Chitosan quaternary ammonium salt/gelatin-based biopolymer film with multifunctional preservation for perishable products.

The postharvest physiological and metabolic activities caused fruits and vegetables (F&V) quality deterioration. Therefore, developing an efficient preservation strategy is a promising approach to relieve this issue. In this study, a modified metal-organic framework (MOF; i.e., Cer@MHKUST-1) was encapsulated into a blended matrix of chitosan quaternary ammonium salt (CQAS)/gelatin to fabricate a multifunctional (water-locking, ethylene-removing, and antibacterial) packaging biopolymer-based film (i.e., CMCGF), the characteristics and preservative effects of the packaging were investigated. Results indicated that the physicochemical (e.g., mechanical, gas/light barrier, wettability) properties of CMCGF were improved compared with the control film (i.e., CGF). CMCGF have a higher ethylene adsorption performance of 65-69 cm3/g STP compared with CGF (7.8 cm3/g STP). Cu ions released from CMCGF destroyed the cell wall and membrane, resulting in the death of bacteria, and the antibacterial efficiency of CMCGF against E. coli and S. aureus was 97-100 % and 98-100 %, respectively. Postharvest storage experiments on tomato and winter jujube confirmed the high-efficiency preservation effect of CMCGF packaging. Therefore, CMCGF provides a multifunctional approach to extending the shelf-life of perishable products to decrease food wastage.

Immobilization of α-galactosidase in polyvinyl alcohol-chitosan-glycidyl methacrylate hydrogels based on directional freezing-assisted salting-out strategy for hydrolysis of RFOs.

Raffinose family oligosaccharides (RFOs) in food are the main factors causing flatulence in Irritable Bowel Syndrome (IBS) patients and the development of effective approaches for reducing food-derived RFOs is of paramount importance. In this study, polyvinyl alcohol (PVA)-chitosan (CS)-glycidyl methacrylate (GMA) immobilized α-galactosidase was prepared by the directional freezing-assisted salting-out technique, aimed to hydrolyze RFOs. SEM, FTIR, XPS, fluorescence and UV characterization results demonstrated that α-galactosidase was successfully cross-linked in the PVA-CS-GMA hydrogels, forming a distinct porous stable network through the covalent bond between the enzyme and the carrier. Mechanical performance and swelling capacity analysis illustrated that α-gal @ PVA-CS-GMA not only had suitable strength and toughness for longer durability, but also exhibited high water content and swelling capacity for better retention of catalytic activity. The enzymatic properties of α-gal @ PVA-CS-GMA showed an improved Km value, pH and temperature tolerance range, anti-enzymatic inhibitor (melibiose) activity compared to the free α-galactosidase and its reusability was at least 12 times with prolonged storage stability. Finally, it was successfully applied in the hydrolysis of RFOs in soybeans. These findings provide a new strategy for the development of α-galactosidase immobilization system to biological transform the RFOs components in the food for diet intervention of IBS.

Amyloid Protein-Biofunctionalized Polydopamine Nanoparticles Demonstrate Minimal Plasma Protein Fouling and Efficient Photothermal Therapy.

Polydopamine (PDA) shows great application potential in photothermal therapy (PTT) of tumors due to its excellent photothermal performance. However, PDA rich in a large number of catechin structures, with strong adhesion, can readily attach to plasma proteins in blood to form protein corona, which greatly hinders the transfer efficiency to tumors and reduces the bioavailability. In this paper, a simple, rapid phase-transitioned albumin biomimetic nanocorona (TBSA) is used for the surface camouflage of PDA nanoparticles for minimal plasma protein fouling and efficient PTT. TBSA coating is formed by the BSA-derived amyloid through the hydrophobic aggregation near the isoelectric point and the rupture of disulfide bonds by tris(2-carboxyethyl) phosphine. The stable PDA@TBSA complexes are formed by camouflaging TBSA onto the surface of PDA through hydrophobic, electrostatic, and covalent binding between TBSA and PDA, which showed excellent anti-plasma protein adsorption properties profited from the surface charge of PDA@TBSA approaching equilibrium and the surface passivation of BSA. The plasma protein thickness of the PDA@TBSA surface is 6 times lower than that of PDA at adsorption saturation. In vitro and in vivo experiments have revealed that PDA@TBSA has an excellent photothermal antitumor effect compared to PDA. Both PDA and PDA@TBSA treatment plus 808 nm laser irradiation result in more than 70% inhibition on tumor cell proliferation. In addition, PDA@TBSA does not cause a significant inflammatory response and tissue damage. Taken together, the TBSA coating endows PDA with low-fouling functions in blood and improves the residence time of PDA in blood and enrichment in the tumor tissue. This work offers a novel and efficient strategy for the design of functional nanosystems exploiting the speciality of the biomolecular corona formation around nanomaterials.

Development, physiochemical characterization and forming mechanism of Flammulina velutipes polysaccharide-based edible films.

Edible films of Flammulina velutipes polysaccharide were prepared and characterized in terms of rheological, optical, morphologic, mechanical and barrier properties to evaluate their potential application in food packaging. Results suggested that FVP film prepared by the solution of 1:150 (w/v) had the optimal mechanical property, smooth and uniform surface, and good barrier property to water (37.92±2.00gmm/m(2)hkPa) and oxygen (37.92±2.01meq/kg). The capacity of film-formation might be related to inter-molecular and intra-molecular hydrogen bonds of FVP and formation of ß-glycosidic bonds during the process of film-formation. These findings will contribute to a theoretical basis for the development of FVP film in food packaging.