Antimicrobial Peptide-Inspired Design of Amino-Modified Lignin with Improved Antimicrobial Activities.

A major challenge to make use of lignin as an antimicrobial material is the weak antimicrobial activity of industrial lignin. Inspired by the antimicrobial mechanism of actions of antimicrobial peptides, alkyldiamines were employed as lysine mimics for lignin modifications. Accordingly, aminoalkyl-modified lignins with different degrees of substitution of amino groups and different hydrophobicity were synthesized. The chemical structure, properties, and antimicrobial activities of the as-prepared aminoalkyl lignins were thoroughly characterized with state-of-the-art technologies. The results indicated that aminobutyl lignin showed enhanced antimicrobial activity against S. aureus and E. coli and performed even better than copper ions. The antimicrobial mechanism of action of the as-prepared aminobutyl lignin was similar to that of polylysine, which damaged the cell membrane, leading to the leakage of intracellular molecules and death of the cell. This study provides a feasible approach to afford modified lignin with enhanced antimicrobial performance, which would facilitate the high-value valorization of lignin as biological materials.

Preparation and antibacterial property of waterborne polyurethane/Zn-Al layered double hydroxides/ZnO nanocomposites.

In this work, a novel environmental-friendly waterborne polyurethane/ZnAl-layered double hydroxides/ZnO nanoparticles composite (WPU/ZnAl-LDHs/ZnO) was synthesized via in-situ polymerization. ZnAl-LDHs and ZnAl-LDHs/ZnO were synthesized by refluxing in an oil bath. In order to disperse ZnAl-LDHs/ZnO homogeneously into WPU matrix, ZnAl-LDHs/ZnO was firstly functionalized by isophorone diisocyanate. The incorporated content of ZnAl-LDHs/ZnO in the composite has profound effect on such physical properties as mechanical strength, thermal stability and water swelling. It is demonstrated that appropriate amount of ZnAl-LDHs/ZnO with good dispersion in the WPU matrix significantly improves the physical performance of the composites. Finally, the antibacterial activity of the composite was tested against G(-) Escherichia coli and G(+) Staphylococcus aureus. The results indicate that WPU incorporated with ZnAl-LDHs/ZnO shows strong antibacterial activity upon contact.

Selecting Suitable Near-Native Lignins for Research.

There are several methods to isolate near-native lignins, including milled-wood lignin, enzymatic lignin, cellulolytic enzyme lignin, and enzymatic mild-acidolysis lignin. Which one is the most representative of the native lignin? Herein, near-native lignins were isolated from different plant groups and structurally analyzed to determine how well these lignins represented their native lignin counterparts. Analytical methods were applied to understand the molecular weight, monomer composition, and distribution of interunit linkages in the structure of the lignins. The results indicated that either enzymatic lignin or cellulolytic enzyme lignin may be used to represent native lignin in softwoods and hardwoods. None of the lignins, however, appeared to represent native lignins in grasses (monocot plants) because of substantial syringyl/guaiacyl differences. Complicating the understanding of grass lignin structure, large amounts of hydroxycinnamates acylate their polysaccharides and, when released, are often conflated with actual lignin monomers.

Poly (γ-glutamic acid)/beta-TCP nanocomposites via in situ copolymerization: Preparation and characterization.

A series biodegradable poly (γ-glutamic acid)/beta-tricalcium phosphate (γ-PGA/TCP) nanocomposites were prepared which were composed of poly-γ-glutamic acid polymerized in situ with ß-tricalcium phosphate and physiochemically characterized as bone graft substitutes. The particle size via dynamic light scattering, the direct morphological characterization via transmission electron microscopy and field emission scanning electron microscope, which showed that γ-PGA and ß-TCP were combined compactly at 80℃, and the γ-PGA/TCP nanocomposites had homogenous and nano-sized grains with narrow particle size distributions. The water uptake and retention abilities, in vitro degradation properties, cytotoxicity in the simulated medium, and protein release of these novel γ-PGA/TCP composites were investigated. Cell proliferation in composites was nearly twice than ß-TCP when checked in vitro using MC3T3 cell line. We also envision the potential use of γ-PGA/TCP systems in bone growth factor or orthopedic drug delivery applications in future bone tissue engineering applications. These observations suggest that the γ-PGA/TCP are novel nanocomposites with great potential for application in the field of bone tissue engineering.