Investigation of nonfouling polypeptides of poly(glutamic acid) with lysine side chains synthesized by EDC·HCl/HOBt chemistry

Abstract

Nonfouling polypeptides with homogenous alternating charges draw peoples’ attentions for their potential capability in biodegradation. Homogenous glutamic acid (E) and lysine (K) polypeptides were proposed and synthesized before. In this work, a new polypeptide formed by poly(glutamic acid) with lysine side chains (poly(E)-K) was synthesized by facile EDC·HCl/HOBt chemistry and investigated. Results show that these polypeptides also have good nonspecific protein resistance determined by enzyme-linked immunosorbent assay. The lowest nonspecific adsorption of the model proteins, anti-IgG and fibrinogen (Fg), on the self-assembling monolayers (SAMs) surface of poly(E)-K was only 3.3 ± 1.8 and 4.4 ± 1.6%, respectively, when protein adsorption on tissue culture polystyrene surface was set as 100%. And, the relative nonspecific protein adsorption increases when the polypeptide molecular weight increases due to the repression of low density polymer brushes. Moreover, almost no obvious cytotoxicity and hemolytic activity in vitro were detected. This work suggests that polypeptides with various formats of homogenous balanced charges could achieve excellent nonspecific protein resistance, which might be the intrinsic reason for the coexistence of high concentration serum proteins in blood.

Keywords:

• polypeptides
• nonfouling
• biocompatibility
• SAMs
• poly(E)-K

Additional information

Funding

Funding. The authors appreciate financial support from the National Nature Science Foundation of China [grant number 21174127]; the PhD Programs Foundation of Ministry of Education of China [grant number 20110101110034]; the Zhejiang Provincial Natural Science Foundation of China [grant number LZ13E030001]; and the department education of Zhejiang province [grant number Z200804487].