Highly-toughened PVA/nanocellulose hydrogels with anti-oxidative and antibacterial properties triggered by lignin-Ag nanoparticles

: In this study, Ag nanoparticles were firstly reduced on the surface of lignin nanoparticles (LNPAg) by direct reaction of silver nitrate without the use of a catalyst. Thermogravimetric analysis, Zeta potential and transmission electron microscopy measurements were performed to give evidence of the effectiveness of the reaction. After that, glutaraldehyde crosslinked PVA hydrogels, were produced by addition of unmodified LNP and Ag loaded LNP (LNPAg) in presence of cellulose nanocrystals (CNC). Thermal, mechanical, rheological, microstructural and biological anti-oxidative and anti-bacterial properties of the resulted hydrogels were investigated. It was proved that all the three nanofillers were homogeneously dispersed in PVA, and the pore diameter of the hydrogels was in the range of 0.5-2.0 μm. Nevertheless, the hydrogels showed high toughness, long-term and repeatable adhesiveness to a variety of substrates. In particular, composite hydrogels containing LNPAg nanoparticles showed excellent radical scavenging and antibacterial activities. Consequently, the effects of PVA-2CNC-2LNPAg on wound healing in mice model of full-thickness skin resection were evaluated by hematoxylin and eosin staining, taking as a reference the PVA-2CNC-2LNP system. The results showed that the wound healing time of PVA-2CNC-2LNPAg group was faster than that of neat PVA and PVA-2CNC, highlighting the role of LNPAg in enhancing the contact-active anti-oxidative and antibacterial activities mechanism in composite hydrogels. We expected that PVA hydrogels incorporating LNPAg could be used as green and efficient biomedical wound dressing materials.