4.3. αvβ3 Integrin Binding Assay

Binding affinities of synthesized peptides E[c(RGDfK)]₂ and 6 for α_vβ₃ integrin were evaluated by competitive inhibition between the peptides and [¹²⁵I]c[RGDy(3-I)V], which was prepared by Fmoc solid-phase synthesis and following ¹²⁵I-labeling with chloramine-T method [23], to α_vβ₃ integrin according to a previously reported procedure [24]. The peptides’ half maximal inhibitory concentration (IC₅₀) values were calculated by curve fitting with nonlinear regression using GraphPad Prism 8.4.3 (GraphPad Software Inc., San Diego, CA, USA). Each data point is the average of four determinations, and IC₅₀ values were expressed as mean ± standard deviation (SD) from three independent experiments.