Highly Compressible, Superabsorbent, and Biocompatible Hybrid Cryogel Constructs Comprising Functionalized Chitosan and St. John's Wort Extract

Biobased porous hydrogels enriched with phytocompounds-rich herbal extracts have aroused great interest in recent years, especially in healthcare. In this study, new macroporous hybrid cryogel constructs comprising thiourea-containing chitosan (CSTU) derivative and a Hypericum perforatum L. extract (HYPE), commonly known as St John's wort, were prepared by a facile one-pot ice-templating strategy. Benefiting from the strong interactions between the functional groups of the CSTU matrix and those of polyphenols in HYPE, the hybrid cryogels possess excellent liquid absorption capacity, mechanical resilience, antioxidant performance, and a broad spectrum of antibacterial activity simultaneously. Thus, owing to their design, the hybrid constructs exhibit an interconnected porous architecture with the ability to absorb over 33 and 136 times their dry weight, respectively, when contacted with a phosphate buffer solution (pH 7.4) and an acidic aqueous solution (pH 2). These cryogel constructs have extremely high compressive strengths ranging from 839 to 1045 kPa and withstand elevated strains of over 70% without developing fractures. Moreover, the water-swollen hybrid cryogels with the highest HYPE content revealed a complete and instant shape recovery after uniaxial compression. The incorporation of HYPE into CSTU cryogels enabled substantial improvement in scavenging reactive oxygen species and an expanded antibacterial spectrum toward multiple pathogens, including Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and fungi (Candida albicans). Cell viability experiments demonstrated the cytocompatibility of the 3D cryogel constructs, which did not induce changes in the fibroblast morphology. This work showcases a simple and effective strategy to immobilize HYPE extracts on CSTU 3D networks, allowing the development of novel multifunctional platforms with promising potential in hemostasis, wound dressing, and dermal regeneration scaffolds.

Trends in polysaccharide-based hydrogels and their role in enhancing the bioavailability and bioactivity of phytocompounds

Over the years, polysaccharides such as chitosan, alginate, hyaluronic acid, k-carrageenan, xanthan gum, carboxymethyl cellulose, pectin, and starch, alone or in combination with proteins and/or synthetic polymers, have been used to engineer an extensive portfolio of hydrogels with remarkable features. The application of polysaccharide-based hydrogels has the potential to alleviate challenges related to bioavailability, solubility, stability, and targeted delivery of phytocompounds, contributing to the development of innovative and efficient drug delivery systems and functional food formulations. This review highlights the current knowledge acquired on the preparation, features and applications of polysaccharide/phytocompounds hydrogel-based hybrid systems in wound management, drug delivery, functional foods, and food industry. The structural, functional, and biological requirements of polysaccharides and phytocompounds on the overall performance of such hybrid systems, and their impact on the application domains are also discussed.

Lignin - A green material for antibacterial application - A review

Lignin's antibacterial properties have become increasingly relevant due to the rise of microbial infectious diseases and antibiotic resistance. Lignin is capable of interacting electrostatically with bacteria and contains polyphenols that cause damage to their cell walls. These features make lignin a desirable material to exhibit antibacterial behavior. Therefore, lignin in antibacterial applications offers a novel approach to address the growing need for sustainable and effective antibacterial materials. Recent research has explored the incorporation of lignin in various biomedical applications, such as wound dressings, implants, and drug delivery systems, highlighting their potential as a sustainable alternative to synthetic antibacterial agents. Furthermore, the development of lignin-based nanomaterials with enhanced antimicrobial activity is an active area of research that holds great promise for the future. In this review, we have provided a summary of how lignin can be incorporated into different forms, such as composite and non-composite synthesis of antibacterial agents and their performances. The challenges and future considerations are also discussed in this review article.

Development of Plantago ovata seed mucilage and xanthan gum-based edible coating with prominent optical and barrier properties

This study investigates the fabrication of edible coating based on Plantago ovata seed mucilage (POSM). The films were prepared from POSM (1 %, w/v), glycerol (75 %, based on POSM mass), and xanthan gum (XG: 20, 30 and 40 %, based on POSM mass) by a casting method, and their physicochemical, mechanical, thermal, morphological, and barrier properties were determined. Results indicated the development of highly transparent (transparency values: 1.36 ± 0.05 to 2.42 ± 0.09) and hydrophobic films (contact angle: 101.57 ± 0.34 to107.08 ± 0.55o) with very low water vapor permeability (WVP: 2.77 ± 0.02 × 10-12 to 1.98 ± 0.04 × 10-12 g s-1m-1Pa-1), slight water solubility (31.14 ± 0.46 to 23.08 ± 0.82 %), and good mechanical properties (tensile strength: 30.87 ± 0.96 to 61.80 ± 0.71 MPa). Morphological studies also indicated smooth and uniform surfaces without pores and cracks. In addition, the films showed good antioxidant activity (61.46 to 68.71 %), and their antibacterial activity against E. coli, S. aureus and P. aeruginosa was also demonstrated. The applicability of the developed films to extend the shelf life of strawberries was shown by comparing the appearance of dip-coated strawberries and the control sample within 8 days at room temperature. Based on the results, the developed biofilms have great potential for edible coating and packaging applications.

Ice-Templated and Cross-Linked Xanthan-Based Hydrogels: Towards Tailor-Made Properties

The use of polysaccharides with good film-forming properties in food packaging systems is a promising area of research. Xanthan gum (XG), an extracellular polysaccharide, has many industrial uses, including as a common food additive (E415). It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. Nevertheless, XG-based polymer films have some disadvantages, such as poor mechanical properties and high hydrophilic features, which reduce their stability when exposed to moisture and create difficulties in processing and handling. Thus, the objective of this work was to stabilize a XG matrix by cross-linking it with glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, or epichlorohydrin below the freezing point of the reaction mixture. Cryogelation is an ecological, friendly, and versatile method of preparing biomaterials with improved physicochemical properties. Using this technique, XG-based cryogels were successfully prepared in the form of microspheres, monoliths, and films. The XG-based cryogels were characterized by FTIR, SEM, AFM, swelling kinetics, and compressive tests. A heterogeneous morphology with interconnected pores, with an average pore size depending on both the nature of the cross-linker and the cross-linking ratio, was found. The use of a larger amount of cross-linker led to both a much more compact structure of the pore walls and to a significant decrease in the average pore size. The uniaxial compression tests indicated that the XG-based cryogels cross-linked with 1,4-butanediol diglycidyl ether exhibited the best elasticity, sustaining maximum deformations of 97.67%, 90.10%, and 81.80%, respectively.

Correlation between Mechanical and Morphological Properties of Polyphenol-Laden Xanthan Gum/Poly(vinyl alcohol) Composite Cryogels

This study aimed to evaluate the effect of the synthesis parameters and the incorporation of natural polyphenolic extract within hydrogel networks on the mechanical and morphological properties of physically cross-linked xanthan gum/poly(vinyl alcohol) (XG/PVA) composite hydrogels prepared by multiple cryo-structuration steps. In this context, the toughness, compressive strength, and viscoelasticity of polyphenol-loaded XG/PVA composite hydrogels in comparison with those of the neat polymer networks were investigated by uniaxial compression tests and steady and oscillatory measurements under small deformation conditions. The swelling behavior, the contact angle values, and the morphological features revealed by SEM and AFM analyses were well correlated with the uniaxial compression and rheological results. The compressive tests revealed an enhancement of the network rigidity by increasing the number of cryogenic cycles. On the other hand, tough and flexible polyphenol-loaded composite films were obtained for a weight ratio between XG and PVA of 1:1 and 10 v/v% polyphenol. The gel behavior was confirmed for all composite hydrogels, as the elastic modulus (G') was significantly greater than the viscous modulus (G″) for the entire frequency range.

Chitosan Sponges with Instantaneous Shape Recovery and Multistrain Antibacterial Activity for Controlled Release of Plant-Derived Polyphenols

Biomass-derived materials with multiple features are seldom reported so far. Herein, new chitosan (CS) sponges with complementary functions for point-of-use healthcare applications were prepared by glutaraldehyde (GA) cross-linking and tested for antibacterial activity, antioxidant properties, and controlled delivery of plant-derived polyphenols. Their structural, morphological, and mechanical properties were thoroughly assessed by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and uniaxial compression measurements, respectively. The main features of sponges were modulated by varying the CS concentration, cross-linking ratio, and gelation conditions (either cryogelation or room-temperature gelation). They exhibited complete water-triggered shape recovery after compression, remarkable antibacterial properties against Gram-positive (Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes)) and Gram-negative (Escherichia coli (E. coli), Salmonella typhimurium (S. typhimurium)) strains, as well as good radical scavenging activity. The release profile of a plant-derived polyphenol, namely curcumin (CCM), was investigated at 37 °C in simulated gastrointestinal media. It was found that CCM release was dependent on the composition and the preparation strategy of sponges. By linearly fitting the CCM kinetic release data from the CS sponges with the Korsmeyer-Peppas kinetic models, a pseudo-Fickian diffusion release mechanism was predicted.

Macroporous 3D Chitosan Cryogels for Fastac 10EC Pesticide Adsorption and Antibacterial Applications

The pesticide pollution of surface water and wastewater has been recognized as a major worldwide concern due to their persistence in the aquatic environment and the potential adverse effects on human, flora, and fauna health. Apart from pesticides, bio-contamination with various bacterial populations leads to waterborne diseases. Hence, it becomes vital to remove the above-mentioned pollutants from water using a suitable process. Consequently, our study emphasized the potential benefits of a highly porous, chemically cross-linked 3D chitosan (CSGA) cryogel in the removal of pesticides and bacteria. The CSGA sponges were prepared using a facile and cost-effective approach that consisted of a three-step cryogenic process: (i) freezing at −18 °C, (ii) storage in a frozen state for a certain period, and (iii) thawing at room temperature. Batch adsorption experiments were performed under different environments, where the effects of several parameters, such as pH, contact time, and initial pollutant concentration were evaluated to identify the appropriate adsorption conditions for maximum pesticide removal. The CSGA-based cryogel sponges exhibited a theoretical maximum adsorption capacity of 160.82 mg g⁻¹ for the Fastac 10EC pesticide and very good recyclability at room temperature. In addition, the antibacterial activities of these sponges were also investigated against various bacterial pathogens. The rates of killing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus were close to 82%, 100%, and 99%, respectively. These results demonstrated that CSGA cryogels could be efficiently used in water remediation and find applications in the removal of pesticides and disinfection.

Multifunctional lignin-based nanocomposites and nanohybrids

Significant progress in lignins valorization and development of high-performance sustainable materials have been achieved in recent years. Reports related to lignin utilization indicate excellent prospects considering green chemistry, chemical engineering, energy, materials and polymer science, physical chemistry, biochemistry, among others. To fully realize such potential, one of the most promising routes involves lignin uses in nanocomposites and nanohybrid assemblies, where synergistic interactions are highly beneficial. This review first discusses the interfacial assembly of lignins with polysaccharides, proteins and other biopolymers, for instance, in the synthesis of nanocomposites. To give a wide perspective, we consider the subject of hybridization with metal and metal oxide nanoparticles, as well as uses as precursor of carbon materials and the assembly with other biobased nanoparticles, for instance to form nanohybrids. We provide cues to understand the fundamental aspects related to lignins, their self-assembly and supramolecular organization, all of which are critical in nanocomposites and nanohybrids. We highlight the possibilities of lignin in the fields of flame retardancy, food packaging, plant protection, electroactive materials, energy storage and health sciences. The most recent outcomes are evaluated given the importance of lignin extraction, within established and emerging biorefineries. We consider the benefit of lignin compared to synthetic counterparts. Bridging the gap between fundamental and application-driven research, this account offers critical insights as far as the potential of lignin as one of the frontrunners in the uptake of bioeconomy concepts and its application in value-added products.

A Comparative Analysis on the Effect of Variety of Grape Pomace Extracts on the Ice-Templated 3D Cryogel Features

Nowadays, there is a growing interest in developing functional packaging materials from renewable resources containing bioactive compounds (such as polyphenols) in order to reduce the use of petroleum-based plastics and their impact on the environment. In this regard, the effect of a variety and concentration of grape pomace extracts (Feteasca Neagra or Merlot) incorporated within ice-templated 3D xanthan-based composites was evaluated by considering their water content, surface and texture properties, radical scavenging and microbiological activities. The embedding of Feteasca Neagra or Merlot grape pomace extracts was studied by static water swelling and contact angle measurements, and SEM, EDX, and TGA analyses. The water contact angle results showed an increase in the surface hydrophobicity of the extract-loaded cryogels with an increase in extract content from 10 to 40 v/v%. SEM micrographs indicated that the entrapment of grape pomace extracts affected the morphology of the pore walls and reduced the pore sizes. The antioxidant activity of grape pomace extract-loaded composite cryogels was closely related to the total phenolic content of grape variety and to their concentration into matrices. The highly hydrophobic character of composite cryogels containing Merlot grape pomace extract and their remarkable antimicrobial activity indicates a great potential of these materials for food packaging applications.

New Trends in the Use of Volatile Compounds in Food Packaging

In the last years, many of the research studies in the packaging industry have been focused on food active packaging in order to develop new materials capable of retaining the active agent in the polymeric matrix and controlling its release into food, which is not easy in many cases due to the high volatility of the chemical compounds, as well as their ease of diffusion within polymeric matrices. This review presents a complete revision of the studies that have been carried out on the incorporation of volatile compounds to food packaging applications. We provide an overview of the type of volatile compounds used in active food packaging and the most recent trends in the strategies used to incorporate them into different polymeric matrices. Moreover, a thorough discussion regarding the main factors affecting the retention capacity and controlled release of volatile compounds from active food packaging is presented.