Fig. 7: Study on the affinity of cyclic RGD peptides to integrins.

a The structures of cyclic RGD peptides 10a and 10c and fluorescent probes 10b with thiol groups. b SPR sensorgrams characterizing the affinity of peptides 10a and 10c to integrins targets. c Flow cytometry assay determining the amount of integrins in HeLa and A549 cells. Living cells were pretreated with 5 µM cyclic peptides 10a for 60 min, and then with 5 µM 10b for 15 min. HUVEC cells were served as a reference. Data were presented as mean ± S.D. n = 3 biologically independent samples per group. P values obtained from two-tailed unpaired t-test. d Confocal fluorescence images of A549 or HeLa cells pretreated with 5 µM cyclic peptides 10a da), 10c db) or 10a and 10c dc) and dd) for 60 min, and then with 5 µM 10b da), dc) and dd) for 15 min, upon one-photon excitation at 488 nm (10c) and 552 nm (10a + 10b). Scale bar: 20 μM. The images were collected at 500–550 nm (10c) and 580–650 nm (10a + 10b). Fluorescence quantitative analysis of FITC and RhB channels in A549 and HeLa cells. Data are expressed as mean ± SD (experiment times n = 3).