Synthesis, nano-scale assembly, and in vivo anti-thrombotic activity of novel short peptides containing l-Arg and l-Asp or l-Glu

Abstract Two tripeptides H-Asp(Arg)-Arg ( 3a ) and H-Glu(Arg)-Arg ( 3b ), four pentapeptides H-Asp(Arg-Asp)-Arg-Asp ( 6a ), H-Glu(Arg-Asp)-Arg-Asp ( 6b ), H-Asp(Asp- Arg)-Asp-Arg ( 10a ), and H-Glu(Asp-Arg)-Asp-Arg ( 10b ), and their Cu(II)–peptide complexes Cu(II)-Asp(Arg)-Arg [ 3a – Cu ( II )], Cu(II)–Glu(Arg)-Arg [ 3b – Cu ( II )], Cu(II)-Asp(Arg-Asp)-Arg-Asp [ 6a – Cu ( II )], Cu(II)–Glu(Arg-Asp)-Arg-Asp [ 6b – Cu ( II )], Cu(II)-Asp(Asp-Arg)-Asp-Arg [ 10a – Cu ( II )], and Cu(II)–Glu(Asp-Arg)-Asp-Arg [ 10b – Cu ( II )] were designed and synthesized. Their self-assembling properties and in vivo anti-thrombotic activities were investigated. In normal saline (NS), the Cu(II)–peptide complexes assembled into stable nano-particles surrounded by negative charges (−4.102 to −9.825 mV), with diameters ranging from 212.1 ± 4.0 to 632.4 ± 36.7 nm. TEM analysis exhibited that the compounds remained as nano-globes in the solid state, with diameters ranging from 15 to 20 nm. In an in vivo anti-thrombotic assay, peptides ( 3 , 6 , 10 ) a , b at 5 μmol/kg reduced the thrombus weights of a rat model by 15–40%. Aspirin, a widely used anti-thrombotic drug, achieved comparable activity in this model system at a dosage of ca. 110 μmol/kg. The required dosage of Cu(II)–peptide complexes [( 3 , 6 , 10 ) a , b ]– Cu ( II ), which assemble into stable nano-particles, was significantly reduced to 0.05 μmol/kg. Therefore, the anti-thrombotic activity of the nano-particles [( 3 , 6 , 10 ) a , b ]– Cu ( II ) increased dramatically by 100-fold over that of the corresponding peptides.