To further verify that the PC5-2 phage would bind to a target molecule expressed on the surface of CL1-5 cells, we measured PC5-2-bound cells using flow cytometry ( Fig. S2 and Text S1, S2). A control phage was used to estimate non-specific background binding (Fig. S2b) . The results showed that 42.6% of CL1-5 cells were bound by PC5-2 ( Fig. S2c) , and this binding was completely inhibited by 27 mg/ml of SP5-2 peptide (Fig. S2d ). PC5-2 did not bind to SAS or NNM ( 