Biodegradable coating constructed from carboxycellulose nanofibers for high photocatalytic decomposition of ethylene and synergistic antibacterial what of perishable fruits.

Postharvest fruits, especially climacteric fruits, are prone to ethylene ripening, browning and aging, microbial growth accelerated decay and other problems in natural environment. Herein, a carboxylated cellulose nanofibers/phytic acid­titanium dioxide nanoparticles (CPT) biodegradable coating with "photocatalytic antibacterial barrier" structure，was developed by homogeneous dispersion of phytic acid(PA) complexed titanium dioxide nanoparticles (TNPs) in carboxylated cellulose nanofibers(CCNF). The CPT coating achieves effective dispersion and efficient utilization of TNPs through the complexation of PA. The coating ethylene clearance rate of CPT up to 70.89 %. Meanwhile, the coating exhibits excellent antibacterial (99.67 %), UV resistance, gas barrier. It was found that the CPT coating delays fruit ripening caused by ethylene, which effectively maintaining the quality of respiratory climacteric fruits and non- climacteric fruits, extending the shelf life of perishable fruit by up to 9 days. In particular, the coating is virtually biodegradable in soil after 21 days, which offers the possibility of replacing non-biodegradable multifunctional coatings in food packaging.

One-pot co-crystallized hexanal-loaded ZIF-8/quaternized chitosan film for temperature-responsive ethylene inhibition and climacteric fruit preservation.

Controlling ethylene production and microbial infection are key factors to prolong the shelf life of climacteric fruit. Herein, a nanocomposite film, hexanal-loaded ZIF-8/CS (HZCF) with "nano-barrier" structure, was developed by a one-pot co-crystallized of ZIF-8 in situ growth on quaternized chitosan (CS) and encapsulation of hexanal into ZIF-8 via microporous adsorption. The resultant film realized the temperature responsive release of hexanal via the steric hindrance and hierarchical pore structure as "nano-barrier", which can inhibit ethylene production in climacteric fruit on demand. Based on this, the maximum ethylene inhibition rate of HZCF was up to 52.6 %. Meanwhile, the film exhibits excellent antibacterial, mechanical, UV resistance and water retention properties, by virtue of the functional synergy between ZIF-8 and CS. Contributed to the multifunctional features, HZCF prolonged the shelf life of banana and mango for at least 16 days, which is 8 days longer than that of control fruit. More strikingly, HZCF is washable and biodegradable, which is expected to replace non-degradable plastic film. Thus, this study provides a convenient novel approach to simplify the encapsulation of active molecule on metal-organic frameworks (MOFs), develops a packaging material for high-efficient freshness preservation, and helps to alleviate the survival crisis caused by food waste.

High-strength, antifogging and antibacterial ZnO/carboxymethyl starch/chitosan film with unique "Steel Wire Mesh" structure for strawberry preservation.

In this work, a multifunctional preservative film of ZnO/carboxymethyl starch/chitosan (ZnO/CMS/CS) with the unique "Steel Wire Mesh" structure is fabricated by the chemical crosslinked of ZnO NPs, CMS and CS. Unlike traditional nano-filled polymer film, the formation of the "Steel Wire Mesh" structure of ZnO/CMS/CS film is based on the synergistic effect of ZnO NPs filled CMS/CS and the coordination crosslinked between CMS/CS and Zn2+ derived from ZnO NPs. Thanks to the "Steel Wire Mesh" structure, the tensile strength and water vapor barrier of 2.5ZnO/10CMS/CS film are 2.47 and 1.73 times than that of CS film, respectively. Furthermore, the transmittance of 2.5ZnO/10CMS/CS film during antifogging test is close to 89 %, confirming its excellent antifogging effects. And the 2.5ZnO/10CMS/CS film also exhibits excellent long-acting antibacterial activity (up to 202 h), so it can maintain the freshness and appearance of strawberries at least 5 days. More importantly, the 2.5ZnO/10CMS/CS film is sensitive to humidity changes, which achieves real-time humidity monitoring of the fruit storage environment. Note that the preparation method of the film is safe, simple and environmentally friendly, and its excellent degradation performance will not bring any problems of food safety and environmental pollution.

Humidity-/Sweat-Sensitive Electronic Skin with Antibacterial, Antioxidation, and Ultraviolet-Proof Functions Constructed by a Cross-Linked Network.

Most electronic skins (e-skins) show unique performance or possess sensory functions. The raw materials used for their preparation are potentially toxic or harmful, and there may be problems such as poor compatibility between the conductive fillers and polymers. In this paper, a silver-loaded nanocomposite film (PVA/CMS/vanillin/nanoAg) was prepared by the in situ reduction method in a greener route. The mechanical properties of this nanocomposite film had improved with a tensile strength of 30.95 MPa, an elongation at break of 101.9%, and a Young's modulus of 10.62 MPa. In the composite matrix, a cross-linked network was constructed based on the coordination and hydrogen bonds, which was conducive to the stability of the reduced AgNPs and AgNWs. When applied as an e-skin in humidity/sweat sensors and wearable electronics, the nanocomposite film responds to humidity within 60 s and records the electric signals of human joint movements and skin sweating with a response range of 0-140% to strain at 93% RH. This kind of e-skin has excellent antibacterial and antioxidant activities and shows an outstanding ultraviolet-proof performance, which provides a greener promising reference route for the design of wearable e-skins to monitor the health and movements of humans.

Polysaccharides synergistic boosting drug loading for reduction pesticide dosage and improve its efficiency.

Overuse of pesticides is an urgent issue to be solved in sustainable agriculture. Based on the synergistic drug loading effect of ß-cyclodextrin (ß-CD) encapsulation and alginate (Alg) cross-linking, a new environment-responsive drug delivery system (TMX-loaded Alg/ß-CD) was constructed. The relationship between carrier structure and solubility of thiamethoxam (TMX) was researched by molecular simulation. ß-CD has good binding affinity with TMX, which can increase TMX solubility by 40 %. Further co-loading with alginate could double the drug loading of the cyclodextrin inclusion complex up to 41 %. TMX-loaded Alg/ß-CD exhibits excellent environment-responsive controlled-release performance, and TMX sustained release time is 7.5 times longer than that of commercial agents. The pest control efficacy of TMX-loaded Alg/ß-CD is 20 days longer than that of commercial TMX, and the crops has no pesticide residues after using. This study provides a promising strategy for the commercial application of polysaccharide in pest control and pesticide reduction.

Convenient, nondestructive monitoring and sustained-release of ethephon/chitosan film for on-demand of fruit ripening.

The microstructure changes (such as micro defects and free volume, etc.) is a deep factor that determines the sustained release behavior of polymer film. However, there are few reports exploring the micro defects of sustained-release materials. Herein, we develop a facile method to non-destructive monitoring and sustained-release ethylene within chitosan. The comprehensive means of positron annihilation lifetime spectroscopy, atomic force microscopy and Raman spectrums are performed together to study the microstructures change of ethylene sustained-release and its mechanism. When ethylene is in chitosan film, it shows good ripening performance and mechanical properties. The sustained-release ethylene improves its bioavailability and can control the fruit-ripening on-demand. More importantly, the microstructural changes of cavities have a significant impact on the sustained release of ethylene, due to the creation of cavities, the free volume of positrons undergoes a process of increasing from less to more and then gradually decreasing, reaching a maximum at 120 h. Furthermore, the ethephon/chitosan film could on-demand control the ripening time of mangoes and bananas. Therefore, this research presents a comprehensive means to study of microstructure change monitoring and controllable sustained release, and provides the possibility to solve the problem of on-demand ripening of fruit and reducing pesticide residue.

Curcumin-loaded HKUST-1@ carboxymethyl starch-based composites with moisture-responsive release properties and synergistic antibacterial effect for perishable fruits.

The spoilage of fruit is one of the most important causes of fruit waste. High humidity by fresh fruit respiration leads to bacterial reproduction, which is the key factor of products corruption. Herein, a biological multifunctional film (Cur-HKUST-1@CMS/PVA) for fruits preservation with a high moisture environment was developed by cross-linking carboxymethyl starch (CMS)/polyvinyl alcohol (PVA) with MOF-199 (HKUST-1), and loaded with curcumin. The hydrophilic CMS facilitates water adsorption and moisture can stimulate curcumin release from HKUST-1. HKUST-1 not only acts as curcumin carriers but also forms synergistic antibacterial with curcumin to improve the antibacterial activity of the composites. XRD and SEM demonstrated that moisture disrupts the structure of HKUST-1 and releases curcumin and the results showed that the release of curcumin increased from 25.11 % to 58.32 % after moisture stimulation. In addition, Cur-HKUST-1@CMS/PVA had excellent antibacterial activity and antioxidant ability. As validation, the film can keep pitaya and avocado freshness at least 4 days longer than the control, confirming the effectiveness of Cur-HKUST-1@CMS/PVA in preventing fruit decay. Consequently, Cur-HKUST-1@CMS/PVA is a promising active packaging material for improve the shelf life of perishable fruits.