Evaluation of antibacterial properties of chemically cross-linked hydrogels based on ℇ-polylysine and hyaluronic acid

In recent years, fabrication of novel hydrogels with certain multifunctional properties has attracted research interest in different fields of biomedicine. The bacterial infections and antibiotic resistance are becoming a global problem in health care sector, and therefore design and development of hydrogels for tissue engineering with an antibacterial function are a main focus in biomedical research. The aim of this study is to develop and investigate novel antibacterial hydrogels based on natural biopolymers: antibacterial ε-polylysine (ε-PL) and intrinsic biocompatible hyaluronic acid (HA). The hydrogel series based on ε-PL and HA (mass ratios of ε-PL and HA are 50:50; 60:40; 70:30 and 80:20 wt%) were in situ synthesized via chemical cross-linking using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) crosslinking agents (with molar ratio of EDC:NHS =1:1) [1]. The molecular structure, phase composition and morphology of all synthesized hydrogels were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometry (XRD) and scanning electron microscopy (SEM). The minimal inhibitory concentrations (MIC) of ε-PL against Gram+ and Gram- bacteria were determined. The antibacterial activity of the fabricated ε-PL-HA hydrogels were tested against E.coli and S.aureus bacterial cultures. FTIR spectra indicated interaction between ε-PL and HA and successful formation of cross-linked copolymer via amide bond linkage. XRD patterns show diffraction maximum of copolymer amorphous phase without external maximums. SEM micrographs of the lyophilized hydrogels revealed homogeneous and microporous structure. The MIC of ε-PL against E.coli and S.aureus were determined to be 25 µg/ mL. In the described study, novel hydrogels based on chemically cross-linked ε-polylysine and hyaluronic acid copolymer system were synthesized and investigated. The antibacterial tests indicated inhibition ability against Gram+ and Gram-bacterial cultures. It is concluded that the developed hydrogels can be considered as promising antibacterial biomaterials for tissue engineering.