Fabrication of Schiff-base crosslinked films modified dialdehyde starch with excellent UV-blocking and antibacterial properties for fruit preservation

Engineered environment-friendly multifunctional food packaging with superior nonleachability, polymer miscibility and antimicrobial activity

This study was conducted primarily to develop an environment-friendly food packaging boasting several advantages, including good water vapor barrier, UV resistance, antimicrobial activity, non-leachability, and polymer miscibility. Initially, the starch-based antimicrobial agent (OCSI) was synthesized through a simple esterification reaction between oxidized corn starch (OCS) and indoleacetic acid (IAA). Subsequently, OCSI was further blended separately with environmentally-friendly materials (PVA, PBAT, PCL), and a series of environment-friendly packaging films were successfully prepared. The resulting films exhibited desirable thermal stability and 100 % barrier against both UV-A and UV-B rays. Moreover, the films presented effective barriers against water vapor, antioxidant, and antimicrobial activity against E. coli and S. aureus. Meanwhile, the films could significantly inhibit the deterioration of fresh fruits and prolong shelf life, considerably expanding their utilization in safe packaging. The environment-friendly packaging not only realized the sustainable utilization of green polymers, but also offered novel insights into the exploration of sustainable packaging.

Preservative for High Antioxidant and Antimicrobial Activity and Low Toxicity

There is an urgent need for highly efficacious and minimally toxic preservatives for vegetables and fruits to ensure extended freshness and safety. Using natural polymer starch as the matrix, we produced nicotinated starch-ethylamine (NSA) based on N,N'-carbonyldiimidazole (CDI) acting as the catalyst and 2-chloroethylaminehydrochloride as the nucleophile. To strengthen the antimicrobial and antioxidant activity, NSA was reacted with three different cinnamic acids to prepare starch derivatives bearing cinnamyl (CNSA, DNSA, and ENSA). With a grafting rate of 27%, ENSA demonstrated notable antioxidant capability reaching ∼85% at 1.6 mg/mL. Also, it displayed inhibitory indices of 88.14%, 89.11%, and 77.90% against Botrytis cinerea, Phomopsis asparagi, and Glomerella cingulate, respectively, at a concentration of 1.0 mg/mL. The cytotoxicity test showed that the 293T cell survival ratio reached 101.5%. In addition, the sample was able to extend the shelf life of the cherry tomatoes by three days. This study has successfully developed a novel starch-based preservative for fruits and vegetables that not only possesses excellent antioxidant and antimicrobial properties but also effectively extends the shelf life of produce, demonstrating its broad application prospects in the field of fruit and vegetable storage and preservation.

Water-dispersible fluorescent COFs disturb lysosomal autophagy to boost cascading enzymatic chemodynamic-starvation therapy

Cascading enzymatic therapy is a promising approach in cancer treatment. However, its effectiveness is often hindered by enzyme inactivation, limited exposure of active sites, cancer cell self-protection mechanisms such as autophagy, and non-specific toxicity, which can lead to treatment failure. To address these challenges, we used a low-temperature aqueous-phase synthesis method to create semi-crystalline, water-dispersible fluorescent COF nanospheres. These nanospheres can stably load glucose oxidase (GOx) and ultrafine Fe2O3 nanozymes, allowing for convenient coating with tumor cell membranes to form a uniform tumor-targeted cascading enzymatic nanosystem (CFGM). This system promotes a cycle of tumor glucose depletion, reactive oxygen species (ROS) generation, and oxygen production, facilitating tumor-targeted starvation therapy (ST) and chemodynamic therapy (CDT). Notably, the semi-crystalline COF carrier within this system can degrade slowly under mildly acidic conditions, forming large aggregates that damage lysosomes and disrupt lysosomal autophagy, thereby eliminating the autophagy protection of cancer cells activated by the combined ST. This synergistic approach enhances the catalytic inhibition of tumors. Our research thus provides an alternative COF-based platform and strategy for effective cancer treatment.

Multifunctional coating with hydrophobicity, antibacterial and flame-retardant properties on cotton fabrics by layer-by-layer self-assembly curing of phytic acid and a tyrosine-derived hyperbranched benzoxazine

The inherent hydrophilicity and biocompatibility of cotton fabrics facilitated bacterial proliferation and safety concerns, limiting their applications. To address these issues, tyrosine-derived polyetherimide, bis(3-aminopropyl)-terminated poly(dimethylsiloxane), and paraformaldehyde were used to synthesize hyperbranched benzoxazine THB-BOZs-PDMS with potent antibacterial and antibiofilm activity. The protonated amino groups of benzoxazine facilitated electrostatic interactions with negatively charged bacteria, and hydrophobic interactions disrupted the cell membrane, leading to bacteria death. Notably, phytic acid interacts with benzoxazines through intermolecular forces, with its phosphoric acid groups facilitating the curing of benzoxazines, thereby imparting flame-retardant properties to the material. Consequently, a multifunctional coating was developed via LBL self-assembly and in-situ curing of benzoxazines and phytic acid on the fabric surfaces. The successful deposition of the coating was confirmed through compositional analysis and morphological characterization. After 4 cycles of LBL modification, the fabrics TBP + PA-CF-4 displayed outstanding antibacterial efficacy, bacterial anti-adhesion properties, and heat resistance. Furthermore, TBP + PA-CF-4 exhibited notable washing and mechanical durability, attributed to the stability conferred by in-situ cured of layers. Compared with other reported modified fabrics, TBP + PA-CF-4 displayed more comprehensive overall performances. These multifunctional fabrics provided a sustainable approach for advancing personal protective materials and public decoration, particularly suited for use in high-humidity environments or military settings.

Fabrication of bamboo nanocellulose fibril-based food packaging with dual-antimicrobial property

The development of cellulose-based packaging films with excellent antimicrobial properties and biocompatibility has garnered significant attention. In this work, nanocellulose fibrils (NCFs) derived from from bamboo parenchyma cells were utilized to fabricate nanocomposite film with antimicrobial properties. This system exhibited distinct release behaviors for two antimicrobial agents, with the slow release of Ag nanoparticle (AgNP) in the initial stage contributed to delaying food spoilage, while the subsequent pH change in the microenvironment facilitated the release of essential oil of sour orange blossoms (SEO) for secondary antimicrobial activity. Additionally, the composite film demonstrated improved thermal stability and UV blocking capacity. Moreover, AgNP has been proven to enhance the mechanical properties, with the tensile strength of the novel composite film increasing by 34.85 % compared to control group. The water vapor permeability and oxygen permeability of the novel composite film were reduced, which could potentially reduce weight loss and slow down the rate of after-ripening. Following the acidification treatment, the films containing EO@MPN (essential oil encapsulated with metal-polyphenol network) component performed different antimicrobial patterns, indicating their pH-responsive antimicrobial capabilities, and they are effective against both Gram-positive and Gram-negative bacteria. After a 24-h exposure to a food simulant, the release amount of Ag was measured at 67.6 μg/dm2, within the acceptable limit, and the release profile of Ag was characterized. Cytotoxicity and Live/Dead staining tests confirmed that the novel composite film film had no significant toxicity, thus making it safe for application in food preservation. Furthermore, in a 15-day preservation experiment with mangoes, the novel composite film demonstrated the best performance, underscoring its potential as a sustainable antimicrobial packaging material.

Characteristics of corn starch/polyvinyl alcohol composite film with improved flexibility and UV shielding ability by novel approach combining chemical cross-linking and physical blending

With the aim of effectively improving the performance of bio-friendly food packaging and circumventing the hazards associated with petroleum-based plastic food packaging, composite films of corn starch and polyvinyl alcohol were prepared using a new method that involved chemical cross-linking of glutaraldehyde and blending with cinnamon essential oil nanoemulsion (CNE). Glutaraldehyde and CNE enhance the film's network structure by chemical bonding and hydrogen bonding, respectively. This results in improved surface smoothness, mechanical properties, and UV shielding ability of the film. However, the films' surface hydrophilicity increased as a result of CNE, which is harmful for food preservation in high humidity. Overall, glutaraldehyde and CNE have a synergistic effect on some of the properties of the film which is mainly attributed to the films' structure improvement. The films have great potential for preparing flexible and UV-shielding films and offer new ideas for developing biodegradable films.

Characterization optimization of synthesis Chitosanclay/benzoin/Fe3O4 composite for adsorption of Thionine dye by design expert study

A novel composite material, magnetic chitosan-clay/benzoin/Fe3O4 (CS-CY/Benz/Fe3O4), was synthesized for effectively removing thionine dye (TH) from water solutions. The structural integrity and suitability of CS- CY/Benz/Fe3O4 composite for adsorption purposes were validated through extensive characterization techniques including BET, XRD, FTIR, and SEM. The adsorption efficiency was optimized through a Box-Behnken design (BBD) employing response surface methodology (RSM), focusing on variables such as adsorbent dose (A: 0.02-0.08 g), solution pH (B: 4-10), temperature (C: 30-60 °C), and time (D: 5-30 min). Experimental results revealed a maximum TH removal of 99% with significant interactions between temperature (C) and time (D) (p-value = 0.0001). The optimal conditions for TH removal were determined as pH ~ 5.91, adsorbent dosage of 0.08 g, temperature of 54.34 °C, and time of 29.7 min. The investigation of kinetics revealed that the adsorption process conformed to a pseudo-second-order (PSO) model, while the equilibrium data were effectively described by the Freundlich isotherm model. At a temperature of 333.15 K and a TH concentration of 350 mg/L, the adsorption capacity was determined to be 660.86 mg/g. The mechanism of adsorption encompassed various interactions such as electrostatic attractions, n-π interactions, hydrogen bonding, and Yoshida H-bonding. Particularly, the CS-CY/Benz/Fe3O4 composite demonstrated strong magnetic responsiveness, enabling straightforward separation from water using an external magnetic field after adsorption. Particularly, the CS-CY/Benz/Fe3O4 composite demonstrated strong magnetic responsiveness, enabling straightforward separation from water using an external magnetic field after adsorption. This research contributes important findings to the advancement of magnetic chitosan-based composites for efficient removal of TH dye pollutants from water environments.

Rapid in situ formation of κ-carrageenan-carboxymethyl chitosan-kaolin clay hydrogel films enriched with arbutin for enhanced preservation of cherry tomatoes

Food waste resulting from perishable fruits and vegetables, coupled with the utilization of non-renewable petroleum-based packaging materials, presents pressing challenges demanding resolution. This study addresses these critical issues through the innovative development of a biodegradable functional plastic wrap. Specifically, the proposed solution involves the creation of a κ-carrageenan/carboxymethyl chitosan/arbutin/kaolin clay composite film. This film, capable of rapid in-situ formation on the surfaces of perishable fruits, adeptly conforms to their distinct shapes. The incorporation of kaolin clay in the composite film plays a pivotal role in mitigating water vapor and oxygen permeability, concurrently bolstering water resistance. Accordingly, tensile strength of the composite film experiences a remarkable enhancement, escalating from 20.60 MPa to 34.71 MPa with the incorporation of kaolin clay. The composite film proves its efficacy by preserving cherry tomatoes for an extended period of 9 days at 28 °C through the deliberate delay of fruit ripening, respiration, dehydration and microbial invasion. Crucially, the economic viability of the raw materials utilized in the film, coupled with the expeditious and straightforward preparation method, underscores the practicality of this innovative approach. This study thus introduces an easy and sustainable method for preserving perishable fruits, offering a cost-effective and efficient alternative to petroleum-based packaging materials.

Arginine and tryptophan-rich dendritic antimicrobial peptides that disrupt membranes for bacterial infection in vivo

The potent antibacterial activity and low resistance of antimicrobial peptides (AMPs) render them potential candidates for treating multidrug-resistant bacterial infections. Herein, a minimalist design strategy was proposed employing the "golden partner" combination of arginine (R) and tryptophan (W), along with a dendritic structure to design AMPs. By extension, the α/ε-amino group and the carboxyl group of lysine (K) were utilized to link R and W, forming dendritic peptide templates αRn(εRn)KWm-NH2 and αWn(εWn)KRm-NH2, respectively. The corresponding linear peptide templates R2nKWm-NH2 and W2nKRm-NH2 were used as controls. Their physicochemical properties, activity, toxicity, and stability were compared. Among these new peptides, the dendritic peptide R2(R2)KW4 was screened as a prospective candidate owing to its preferable antibacterial properties, biocompatibility, and stability. Additionally, R2(R2)KW4 not only effectively restrained the progression of antibiotic resistance, but also demonstrated synergistic utility when combined with conventional antibiotics due to its unique membrane-disruptive mechanism. Furthermore, R2(R2)KW4 possessed low toxicity (LD50 = 109.31 mg/kg) in vivo, while efficiently clearing E. coli in pulmonary-infected mice. In conclusion, R2(R2)KW4 has the potential to become an antimicrobial regent or adjuvant, and the minimalist design strategy of dendritic peptides provides innovative and encouraging thoughts in designing AMPs.

Edible chitosan-based Pickering emulsion coatings: Preparation, characteristics, and application in strawberry preservation

The long-term application of plant essential oils in food preservation coatings is limited by their poor water solubility and high volatility, despite their recognized synergistic antimicrobial effects in postharvest fruit preservation. To overcome these limitations, a Pickering emulsion loaded with thyme essential oil (TEO) was developed by utilizing hydrogen bonding and electrostatic interactions to induce cross-linking of chitosan particles. This novel emulsion was subsequently applied in the postharvest storage of strawberries. The shear-thinning behavior (flow index <1) and elastic gel-like characteristics of the emulsion made it highly suitable for spray application. Regarding TEO release, the headspace concentration of TEO increased from 0.21 g/L for pure TEO to 1.86 g/L after two instances of gas release due to the stabilizing effect of the chitosan particles at the oil-water interface. Notably, no phase separation was observed during the 10-day storage of the emulsion. Consequently, the emulsion was successfully employed for the postharvest storage of strawberries, effectively preventing undesirable phenomena such as weight loss, a decrease in firmness, an increase in pH, and microbial growth. In conclusion, the developed Pickering emulsion coating exhibits significant potential for fruit preservation applications, particularly for extending the shelf life of strawberries.

Interaction mechanisms of edible film ingredients and their effects on food quality

Traditional food packaging has problems such as nondegradable and poor food safety. Edible films play an important role in food packaging, transportation and storage, having become a focus of research due to their low cost, renewable, degradable, safe and non-toxic characteristics. According to the different materials of edible films substrate, edible films are usually categorized into proteins, polysaccharides and composite edible films. Functional properties of edible films prepared from different substrate materials also vary, single substrate edible films are defective in some aspects. Functional ingredients such as proteins, polysaccharides, essential oils, natural products, nanomaterials, emulsifiers, and so on are commonly added to edible films to improve their functional properties, extend the shelf life of foods, improve the preservation of sensory properties of foods, and make them widely used in the field of food preservation. This paper introduced the classification, characteristics, and modification methods of common edible films, discussed the interactions among the substrate ingredients of composite edible films, the influence of functional ingredients on the properties of edible films, and the effects of modified edible films on the quality of food, aiming to provide new research ideas for the wide application and further study of edible films.

Recent advances on the preparation conditions, structural characteristics, physicochemical properties, functional properties and potential applications of dialdehyde starch: A review

Starch, a natural storage polysaccharide of plant kingdom, has many industrial applications. However, native starch has some inherent shortages, which can be overcome by structural modification. Dialdehyde starch, one kind of oxidized starch produced by periodate oxidation, has good physical properties and bioactivities with wide applications in different fields. Dialdehyde starch is typically achieved by oxidizing native starch slurry through periodate oxidation under controlled reaction conditions. Several factors including the source of starch, the type of oxidant, the molar ratio of oxidant to starch, reaction temperature, reaction time and solution pH value can influence the synthesis of dialdehyde starch. Dialdehyde starch shows different spectroscopic/chromatographic characters and physicochemical properties from native starch. Moreover, dialdehyde starch exhibits good antioxidant activity, antimicrobial activity and cross-linking property. Based on these functional properties, dialdehyde starch has shown application potentials in food packaging, thermoplastic production, enzyme immobilization, heavy metal ion adsorption, drug delivery, wood adhesion and leather tanning. In this review, the preparation conditions, structural characteristics, physicochemical properties, functional properties and potential applications of dialdehyde starch are summarized for the first time. The future research and development prospects of dialdehyde starch are also discussed.