Toggle-Cell SELEX against multiple Gram-negative bacteria. (a) Schematic illustration of Toggle-Cell SELEX against three different Gram-negative bacteria. (b) Relative binding efficiency was tested using qPCR to confirm the enrichment of ssDNA after 4th round of Toggle SELEX. Data represented mean ± SD values of three independent experiments. (c) Predicted secondary structures of two isolated aptamers, GN6 and GN12, using M-fold algorithm at 25 °C, [Na+] = 100 mM, and [Mg2+] = 5 mM.