Synthesis of fluorescene labeled peptide/poly(ether-amide) with targeting function to liver cancer cells

To develop and characterize a new cancer target gene delivery carrier, which could be used as potential blood pool magnetic resonance (MR) contrast agents, a novel FAM-AGKGTPSLETTPC-COOH/ poly (ether-amide) (FAM-13/PEG/DTPA) copolymer (III)with fluorescence probe was designed and obtained first from the reaction of the amino group terminated poly(ether-amide) (PEG/DTPA) copolymer ligand (II) with heterobifunctional cross-linker m-maleimidobenzoyl-N- hydroxysuccinimide ester (MBS) (Step 2) , and then Michael addition of C = C double bond in MBS moiety with SH group in FAM-labeled hepatocarcinoma specific adhesin peptide, FAM-AGKGTPSLETTPC-(SH)-COOH (FAM-13), in high yield (Step 3). II was prepared by the reaction of diethylenetriamine pentaacetic acid dianhydrid (DTPAA) with amino group terminated PEG(I) (Step 1). The two copolymers of II and III were characterized by ¹H-NMR and ¹³C-NMR measurements. The liver tumor-specific identification and antigen localization of III with the fluorescin-labeled FAM-13 peptide were performed under cellular level. Targeting properties of III were tested on the normal cells and liver cancer cells, respectively. No fluorescence was observed on normal liver cells L-02, while strong yellowish green fluorescence was observed on the liver cancer cells BEL-7404. The property of FAM-13 peptide in III for recognizing specifically the liver cancer cells was demonstrated. It was also demonstrated that the chemically synthesized III with peptide FAM-13 still had the property for targeting on the surface membrane of liver cancer cells in vitro, thus further indicating that the specific targeting effect of the objective tissue was mediated by the peptides of HI insert into the cell membrane. It is evident that the III with FAM-13 peptide would be an excellent candidate for the targeting therapy to hepatocarcinoma. So ligand molecules III with targeting peptides can target hepatocellular carcinoma. Ligand III is a promising candidate, which can be coordinated with Gd³⁺ ion to give the macromolecular contrast agent.