Improving the antiradical activity and UV resistance of PBAT/nanolignin composite films through amination of various amino acids

Abstract

In this work, lignin nanoparticles (LNP) was prepared by a simple acidolysis method. Subsequently, various amino acids such as tryptophan (Trp), tyrosine (Tyr) and histidine (His) were then used to modify lignin nanoparticles through Mannich reaction by amination reaction, named as LNP-Trp, LNP-Tyr and LNP-His, respectively. The FTIR and SEM measurement results proved that the modification was successful. Antiradical were evaluated by DPPH assay and the results showed that the antiradical capacity was as following: LNP-His>LNP-Tyr>LNP>LNP-Trp. Antibacterial tests show that LNP-His also has the strongest inhibiting influence on the E.coli and S.aureus bacteria. Then LNP-His was incorporated into PBAT to prepare the composite films, the results showed that the film with 1.5% of LNP-His have 92.5% of antiradical efficiency and 98.7% of UV absorption efficiency. The mechanism of the antiradical and antibacterial activities of aminated LNP was proposed to be responsible for the electron-donating behavior of the replaced groups at o-position of Ph-OH of aminated LNP, since the imidazole of group of histidine are more conducive to dissociate the Ph–O···H bond than the indole group of tryptophan and phenolic group of tyrosine. Hence, the antiradical and antibacterial activities of LNP-His are more prominent than LNP-Trp and LNP-Tyr.