FIG. 1.

Cell binding and PSMA specificity analysis of the anti-PSMA aptamer A9.min. (A) LNCaP, (B) PC3-PSMA, and (C) PC3 cells were incubated with an anti-PSMA antibody, and isotype controls or increasing concentrations of AF488-labeled A9.min or a nonfunctional aptamer control, AF488-labeled C36. LNCaP and PC3-PSMA cells both express PSMA. PC3 cells are a PSMA-negative cell line as confirmed by antibody staining. Cell staining experiments were performed in growth media containing 10% FBS supplemented with 1 mg/mL ssDNA as a non-specific blocking agent. Incubations were performed for 1 h after which the cells were washed to remove unbound aptamers, trypsinized from the plate and analyzed by flow cytometry. The identity and concentration of each plot in the histograms are as indicated. For each data set, we also generated a plot of the relative median fluorescence intensity versus concentration, which was used to determine the apparent binding constant (_appKd) on each cell type. The _appKd values are reported in Table 1. FBS, fetal bovine serum; PSMA, prostate-specific membrane antigen. Color images available online at www.liebertpub.com/nat