Anti-inflammatory and anti-oxidant properties of laccase-synthesized phenolic-O-carboxymethyl chitosan hydrogels

A bioactive O-carboxymethyl chitosan (CMCS) hydrogel crosslinked with natural phenolics with potential application in wound dressings was synthesized using a laccase from Myceliophthora thermophila (MTL). The highest degree of cross-linking (49.7%) was achieved with catechol. All the phenolic-CMCS hydrogels synthesized showed excellent anti-oxidant properties with a free radical scavenging activity up to 4-fold higher than in the absence of the phenolics, as quantified by the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assay. In addition, the hydrogels produced showed an anti-inflammatory effect as evidenced by the inhibition of enzymes [myeloperoxidase (MPO), matrix-metalloproteinase-1 (MMP-1) and human neutrophil elastase (HNE)] over-expressed in chronic wounds. Sinapyl-CMCS hydrogels showed an MMP-1 inhibition of 37%. Further, the phenolic-CMCS hydrogels did not affect the viability of the NIH 3T3 mouse fibroblast cell line and were also able to slowly release human fibroblast growth factor 2, reaching 48.3% over a period of 28 days. This study thus shows the possibility of synthesizing multifunctional bioactive chitosan based hydrogels with anti-oxidant and anti-inflammatory properties using natural occurring phenolics as crosslinkers.