotin could preferentially target folate receptor (FR) of ovarian cancer SKOV3 cells which were identified as FR-positive cells. To verify the targeting specificity of this fluorescent probe, lung adenocarcinoma A549 cells with low expression of FR and the SKOV3 cells pretreated with FA were used as the controls. Simultaneously, the dual fluorescence amplification effect was verified by using the control fluorescent probe not containing the carrier PAMAM [FA-polyethylene glycol (PEG)-biotin combined with SA-QDs] or not mediated by biotin-avidin-system (FA-PAMAM-QDs).Results: The FR-positive SKOV3 cells specifically identified by using FA-PAMAM-biotin combined with SA-QDs had an average fluorescent intensity up to 114.92±2.87, which was significantly higher than those of the SKOV3 cells pretreated with FA followed by treatment with FA-PAMAM-biotin combined with SA-QDs (57.86±7.59) and the A549 cells treated with FA-PAMAM-biotin combined with SA-QDs (14.94±0.83) (both P < 0.000 1). The fluorescent intensity of SKOV3 cells labeled by FA-PAMAM-biotin combined with SA-QDs (120.89±3.80) was also higher than those of the SKOV3 cells labeled by FA-PEG-biotin combined with SA-QDs (77.50±2.43) and the cells labeled by FA-PAMAM-QDs (47.81±1.35) (both P < 0.000 1).Conclusion: FA-PAMAM-biotin combined with SA-QDs, which specifically targets FR in SKOV3 cells, may become a potential candidate with high specificity and sensitivity in early diagnosis of ovarian cancer. DOI:10.3781/j.issn.1000-7431.2015.11.425