Preparation and properties of EDC/NHS mediated crosslinking poly (gamma-glutamic acid)/epsilon-polylysine hydrogels

• Published in: Materials Science & Engineering C Vol. 61; pp. 879 - 892
• Main Authors: Hua, Jiachuan, Li, Zheng, Xia, Wen, Yang, Ning, Gong, Jixian, Zhang, Jianfei, Qiao, Changsheng
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2016
• Subjects: Animals; Biocompatibility; Biocompatible Materials - chemistry; Biocompatible Materials - pharmacology; Cell Adhesion - drug effects; Cell Line; Cell Proliferation - drug effects; Crosslinking; Ethyldimethylaminopropyl Carbodiimide - chemistry; Hydrogel; Hydrogels; Hydrogels - chemistry; Hydrogen-Ion Concentration; Infrared spectroscopy; Mice; Microscopy, Electron, Scanning; Photoelectron Spectroscopy; Poly γ-glutamic acid; Polyglutamic Acid - analogs & derivatives; Polyglutamic Acid - chemistry; Polylysine - chemistry; Pore size; Porosity; Scanning electron microscopy; Spectroscopy, Fourier Transform Infrared; Succinimides - chemistry; Swelling; Swelling kinetics; X-ray photoelectron spectroscopy; ε-Polylysine; Biocompatibility; Poly γ-glutamic acid; Hydrogel; Swelling kinetics; ε-Polylysine
• ISSN: 0928-4931; 1873-0191
• DOI: 10.1016/j.msec.2016.01.001

In this paper, a novel pH-sensitive poly (amino acid) hydrogel based on poly γ-glutamic acid (γ-PGA) and ε-polylysine (ε-PL) was prepared by carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mediated polymerization. The influence of PGA/PL molar ratio and EDC/NHS concentration on the structure and properties was studied. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) proved that hydrogels were crosslinked through amide bond linkage, and the conversion rate of a carboxyl group could reach 96%. Scanning electron microscopy (SEM) results showed a regularly porous structure with 20μm pore size in average. The gelation time in the crosslink process of PGA/PL hydrogels was within less than 5min. PGA/PL hydrogels had excellent optical performance that was evaluated by a novel optotype method. Furthermore, PGA/PL hydrogels were found to be pH-sensitive, which could be adjusted to the pH of swelling media intelligently. The terminal pH of swelling medium could be controlled at 5±1 after equilibrium when the initial pH was within 3–11. The swelling kinetics was found to follow a Voigt model in deionized water but a pseudo-second-order model in normal saline and phosphate buffer solution, respectively. The differential swelling degrees were attributed to the swelling theory based on the different ratio of –COOH/–NH2 and pore size in hydrogels. The results of mechanical property indicated that PGA/PL hydrogels were soft and elastic. Moreover, PGA/PL hydrogels exhibited excellent biocompatibility by cell proliferation experiment. PGA/PL hydrogels could be degraded in PBS solution and the degradation rate was decreased with the increase of the molar ratio of PL. Considering the simple preparation process and pH-sensitive property, these PGA/PL hydrogels might have high potential for use in medical and clinical fields. [Display omitted] •We prepared a biocompatible and degradable poly amino acids hydrogel via EDC/NHS polymerization.•The PGA/PL hydrogel was pH-sensitive and could adjust the pH of swelling media intelligently.•A novel method was made to qualitatively test the optical transparency of translucent materials.•A novel optical rheology technique was used to detected gelation time of hydrogel.