Search Results (255)

Mechanical damage and microbial contamination are major challenges in the postharvest logistics of perishable fruit. In this study, two types of functionally modified chitosan-based aerogel pads were developed to enhance cushioning and preservation of wax apples. A chitosan/polyvinyl alcohol (CP) aerogel was first optimized by adjusting solid content, CS:PVA ratio, and crosslinker concentration. The optimal formulation (2% solids, 1:1 CS: PVA, 3% glutaraldehyde) exhibited a uniform porous structure and improved compressive strength. A chitosan/montmorillonite (CM) aerogel with 5% montmorillonite (MMT) showed high porosity, low density, and excellent cyclic stability. Incorporating 10% copper nanoparticle-loaded antibacterial fibers (CuNPs-TNF) into CM aerogels yielded CM-Cu aerogels with enhanced cushioning and antimicrobial properties. Under simulated transport and cold storage conditions, all aerogel-packaged groups reduced mechanical damage and decay of wax apples. Compared to the control, the CM-Cu group showed 66% lower decay, 5% less weight loss, 6 N greater firmness, 7% less juice yield, and a 13% reduction in relative electrical conductivity. Additionally, it better preserved fruit color and total soluble solids, extending shelf life by 4 d at 20 °C. These results demonstrate the potential of chitosan-based aerogels as multifunctional packaging materials that combine mechanical protection with antimicrobial activity for perishable fruit preservation. Full article

This study aimed to develop an environmentally friendly composite film with effective antibacterial and preservation properties. Silver nanoparticles (AgNPs) were green-synthesized using grape skin extract as a natural reducing agent and incorporated into a PVA/chitosan matrix. The composition of the extract and the structural characteristics of the AgNPs were characterized by UPLC-MS and TEM. The barrier, mechanical performance, antibacterial, and fruit preservation properties of the resulting films were systematically evaluated. The results showed that the incorporation of AgNPs significantly improved the water vapor and oxygen barrier properties of the film and imparted excellent broad-spectrum antibacterial activity. In grape storage experiments, films with higher AgNPs content effectively delayed skin aging and moisture loss, maintaining better visual quality of the fruit. This work provides a green and feasible approach for the preparation of nanoparticle-enhanced antibacterial packaging materials based on natural products, with promising application potential. Full article

Degradable polymers are essential in tissue engineering due to their capacity to mimic the extracellular matrix and promote regeneration. To be functional, they require interconnected porous structures that allow for nutrient exchange and cell migration. Although methods exist to optimize porosity, many compromise biocompatibility because pore-forming substances are used. In this context, hydrothermal pretreatment emerges as a promising technique to simultaneously improve both the porosity and mechanical properties of polymers without using potentially toxic reagents. This study proposes a novel route that combines hydrothermal pretreatment with supercritical CO₂ foaming, evaluating whether the structures obtained present better characteristics for biomedical applications compared to those obtained using supercritical CO₂ foaming alone. A screening of this novel route has been tested on individual polymers (PCL, PLA, PLGA, PVA, PBS, chitosan) and various binary combinations (PCL-PBS, chitosan-PBS, PVA-PBS, PLGA-PEDOT: PSS). The resulting materials were characterized using electron microscopy to analyze pore diameter and distribution, as well as structural stability and homogeneity. For the individual polymers, the hydrothermal pretreatment clearly improved the results obtained. However, most polymer combinations showed drawbacks such as mass losses, heterogeneity, or unsatisfactory pore formation. This research highlights the potential of hydrothermal pretreatment to optimize scaffolds, which is crucial for viability in biomedical applications. Full article

Pineapple waste is an underexplored source for producing nanocomposites, from which nanocellulose, namely cellulose nanocrystals (CNCs) or cellulose nanofibers (CNFs), can be produced. This review summarizes extraction methods from different pineapple residues (leaves, crown leaves, stem, peel, pulp, and pomace), covering top-down processes (hydrolysis, oxidation, carboxymethylation, and mechanical fibrillation) and bottom-up strategies (ionic liquids and deep eutectic solvents). The review examines the influence of the morphology and crystallinity of nanocellulose on the functional performance of the nanocomposites. Strategies for processing pineapple-derived nanocellulose composites are analyzed by technique (solution casting, film stacking, and melt blending/extrusion) and polymer matrices (starch, PVA, chitosan, PLA, PHBV, PBAT, proteins, and polysaccharides), including typical loading levels for most polymer-reinforced systems (0.5–5 wt.%), while higher levels (15–50 wt.%) are used in particular cases such as PVA, CMC, and cellulosic matrices. The impact on mechanical strength, barrier behavior, UV shielding, and optical properties is summarized, along with reports of self-reinforced and hybrid cellulose-derived matrices. A benchmarking section was prepared to show nanocellulose loading ranges, trends in properties, and processing-relevant information categorized by type of matrix. Finally, the review describes the potential roles of pineapple waste within a bioeconomy context and identifies some extraction by-products that could be incorporated into diverse value chains. Full article

Aluminum alloys used in harsh environments often suffer from inadequate protection due to the limited compactness and stability of existing chromate-free conversion coatings. This study designs and optimizes a corrosion-resistant vanadium-based conversion coating on 6061 aluminum alloy and investigates the influence of additives on its structure and performance. The effects of solution pH (2–4), reaction temperature (35–75 °C), and immersion time (10–30 min) on coating corrosion resistance were examined. The optimal parameters were determined as pH = 3, 55 °C, and 25 min, yielding a compact coating with excellent corrosion resistance (i_corr = 0.335 μA·cm⁻², E_corr = −0.596 V, |Z| = 48.7 kΩ·cm²). To further enhance performance, polyvinyl alcohol (PVA), chitosan (CS), and a combination of sodium hexametaphosphate and cerium nitrate (SHMP + Ce(NO₃)₃) were introduced into the conversion solution. Characterization by SEM, AFM, and contact angle measurements showed that SHMP + Ce(NO₃)₃ significantly improved coating uniformity and compactness (Rq = 131 nm, Ra = 107 nm), resulting in superior corrosion resistance (i_corr = 0.055 μA·cm⁻², |Z| = 67.9 kΩ·cm²). The coating exhibited strong adhesion (grade 5B) and no visible corrosion after 72 h of neutral salt spray exposure, demonstrating excellent protective capability. In contrast, PVA produced porous coatings with reduced resistance, while CS provided only limited improvement. Full article

Biodegradable chitosan/poly(vinyl alcohol) (PVA) composite films were reinforced either with nanocrystalline cellulose (CNC) or nano-lignocellulose (NLC) and evaluated across a polyparametric design of five matrix ratios and three filler levels for active food packaging applications. ATR-FTIR, DSC, XRD, and SEM demonstrated that 1–5% nanocellulose loading induced a single relaxation temperature (T_g), homogenized the morphology, and enhanced the crystallinity of blend material, evidencing improved thermodynamic compatibility. SEM confirmed uniform filler dispersion up to 5% loading in PVA-rich matrices, whereas limited aggregation appeared in chitosan-dominant systems. CO₂ barrier property (CO₂ permeability coefficients) was diminished by more than two orders of magnitude and fell below 0.01 Barrer in CNC-filled 25-75 and NLC-filled 75-25 blends, while permeability to O₂ and N₂ remained undetectable under identical conditions. Meanwhile, Young’s modulus increased to 3.9 GPa, and tensile strengths of up to 109 MPa were achieved, without affecting the ductility in specific loading values. These data confirm that tailored selection of the filler/matrix combination, rather than elevated nanocellulose content, can simultaneously optimize barrier performance and mechanical integrity. The study therefore offers a scalable, water-based route for producing optically transparent nanocomposite membranes that satisfy either strict modified atmosphere or/and rigid packaging applications and advance the transition toward compostable/or even edible high-performance food contact materials. Full article

Zinc ions, as essential trace elements in the human body, play a crucial role in promoting wound healing. They have significant applications in the medical field. In this paper, chitosan (CS)/polyvinyl alcohol (PVA)/zinc gluconate hydrogel was synthesized via gamma ray irradiation cross-linking. The hydrogel exhibited excellent antibacterial properties, and could continuously release zinc ions. Antibacterial assays demonstrated that the combination of CS and zinc ions improved the antibacterial properties of hydrogel. The inhibition zones against both Staphylococcus aureus and Escherichia coli exceed 12 mm. The cell viability can reach 108.25%. The prepared hydrogel could continuously release zinc ions over a period of 70 h. The pore and chemical structure were, respectively, performed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). And its comprehensive properties, such as gel content, water evaporation ratio and swelling behavior were investigated. The hydrogels showed potential application value in the hydrogel dressing for zinc ion delivery. Full article

The burning of coal in thermal power plants throughout Serbia produces significant amounts of industrial waste, primarily in the form of fly ash, boiler ash, and slag. Given their annual production, availability, and fine grain structure, it is necessary that sustainable strategies are developed for their reuse, instead of depositing them directly in landfills. In this research, the possibility of using fly ash, slag, and diatomaceous earth as raw materials for the synthesis of geopolymers at low temperatures was examined, in order to replace cement in construction materials, with the aim of reducing carbon dioxide emissions. Special emphasis was put on the effect of addition of organic macromolecules—polyvinyl alcohol (PVA), chitosan, and starch—upon the structure and mechanical properties of the obtained materials. In addition, the behavior of the materials with regard to the leaching of heavy metals in different environmental conditions was examined. Chemometric methods of multivariate analysis were used to examine the correlations between the obtained physical–chemical parameters, while the dependence of mechanical properties on the composition of the raw mixture was analyzed using the Mixture Design of Experiments method. The results obtained indicate that the examined waste materials have potential to be used as an environmentally friendly alternative to cement. The addition of PVA and chitosan had a positive effect on the mechanical properties of the geopolymers, with the highest strength achieved in formulations based solely on fly ash, containing 2.5% PVA, which reached 12.6 MPa. It was also shown that the addition of 30% diatomaceous earth increases the density and compressive strength of the material, while reducing the number of microcracks present in its structure, with a compressive strength of 13 MPa. Full article

The release of industrial wastewater containing synthetic dyes poses a major environmental issue because of their toxicity and persistence. Among treatment options, natural materials, specifically chitosan–polyvinyl alcohol (chitosan–PVA) hydrogel, have shown high effectiveness in dye removal due to their abundant functional groups and proven adsorption capacity. However, optimizing these systems experimentally is often time-consuming and requires many resources. This study introduces an artificial neural network (ANN) model to predict the adsorption capacity ($q_e$) and the time needed to reach equilibrium during the removal of tartrazine dye using chitosan–PVA hydrogel beads of different mean sizes, categorized as small, medium and large (2.1, 2.5, and 3.2 mm, respectively) at temperatures of 10, 30, and 50 °C The ANN model was compared with traditional kinetic models: pseudo-first-order, pseudo-second-order, and Elovich. Results showed that the ANN outperformed conventional models in predicting $q_e$ and equilibrium time, especially for small beads at 10 °C, where it predicted $q_e$ = 945 mg/g in 40 h with an $R^2$ of $0.9428$. Across all conditions, the ANN achieved strong correlation coefficients ($R^2>0.94$) and significantly shortened prediction times. Although the pseudo-second-order model achieved high $R^2$ values (up to $0.9929$), it took over 72 h to reach equilibrium prediction. These results demonstrate that ANN-based modeling can reduce experimental effort by up to 50% in prediction time while maintaining high predictive accuracy ($R^2>0.94$), offering a sustainable and efficient approach for designing wastewater treatment processes. Full article

Shape memory polymers (SMPs) are a class of smart materials that exhibit unique shape-fixing and recovery abilities, attracting wide attention for applications in electronics, aerospace, and biomedical engineering. Chitosan (CS) as a renewable biopolymer, possessing good biocompatibility, biodegradability, and antimicrobial properties; its use as a matrix enhances the environmental compatibility and bio-adaptability of SMPs. MXene, as a novel two-dimensional material, is characterized by high electrical conductivity, abundant surface functional groups and good hydrophilicity, showing potential in energy storage, electromagnetic shielding and sensing. In this work, CS and poly (vinyl alcohol) (PVA) were used as the polymer matrix, and carbon nanotubes (CNTs) together with MXene were introduced as co-fillers to construct multifunctional composites. The effect of the CNTs/MXene hybrid fillers on mechanical properties, electromagnetic shielding and multi-stimuli-responsive shape memory behavior was systematically investigated. After ratio optimization, the composites showed excellent comprehensive performance: tensile strength reached up to 20.0 MPa, Young’s modulus up to 292.2 MPa, and maximum elongation at break of 23.2%; electromagnetic interference shielding effectiveness (SE_T) in the X-band (8.2–12.4 GHz) reached a maximum of 10.6 dB; shape fixation rates exceeded 90%; under thermal stimulation, a shape recovery ratio of 98.3% was achieved within 41.7 s; light-driven recovery rate reached 86.5% with a minimal recovery time of 82.3 s; under electrical stimulation the highest recovery rate was 94.1% with a shortest recovery time of 30 s. This study successfully prepared functional multi-stimuli-responsive shape memory composite films and provided a new strategy for the design of green smart materials. Full article

Chitosan is a biopolymer with excellent properties such as biodegradability, biocompatibility, bioactivity, and non-toxicity, making it an attractive material for various applications. In this study, to enhance these properties particularly for the development of food coatings chitosan derivatives (1,2,3-triazoles) were synthesized via microwave-assisted 1,3-dipolar cycloaddition (CuAAC) using different terminal alkynes. The resulting compounds were obtained in high yields 79.7–88.0% and characterized by vibrational (IR) and electronic (UV–Visible) spectroscopy. Films were formed by combining the derivatives with PVA and characterized using differential scanning calorimetry (DSC), tensile strength testing, and water vapor permeability analysis. The resulting films exhibited improved mechanical properties, homogeneous thicknesses, low-porosity surfaces, and favorable barrier properties, highlighting their potential applicability as food coating materials. Full article

The valorization of agricultural by-products through their integration into biodegradable materials represents a promising approach for sustainable food preservation. In this study, nanostructured chitosan/polyvinyl alcohol (PVA)/orange peel–bagasse waste (OPB) (0.125%, 0.25%, and 0.5% OPB) films were developed and characterized for their physicochemical, mechanical, and biodegradation properties. Scanning electron microscopy and confocal laser scanning microscopy revealed that OPB concentration influenced structural homogeneity. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) revealed possible molecular interactions among components through hydrogen bonding (peaks at 1570, 1416 cm⁻¹, and 1020 cm⁻¹) and imine (C = N) formation (broadening of the peak at 1425 cm⁻¹). As OPB increased, water vapor diffusion and film rigidity increased, while elongation at break decreased. After composting, weight loss was 93.7% and 100% for the chitosan and PVA films, respectively. For the nanostructured films, weight loss was between 94.7% (30PVA/0.5OPB) and 99.7% (30PVA/0.125OPB). Regarding ATR-FTIR of the blends, the intensity of the peaks located between 3625 and 3005 cm⁻¹, at 2919 cm⁻¹, at 1729 cm⁻¹, at 1621 cm⁻¹, at 1521 cm⁻¹, and between 1160 and 885 cm⁻¹, corresponding to the OPB functional groups, decreased. These results demonstrate that incorporating citrus waste enhances biodegradability and provides films barrier properties suitable for fresh produce preservation. Full article

Diabetic foot ulcers (DFUs) are complex to heal and can lead to amputations and high healthcare costs. To address this, a promising alternative is the creation of electrospun fiber scaffolds for wound dressings. This study fabricated these scaffolds using a blend of natural polymers—chitosan (CTS), polyvinyl alcohol (PVA), and hyaluronic acid (HA)—along with antibacterial silver (Ag) and zinc oxide (ZnO) nanoparticles. The researchers conducted comprehensive analyses, including physicochemical, morphological, and biological assessments. The Ag structures showed potential as microbicidal agent, while the ZnO nanoparticles demonstrated photoactivity and the ability to generate reactive oxygen species (ROS) for antibacterial action. The resulting PVA-CTS-HA-Ag-ZnO scaffolds were found to be both hemocompatible and non-hemolytic, meaning they are safe for use with blood. The cytotoxicity evaluation using the ISO 10993-5 standard showed that the incorporation of CTS and HA decreased cytotoxicity of pure PVA, obtaining non-cytotoxic scaffolds (viability > 70%). Electrospun scaffolds composed with Ag-ZnO NPs in 50-50 and 70-30 ratios also maintained this biocompatibility, while the 30-70 ratio (Ag-ZnO) showed a cytotoxic effect, suggesting a ZnO concentration-dependent effect. These findings confirm that these materials are suitable for supporting skin cell regeneration, having a high potential for use as interactive dressings for treating chronic wounds. Full article

Winery wastewater, characterized by high organic load, fluctuating pH, and seasonal variability, presents a major environmental challenge for sustainable water management in viticulture regions. Recent advances in bio-based polymer composites, particularly those incorporating cellulose and chitosan matrices blended with synthetic polymers such as polyacrylamide (PAM), polyvinyl alcohol (PVA), and polyethylene glycol (PEG), provide promising possibilities for effective wastewater treatment and water reuse in irrigation. This review critically explores the synthesis, structural properties, and functional performance of cellulose/chitosan-based composites, with a particular emphasis on their adsorption, flocculation, and biodegradability in the context of winery effluent treatment. Evidence from recent laboratory- and pilot-scale studies highlights the significance of pH-responsive functional groups, electrostatic interactions, and hydrogen bonding in controlling pollutant capture and regeneration efficiency. While notable removal efficiencies of these composites have been demonstrated to exceed 85–95% for COD, 80–98% for turbidity, and >90% for heavy metals, challenges remain in terms of regeneration, long-term field applicability, and scale-up. Overall, biopolymer composites represent a promising pathway toward sustainable wastewater treatment and irrigation reuse in winery operations. Full article

In the field of water treatment, the development of efficient and environmentally friendly antibacterial materials to combat pathogenic contamination is of great significance. This work aimed to synthesize copper nanoparticles (CuNPs) using Rosa roxburghii extract (RRT) and Trichoderma harzianum mycelia-free cell filtrate (MFCF) as reducing agents. It was found that RRT-CuNPs had higher antibacterial ability than MFCF-CuNPs. Therefore, RRT-CuNPs were selected for further study. Through a functionalization modification strategy, polyvinyl alcohol (PVA) and chitosan (CTS) served as carrier matrices, with RRT-CuNPs as the highly efficient antibacterial active component and montmorillonite (MMT) as a reinforcing filler. The CTS/PVA/MMT/RRT-CuNPs composite gel beads were successfully fabricated via a cross-linking and blending method. For RRT-CuNPs-based gel beads, Fourier transform infrared spectroscopy (FTIR) displays that the composite hydrogel particles contain characteristic peaks of PVA, CTS, and MMT. By comparison, it is confirmed that MMT acts as both a reinforcing agent and a molecular structure regulator through interfacial interactions. X-ray diffraction (XRD) shows that MMT and CuNPs are dispersed in the particles. The study illustrates that the optimal initial concentrations of MMT, CTS, and CuNPs added to RRT-CuNPs-based composite gel beads were 4, 30, and 0.5 g/L, respectively. The prepared composite gel beads exhibited significant inhibitory activity towards Gram–positive bacteria (S. aureus) and Gram–negative bacteria (P. aeruginosa and E. coli), acquiring inhibition zone diameters of nearly 21 mm. As the dose of gel beads was 0.3 g/L and the action time was four h, the inhibition rate reached 100% through the plate counting method analysis. In conclusion, RRT-CuNPs-based composite gel beads have excellent antimicrobial activity, showing high potential application in the fields of water treatment. Full article