Syntheses and in vitro antitumor activities of ferrocene-conjugated Arg-Gly-Asp peptides

► Ferrocene-conjugated Arg-Gly-Asp peptides were synthesized in solution. ► Cell uptake of the ferrocenoyl conjugates was tested by HPLC-electrochemical method. ► Fc-Am-RGD shows much higher antitumor activity than Fc-COOH. ► The flexible alkyl spacer between ferrocene and RGD enhances the cell uptake.