Gelatin-based multifunctional composite films integrated with dialdehyde carboxymethyl cellulose and coffee leaf extract for active food packaging.

In this study, dialdehyde carboxymethyl cellulose (DCMC, 10 wt% based on gelatin) and varying contents of coffee leaf extract (CLE, 1, 3, 5 and 7 wt% based on gelatin) were incorporated into gelatin (GEL) matrix to develop multifunctional food packaging films. DCMC acted as a physical reinforcing filler through crosslinking with GEL matrix by Schiff-base reaction, CLE served as an active filler to confer film functional properties. The micro-morphology, micro-structure, physicochemical and functional properties of the GEL/DCMC/CLE composite film were investigated. The results demonstrated that mechanical, barrier properties and thermal stability of films were significantly improved by incorporation of CLE. Compared with pure GEL film, the GEL/DCMC/5%CLE film exhibited excellent UV light blocking while kept enough transparency, the best mechanical property, water resistance, water vapor and oxygen barrier, as well as thermal stability. GEL/DCMC/5%CLE film also possessed strong antioxidant activity and some antibacterial activity against E. coli and S. aureus. Packaging application testing demonstrated that the resultant GEL/DCMC/5%CLE film effectively delayed the lipid oxidation of walnut oil and preserved the postharvest freshness of fresh walnut kernels under ambient conditions.

Humidity-adjustable functional gelatin hydrogel/ethyl cellulose bilayer films for active food packaging application.

A sustainable functional bilayer film composed of gelatin hydrogel/ethyl cellulose was fabricated using a simple LBL casting method. The outer layer was hydrophobic ethyl cellulose (EC), while the inner layer was hydrophilic gelatin (GEL) hydrogel. Tannic acid (TA) served as a green cross-linker for GEL hydrogel preparation and as a reductant for AgNPs synthesis in-situ within the hydrogel network. Physicochemical and functional properties of the bilayer films containing different TA content were studied. When 3 wt% TA was added, the AgNPs@GT-3/EC bilayer film exhibited superior UV-light barrier, possessed desirable humidity-adjustable capability and oxygen barrier due to denser hydrogel network structure, and effectively inactivated foodborne pathogens S. aureus and E. coli with bacteriostatic rates of 99 %. The application results indicated that this bilayer film effectively maintained the postharvest quality of white button mushrooms and prolonged their shelf-life to 7 days under ambient storage, demonstrating its promising potential for fresh food packaging.

Chitosan-plasmid DNA nanoparticles encoding small hairpin RNA targeting MMP-3 and -13 to inhibit the expression of dedifferentiation related genes in expanded chondrocytes.

Overexpression of matrix metalloproteinase (MMP)-3 and -13 can lead to the dedifferentiation of expanded chondrocytes. After implanting dedifferentiated cells for cartilage defect repair, graft failure may occur. Short hairpin RNA (shRNA) is a powerful genetic tool to reduce the expression of target genes. This study investigated the effects of chitosan-plasmid DNA (pDNA) nanoparticles encoding shRNA targeting MMP-3 and -13 on the dedifferentiation of expanded chondrocytes. The objective was to optimize the parameters of chitosan-pDNA formulation for achieving higher efficiency of pDNA delivery and gene silencing. The chitosan-pDNA nanoparticles were prepared using a complex coacervation process. Then the characteristics including size, shape, stability, and transfection efficiency were compared in different groups. The results indicated that chitosan of 800 kDa at N/P ratio of 4 and pH 7.0 was optimal to prepare chitosan-pDNA nanoparticles. These nanoparticles showed high DNA loading efficiency (95.8 ± 1.5%) and high gene transfection efficiency (24.5 ± 1.6%). After the expanded chondrocytes were transfected by chitosan-pDNA nanoparticles, MMP-3-610 and MMP-13-2024 groups showed greater suppression in mRNA and protein levels. The results indicated that chitosan-pDNA nanoparticles encoding shRNA targeting MMP-3 and -13 had great potential in silencing the dedifferentiation-related genes for regenerating prolonged and endurable cartilage.