Ionic Conductivity and Structure of Chitosan Films Modified with Lactic Acid-Choline Chloride NADES

Bioactive biopolymer films reinforced with cellulose nanocrystals and green-extracted polyphenols from date seeds for veal meat preservation

This study investigated the effectiveness of bioactive films fabricated using chitosan (Cs) reinforced with cellulose nanocrystals (CNC) and polyphenolic components extracted using natural deep eutectic solvents (NADES), both derived from date seeds. The CsCNC films with NADES-extracted date seed polyphenols (DSP) showed significant antimicrobial activity against Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, and Escherichia coli. Total phenolic content (0.01 to 0.20 mg GAE/mL), 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (0.10 to 3.22 mmol TE/mL), and ferric-ion reducing antioxidant power (0.49 to 3.31 μmol TE/mL) improved significantly. Elongation at break (46.53 % to 90.87 %) and thickness (0.08 mm to 0.17 mm) increased while tensile strength (11.62 MPa to 3.30 MPa) decreased after incorporating DSP. The films improved UV-shielding ability, although DSP affected water barrier properties (2.91 to 7.83 × 10-10 g/m.s.Pa) and increased solubility and swelling rate. The performance of CsCNC bioactive film containing 4 % DSP for preserving veal meat during refrigeration for 8 days was studied. Compared to conventional cling film, the bioactive film retained meat quality by preserving pH, color, and lipid stability while delaying microbial spoilage. This study demonstrates the potential of valorizing both phenolic and cellulosic fractions from date seeds to develop an eco-friendly and bioactive packaging film.

Structural insights into carboxylic-acid based DES across H-bond donor ratios: impact of CL&Pol refinement

Deep eutectic solvents (DES) are of significant interest due to their eco-friendly nature and vast applications. Carboxylic-acid-based choline chloride (ChCl) DES are notable for their roles in electrochemical, drug delivery, and biomass processing applications, with efficiency influenced by the ChCl : carboxylic acid ratio. Understanding these mechanisms requires detailed knowledge of their structure. This study investigates the choline chloride-lactic acid (ChCl:LA) DES structure using ab initio molecular dynamics simulations to assess the accuracy of the transferable and polarizable CL&Pol force field. We observe that the CL&Pol force field qualitatively captures primary interactions within the system, despite numerical discrepancies due to its transferable nature. To refine the original force field, we incorporate two improvements: tuning the σ parameter of the strongest hydrogen-bond interactions and incorporating the Tang-Toennies damping function to correct chloride ion overpolarization. The first adjustment enhances the targeted interactions and significantly improves the short-range structure of the entire hydrogen-bond network. The second refinement, although minimally impacting the structure at low LA ratios, proves critical at higher ratios by correcting the oversegregation of ionic molecules in the original force field. Consequently, it becomes essential for reliably depicting the medium and long-range structure of the system, highlighting that the specific parameter of the force field to be refined depends on the structural scale under investigation. Notably, the long-range structure results from the competition between choline and carboxylic acid for chloride, rebalanced by the suggested modifications, especially the overpolarization correction.

Unveiling the effect of natural deep eutectic solvents-based date seed polyphenolic extract on the properties of chitosan-PVA films and its application in shrimp packaging

This study explored natural deep eutectic solvent-based polyphenolic extract from date fruit seed as a functional and bioactive compound in chitosan-poly(vinyl)alcohol (CSPVA) films. Various concentrations of the extract (1.5 %, 2 %, 2.5 %, and 3 %) were added to study the effect on the film's bioactive, physicochemical, mechanical and structural properties. The extract increased the total phenolic content (0.01 to 0.16 mg GAE/mL), and antioxidant activities determined via 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity assay (1.45 to 5.53 mmol GAE/mL), and ferric ion reducing antioxidant power assay (0.12 to 2.4 μmol TE/mL) assays. It also enhanced antibacterial activities against Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, and Escherichia coli. The extract was also successful in increasing the elongation at break (45.51 % to 58.16 %) and thickness (0.10 to 0.19 mm) while reducing tensile strength (11.18 MPa to 3.02 MPa) and Young's modulus (24.5 MPa to 5.7 MPa). UV-shielding ability, opacity, water vapor permeability (3.7 to 7.6 × 10-10 g/m.s.Pa) and solubility (53.7 % to 73.9 %) also increased. CSPVA films with 3 % DSP preserved white shrimps better than cling film by reducing quality deterioration (i.e., color, lipid oxidation, and bacterial population) after 4 days of refrigeration. These findings suggest that CSPVA films enriched with green-extracted date seed polyphenolic compounds hold significant potential for sustainable food packaging.

Synthesis and characterization of chitosan-corn starch-SiO2/silver eco-nanocomposites: Exploring optoelectronic and antibacterial potential

This work discusses the physicochemical and antimicrobial characteristics of chitosan-corn starch eco-nanocomposites integrated with silica@Ag nano-spheres. These composites were synthesized through sol-gel polymerization and subsequently exposed to simulated body fluid (SBF). The incorporation of Ag into the eco-nanocomposites led to a decrease in diffuse reflectance across the entire wavelength range. The dielectric permittivity exhibited an increase up to 52.1 at a frequency of 100 kHz, while the ac conductivity reached a value of 5.2 ∗ 10-6 (S cm-1) at the same frequency for the sample with the highest Ag content. The study utilized XRD and FTIR techniques to examine the materials before and after in vitro testing and evaluated the antibacterial properties of the eco-nanocomposites against several pathogenic microorganisms, including Staphylococcus haemolyticus, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli, using the agar diffusion method. The eco-nanocomposites demonstrated bioactivity by forming a hydroxy appetite layer on their surfaces and were capable of releasing silver (Ag) at concentrations of 1.3, 1.9, and 2.5 mol%. This study suggests that chitosan-corn starch-SiO2-based doped with Ag eco-nanocomposite has the potential for various applications, including biomedical and environmental fields, where their antibacterial properties can be utilized to combat harmful microorganisms.

Tyrosinase Magnetic Cross-Linked Enzyme Aggregates: Biocatalytic Study in Deep Eutectic Solvent Aqueous Solutions

In the field of biocatalysis, the implementation of sustainable processes such as enzyme immobilization or employment of environmentally friendly solvents, like Deep Eutectic Solvents (DESs) are of paramount importance. In this work, tyrosinase was extracted from fresh mushrooms and used in a carrier-free immobilization towards the preparation of both non-magnetic and magnetic cross-linked enzyme aggregates (CLEAs). The prepared biocatalyst was characterized and the biocatalytic and structural traits of free tyrosinase and tyrosinase magnetic CLEAs (mCLEAs) were evaluated in numerous DES aqueous solutions. The results showed that the nature and the concentration of the DESs used as co-solvents significantly affected the catalytic activity and stability of tyrosinase, while the immobilization enhanced the activity of the enzyme in comparison with the non-immobilized enzyme up to 3.6-fold. The biocatalyst retained the 100% of its initial activity after storage at -20 °C for 1 year and the 90% of its activity after 5 repeated cycles. Tyrosinase mCLEAs were further applied in the homogeneous modification of chitosan with caffeic acid in the presence of DES. The biocatalyst demonstrated great ability in the functionalization of chitosan with caffeic acid in the presence of 10% v/v DES [Bet:Gly (1:3)], enhancing the antioxidant activity of the films.

Construction of chitosan-based supramolecular biofilm material for wound dressing based on natural deep eutectic solvents

Bacterial infection is still one of the main problems observed in the clinical process of wound healing, so the development of new multifunctional biocompatible materials is an urgent clinical need. A kind of supramolecular biofilm crosslinked by hydrogen bond between natural deep eutectic solvent and chitosan was studied and successfully prepared to reduce bacterial infection. Its killing rates of Staphylococcus aureus and Escherichia coli can reach 98.86 % ± 1.90 % and 99.69 % ± 0.53 %, and it can be degraded in both soil and water, showing excellent biocompatibility and biodegradability. In addition, the supramolecular biofilm material also has the UV barrier property, which can effectively avoid the secondary injury of UV to the wound. Interestingly, the cross-linking effect of hydrogen bond makes the biofilm have a more compact structure and rough surface, and gives the biofilm strong tensile properties. Overall, owing to these unique advantages, NADES-CS supramolecular biofilm has great potential for medical applications, laying the foundation for the realization of sustainable polysaccharide materials.

Computer Simulations of Deep Eutectic Solvents: Challenges, Solutions, and Perspectives

Deep eutectic solvents (DESs) are one of the most rapidly evolving types of solvents, appearing in a broad range of applications, such as nanotechnology, electrochemistry, biomass transformation, pharmaceuticals, membrane technology, biocomposite development, modern 3D-printing, and many others. The range of their applicability continues to expand, which demands the development of new DESs with improved properties. To do so requires an understanding of the fundamental relationship between the structure and properties of DESs. Computer simulation and machine learning techniques provide a fruitful approach as they can predict and reveal physical mechanisms and readily be linked to experiments. This review is devoted to the computational research of DESs and describes technical features of DES simulations and the corresponding perspectives on various DES applications. The aim is to demonstrate the current frontiers of computational research of DESs and discuss future perspectives.

Effect of Curcumin Addition on the Properties of Biodegradable Pectin/Chitosan Films

A pectin/chitosan matrix-loaded curcumin film (PCCF) with a deep eutectic solvent (DES) as the solvent and plasticizer was prepared in this study. Different quantities of curcumin (identified as PCCF-0, PCCF-1, PCCF-2. PCCF-3) were loaded on the pectin/chitosan film in order to evaluate their effects on the film properties. Results showed that curcumin could interact with the pectin/chitosan matrix and form a complex three-dimensional network structure. PCCF could promote the thickness, tensile strength, thermal properties, antioxidant and antiseptic capacities, but deteriorate the light transmission and elongation at the same time. The addition of curcumin would change the color of the film, without significantly affecting the moisture content. The tensile strength of PCCF-3 reached the maximum value of 3.75 MPa, while the elongation decreased to 10%. Meanwhile, the water-resistance properties of PCCF-3 were significantly promoted by 8.6% compared with that of PCCF-0. Furthermore, PCCF showed remarkable sustained antioxidant activities in a dose-dependent manner. PCCF-3 could inhibit DPPH and ABTS free radicals by 58.66% and 29.07%, respectively. It also showed antiseptic capacity on fresh pork during storage. Therefore, curcumin addition could improve the barrier, mechanical, antioxidant and antiseptic properties of the polysaccharide-based film and PCCF has the potential to be used as a new kind of food packaging material in the food industry.

Biocomposite Materials Based on Chitosan and Lignin: Preparation and Characterization

In this study, bioactive composite systems based on natural polymers (chitosan and lignin) were prepared in this study. The structural, mechanical, and morphological properties of chitosan-based materials containing various amounts of lignin filler were investigated. The infra-red IR spectroscopy data confirmed the formation of chemical bonds between the components of the obtained composites. The mechanical properties of film samples were studied in air and in physiological solution. It was demonstrated that the breaking elongation values of the obtained film samples in the wet state were higher (150–160%) than the corresponding (average) value of a pure chitosan film (100%). The scanning electron microscopy and atomic force microscopy data demonstrated that the introduction of lignin had caused significant changes in the surface morphology of films. The appearance of a strongly pronounced texture and porosity facilitated cell proliferation on the surface of composites, i.e., the bioactivity of film samples was enhanced with an increasing lignin content in the chitosan matrix.

Understanding Electrodeposition of Chitosan-Hydroxyapatite Structures for Regeneration of Tubular-Shaped Tissues and Organs

Tubular-shaped hydrogel structures were obtained in the process of cathodic electrodeposition from a chitosan-hydroxyapatite solution carried out in a cylindrical geometry. The impact of the initial concentration of solution components (i.e., chitosan, hydroxyapatite, and lactic acid) and process parameters (i.e., time and voltage) on the mass and structural properties of deposit was examined. Commercially available chitosan differs in average molecular weight and deacetylation degree; therefore, these parameters were also studied. The application of Fourier-transform infrared spectroscopy, scanning electron microscopy, and time-of-flight secondary ion mass spectrometry allowed obtaining fundamental information about the type of bonds and interactions created in electrodeposited structures. Biocompatible tubular implants are highly desired in the field of regeneration or replacement of tubular-shaped tissues and organs; therefore, the possibility of obtaining deposits with the desired structural properties is highly anticipated.

The role of a deep eutectic solvent in changes of physicochemical and antioxidative properties of chitosan-based films

In this work deep eutectic solvent (DES), based on the mixture of choline chloride and lactic acid, were suggested as chitosan films plasticizers. The molecular structure and properties of films obtained using chitosan, with different degree of deacetylation and 0-80 wt.% DES content (ω_DES), were studied by means of FTIR spectroscopy, SEM and AFM microscopy (films' surface properties) together with optical characteristics, water vapor transmission rate (WVTR), water vapor permeability (WVP), tensile strength (TS) and elongation at break (E_b). Scanning electron micrographs revealed that all chitosan-DES films were smooth and uniform. DES significantly improves the film flexibility (E_b increases of ca. 160 % after incorporation of 80 wt.% DES), slightly decreases tensile strength and also improves antioxidative properties while simultaneously, increasing water vapor permeability (WVP). Films prepared in this study exhibit characteristics that qualify them for potential use as an active packaging material.