Effect of hydration on water state, glass transition dynamics and crystalline structure in chitosan films

Nanoencapsulation of Curcumin and Quercetin in Zein-chitosan Shells for Enhanced Broad-spectrum Antimicrobial Efficacy and Shelf-life Extension of Strawberries

Strawberries face significant postharvest microbial spoilage risks due to high water and sugar content as well as low organic acid contents in their flesh. The study aimed to develop and characterize a novel strategy to delay microbiological spoilage in strawberries using single and coencapsulation of curcumin (Cm) and quercetin (Q), creating stable nanoencapsulates specifically designed to target mold spores, vegetative fungi, and bacteria, with potential applications for both foodservice and consumer use. Using a layer-by-layer antisolvent method, nanoencapsulates of Cm and Q were synthesized, characterized, and assayed against both human and plant pathogenic bacteria and fungi in vitro and in situ. The nanoencapsulates formed stable, spherical emulsion droplets with monodisperse size distribution, high specific surface area, and moderately electro-positive ζ-potentials. Encapsulation efficiencies were 56% (Cm), 65% (Q), and 46.05 ± 4.78% (Cm) and 53.68 ± 4.83% (Q) for CmQ. The nanoencapsulated compounds exhibited strong antimicrobial activity against Pseudomonas aeruginosa, Listeria monocytogenes, Salmonella Montevideo, Saccharomyces cerevisiae, as well as Botrytis cinerea and Aspergillus niger spores in vitro. In strawberries, Cm and Q nanoencapsulates reduced decay incidence by 60% and 80% at 25 °C and 4 °C, respectively, significantly lowering aerobic bacteria by 3.55 ± 0.20 log CFU/g for Cm and 1.97 ± 0.35 log CFU/g for Q, respectively. Yeast and mold counts were likewise reduced by 2.46 ± 0.02 log CFU/g for Cm and 1.43 ± 0.16 log CFU/g for Q. Strawberry quality parameters (firmness, pH, and color) remained stable (P ≥ 0.05) after five days at 25 °C and 15 days at 4 °C. This study highlights a sustainable and effective nanoencapsulation approach for extending the microbiological shelf life of strawberries offering a promising opportunity in food preservation to mitigate spoilage and reduce postharvest losses on perishable fruits and vegetables.

Bio-crosslinking of oxidized hardwood kraft lignin as fully bio-based adhesives for wood bonding

Lignin's low reactivity and crosslinking challenges limit its applications. To address this, many synthetic crosslinkers have been used, but they often involve hazardous chemicals, raising environmental concerns. In particular, it is also true for hardwood kraft lignin (HKL) being burned or wasted in kraft pulping mills. This study reports the successful chitosan bio-crosslinking of oxidized HKL with sodium periodate rather than toxic and environmentally harmful crosslinkers. Both low oxidation (LO) and high oxidation (HO) levels enhance the reactivity of HKL by introducing aldehyde groups, thereby facilitating the formation of imine and amide bonds with chitosan, leading to higher glass transition temperature (Tg), higher viscosity, and greater adhesion strength. The results indicate that the crosslinking of acetone soluble HKL (ASHKL) at LO level with chitosan exhibits excellent dry adhesion strength (1.15 ± 0.2 MPa) for plywood, which meet the required adhesion level of Korean Standard (0.6 MPa) and European Norm 314-2 (1 MPa). These results reveal that chitosan is an outstanding polysaccharide-based crosslinker for the bio-crosslinking of HKL owing to its sustainability, biocompatibility, functional properties, and capability to form covalent bonds.

Effect of dialdehyde nanocellulose-tannin fillers on antioxidant, antibacterial, mechanical and barrier properties of chitosan films for cherry tomato preservation

In this study, bio-based composite films from nanocellulose, tannin and chitosan were fabricated. First, tannin was covalently immobilized onto dialdehyde CNCs (DACNCs) through the nucleophilic reaction to obtain TA-CNCs. TA-CNCs were then added into chitosan matrix as the nanofillers to obtain chitosan-TA-CNC (CS-TA-CNC) films. Compared with pure chitosan film, the water solubility, swelling ratio, water vapor and oxygen barrier properties of CS-TA-CNC films decreased, indicating the improved water-resistant and barrier properties. The composite films exhibited high UV blocking, antioxidant capacity and antimicrobial properties against both E. coli and S. aureus. CS-TA-CNC film with a TA-CNC content of 10 % exhibited the highest tensile strength (77.57 MPa) and toughness (23.51 MJ/m3), 2.23 and 2.5 times higher than that of pure chitosan film, respectively. The composite films extended postharvest life of tomato cherries compared to the pure chitosan film. Films prepared from sustainable bioresources show promising potential for use in active packaging.

A review on the hydration properties of dietary fibers derived from food waste and their interactions with other ingredients: opportunities and challenges for their application in the food industry

Dietary fiber (DF) significantly affects the quality attributes of food matrices. Depending on its chemical composition, molecular structure, and degree of hydration, the behavior of DF may differ. Numerous reports confirm that incorporating DF derived from food waste into food products has significant effects on textural, sensory, rheological, and antimicrobial properties. Additionally, the characteristics of DF, modification techniques (chemical, enzymatic, mechanical, thermal), and processing conditions (temperature, pH, ionic strength), as well as the presence of other components, can profoundly affect the functionalities of DF. This review aims to describe the interactions between DF and water, focusing on the effects of free water, freezing-bound water, and unfreezing-bound water on the hydration capacity of both soluble and insoluble DF. The review also explores how the structural, functional, and environmental properties of DF contribute to its hydration capacity. It becomes evident that the interactions between DF and water, and their effects on the rheological properties of food matrices, are complex and multifaceted subjects, offering both opportunities and challenges for further exploration. Utilizing DF extracted from food waste exhibits promise as a sustainable and viable strategy for the food industry to create nutritious and high-value-added products, while concurrently reducing reliance on primary virgin resources.

Effect of frozen storage on the quality of frozen instant soup rice noodles: From the moisture and starch characteristics

This study aimed to simulate frozen instant soup rice noodles (FISRN) and investigate the effects of long-term frozen storage (-18 °C, 180 days) on the quality characteristics, moisture status, and starch retrogradation of FISRN. The findings indicated that the extent of starch retrogradation gradually increased over 90 days, which elevated the RS rate and inhibited starch digestibility. However, recrystallization resulted in a gradual increase in ice crystal size after 90 days, which disrupted the ordered structure formed by starch retrogradation, reduced the degree of starch order, and accelerated the rate of starch digestion. Furthermore, a longer relaxation time (T24) was detected by NMR with increasing storage time. The weakly bound water in FISRN was gradually converted to free water. Texture results suggested that the hardness of FISRN experienced a general decrease. The cooking loss increased progressively from 3.66 % to 8.10 %. Scanning electron microscope demonstrated that the internal porous network structure of FISRN became inhomogeneous, and a significant number of apertures were formed on the surface. Overall, starch retrogradation and ice recrystallization significantly impact the quality of FISRN during long-term frozen storage. The findings may potentially influence the consumption and market circulation of FISRN positively.

Higher molecular weight pectin inhibits ice crystal growth and its effect on the microstructural and physical properties of pectin cryogels

Understanding the formation of ice crystals is essential for tailoring the microstructure and physical properties of cryogels. This study investigated the effects and mechanisms of pectin molecular weight (Mw) on impacting ice crystal formation. Pectin fractions various Mw (10.13-212.20 kDa) were prepared by hydrothermal method. The solution of high Mw pectin fractions exhibited higher contact angle, lower water freedom, and stronger adsorption of water molecules. The splat experiment and molecular dynamic (MD) results confirmed that higher Mw pectin have stronger ice crystal growth inhibition activity than lower Mw pectin. Furthermore, the pore size distribution of the cryogel increased from 98-203 μm to 105-267 μm as the molecular weight decreased from 212.2 kDa to 121.0 kDa. Additionally, in the higher Mw pectin cryogel, stronger mechanical strength was observed. These findings suggested that changing the molecular weight of pectin has the potential to regulate the ice crystal growth, microstructure and physical properties of frozen products.

Strategies for preparation of chitosan based water-soluble fluorescent probes to detect Cr3+ and Cu2+ ions

The low solubility of chitosan (CS) imposes adverse effects on its application. In this work, one of the aims is to improve the water solubility of CS. By introducing water-soluble side chains to CS, this aim was achieved. Besides, fluorescent moieties were incorporated into the side chains, the fluorescent copolymers were endowed with Cr3+ and Cu2+ ions recognition ability. Firstly, a reversible addition-fragmentation chain transfer polymerization (RAFT) reagent with naphthalimide units and CC groups was prepared. Water-soluble monomer methyl acrylic acid (MAA) was employed in the RAFT polymerization. Thus, water-soluble polymer with fluorescent unit and -C ≡ C on both ends of the polymer was obtained. They were introduced into CS, and the CS-based fluorescent copolymers were obtained eventually. The amount of MAA introduced could be tuned to obtain three side chains of different lengths. It was found that the more MAA was introduced, the better the solubility of CS-TP was. The detection limits (LOD) of Cr3+ and Cu2+ were 44.6 nM and 54.5 nM, respectively. The detection of Cr3+ and Cu2+ ions is further combined with a mobile APP to realize real-time, portable, and visual detection. And the application in the logic gate, a new detection platform, is prepared.

Chitosan-based film incorporated with silver-loaded organo-bentonite or organo-bentonite: Synthesis and characterization for potential food packaging material

Biopolymer-clay composite films were synthesized and characterized for food packaging material. The synthesis was conducted in two stages. Cetrimonium bromide-modified bentonite (CTAB-bentonite) was first exchanged with Ag ions to obtain Ag-CTAB-bentonite. Biopolymer-clay composite films were then performed by a solution-casting method between chitosan (biopolymer) and Ag-CTAB-bentonite or between chitosan and CTAB-bentonite. Different weights of CTAB-bentonite (3% and 5% wt.) and Ag-CTAB-bentonite (3% and 5% wt.) were used during the second stage. The resultant films were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscope coupled with energy dispersive X-ray spectroscopy, atomic force microscopes, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, optical measurement, and others (moisture content, swelling behavior, water solubility, antibacterial, shredded carrot preservation, and biodegradability). Results indicated that the properties (thermal stability, thermomechanical ability, UV-visible light barrier, shredded carrot preservation) of the chitosan-based film incorporated with the synthesized composites were enhanced compared to those of the CS film. The CS/(CTAB-bentonite)-3% and CS/(Ag-CTAB-bentonite)-3% films exhibited antibacterial properties against Escherichia coli, Salmonella enterica subp. enterica, Staphylococcus aureus, and Listeria monocytogenes. The chitosan-based film reinforced with the two prepared composites can be potential for food preservation and packaging.

Comparative Analysis of Electrospun Silk Fibroin/Chitosan Sandwich-Structured Scaffolds for Osteo Regeneration: Evaluating Mechanical Properties, Biological Performance, and Drug Release

An intensive idea of bone tissue engineering is to design regenerative nanofibrous scaffolds that could afford a natural extracellular matrix (ECM) microenvironment with the ability to induce cell proliferation, biodegradation, sustained drug release, and bioactivity. Even the mechanical properties and orientation of the nanofibers may enhance the performance of the scaffolds. To address this issue, we designed novel sandwich-like hybrid silk fibroin (SF)/silica/poly(vinyl alcohol) (PVA) nanofibers scaffolds. The developed scaffold was further characterized using scanning electron microscopy (SEM), elemental mapping, X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and water/blood contact angle measurements. Owing to the interfacial interaction between the layers of organic (chitosan/silk fibroin) and inorganic (silica) in the nanofibrous scaffold, a biocompatibility study has been made on an osteoblast-like (MG63) cell line, which has significant statistical differences; hemocompatibility and the mechanical profile were evaluated in detail to understand the suitability as a biomaterial. To endow the scaffold biodegradation rate, antibacterial activity, porosity profile, and cephalexin monohydrate (CEM), a drug-loading/drug release study was also performed for all of the nanofibers. This strategy explored superior mechanical strength with higher biomineralization on SF/silica/PVA nanofibers. Eventually, the proposed article compared the observation of monolayered scaffolds with designed sandwich-structured scaffolds for the enhancement of bone regeneration.

Influence of Spider Silk Protein Structure on Mechanical and Biological Properties for Energetic Material Detection

Spider silk protein, renowned for its excellent mechanical properties, biodegradability, chemical stability, and low immune and inflammatory response activation, consists of a core domain with a repeat sequence and non-repeating sequences at the N-terminal and C-terminal. In this review, we focus on the relationship between the silk structure and its mechanical properties, exploring the potential applications of spider silk materials in the detection of energetic materials.

Physically cross-linked chitosan gel with tunable mechanics and biodegradability for tissue engineering scaffold

Chitosan, a cationic polysaccharide, exhibits promising potential for tissue engineering applications. However, the poor mechanical properties and rapid biodegradation have been the major limitations for its applications. In this work, an effective strategy was proposed to optimize the mechanical performance and degradation rate of chitosan gel scaffolds by regulating the water content. Physical chitosan hydrogel (HG, with 93.57 % water) was prepared by temperature-controlled cross-linking, followed by dehydration to obtain xerogel (XG, with 2.84 % water) and rehydration to produce wet gel (WG, with 56.06 % water). During this process, changes of water content significantly influenced the water existence state, hydrogen bonding, and the chain entanglements of chitosan in the gel network. The mechanical compression results showed that the chitosan gel scaffolds exhibited tunable compressive strength (0.3128-139 MPa) and compressive modulus (0.2408-1094 MPa). XG could support weights exceeding 65,000 times its own mass while maintaining structural stability. Furthermore, in vitro and in vivo experiments demonstrated that XG and WG exhibited better biocompatibility and resistance to biodegradation compared with HG. Overall, this work contributes to the design and optimization of chitosan scaffolds without additional chemical crosslinkers, which has potential in tissue engineering and further clinical translation.

Biobran-loaded core/shell nanofibrous scaffold: a promising wound dressing candidate

This research examined the effectiveness of Biobran as a bioactive substance that could potentially improve wound healing. It also looked at how Biobran affects the properties of a nanofibrous scaffold made through coaxial electrospinning. This is the first study exploring the use of Biobran in this context and its interaction with nanofibrous scaffolds. The scaffolds were composed of poly(ε-caprolactone) (PCL) in the shell and various concentrations of Biobran blended with polyvinyl alcohol (PVA) in the core. The properties of the scaffolds were characterized by SEM, TEM, FTIR, XRD, TGA, DSC, stress-strain test, WCA, release test, MTT cytotoxicity assay, wound scratching assay, and the dye exclusion method using trypan blue. The scaffolds loaded with Biobran exhibited a more compact and smooth morphology compared with the scaffold without Biobran. The physical interaction and crystallinity of the polymers in the scaffolds were also affected by Biobran in a concentration-dependent manner. This positively influenced their tensile strength, elongation at break, thermal stability, and hydrophilicity. The porosity, water uptake capacity, and WVTR of the nanofibrous scaffolds are within the optimal ranges for wound healing. The release rate of Biobran, which revealed a biphasic release pattern, decreased with increasing Biobran concentration, resulting in controlled and sustained delivery of Biobran from the nanofiber scaffolds. The cell viability assays showed a dose-dependent effect of Biobran on WISH cells, which might be attributed to the positive effect of Biobran on the physicochemical properties of the nanofibrous scaffolds. These findings suggest that Biobran-loaded core/shell nanofiber scaffolds have a potential application in wound healing as an ideal multifunctional wound dressing.

Chitosan Film Sensor for Ammonia Detection in Microdiffusion Analytical Devices

Chitosan films have attracted increased attention in the field of sensors because of chitosan's unique chemico-physical properties, including high adsorption capacity, filmability and transparency. A chitosan film sensor was developed through the dispersion of an ammonia specific reagent (Nessler's reagent) into a chitosan film matrix. The chitosan film sensor was characterized to assess the film's properties by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). A gas diffusion device was prepared with the chitosan film sensor, enabling the collection and detection of ammonia vapor from biological samples. The chitosan film sensor color change was correlated with the ammonia concentration in samples of human serum and artificial urine. This method enabled facile ammonia detection and concentration measurement, making the sensor useful not only in clinical laboratories, but also for point-of-care devices and wherever there is limited access to modern laboratory facilities.

Physicochemical Characterization of Chitosan/Poly-γ-Glutamic Acid Glass-like Materials

This paper sets up a new route for producing non-covalently crosslinked bio-composites by blending poly-γ-glutamic acid (γ-PGA) of microbial origin and chitosan (CH) through poly-electrolyte complexation under specific experimental conditions. CH and two different molecular weight γ-PGA fractions have been blended at different mass ratios (1/9, 2/8 and 3/7) under acidic pH. The developed materials seemed to behave like moldable hydrogels with a soft rubbery consistency. However, after dehydration, they became exceedingly hard, glass-like materials completely insoluble in water and organic solvents. The native biopolymers and their blends underwent comprehensive structural, physicochemical, and thermal analyses. The study confirmed strong physical interactions between polysaccharide and polyamide chains, facilitated by electrostatic attraction and hydrogen bonding. The materials exhibited both crystalline and amorphous structures and demonstrated good thermal stability and degradability. Described as thermoplastic and saloplastic, these bio-composites offer vast opportunities in the realm of polyelectrolyte complexes (PECs). This unique combination of properties allowed the bio-composites to function as glass-like materials, making them highly versatile for potential applications in various fields. They hold potential for use in regenerative medicine, biomedical devices, food packaging, and 3D printing. Their environmentally friendly properties make them attractive candidates for sustainable material development in various industries.

Interpretation of the effects of hydroxypropyl starch and hydroxypropyl distarch phosphate on frozen raw noodles quality during frozen storage: Studies on water state and starch-gluten network properties

The impacts of both structural variations induced by low temperature and physiochemical changes induced by modified starch on the qualities of frozen raw noodles (FRNs) were investigated during long-term freezing storage. The addition of modified starch was a potentially effective method to delay the loss of FRNs qualities during storage. In this study, hydroxypropyl starch (HPS) and hydroxypropyl distarch phosphate (HPDSP) were added to improve the cooking and textural characteristics of FRNs. The cooking loss rate of FRNs with the addition of 12%HPS was consistent with that of the control (4.39 % and 4.37 %, respectively), while after 8 weeks of storage showed the significant decrease effect (5.01 % and 5.78 %, respectively). In addition, adding HPS or HPDSP could change the colour and lustre of FRNs to that preferred by consumers. When 6 % HPS or HPDSP were added, the FRNs showed the lowest of freezable water content during storage. The test results of FTIR showed the secondary structure of FRNs was maintained with the introduction of HPS or HPDSP during refrigeration, and the microstructure was improved during the frozen storage period. Consequently, the results provided a theoretical basis and new insight for the production and transportation of FRNs.

Films composed of white angico gum and chitosan containing chlorhexidine as an antimicrobial agent

Anadenanthera colubrina, popularly known as white angico, is a species extensively cultivated in Brazil, mainly in the cerrado region, including the state of Piauí. This study examines the development of films composed of white angico gum (WAG) and chitosan (CHI) and containing chlorhexidine (CHX), an antimicrobial agent. The solvent casting method was used to prepare films. Different combinations and concentrations of WAG and CHI were used to obtain films with good physicochemical characteristics. Properties such as the in vitro swelling ratio, the disintegration time, folding endurance, and the drug content were determined. The selected formulations were characterised by scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction, and the CHX release time and antimicrobial activity were evaluated. CHX showed a homogenous distribution in all CHI/WAG film formulations. The optimised films showed good physicochemical properties with 80% CHX release over 26 h, which is considered promising for local treatment of severe lesions in the mouth. Cytotoxicity tests of the films did not show toxicity. The antimicrobial and antifungal effects were very effective against the tested microorganisms.

Organic-soluble chitosan-g-PHMA (PEMA/PBMA)-bodipy fluorescent probes and film by RAFT method for selective detection of Hg2+/Hg+ ions

Chitosan as the plentiful and easily available natural polymer, its solubility in organic solvents is still a challenge. In this article, three different chitosan-based fluorescent co-polymers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. They could not only dissolve in several organic solvents, but also could selectively recognize Hg²⁺/Hg⁺ ions. Firstly, allyl boron-dipyrrolemethene (bodipy) was prepared, and used as one of the monomers in the subsequent RAFT polymerization. Secondly, chitosan-based chain transfer agent (CS-RAFT) was synthesized through classical reactions for dithioester preparation. Finally, three methacrylic ester monomers and bodipy bearing monomers were polymerized and grafted as branched-chains onto chitosan respectively. By RAFT polymerization, three chitosan-based macromolecular fluorescent probes were prepared. These probes could be readily dissolved in DMF, THF, DCM, and acetone. All of them exhibited the 'turn-on' fluorescence with selective and sensitive detection for Hg²⁺/Hg⁺. Among them, chitosan-g-polyhexyl methacrylate-bodipy (CS-g-PHMA-BDP) had the best performance, its fluorescence intensity could be increased to 2.7 folds. In addition, CS-g-PHMA-BDP could be processed into films and coatings. When loading on the filter paper, fluorescent test paper was prepared and it could realize the portable detection of Hg²⁺/Hg⁺ ions. These organic-soluble chitosan-based fluorescent probes could enlarge the applications of chitosan.

Molecular Changes in Spider Viscid Glue As a Function of Relative Humidity Revealed Using Infrared Spectroscopy

Spider aggregate glue can absorb moisture from the atmosphere to reduce its viscosity and become tacky. The viscosity at which glue adhesion is maximized is remarkably similar across spider species, even though that viscosity is achieved at very different relative humidity (RH) values matching their diverse habitats. However, the molecular changes in the protein structure and the bonding state of water (both referred to here as molecular structure) with respect to the changes in RH are not known. We use attenuated total reflectance-infrared (ATR-IR) spectroscopy to probe the changes in the molecular structure of glue as a function of RH for three spider species from different habitats. We find that the glue retains bound water at lower RH and absorbs liquid-like water at higher RH. The absorption of liquid-like water at high RH plasticizes the glue and explains the decrease in glue viscosity. The changes to protein conformations as a function RH are either subtle or not detectable by IR spectroscopy. Importantly, the molecular changes are reversible over multiple cycles of RH change. Further, separation of glue constituents results in a different humidity response as compared to pristine glue, supporting the standing hypothesis that the glue constituents have a synergistic association that makes spider glue a functional adhesive. The results presented in this study provide further insights into the mechanism of the humidity-responsive adhesion of spider glue.

Structure and properties of chitosan/sodium dodecyl sulfate composite films

In this study, we investigated the effect of sodium dodecyl sulfate (SDS) content on the structure and properties of chitosan films. It is found that the binding of SDS to chitosan was realized through the interactions between -SO4 - and -NH3 +, forming an ionically cross-linked film. Structural analysis revealed that the crystallization was greatly hindered by introducing SDS. With an increase of SDS content, the glass transition temperatures (T g) of chitosan films increased due to the formation of crosslinks. Compared to pure chitosan film, the composite films had lower content of moisture and possessed better thermal stability. In addition, the mechanical properties of the as-obtained composite films were closely related to the content of SDS, and were significantly improved in the biopolymer films with moderate SDS content. These results indicate that the microstructure as well as properties of the chitosan films can be regulated by adding SDS.

Preparation and Physicochemical Properties of Modified Corn Starch-Chitosan Biodegradable Films

Starch is a biopolymer with enormous potential for generating new biodegradable packages due to its easy availability and low cost. However, due to its weak functional properties, limitation of its interaction with some hydroxyl groups and evaluation of blends with other polymers are necessary in order to improve its performance. Glycerol-plasticized acetylated corn starch films were developed using the casting method, and the impact of incorporating chitosan (TPS:CH) in various proportions (75:25, 50:50, and 25:75 v/v) was studied in the present research. The effect of chitosan ratios on the physical, mechanical, water-vapor barrier, and thermal properties of the film was studied. Chitosan-protonated amino groups promoted the formation of intermolecular bonds, improving tensile strength, thermal stability, hydrophobicity, water adsorption capacity, and the gas barrier of starch films. The results show that the film composed of TPS25-CH75 proved to be the best barrier to water vapor; thus, these composite films are excellent choices for developing biodegradable packaging for the food industry.

Determination of Antimicrobial and Antibiofilm Activity of Combined LVX and AMP Impregnated in p(HEMA) Hydrogel

Catheter-associated urinary tract infections (CAUTIs) are nosocomial infections, causing more than one million cases per year. CAUTIs cause serious health issues; in addition, the cost of replacement of the device constrains the employment of urological devices. Therefore, there is an urgent need to develop novel biomaterials for use in catheters. In this study, poly hydroxyethyl-methacrylate p(HEMA) and drugs-loaded p(HEMA) with ampicillin trihydrate (AMP), levofloxacin (LVX), and drug combinations were prepared using free radical polymerization. The characterization of the dried films included the determination of glass transition temperature (Tg), ultimate tensile strength, elongation percentage, and Young’s modulus. Formulation toxicity, antimicrobial activity, and biofilm-formation ability were tested. Decreases in Tg value, U.T.S., and Young’s modulus, and an increase in elongation percentage were observed in AMP-loaded p(HEMA). Different ratios of drug combinations increased the Tg values. The films exhibited a cell viability higher than 80% on HEK 293 cells. Antimicrobial activity increased when p(HEMA) was loaded with LVX or a combination of LVX and AMP. Biofilm-forming ability reduced after the addition of antimicrobial agents to the films. p(HEMA) impregnated with AMP, LVX, and drug combinations showed significantly increased antimicrobial activity and decreased biofilm-forming ability compared with p(HEMA), in addition to the effects on (HEMA) mechanical properties.

Glass transition and crystallization of solid model system of jujube slice as influenced by sugars and organic acids

To understand the specific contributions of amorphous sugars and organic acids to the quality of food matrix, the solid model system of jujube slice skeleton (JSS) was firstly established. Effects of fructose (F), glucose (G), malic acid (M) and citric acid (C) on the glass transition temperature (T_g) and crystallization of JSS were studied. JSS-F/G/M/C blends were prepared by osmosis in the solution at a range of 0 ~ 32 g/100 g. Sugars reduced the T_g in the system, structure of JSS-G/M blends was changed from "amorphous glassy" to "amorphous rubbery" by increasing the osmotic solute concentration. T_g was decreased from 50.8 to 14.0 °C when JSS was osmosed in a 4 g/100 g fructose solution. Organic acids induced their crystallization in JSS. The crystallinity of JSS-M immersed in 32 g/100 g osmotic solution concentration was increased from 2% to 75%. Fructose presented greater influence on the adverse quality of jujube slices.

Development and characterization of chitosan films carrying Artemisia campestris antioxidants for potential use as active food packaging materials

Active food packaging films based on chitosan and enriched with Artemisia campestris hydroalcoholic extract (ACHE), aqueous extract (ACAE) and essential oil (ACEO) were developed. The effects of incorporating A. campestris were investigated on the physical, mechanical, thermal and antioxidant characteristics of the films. The structural properties of the films were evaluated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that adding ACHE and ACEO improved the water resistance of chitosan films. The FTIR spectroscopy analysis revealed covalent interaction and hydrogen bonding between chitosan and ACHE. The XRD and SEM analyses indicated that interactions occurred between the film matrix and A. campestris active compounds, which could be reflected by the physical and mechanical properties of composite films. Incorporating ACHE and ACAE in the chitosan matrix decreased the tensile strength. The film extensibility was reduced when ACHE and ACEO were added. All films exhibited great thermal stability as the degradation occurred above 300 °C. The addition of A. campestris active compounds, particularly extracts, to chitosan films notably increased the antioxidant and UV-Vis barrier properties. Chitosan films enriched with the A. campestris antioxidant compounds could be applied as food packaging alternatives.

Waste Cleaning Waste: Combining Alginate with Biowaste-Derived Substances in Hydrogels and Films for Water Cleanup

Biowaste-derived substances isolated from green compost (BBS-GC) are environmentally friendly reactants similar to humic substances, which contain multiple functionalities, that are suitable for adsorbing different kinds of pollutants in wastewater. Herein, sodium alginate (derived from brown algae) cross-linked with both Ca2+ ions and BBS-GC in the form of hydrogels and dried films are proposed as green, easy-to-form, and handleable materials for tertiary water treatments. The results show that both hydrogels and films are mechanically stable and can effectively remove differently charged dyes through an adsorption mechanism that can be described by the Freundlich model. BBS-GC-containing gels always performed better than samples prepared without BBS-GC, revealing that such unconventional materials can integrate waste valorization and water decontamination, potentially providing social and environmental benefits.

Polydopamine-assisted grafting of chitosan on porous poly (L-lactic acid) electrospun membranes for adsorption of heavy metal ions

In this study, a versatile method for the manufacturing of chitosan-grafted porous poly (L-lactic acid) (P-PLLA) nanofibrous membrane by using polydopamine (PDA) as an intermediate layer has been developed. P-PLLA fibres were electrospun and collected as nano/micro fibrous membranes. Highly porous fibres could serve as a substrate for chitosan to adsorb heavy metal ions. Moreover, PDA was used to modify P-PLLA surface to increase the coating uniformity and stability of chitosan. Due to the very high surface area of P-PLLA membranes and abundant amine groups of both PDA and chitosan, the fabricated membranes were utilized as adsorbent for removal of copper (Cu²⁺) ions from the wastewater. The adsorption capability of Cu²⁺ ions was examined with respect to the PDA polymerization times, pH, initial metal ion concentration and time. Finally, the equilibrium adsorption data of chitosan-grafted membranes fitted well with the Langmuir isotherm with the maximum adsorption capacity of 270.27 mg/g.

Reduction in Spoilage Microbiota and Cyclopiazonic Acid Mycotoxin with Chestnut Extract Enriched Chitosan Packaging: Stability of Inoculated Gouda Cheese

Active chitosan-based films, blended with fibrous chestnut (Castanea sativa Mill.) tannin-rich extract were used to pack Gouda cheese that has been contaminated with spoilage microflora Pseudomonas fluorescens, Escherichia coli, and fungi Penicillium commune. A comprehensive experimental plan including active chitosan-based films with (i) chestnut extract (CE), (ii) tannic acid (TA), and (iii) without additives was applied to evaluate the film's effect on induced microbiological spoilage reduction and chemical indices of commercial Gouda cheese during 37 days while stored at 4 °C and 25 °C, respectively. The cheese underwent microbiology analysis and chemical assessments of ultra-high-performance liquid chromatography (UHPLC) (cyclopiazonic acid), pH, and moisture content. The biopackaging used for packing cheese was characterized by mechanical properties before food packaging and analyzed with the same chemical analysis. The cheese microbiology showed that the bacterial counts were most efficiently decreased by the film without additives. However, active films with CE and TA were more effective as they did not break down around the cheese and showed protective properties against mycotoxin, moisture loss, and pH changes. Films themselves, when next to high-fat content food, changed their pH to less acidic, acted as absorbers, and degraded without plant-derived additives.

Theoretical investigation into the cooperativity effect of 1,4-dimethoxy-D-glucosamine complex with Na+ and H2O

In order to explore the essence of the hydration process of chitin or chitosan in the presence of cation, the cooperativity effects between the H-bonding and Na⁺···molecule interactions in the 1,4-dimethoxy-D-glucosamine (DMGA) complexes with H₂O and Na⁺ were investigated at the B3LYP/6-311++G(d,p), M06-2X/6-311++G(2df,2p), and ωB97X-D/6-311++G(2df,2p) levels. The result shows that the complexes in which Na⁺ or H₂O is bonded simultaneously to the -NH and -OH groups connected to the C3 atom of DMGA are the most stable. The cooperativity and anti-cooperativity effects occur in DMGA···H₂O···DMGA and DMGA···Na⁺···H₂O, while only the cooperativities are confirmed in DMGA···Na⁺···DMGA. The cooperativity occurs in the DMGA···Na⁺···H₂O complexes without the hydration, while the anti-cooperativity occurs in those with the hydration. Furthermore, the cooperativity and anti-cooperativity in DMGA···Na⁺···H₂O are far stronger than those in DMGA···Na⁺···DMGA or DMGA···H₂O···DMGA. Therefore, a deduction is given that the cooperativity and anti-cooperativity effects play an important role in the hydration of chitin or chitosan in the presence of Na⁺. When only Na⁺ is linked with -OH and -NH groups of chitosan or chitin, due to the cooperativity effect, the hydration does not occur. When both Na⁺ and H₂O are linked with -OH and -NH groups, the anti-cooperativities are dominant in controlling of the aggregation process of Na⁺, H₂O, chitosan, and chitin, leading to the possible hydration. Atoms in molecules (AIM) analysis confirms the cooperativity and anti-cooperativity effects. Graphical abstract.

Tuning the physicochemical properties of apple pectin films by incorporating chitosan/pectin fiber

Various biodegradable or edible films were designed to deal with the environmental threats from plastic films. To overcome the defects of pectin film, the feasibility for the incorporation of CH/PE fiber was explored. Micron-scale novel artificial CH/PE fibers in needle, spindle or whisker shape with a diameter around 25 μm were fabricated via a shearing regime in virtue of electrostatic complexing. The incorporation of CH/PE fiber (mixture) and its size-fractioned portions (small and large) substantially changed PE films in diverse ways. Structurally, the fiber-incorporated films were heterogeneous with the fibers concentrated in the upper layer, although they presented similar FT-IR spectra and XRD pattern to PE film. Regarding the film performance, the incorporation of CH/PE fibers, especially the small portion, rendered the PE film with higher values in water-proof ability, thermal stability, break resistibility, stretchability and UV blocking capacity. More importantly, this work provided an innovative strategy to improve the performance of edible films.