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In recent decades, significant progress has been made on the development of low environmental impact plastic materials, as alternatives to conventional plastics for food packaging. Research has focused on the...

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non-toxicity, low-density, biocompatibility properties, and low cost. [1][2][3][4][5] The main drawback associated with the use of cellulose in specific composites-related applications is its water sensitivity and ability to uptake significant amounts of moisture. [6][7][8] On the other hand, cellulose fibers have very good mechanical properties, and because of this, they have been employed to reinforce many petroleum polyolefins or bio-based resins. [9][10][11] Advances in the development of cellulose nanofibers and bacterial cellulose have led to many new generation cellulose composites with superior mechanical properties and functionality. [12][13][14][15][16] In addition, many different physicochemical methods have also been developed to extract cellulose from agricultural and food wastes including biomass that can potentially reduce deforestation related to cellulose production feedstock. [17][18][19][20] Many sustainable packaging solutions and technologies must guarantee product safety and increase shelf life while decreasing pollution related to nondegrading plastics. It is believed that biobased responsive polymers and composites can address this necessity if accompanying economic and environmental benefits are also demonstrated. This study is motivated by these recent advances. At the same time, recent awareness in reducing environmental plastic pollution has fueled a significant momentum towards using natural polymers Development of responsive bio-based and biodegradable materials is particularly important in food preservation and monitoring technologies. Although replacing conventional plastic products with sustainable alternatives is still a challenge, promising advances have been reported. In this work, the fabrication of responsive bio-composite films from polycaprolactone (PCL) and magnesium carbonate (MgCO 3 ), known as food additive E504 with melt impregnation into cellulose, is reported. Cellulose fibers are stained/coated with ethanoic curcumin solutions, primarily to protect them against oxidative degradation. The films demonstrate a strong antioxidant effect against fatty and aqueous food simulants with improved oxygen gas barrier properties. Interestingly, the natural chelation of curcumin with magnesium within the composites improves the bioavailability and antioxidant potency of curcumin. Moreover, the composites show reversible color change response detectable by the naked eye in basic solutions or vapors. This response is tested by placing the composite film inside a sealed plastic container containing shrimp at room temperature, but not in direct contact. Due to spoilage, a noticeable color change in the bio-composites is recorded. These simple, cost-effective, non-toxic, and paper-like flexible bio-composites can be fabricated on large scale and be used in diverse applications ranging from sustainable packaging to medical applications and freshness indicators.

Applications of cyanoacrylate monomers are generally limited to adhesives/glues (instant or superglues) and forensic sciences. They tend to polymerize rapidly into rigid structures when exposed to trace amounts of moisture. Transforming cyanoacrylate monomers into transparent polymeric films or coatings can open up several new applications, as they are biocompatible, biodegradable and have surgical uses. Like other acrylics, cyanoacrylate polymers are glassy and rigid. To circumvent this, we prepared transparent cyanoacrylate films by solvent casting from a readily biodegrade solvent, cyclopentanone. To improve the ductility of the films, poly(propylene carbonate) (PPC) biopolymer was used as an additive (maximum 5 wt.%) while maintaining transparency. Additionally, ductile films were functionalized with caffeic acid (maximum 2 wt.%), with no loss of transparency while establishing highly effective double functionality, i.e., antioxidant effect and effective UV-absorbing capability. Less than 25 mg antioxidant caffeic acid release per gram film was achieved within a 24-h period, conforming to food safety regulations. Within 2 h, films achieved 100% radical inhibition levels. Films displayed zero UVC (100–280 nm) and UVB (280–315 nm), and ~15% UVA (315–400 nm) radiation transmittance comparable to advanced sunscreen materials containing ZnO nanoparticles or quantum dots. Transparent films also exhibited promising water vapor and oxygen barrier properties, outperforming low-density polyethylene (LPDE) films. Several potential applications can be envisioned such as films for fatty food preservation, biofilms for sun screening, and biomedical films for free-radical inhibition.

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Walnut shell (WS) has been demonstrated to be a promising and sustainable reinforcement in polymer composites. However, the evaluation of the overall properties provided by this lignin-rich food residue to biopolymer composites, for their use in the food packaging market, has not been evaluated yet. In this work, composite films of thermoplastic starch (TPS) containing either WS or hydrolyzed WS (HWS) and plasticized with a polyglycerol were prepared by spray drying, followed by extrusion and compression molding. TPS composites with HWS exhibited excellent UV light-blocking properties and sustained antioxidant activity for 2 weeks, ideal for preserving fatty foods. Furthermore, the compatibility of WS with TPS has been improved after the hydrolysis of WS with acetic acid. This treatment reduced the dimensions of the WS particles and exposed their hydroxyl groups, improving their compatibility with TPS, and consequently enhancing the mechanical and water vapor barrier properties. Overall, the composites containing 5 wt % of HWS exhibited the best compromise between the mechanical properties and antioxidant activity. Moreover, these composites complied with the safety requirements of the EU legislation regarding the migration of substances from the packaging to the food, in order to be used as food contact materials.

The excellent catalytic properties of copper nanoparticles (CuNPs) for the degradation of the highly toxic and recalcitrant chlorpyrifos pesticide are widely known. However, CuNPs generally present low stability caused by their high sensitivity to oxidation, which leads to a change of the catalytic response over time. In the current work, the immobilization of CuNPs into a polycaprolactone (PCL) matrix via electrospinning was demonstrated to be a very effective method to retard air and solvent oxidation and to ensure constant catalytic activity in the long term. CuNPs were successfully anchored into PCL electrospun fibers in the form of Cu 2 O at different concentrations (from 1.25 wt % to 5 wt % with respect to the PCL), with no signs of loss by leaching out. The PCL mats loaded with 2.5 wt % Cu (PCL-2.5Cu) almost halved the initial concentration of pesticide (40 mg/L) after 96 h. This process was performed in two unprompted and continuous steps that consisted of adsorption, followed by degradation. Interestingly, the degradation process was independent of the light conditions (i.e., not photocatalytic), expanding the application environments (e.g., groundwaters). Moreover, the PCL-2.5Cu composite presents high reusability, retaining the high elimination capability for at least five cycles and eliminating a total of 100 mg/L of chlorpyrifos, without exhibiting any sign of morphological damages.