Abstract: Objective To synthesize poly asparagine derivatives and to evaluate its safety at the cellular level, which provide research platform for its potential application as drug carrier. Methods Polysuccinimide was synthesized by thermal polymerization of L-polyaspartic acid, and the target product of PSI-Phe-EA was obtained by the ring-opening reaction of polysuccinimide using L- phenylalanine methyl ester hydrochloride and ethanol amine. The structure of PSI- Phe- EA
were characterized by 1H NMR. The rate of ring-opening of PSI was calculated by internal standard method of 1H NMR. The change of hydrophilicity was studied by the comparison of solubility. The cytotoxicity and morphology modification by PSIPhe-EA at designate concentrations was investigated by MTT method and inverted microscopy respectively. The effects on cell cycles were analyzed by flow cytometry after propidium iodide (PI) staining. Results 1H NMR results confirmed the structure of PSI-Phe-EA and the ring-openning rate of PSI was 40%. The hydrophilicity of PSI-Phe-EA was greatly increased upon ring opening using ethanol amine. MTT test showed that the cell survival rates of NIH 3T3 and HepG2 cells were higher than 80% under the examined concentration (<100 mg/L). Inverted microscopy showed that 50 mg/L of PSI-PheEA treatment had no adverse effects on cell morphology. Cell cycle analysis indicated that PSI-Phe-EA treatment had no influence on cell cycles of NIH 3T3 and HepG2 cell lines. Conclusion PSI-Phe-EA showed high hydrophilicity without significant effects on the cells survival, cells morphology and cell cycles. It is a kind of safe polymer material.

Key words: asparagine, phenylalanine, ethanolamine, drug carriers, cell cycle, polyasparagine derivative, cytotoxicity