Supramolecular Chemistry-Driven Preparation of Nanostructured, Transformable, and Biologically Active Chitosan-Clustered Single, Binary, and Ternary Metal Oxide Bioplastics

Evaporation-Induced Reticular Growth of UiO-66_NH2 in Chitosan Films: Adsorption of Iodine

Metal-organic frameworks (MOFs) combined with polymers as hybrid materials offer numerous advantages such as enhanced performances through synergistic effects at their interface. The primary challenge in developing polymer/MOF hybrid matrix films is ensuring optimal dispersion and strong adhesion of crystalline MOFs to the polymer without aggregation, weak interaction, or phase separation. In this study, hierarchically porous UiO-66_NH2/chitosan (ZrCSx-f) films were designed by crystallizing UiO-66_NH2 within a chitosan (CS) skeleton. The resulting ZrCSx-f films displayed remarkable homogeneity with high loadings of UiO-66_NH2 crystals, up to 45 wt %, coupled to a high adsorption capacity of iodine in gas phase, up to 317 mg.g-1.

Antifungal Chitosan Nanocomposites-A New Perspective for Extending Food Storage

Chitosan, a biopolymer derived from chitin, exhibits significant antifungal properties, making it a valuable compound for various applications in agriculture food preservation, and biomedicine. The present study aimed to assess the antifungal properties of chitosan-modified films using sol-gel derivatives (CS:ZnO) or graphene-filled chitosan, (CS:GO and CS:rGO) against two strains of fungi that are the most common cause of food spoilage: Aspergillus flavus ATCC 9643 and Penicillium expansum DSM 1282. The results indicate important differences in the antifungal activity of native chitosan films and zinc oxide-modified chitosan films. CS:ZnO nanocomposites (2:1 and 5:1) completely inhibited spore germination of the two tested fungal strains. Furthermore, a decrease in spore viability was observed after exposure to CS:Zn films. Significant differences in the permeability of cell envelopes were observed in the A. flavus. Moreover, the genotoxicity of the materials against two cell lines, human BJ fibroblasts and human KERTr keratinocytes, was investigated. Our studies showed that the tested nanocomposites did not exhibit genotoxicity towards human skin fibroblasts, and significant damage in the DNA of keratinocytes treated with CS:ZnO composites. Nanocomposites based on chitosan may help reduce synthetic fungicides and contribute to sustainable food production and food preservation practices.

Biodegradable Chitosan-Based Films as an Alternative to Plastic Packaging

The impact of synthetic packaging on environmental pollution has been observed for years. One of the recent trends of green technology is the development of biomaterials made from food processing waste as an alternative to plastic packaging. Polymers obtained from some polysaccharides, such as chitosan, could be an excellent solution. This study investigated the biodegradability of chitosan-metal oxide films (ZnO, TiO2, Fe2O3) and chitosan-modified graphene films (CS-GO-Ag) in a soil environment. We have previously demonstrated that these films have excellent mechanical properties and exhibit antibacterial activity. This study aimed to examine these films' biodegradability and the possibility of their potential use in the packaging industry. The obtained results show that soil microorganisms were able to utilize chitosan films as the source of carbon and nitrogen, thus providing essential evidence about the biodegradability of CS, CS:Zn (20:1; 10:1), and CS:Fe2O3 (20:1) films. After 6 weeks of incubation, the complete degradation of the CS-Fe2O3 20:1 sample was noted, while after 8 weeks, CS-ZnO 20:1 and CS-ZnO 10:1 were degraded. This is a very positive result that points to the practical aspect of the biodegradability of such films in soil, where garbage is casually dumped and buried. Once selected, biodegradable films can be used as an alternative to plastic packaging, which contributes to the reduction in pollution in the environment.

Separation of mercuric ions using 2-thienylbenzimidazole/cucurbit[7]uril/iron-oxide nanoparticles by pH control

2-Thienylbenzimidazole (TBI)/cucurbit[7]uril (CB7) host-guest complex was used as a motif to significantly improve the turnover of γ-Fe₃O₄ magnetic nanoparticles for potential application in the separation of toxic mercuric ions in polluted water samples. The mechanism of restoring the original solid materials is based on applying the pH-controlled preferential binding of the CB7 host to the TBI guest. The analytical application of this concept has not been realized in the literature. The pH-controlled stimuli-responsive abilities were confirmed in aqueous solution by the three-order of magnitudes higher stability constant of the protonated TBIH⁺/CB7 complex (e.g., K = 4.8 × 10⁸ M^-1) when compared to neutral TBI/CB7 complex (e.g., K = 2.4 × 10⁵ M^-1), also manifested in an increase in pK_a values by ~ 3.3 units in the ground state. The supramolecular interaction and adsorption on iron oxide nanoparticles (NPs) were also spectroscopically confirmed in the solid state. The excited-state lifetime values of TBI/CB7NPs increased upon lowering the pH values (e.g., from 0.6 to 1.3 ns) with a concomitant blue shift of ~ 25 nm because of polarity effects. The time-resolved photoluminescent behaviors of the final solids in the presence of CB7 ensured pH-driven reusable systems for capturing toxic mercuric ions. The study offers a unique approach for the controllable separation of mercury ions using an external magnet and in response to pH through preferential binding of the host to guest molecules on the top of magnetic surfaces.

Chitin, Chitosan, and Nanochitin: Extraction, Synthesis, and Applications

Crustacean shells are a sustainable source of chitin. Extracting chitin from crustacean shells is ongoing research, much of which is devoted to devising a sustainable process that yields high-quality chitin with minimal waste. Chemical and biological methods have been used extensively for this purpose; more recently, methods based on ionic liquids and deep eutectic solvents have been explored. Extracted chitin can be converted into chitosan or nanochitin. Once chitin is obtained and modified into the desired form, it can be used in a wide array of applications, including as a filler material, in adsorbents, and as a component in biomaterials, among others. Describing the extraction of chitin, synthesis of chitosan and nanochitin, and applications of these materials is the aim of this review. The first section of this review summarizes and compares common chitin extraction methods, highlighting the benefits and shortcomings of each, followed by descriptions of methods to convert chitin into chitosan and nanochitin. The second section of this review discusses some of the wide range of applications of chitin and its derivatives.

Glassy-like Metal Oxide Particles Embedded on Micrometer Thicker Alginate Films as Promising Wound Healing Nanomaterials

Micrometer-thicker, biologically responsive nanocomposite films were prepared starting from alginate-metal alkoxide colloidal solution followed by sol-gel chemistry and solvent removal through evaporation-induced assembly. The disclosed approach is straightforward and highly versatile, allowing the entrapment and growth of a set of glassy-like metal oxide within the network of alginate and their shaping as crake-free transparent and flexible films. Immersing these films in aqueous medium triggers alginate solubilization, and affords water-soluble metal oxides wrapped in a biocompatible carbohydrate framework. Biological activity of the nano-composites films was also studied including their hemolytic activity, methemoglobin, prothrombin, and thrombine time. The effect of the films on fibroblasts and keratinocytes of human skin was also investigated with a special emphasis on the role played by the incorporated metal oxide. This comparative study sheds light on the crucial biological response of the ceramic phase embedded inside of the films, with titanium dioxide being the most promising for wound healing purposes.

Cooperative assembly of redistributed arylgermanium-bearing alkoxysilanes in a mesostructured siloxane network

Three redistributed arylgermanium-bearing mono-, bis- and tris-triethoxysilyl arms were designed, cocondensed with TEOS to access SBA-15-type materials and embedded in chitosan to prepare functional bioplastics.

Insight into Factors Influencing Wound Healing Using Phosphorylated Cellulose-Filled-Chitosan Nanocomposite Films

Marine polysaccharides are believed to be promising wound-dressing nanomaterials because of their biocompatibility, antibacterial and hemostatic activity, and ability to easily shape into transparent films, hydrogels, and porous foams that can provide a moist micro-environment and adsorb exudates. Current efforts are firmly focused on the preparation of novel polysaccharide-derived nanomaterials functionalized with chemical objects to meet the mechanical and biological requirements of ideal wound healing systems. In this contribution, we investigated the characteristics of six different cellulose-filled chitosan transparent films as potential factors that could help to accelerate wound healing. Both microcrystalline and nano-sized cellulose, as well as native and phosphorylated cellulose, were used as fillers to simultaneously elucidate the roles of size and functionalization. The assessment of their influences on hemostatic properties indicated that the tested nanocomposites shorten clotting times by affecting both the extrinsic and intrinsic pathways of the blood coagulation system. We also showed that all biocomposites have antioxidant capacity. Moreover, the cytotoxicity and genotoxicity of the materials against two cell lines, human BJ fibroblasts and human KERTr keratinocytes, was investigated. The nature of the cellulose used as a filler was found to influence their cytotoxicity at a relatively low level. Potential mechanisms of cytotoxicity were also investigated; only one (phosphorylated microcellulose-filled chitosan films) of the compounds tested produced reactive oxygen species (ROS) to a small extent, and some films reduced the level of ROS, probably due to their antioxidant properties. The transmembrane mitochondrial potential was very slightly lowered. These biocompatible films showed no genotoxicity, and very importantly for wound healing, most of them significantly accelerated migration of both fibroblasts and keratinocytes.

Antimicrobial Effect of Chitosan Films on Food Spoilage Bacteria

Synthetic materials commonly used in the packaging industry generate a considerable amount of waste each year. Chitosan is a promising feedstock for the production of functional biomaterials. From a biological point of view, chitosan is very attractive for food packaging. The purposes of this study were to evaluate the antibacterial activity of a set of chitosan-metal oxide films and different chitosan-modified graphene (oxide) films against two foodborne pathogens: Campylobacter jejuni ATCC 33560 and Listeria monocytogenes 19115. Moreover, we wanted to check whether the incorporation of antimicrobial constituents such as TiO2, ZnO, Fe2O3, Ag, and graphene oxide (GO) into the polymer matrices can improve the antibacterial properties of these nanocomposite films. Finally, this research helps elucidate the interactions of these materials with eukaryotic cells. All chitosan-metal oxide films and chitosan-modified graphene (oxide) films displayed improved antibacterial (C. jejuni ATCC 33560 and L. monocytogenes 19115) properties compared to native chitosan films. The CS-ZnO films had excellent antibacterial activity towards L. monocytogenes (90% growth inhibition). Moreover, graphene-based chitosan films caused high inhibition of both tested strains. Chitosan films with graphene (GO, GOP, GOP-HMDS, rGO, GO-HMDS, rGOP), titanium dioxide (CS-TiO2 20:1a, CS-TiO2 20:1b, CS-TiO2 2:1, CS-TiO2 1:1a, CS-TiO2 1:1b) and zinc oxide (CS-ZnO 20:1a, CS-ZnO 20:1b) may be considered as a safe, non-cytotoxic packaging materials in the future.

Novel quaternarized N-halamine chitosan and polyvinyl alcohol nanofibrous membranes as hemostatic materials with excellent antibacterial properties

The aim of this study was to develop novel nanofibrous membranes based on the quaternary ammonium N-halamine chitosan (CSENDMH) and polyvinyl alcohol (PVA) for antibacterial and hemostasis wound dressing. To improve the antimicrobial properties of nanofibrous membranes, a new chitosan-quaternary ammonium N-halamine derivative was successfully synthesized, and the structure was analyzed by 1H NMR and 13C NMR, fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The morphological and water absorption ability studies showed that the membrane had a uniform bead-free network and high porosity structure like natural extracellular matrix as well as high hydrophilicity. For in vitro evaluation of the hemostatic effect, the membranes showed excellent blood clotting capacity, especially the PVA/CSENDMH membranes. The antimicrobial assay demonstrated excellent antibacterial activity of nanofibrous membranes against both gram-negative and gram-positive bacteria. Furthermore, the cytocompatibility assay results indicated that human fibroblasts could adhere and proliferate on the membranes, thus corroborating their biocompatibility.

Aldehyde-conjugated chitosan-graphene oxide glucodynamers: Ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (Ar_xCHO; x = 1-4) on chitosan biopolymer (CS) affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Ar_x-f films. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Ar_x-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar₁ while the para-hydroxybenzaldehyde Ar₄ was prone to packing inside. Textural and mechanical properties were investigated and expectedly, significant improvement was found for CS-Ar₁-GO-f because of the great dispersion of the aromatic and the presence of the filler. The sensitivity of unsaturated CN imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Ar_x-GO-f compared to CS-Ar_x-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through π-π stacking and additional hydrogen bonding interactions. This finding shows that beyond the conventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites.