A green mussel-bioinspired strategy for grafting 3-ene urushiol and AgNPs into soy protein isolate and fabricating a high-strength antimicrobial bioplastic film

Abstract

Inadequate mechanical stretching, poor barrier performance, and easy microbial breeding of soy protein isolate (SPI) and chitosan (CS) composite film limit its application. Inspired by the mussel phenolic-protein structure, novel cross-linked nanoparticles (U/SPI/Ag) were first fabricated to graft 3-ene urushiol (3-U) and Ag+ into SPI through laccase-oxidation. Then, it was blended with appropriate amounts of CS to prepare facile and sustainable composite films (CMs). The covalent binding rate of 3-U to SPI was 69 %–76 % by laccase-oxidation. Moreover, 3-U partially stretched the polypeptide chain of SPI, reduced the hydrophobicity of the protein surface, and increased the sulfhydryl content to (0.8–2.6) × 10−5 mol/g. In addition, 1.5%U/SPI/Ag had a wide particle size distribution ranging from 40 nm to 200 nm. The tensile strength of the 50%CMs increased substantially to 29.6 MPa, and the elongation at break reached 15.2 %. Interestingly, the water vapor permeability coefficient of the incorporated 50%CMs came up to 3.65 × 10−13 (g·cm)/(cm2·s·Pa). Furthermore, 50%CMs in vitro significantly stimulated the form of ROS in E. coli, led to the fundamental damage to bacteria, and did not induce any significant toxicity in HUVEC cells.