Non-toxic chitosan-pyrazole adsorbent enriched with greenly synthesized zinc oxide nanoparticles for dye removal from wastewater.

The limited usage of chitosan as a dye adsorbent is attributed to its compact structure and low swelling ability, despite its exceptional properties. The present study aimed to prepare novel chitosan/pyrazole Schiff base (ChS) adsorbents enriched with greenly synthesized zinc oxide nanoparticles. The preparation of ZnO-NPs was carried out through a green approach using the Coriandrum sativum extract. The presence of ZnO-NPs at the nanoscale was validated through TEM, DLS and XRD analyses. FTIR and 1H NMR confirmed the successful preparation of the Schiff base and its ZnO-NPs adsorbents. The incorporation of ZnO-NPs improved the thermal, swelling and antimicrobial properties of the chitosan Schiff base. In addition, a significant improvement in the adsorption of Maxilon Blue dye from its aqueous solution by the Schiff base/ZnO-NPs adsorbent was achived. The prepared ChS/ZnO-NPs adsorbent has the potential to be used as an alternative to conventional adsorbents for the removal of dyes from wastewater.

Development of alginate-based edible coatings of optimized UV-barrier properties by response surface methodology for food packaging applications.

Despite the outstanding characteristics of alginate, it suffers from bad UV-barrier, water barrier, and antimicrobial properties limiting its wide usage in food packaging. For this concern, Box-Behnken design (BBD) was applied to prepare an alginate-based edible coating of the best optimized UV-shielding properties upon the incorporation of both Aloe vera (AV) and zinc oxide nanoparticles (ZnO-NPs). The optimized minimum UV-transmittance was 4.96% when the optimized compositions of alginate (1.05 g), AV (2.95 g), and ZnO-NPs (4.93 wt%) were used. FTIR was used to verify the successful edible coating preparation while the wide-angle X-ray diffraction (XRD) was used to identify the interactions between the film's components. The incorporation of both AV and ZnO-NPs significantly improved alginate's thermal, water vapor permeability (WVP), mechanical and antimicrobial properties. In addition, the films incorporated with both AV and ZnO-NPs exhibited excellent UV-barrier properties compared with neat alginate. The optimized alginate film incorporated with both ZnO-NPs and AV significantly extended the shelf-life of tomato fruits up to 16 days without any defects. Due to the outstanding physical, UV-shielding, and antimicrobial properties of the optimized alginate/AV/ZnO-NPs film, it could be used potentially in food packaging industries.

Developing multifunctional edible coatings based on alginate for active food packaging.

The applications of edible coatings stemmed exclusively from alginate in food packaging are restricted due to their inherent deficient antimicrobial, barrier, and UV-barrier properties. In this work, we aimed to design smart alginate-based coatings for active food packaging through the addition of both aloe vera (AV) and garlic oil (GO). The interactions between the film components were verified by FTIR and XRD. Thermal and mechanical properties were improved by the presence of AV and GO. The presence of AV and GO did not significantly influence the transparency of alginate films. The films exhibited a significant UV-shielding to all UV regions. Water vapor permeability was significantly (p < 0.05) reduced either through the incorporation of AV or GO. The antimicrobial properties of the prepared films were considerably improved by the presence of AV and GO. The shelf-life of tomatoes (Solanum lycopersicum L.) was extended when coated with the alginate film incorporated with AV and GO. Owing to the outstanding UV-shielding, mechanical, thermal, and antimicrobial properties, the alginate/AV/GO active coatings could potentially be implemented in the food packaging industry.

Optimized carboxymethyl cellulose and guanidinylated chitosan enriched with titanium oxide nanoparticles of improved UV-barrier properties for the active packaging of green bell pepper.

Edible films based on chitosan biguanidine hydrochloride and CMC were optimized for the minimum water vapor permeability (WVP) using the 3-level factorial design. Titanium oxide nanoparticles (nTiO2) were incorporated in different contents into the optimized film (Owvp). FTIR and 1H NMR confirmed the successful preparation of films. FE-SEM showed that nTiO2 was homogeneously distributed, with a size of about 25.78 nm for the film containing 5 wt% of nTiO2. XRD was used to study the film's crystallinity, and calculate the crystallite size of nTiO2 using Debye-Scherrer Equation. Thermal stability, by TGA, was improved while the water vapor permeability was reduced upon increasing the nTiO2 content. Color measurements showed that the nTiO2 incorporation didn't significantly affect the transparency. Elongation at break was decreased upon nTiO2 incorporation while tensile strength and Young's modulus were increased with increasing nTiO2 up to 3 wt% then begin to decrease. The nanocomposites exhibited significant UV-barrier properties and enhanced antimicrobial activity especially at high contents of nTiO2. Shelf-life studies on green bell pepper coated with the nanocomposite films showed excellent resistance to mass loss and spoilage during storage. The obtained data confirm the efficiency of the prepared nTiO2 nanocomposite films to extend the shelf-life of food.

Optimized alginate and Aloe vera gel edible coating reinforced with nTiO2 for the shelf-life extension of tomatoes.

This work aims to prepare multifunctional edible coating based on alginate and Aloe vera (AV) optimized to minimum water vapor permeability (WVP) using Box-Behnken design. Titanium oxide nanoparticles (nTiO2) were incorporated into the optimized film at different contents. FTIR confirmed the structures, while XRD confirmed nTiO2 incorporation with a size ranging from 20.38 to 28.81 nm. The UV-shielding was enhanced either in the presence of AV or nTiO2. Thermal stability by TGA was improved upon increasing the nTiO2 content. WVP was significantly decreased from 21.53 g mm/m2 day kPa for calcium alginate to 7.18 g mm/m2 day kPa in the presence of AV and nTiO2 (5 wt%). Color measurements showed non-significant changes in the film's transparency after AV and nTiO2 incorporation. Mechanical and antimicrobial properties were improved in the presence of nTiO2. Shelf-life studies on tomatoes showed significant resistance to mass loss and spoilage when coated with (alginate/AV) film containing 5 wt% of nTiO2.

Carboxymethyl cellulose/sodium alginate/chitosan biguanidine hydrochloride ternary system for edible coatings.

Chitosan biguanidine hydrochloride (CBg) was prepared as a novel multifunctional biodegradable polymer with antimicrobial and excellent water-solubility properties, and used as a crosslinker to prepare carboxymethyl cellulose (CMC)/alginate (A)/CBg edible coating. FTIR confirmed the successful preparation of CBg and CMC/A/CBg films. Wide-angle X-ray diffraction showed that the amorphous structure of CMC/A had some degree of order after CBg addition. The film thickness and solubility were decreased after CBg addition due to the formation of a dense crosslinked structure. CBg addition significantly improved the thermal properties of the films as detected from the calculated IPDT values from TGA curves. Water vapor permeability was reduced to 54% of the value of CMC/A when CBg was added by15 wt%. The addition of CBg didn't change the transparency of CMC/A films. The mechanical properties and antibacterial properties were significantly enhanced after the addition of CBg. CMC/A/CBg were coated on tomato fruits, and the shelf-life studies showed that the storage weight loss was significantly reduced, and the spoilage was inhibited after coating. These results suggest that CMC/A/CBg edible coating might be a promising candidate in food preservation industries.

Development of antibacterial carboxymethyl cellulose/chitosan biguanidine hydrochloride edible films activated with frankincense essential oil.

This study aims to prepare binary edible films made from carboxymethyl cellulose (CMC) and chitosan biguanidine hydrochloride (CBg) activated with frankincense oil (FO). The interactions between CMC, CBg and FO were confirmed by FTIR. XRD showed that the addition of FO led to decreasing the crystallinity of CMC/CBg films. The water vapour permeability was reduced upon increasing the FO content. The presence of FO made the films brighter and didn't change their transparency as detected from the color measurements. The films exhibited better mechanical properties in the presence of FO as detected from the improved values of both tensile strength and elongation at break. The prepared films exhibited excellent antibacterial activity especially at high content of FO (5%). CMC/CBg/FO films might be used potentially in the production of edible films due to their excellent physical and antibacterial properties.

Effect of vinyl montmorillonite on the physical, responsive and antimicrobial properties of the optimized polyacrylic acid/chitosan superabsorbent via Box-Behnken model.

This work aims to study the effect of a vinyl-modified montmorillonite (VMT) on the physical and antimicrobial properties of chitosan-graft-polyacrylic acid superabsorbent (Ch-g-PA). Ch-g-PA was first optimized using Box-Behnken design to obtain the maximum equilibrium swelling, and the model was efficient to express the experimental swelling data (R2 = 0.999). VMT was further added to the optimized Ch-g-PA in different contents 0, 4, 7 and 10 wt%. FTIR confirmed the successful synthesis of the copolymers and their nanocomposites. Morphology and the average pores size were studied using SEM. Wide angle X-ray diffraction showed the formation of exfoliated nanocomposites after VMT addition. Thermal stability studied by TGA was greatly enhanced in the presence of VMT. The swelling kinetics by Voigt-based viscoelastic model showed that the equilibrium swelling was increased by increasing the VMT up to 7 wt% then decreased after further incorporation. The superabsorbents exhibited salt and pH-responsive properties and showed a pH-reversibility at two buffer solutions (pH = 2 and pH = 9). Moreover, the prepared superabsorbents exhibited a strong bacterial and fungal killing ability which becomes more pronounced upon increasing the VMT content. The obtained results encourage the usage of the prepared copolymer nanocomposites in many fields as antimicrobial superabsorbents of improved physical properties.

Novel biodegradable and antibacterial edible films based on alginate and chitosan biguanidine hydrochloride.

Novel bioactive edible films based on sodium alginate (A) and chitosan biguanidine hydrochloride (CG) with different weight percents were successfully prepared. 13C NMR and 1H NMR confirmed the successful guanidylation of chitosan. Fourier transform infrared confirmed the successful reaction between CG and A. The interaction between CG and A was confirmed through the reduction of the crystalline peaks of both CG and A as detected from their wide-angle X-ray diffraction. Thermogravimetric analysis confirmed that CG enhanced the thermal stability of films as detected from the calculated integral procedure decomposition temperature (IPDT) values. CG incorporation improved the mechanical properties of dry and wet samples. A/CG films exhibited a reduced water vapor permeability and good color properties. The antibacterial study proved that the prepared films showed a remarkable antibacterial killing ability. These results revealed that A/CG films could be an alternative candidate to be used as antibacterial edible films in food industries.

Synthesis, characterization and antimicrobial activity of biguanidinylated chitosan-g-poly[(R)-3-hydroxybutyrate].

Chitosan biguanidine hydrochloride (ChG) and low molecular weight poly[(R)-3-hydroxybutyrate] (PHB) were successfully prepared to overcome the solubility problem of chitosan and PHB and also to enhance antimicrobial activity of chitosan. The graft copolymers based on ChG and PHB (ChG-grafted PHB) were then prepared via condensation reaction of the carboxylic groups of PHB with the amino groups of ChG. These graft copolymers swell in water. The prepared graft copolymers were characterized by FTIR, 1H NMR, X-ray diffraction (XRD) and thermal analyses (TGA and DSC). TGA and DSC results revealed that the thermal stability and crystallinity of the graft copolymers were found to increase as the content of PHB increased. The antimicrobial activity of both ChG and ChG-grafted PHB, against Streptococcus pneumoniae, Bacillus subtilis, Escherichia coli (as examples of bacteria) and Aspergillus fumigatus, Geotricum candidum and Syncephalastrum recemosum (as examples of fungi), were tested. Among them, ChG and ChG-grafted PHB with the highest grafting percent investigated showed to possess relatively higher antimicrobial activity with low MIC values in the range of 0.49-3.90µgmL-1.

Synthesis, characterization, and biological activity of cross-linked chitosan biguanidine loaded with silver nanoparticles.

Chitosan biguanidine hydrochloride (ChG) and glutaraldehyde cross-linked chitosan biguanidine (CChG) were synthesized and characterized by Fourier transform infrared spectroscopy, 1H NMR and 13C NMR, X-ray diffraction, scanning electron microscopy (SEM) and thermal analyses (TGA and DTA). The results showed that ChG and CChG had a more amorphous structure than that of chitosan, and their thermal stability were slightly lower than that of chitosan. Colloidal silver nanoparticles (AgNPs) were prepared using borohydride reduction method and then investigated as fillers in partially cross-linked chitosan biguanidine. The obtained nanoparticles were uniform and spherical with average size of 9.6 ± 0.5 nm. The prepared CChG/AgNPs composites were characterized for their morphology, thermal properties, cytotoxicity and antimicrobial activity. The SEM images showed that the AgNPs are well imbedded in the CChG matrix. The thermal stability of CChG was improved with incorporation of AgNPs. The CChG and CChG/AgNPs showed less cytotoxicity to breast cancer cells (MCF-7). Compared with chitosan and CChG, the ChG and CChG/AgNPs showed better antimicrobial activity against Streptococcus pneumoniae and Bacillus subtilis as Gram-positive bacteria, Escherichia coli as Gram-negative bacteria and Aspergillus fumigatus, Geotricum candidum and Syncephalastrum recemosum as fungi.

Synthesis, characterization and biological activity of Schiff bases based on chitosan and arylpyrazole moiety.

The Schiff bases of chitosan were synthesized by the reaction of chitosan with 3-(4-substituted-phenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde. The structure of the prepared chitosan derivatives was characterized by FT-IR spectroscopy, elemental analysis, and X-ray diffraction studies and thermogravimetric analysis (TG). The results show that the specific properties of Schiff bases of chitosan can be altered by modifying the molecular structures with proper substituent groups.TG results reveal that the thermal stability of the prepared chitosan Schiff bases was lower than chitosan. The activation energy of decomposition was calculated using Coats-Redfern model. The antimicrobial activity of chitosan and Schiff bases of chitosan were investigated against Streptococcus pneumonia, Bacillis subtilis, Escherichia coli (as examples of bacteria) and Aspergillus fumigatus, Geotricum candidum and Syncephalastrum recemosum (as examples of fungi). The results indicated that the antimicrobial activity of the Schiff bases was stronger than that of chitosan and was dependent on the substituent group. The activity of un-substituted arylpyrazole chitosan derivative toward the investigated bacteria and fungi species was better than the other derivatives.