Synthesis of new chitosan Schiff base and its Fe2O3 nanocomposite: Evaluation of methyl orange removal and antibacterial activity

Fabrication of a novel polyvinylpyrrolidone/chitosan-Schiff base/Fe2O3 nanocomposite for efficient adsorption of Pb(II) and Hg(II) ions from aqueous solution

A novel magnetic polyvinylpyrrolidone/chitosan-Schiff base/Fe2O3 (PVP/CS-SB/Fe2O3) adsorbent was prepared by one-pot facile co-precipitation route for adsorption of Pb(II) and Hg(II) ions from aqueous solution. Fourier transform infrared-spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET) were used to characterize the synthesized PVP/CS-SB/Fe2O3. The results predicted that the successfully synthesis of magnetic CSSB-PVP@Fe2O3. The effects of important factors such as pH solution, contact time, concentration of metal ions, adsorbent dose and co-existing ions on Pb(II) and Hg(II) adsorption were investigated. The maximum adsorption capacities of Pb(II) and Hg(II) ions at optimal conditions were 120 mg/g and 102.5 mg/g, respectively. The kinetic studies predicted that the adsorption followed the pseudo-second-order (PSO) model as chemisorption using the coordination of active sites of PVP/CS-SB/Fe2O3 with the metal ions and also n-π interactions. Reproducibility results predicted that the excellent regeneration ability after 6 adsorption cycles. According to the results of this work, the PVP/CS-SB/Fe2O3 nanocomposite is promising for Pb(II) and Hg(II) ions adsorption and can be potential as a simple, low-cost, high-efficient adsorbent for decontamination of other heavy metal ions from aqueous solution.

Bactericidal Chitosan Derivatives and Their Superabsorbent Blends with ĸ-Carrageenan

The aim of this work is research dedicated to the search for new bactericidal systems for use in cosmetic formulations, dermocosmetics, or the production of wound dressings. Over the last two decades, chitosan, due to its special biological activity, has become a highly indispensable biopolymer with very wide application possibilities. Reports in the literature on the antibacterial effects of chitosan are very diverse, but our research has shown that they can be successfully improved through chemical modification. Therefore, in this study, results on the synthesis of new chitosan-based Schiff bases, dCsSB-SFD and dCsSB-PCA, are obtained using two aldehydes: sodium 4-formylbenzene-1,3-disulfonate (SFD) and 2-pyridine carboxaldehyde (PCA), respectively. Chitosan derivatives synthesized in this way demonstrate stronger antimicrobial activity. Carrying out the procedure of grafting chitosan with a caproyl chain allowed obtaining compatible blends of chitosan derivatives with κ-carrageenan, which are stable hydrogels with a high swelling coefficient. Furthermore, the covalently bounded poly(ε-caprolactone) (PCL) chain improved the solubility of obtained polymers in organic solvents. In this respect, the Schiff base-containing polymers obtained in this study, with special hydrogel and antimicrobial properties, are very promising materials for potential use as a controlled-release formulation of both hydrophilic and hydrophobic drugs in cosmetic products for skin health.

A novel chitosan-alginate@Fe/Mn mixed oxide nanocomposite for highly efficient removal of Cr (VI) from wastewater: Experiment and adsorption mechanism

In this study, the synthesis and experimental theoretical evaluation of a new chitosan/alginate/hydrozyapatite nanocomposite doped with Mn2 and Fe2O3 for Cr removal was reported. The physicochemical properties of the obtained materials were analyzed using the following methods: SEM-EDX, XRD, FTIR, XPS, pH drift measurements, and thermal analysis. The adsorption properties were estimated based on equilibrium and adsorption kinetics measurements. The Langmuir, Freundlich and Temkin isotherms were applied to analyze the equilibrium data. The thermodynamic analysis of adsorption isotherms was performed. A number of equations and kinetic models were used to describe the adsorption rate data, including pseudo-first (PFOE) and pseudo-second (PSOE) order kinetic equations. The obtained test results show that the synthesized biomaterial, compared to pure chitosan, is characterized by greater resistance to high temperatures. Moreover, this biomaterial had excellent adsorption properties. For the adsorption of Cr (VI), the equilibrium state was reached after 120 min, and the sorption capacity was 455.9 mg/g. In addition, DFT calculations and NCI analyses were performed to get more light on the adsorption mechanism of Cr (VI) on the prepared biocomposite.

Bactericidal, anti-biofilm, anti-oxidant potency and catalytic property of silver nanoparticles embedded into functionalised chitosan gel

Chitosan is a versatile biocompatible polysaccharide which has attracted great attention for gel synthesis. Its reducing character is specifically exploited for nanoparticle synthesis via green approach. A silver nanocomposite synthesized using this gel, with a novel gelling agent 2,4,6-trihydroxy benzaldehyde, was found to be a promising candidate for several applications including anti-bacterial, anti-biofilm and anti-oxidant activity as well as catalysis. The nanocomposite was well characterized using various spectroscopic and microscopic techniques such as IR, TGA, XRD, XPS, SEM and TEM. The nanocomposite exhibited high bactericidal activity against both S. aureus and E. coli. Further, it was evaluated for anti-biofilm forming property and its potency as antioxidant agent. The nanocomposite served as a catalyst for degradation of Methyl Orange and Rhodamine B at high concentrations (in the range of mM) with a catalytic efficiency of 98.58 % and 99.56 % within 3 min and 5 min respectively.

Synthesis and biological evaluation against H. pylori of chitosan menthone Schiff base hybrid with different types of inorganic nanoparticles

The production of novel natural medicines for the treatment of Helicobacter pylori (H. pylori) has lately attracted a lot of interest. Some bacterial infections have traditionally been alleviated by terpenes. The present work intended to examine the impact of several chitosan menthone Schiff base nanocomposites on the treatment of H. pylori infection as well as on its anti-inflammatory capacity. Chitosan (Cs) was condensed with menthone with different molar ratios of Cs:menthone (1:0.5, 1:1, and 1:2) to produce chitosan Schiff bases namely; Cs-SB1, Cs-SB2, and Cs-SB3, respectively. Cs-SB3 Schiff base nanocomposites were prepared individually by adding 2%Ag, 2%Se, (1%Ag + 1%Se), and 2%Fe2O3 nanoparticles to produce compounds denoted as Cs-SB-Ag, Cs-SB-Se, Cs-SB-Ag/ Se, and Cs-SB-Fe, respectively. The anti-H. pylori activity of Cs-SB-Se was detected at a minimal inhibitory concentration MIC of 1.9 μg/mL making it the most biologically active compound in our study. Cs-SB-Se nanocomposite was tested for its cyclooxygenases (COX-1 and COX-2) inhibitory potential which demonstrated inhibitory efficacy towards COX enzymes with inhibition value against COX-1 (IC50 = 49.86 ± 1.784 μg/mL) and COX-2 (IC50 = 12.64 ± 0.463 μg/mL) which were less than the well-known Celecoxib (22.65 ± 0.081 and 0.789 ± 0.029 μg/mL) and Indomethacin (0.035 ± 0.001 and 0.08 ± 0.003 μg/mL) inhibitors. The selectivity index SI = 3.94 for tested nanocomposites indicated higher selectivity for COX-1. The cytotoxicity of the Cs-SB-Se nanocomposite was evaluated in Vero cells (CCL-81) and it showed that at a concentration of 62.5 μg/mL, cell viability was 85.43 %.

Functionalization of Shorea faguetiana biochar using Fe2O3 nanoparticles and MXene for rapid removal of methyl blue and lead from both single and binary systems

The synthesis of polymeric magnetic composites is a promising strategy for the rapid and efficient treatment of wastewater. Lead and methyl blue are extremely hazardous to living organisms. The sorption of Pb2+ and the dye methyl blue (MB) by biochar is an ecologically sustainable method to remediate this type of water pollution. We functionalized Shorea faguetiana biochar with Fe2O3 and MXene, resulting in Fe2O3/BC/MXene composites with an efficient, rapid, and selective adsorption performance. Based on X-ray photoelectron and Fourier transform infrared spectrometry, we found that the Fe2O3/BC/MXene composites had an increased number of surface functional groups (F-, C[double bond, length as m-dash]O, CN, NH, and OH-) compared with the original biochar. The batch sorption findings showed that the maximum sorption capacities for Pb2+ and MB at 293 K were 882.76 and 758.03 mg g-1, respectively. The sorption phenomena obeyed a pseudo-second-order (R2 = 1) model and the Langmuir isotherm. There was no competition between MB and Pb2+ in binary solutions, indicating that MB and Pb2+ did not influence each other as a result of their different adsorption mechanisms (electrostatic interaction for Pb2+ and hydrogen bonding for MB). This illustrates monolayer sorption on the Fe2O3/BC/MXene composite governed by chemical adsorption. Thermodynamic investigations indicated that the sorption process was spontaneous and exothermic at 293-313 K, suggesting that it is feasible for practical applications. Fe2O3/BC/MXene can selectively adsorb Pb2+ ions and MB from wastewater containing multiple interfering metal ions. The sorption capacities were still high after five reusability experiments. This work provides a novel Fe2O3/BC/MXene composite for the rapid and efficient removal of Pb2+ and MB.

Rapid and convenient synthesis of "green" ammonium-modified chitosan composite sponge with the existence of ascorbic acid for highly efficient removal of Congo red (CR)

In this study, a new green composite sponge made of chitosan and modified with ammonium ascorbate (ACS-CIT) was synthesized in just 10 min. Compared with CS-CIT (sponge prepared from acetic acid), ACS-CIT exhibits significantly enhanced adsorption performance for CR, with the saturated adsorption capacities increased from 353.667 to 1261.639 mg·g-1. The adsorption mechanism can be summarized as the generation of more hydrogen bonds, electrostatic attraction, and intra particle diffusion, revealing the addition of ascorbic acid introduced more hydroxyl groups, thereby enhancing the hydrogen bonding force, and the ammonium modification of chitosan improved the electrostatic attraction of the material, resulting in a significant increase in its adsorption capacity. Additionally, the prepared ACS-CIT showed excellent CR removal performance even in the presence of multiple interfering factors coexisting in the simulated wastewater, and the adsorption capacity remained stable after at least five cycles. Furthermore, the maximum bed capacity of ACS-CIT for CR is 1152.829 mg·g-1 under the given conditions of a flow rate of 1 mL·min-1, inlet concentration of 150 mg·L-1, a bed height of 1 cm respectively, and the breakthrough curve followed the Thomas model. The results indicated the eco-friendly and recyclable ACS-CIT is a promising adsorbent for CR dye removal in water.

The modified biochar from wheat straw by the combined composites of MnFe2O4 nanoparticles and chitosan Schiff base for enhanced removal of U(VI) ions from aqueous solutions

In the last few decades, U(VI) is a significant environmental threat. The innovative and environmentally friendly adsorbent materials for U(VI) removal were urgent. Preparation of the modified biochar from wheat straw by combined composites of MnFe2O4 nanoparticles and chitosan Schiff base (MnFe2O4@CsSB/BC) was characterized, and adsorption experiments were carried out to investigate the performance and interfacial mechanism of U(VI) removal. The results showed that MnFe2O4@CsSB/BC exhibited high adsorption capacity of U(VI) compared with BC. The adsorption process of U(VI) removal by MnFe2O4@CsSB/BC could be ascribed as pseudo-second-order model and Langmuir model. The maximum adsorption capacity of U(VI) removal by MnFe2O4@CsSB/BC reached 19.57 mg/g at pH4.0, 30 mg/L of U(VI), and 25 °C. The possible mechanism was a chemical adsorption process, and it mainly contained electrostatic attraction and surface complexation. Additionally, it also was an economic and environmental friendly adsorbent.

2-Pyridinecarboxaldehyde-Modified Chitosan-Silver Complexes: Optimized Preparation, Characterization, and Antibacterial Activity

The widespread prevalence of infectious bacteria is one of the greatest threats to public health, and consequently, there is an urgent need for efficient and broad-spectrum antibacterial materials that are antibiotic-free. In this study, 2-pyridinecarboxaldehyde (PCA) was grafted onto chitosan (CS) and the modified CS coordinated with silver ions to prepare PCA-CS-Ag complexes with antibacterial activity. To obtain complexes with a high silver content, the preparation process was optimized using single-factor experiments and response surface methodology. Under the optimal preparation conditions (an additional amount of silver nitrate (58 mg), a solution pH of 3.9, and a reaction temperature of 69 °C), the silver content of the PCA-CS-Ag complex reached 13.27 mg/g. The structure of the PCA-CS-Ag complex was subsequently verified using ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. Furthermore, three possible complexation modes of the PCA-CS-Ag complex were proposed using molecular mechanics calculations. The results of the antibacterial assay in vitro showed that the PCA-CS-Ag complex exhibited strong antibacterial activity against both Gram-positive and Gram-negative bacteria, exerting the synergistic antibacterial effect of modified chitosan and silver ions. Therefore, the PCA-CS-Ag complex is expected to be developed as an effective antibacterial material with promising applications in food films, packaging, medical dressings, and other fields.

Chitosan cross-linked and grafted with epichlorohydrin and 2,4-dichlorobenzaldehyde as an efficient adsorbent for removal of Pb(II) ions from aqueous solution

Epichlorohydrin-modified chitosan-Schiff base composite (CS/24Cl/ECH) prepared via the one-pot reaction as characterized by Fourier transform Infra-Red spectroscopy (FT-IR), X-ray powder diffraction (XRD), Differential scanning calorimetry (DSC) and Scanning electron microscope (SEM). Its removal ability of Pb(II) ions from aqueous solution was investigated. The adsorption of Pb(II) ions carried out at different initial pH, dose of CS/24-Cl/ECH, contact time and co-existing ions. The maximum adsorption capacity of Pb(II) ions was 170 mg/g. Finally, based on the absorption results, the adsorption of Pb(II) ions was fitted by single-layer Langmuir isotherm model and the pseudo-second-order (PSO) kinetics model. The absorption mechanism of Pb(II) ions was controlled by chemical coordination Pb(II) ions with the active sites on the surface of CS/24Cl/ECH composite. Also, CS/24Cl/ECH showed excellent recyclable efficiency up to 5 cycle and potential sorbent for other heavy metal ions.

Synthesis and characterization of pendant N,N-dimethylaminobenzaldehyde-functionalized chitosan Schiff base composite (CS@MABA) as a new sorbent for removal of Pb(II) ions from aqueous media

In this work, new pendant N,N-dimethylaminobenzaldehyde-functionalized chitosan Schiff base composite (CS@MABA) was prepared from the simple and convenient condensation reaction between chitosan (CS) and N,N-dimethylaminobenzaldehyde (MABA) in ethanol-glacial acetic acid (1:1 v/v) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscope (SEM). The as-prepared composite CS@MABA was applied for the removal of Pb(II) ions, due to the presence of imine, hydroxyl and phenyl groups, and the effects of important parameters such as solution pH, contact time and sorbent dosage on the removal percentage and adsorption capacity were investigated and discussed. The optimum conditions were found to be at pH 5, adsorbent dosage of 0.1 g, Pb(II) concentration of 50 mg/L and contact time of 60 min. The maximum Pb(II) removal percentage was found to be 94.28 % with the high adsorption capacity of 165 mg/g. The adsorption capacity of CS@MABA is remain 87 % after 5 adsorption-desorption cycles. The adsorption kinetic and isotherm studies indicated that the Pb(II) removal by CS@MABA follows a pseudo-first order and Langmuir models, respectively. Compared to similar compounds, the synthesized CS@MABA composite has shown a relatively high yield for removing Pb(II) ions. According to these results, the CS@MABA suggested for the sorption of other heavy metals.

Functionalization of chitosan with poly aromatic hydroxyl molecules for improving its antibacterial and antioxidant properties: Practical and theoretical studies

In this study, the chitosan backbone was functionalized with 2,2',4,4'-tetrahydroxybenzophenone by Schiff base, bonding the molecules into the repeating amine groups. The use of ¹H NMR, FT-IR, and UV-Vis analyses provided compelling evidence of the structure of the newly developed derivatives. The deacetylation degree was calculated to be 75.35 %, and the degree of substitution was 5.53 % according to elemental analysis. The thermal analysis of samples using TGA demonstrated that CS-THB derivatives are more stable than chitosan itself. SEM was used to investigate the change in surface morphology. The improvement of the biological properties of chitosan was investigated in terms of its antibacterial activity against pathogenic antibiotic-resistant bacteria. The antioxidant properties showed an improvement in activity compared to chitosan by two times against ABTS radicals and four times against DPPH radicals. Furthermore, the cytotoxicity and anti-inflammatory properties were investigated using normal skin cells (HBF4) and WBCs. Quantum chemistry calculations revealed that combining polyphenol with chitosan makes it more effective as an antioxidant than either chitosan or polyphenol alone. Our findings suggest that the new chitosan Schiff base derivative could be utilized for tissue regeneration applications.

Synthesis of Xanthan Gum Anchored α-Fe2O3 Bionanocomposite Material for Remediation of Pb (II) Contaminated Aquatic System

Increases in community and industrial activities have led to disturbances of the environmental balance and the contamination of water systems through the introduction of organic and inorganic pollutants. Among the various inorganic pollutants, Pb (II) is one of the heavy metals possessing non-biodegradable and the most toxic characteristics towards human health and the environment. The present study is focussed on the synthesis of efficient and eco-friendly adsorbent material that can remove Pb (II) from wastewater. A green functional nanocomposite material based on the immobilization of α-Fe₂O₃ nanoparticles with xanthan gum (XG) biopolymer has been synthesized in this study to be applied as an adsorbent (XGFO) for sequestration of Pb (II). Spectroscopic techniques such as scanning electron microscopy with energy dispersive X-ray (SEM-EDX), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet visible (UV-Vis) and X-ray photoelectron spectroscopy (XPS) were adopted for characterizing the solid powder material. The synthesized material was found to be rich in key functional groups such as -COOH and -OH playing important roles in binding the adsorbate particles through ligand-to-metal charge transfer (LMCT). Based on the preliminary results, adsorption experiments were conducted, and the data obtained were applied to four different adsorption isotherm models, viz the Langmuir, Temkin, Freundlich and D-R models. Based on the high values of R² and low values of χ², the Langmuir isotherm model was found to be the best model for simulation of data for Pb (II) adsorption by XGFO. The value of maximum monolayer adsorption capacity (Q_m) was found to be 117.45 mg g^-1 at 303 K, 126.23 mg g^-1 at 313 K, 145.12 mg g^-1 at 323 K and 191.27 mg g^-1 at 323 K. The kinetics of the adsorption process of Pb (II) by XGFO was best defined by the pseudo-second-order model. The thermodynamic aspect of the reaction suggested that the reaction is endothermic and spontaneous. The outcomes proved that XGFO can be utilized as an efficient adsorbent material for the treatment of contaminated wastewater.

Application of new chitosan 2,4-dihydroxyacetophenone Schiff base @SrFe12O19 nanocomposite for remove of Pb(II) ion from aqueous solution

A new chitosan 2,4-dihydroxyacetophenone Schiff base @SrFe₁₂O₁₉ (Cs-SB@SrFe₁₂O₁₉) nanocomposite was successfully prepared by one-pot reaction and fully characterized for its functional groups, morphology, elemental analysis and thermal behavior by FT-IR, XRD, VSM, DSC, TGA, zeta potential, FE-SEM and EDS techniques. The VSM result showed that Cs-SB@SrFe₁₂O₁₉ has M_s of 11.81 emu/g and H_c of 5488 Oe, known as hard magnetic material. Finally, the as-prepared sample utilized as a new sorbent for the removal of Pb(II) ions from aqueous solution by using batch adsorption experiments. The adsorption of Pb(II) was carried out at different pH, contact time and initial dose of Cs-SB@SrFe₁₂O₁₉. The maximum adsorption capacity was found to be 132 mg/g (99 %) at pH 5 and the contact time of 120 min. Finally, the kinetic studies reveals that the adsorption process of Cs-SB@SrFe₁₂O₁₉ followed by the pseudo second order kinetics model. Also, the sample showed excellent recyclable efficiency up to 5 cycles.

Interplay of conformational relaxation and hydrogen bond dynamics in the excited states of fluorescent Schiff base anions

Time resolved fluorescence spectroscopic investigation of four Schiff base anions has established that their excited state dynamics is governed by several solvent properties: polarity, viscosity and hydrogen bond donating ability. With viscous protic solvents like glycerol, fluorescence lifetimes of anions have been found to be markedly longer than those in ethanol, implying that conformational relaxation of molecules plays a key role in their nonradiative relaxation. Surprisingly, the lifetimes in less viscous aprotic solvents, like acetonitrile, are found to be even longer. The only plausible rationalization of this observation is in the light of hydrogen bond-assisted nonradiative phenomena that are operative in protic solvents. This contention draws support from a time evolution of the emission in the red end of the spectrum in low to moderately hydrogen bond donating protic solvents, with regard to an absence of such a rise time in aprotic solvents and strongly hydrogen bond donating solvents, viz., 2,2,2-trifluoroethanol. Rudimentary quantum chemical calculations provide a preliminary idea about the nature of excited state hydrogen bond redistribution involved in the process.

Facile Synthesis of Magnetic Iron-Based Nanoparticles from the Leach Solution of Hyperaccumulator Plant Pinus brutia for the Antibacterial Activity and Colorimetric Detection of Ascorbic Acid

It has been well known that metallic nanoparticles with striking properties possess wide application prospects in the processes of colorimetric detection, catalysis, disease diagnosis and treatment, energy, wastewater treatment, remediation, and antibacterial activity in recent years. Herein, iron-based nanoparticles (FeNPs), metallic nanoparticles, were synthesized via a facile chemical reduction method using a hyperaccumulator plant. Also, their use in antibacterial activity applications and colorimetric ascorbic acid (AA) detection was investigated. It was observed that FeNPs presented high antibacterial potency against Gram-positive bacteria of Listeria monocytogenes and Staphylococcus aureus and also Gram-negative bacteria of Escherichia coli(O157: H7), E. coli(ATCC 25922), Salmonella enteritidis, and Salmonella typhimurium. Moreover, it was found that FeNPs exhibited superior peroxidase-like activity to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue color product, oxidized TMB (oxTMB), in the presence of H₂O₂. The colorimetric AA detection could be carried out by making the solution color lighter owing to the antioxidant property of AA. The quantitative detection of AA could be performed simply, selectively, and sensitively with FeNPs with a detection limit (LOD) of 0.5462 μM in a linear range of 30-200 μM.

Synthesis of novel chitosan Schiff base and its ZnO nanocomposite for removal of synthetic dye, antimicrobial, and cytotoxicity activity

In this work, a novel chitosan Schiff base 4-(2-Hydroxyaniline)pent-3-en-2-one chitosan (2-HyA-CS) and its ZnO nanocomposite (2-HyA-CS/ZnO) were sensitized and characterized by appropriate methods; FTIR, XRD, Elemental analysis, SEM, TEM and TGA. The result of characterization methods confirms the preparation of 2-HyA-CS and 2-HyA-CS/ZnO. The SEM images reveal that chitosan, 2-HyA-CS, and 2-HyA-CS/ZnO have a varied roughness and porous surfaces. The reason for this difference was attributed to the formation of Schiff base 2-HyA-CS and the presence of ZnO nanoparticles in 2-HyA-CS/ZnO. The patterns of XRD and FTIR confirm the formation of 2-HyA-CS and 2-HyA-CS/ZnO. The degree of substitution (DS) of modified chitosan 2-HyA-CS was calculated using Elemental analysis and FTIR.ATR, it was found to be 74%. The adsorption efficiency of the produced adsorbents was compared with pure chitosan to remove of Remazol Brilliant Blue R (RBBR) from an aqueous medium and antimicrobial activity. The removal percentage of RBBR by chitosan, 2-HyA-CS, and 2-HyA-CS/ZnO are 47.12%, 91.9%, and 96.56%, respectively with the following order: 2-HyA-CS/ZnO > 2-HyA-CS > chitosan. Their antimicrobial activities were studied against two Gram negative bacteria ( E. coli and P. aeruginosa), two Gram positive bacteria ( S. aureus and B. cereus) and ( C. albicans) as a yeast strain, the inhibitory zone measurements revealed that the activity of 2-HyA-CS/ZnO is excellent and higher than 2-HyA-CS and pure chitosan. The cytotoxicity of the prepared compound 2-HyA-CS and 2-HyA-CS/ZnO along with pure chitosan was estimated against two human cancer cells MCF-7 cells and HepG-2 cells, the result indicates that 2-HyA-CS/ZnO having higher Inhibitory activity against both MCF-7 and HepG-2 cells with 53.5 ± 2.86 and 27.4 ± 1.23 µg/mL respectively and 2-HyA-CS possessing moderate Inhibitory activity against both MCF-7 and HepG-2 cancer cells with IC50 = 216.5 ± 7.48 and 135.6 ± 6.49 µg/ml respectively.

Microwave-assisted synthesis of cross-linked chitosan-metal oxide nanocomposite for methyl orange dye removal from unary and complex effluent matrices

Textile/Dyeing industries have been considered as one of the intense water-consuming units, resulting in the generation of a large volume of dye(s) contaminated effluent posing a heavy burden on the receiving water bodies. Therefore, the identification of methods to synthesize bulk quantity of adsorbent(s) and further their evaluation for the efficient treatment of effluent is one of the most prominent topics. Hence, microwave-assisted method was proposed for the rapid synthesis of nanocomposite (C-CS@ZnO) from natural biomolecule (chitosan-CS), a well-known crosslinker (tripolyphosphate) and metal-oxide (ZnO) nanoparticles. Detailed characterization was performed to identify the structure (SEM, XRD) and composition (FT-IR, XPS) of the sorbent. Sorption experiments with methyl orange (MO) dye solution were carried out under different pH (2.0-12.0), dye concentrations (150-350 mg L^-1), reaction times (0-210 min) and temperature (25-45 °C) to establish the adsorbent at the lab-scale. The maximum sorption capacity (185.2 mg g^-1) was obtained because of the ligand-exchange, Yoshida H-bonding and electrostatic interactions and was best elucidated by Freundlich (R² ≥ 0.99) and pseudo-second-order (R² ≥ 1) models. To simulate the field conditions, the effects of co-existing ions (anions/cations), cocktail dyes/ions mixture and regenerant were also studied. The obtained results suggest its promising applicability at a large scale for textile effluent treatment.

Enhanced antifungal and antioxidant activities of new chitosan derivatives modified with Schiff base bearing benzenoid/heterocyclic moieties

In this work, chitosan derivatives modified with Schiff base bearing benzenoid/heterocyclic moieties were successfully prepared via amidation reaction. Specific structural characterization was implemented using FTIR and ¹H NMR, and the DS of chitosan derivatives were quantitatively calculated by ratio of hydrogen proton integral. Meanwhile, the antifungal activity against two common plant pathogenic fungi (Fusarium oxysporum f. sp. cubense and Glomerella cingulata) was assayed in vitro by hyphal measurement, and data proved that the introduction of functional groups including benzene/heterocyclic compounds and Schiff base groups greatly enhanced the antifungal activity. Besides, the antioxidant efficiency was investigated in vitro, and all chitosan derivatives exhibited significantly increased antioxidant activity. Specially, the scavenging effect of 2SATCS was 96.62% at 1.6 mg/mL, which was close to the positive control VC (98.84%). These results indicated that chitosan derivatives with enhanced antifungal and antioxidant activities could serve as potential biomaterial for antifungal and antioxidant applications.

Novel Chitosan-Based Schiff Base Compounds: Chemical Characterization and Antimicrobial Activity

Chitosan (CS) and its derivatives are receiving considerable attention for their great biocompatibility and broad-spectrum activities in many fields. In this work, we aimed to characterize the antimicrobial activity of novel chitosan Schiff bases (CSSB). CS was synthesized by double deacetylation of chitin (Cn) after its extraction from the armors of crustaceans Astacus leptodactylus, and CSSB-1 and CSSB-2 were synthesized by interaction of CS with 4-(2-chloroethyl) benzaldehyde (aldehyde-1) and 4-(bromoethyl) benzaldehyde (aldehyde-2), respectively, at room temperature. The synthesized compounds were characterized by elemental analysis, gel permeation chromatography (GPC), infrared spectroscopy (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The antimicrobial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria and against yeasts (Candida albicans) was significantly increased due to their higher solubility as compared to unmodified CS opening perspectives for the use of these compounds for antimicrobial prevention in different fields as, for example, food industry, cosmetics, or restoration.

The influence of bioactive glyoxylate bearing Schiff base on antifungal and antioxidant activities to chitosan quaternary ammonium salts

In this study, to investigate the influence of glyoxylate bearing Schiff base on bioactivity to chitosan quaternary ammonium salts, different chitosan derivatives were synthesized by ion exchange of glyoxylate bearing Schiff base with chitosan quaternary ammonium salts (TMCI and HACC). For this purpose, glyoxylate was prepared by Schiff base reaction of glyoxylic acid and amino heterocycles and it was further ionization to substitute iodide ions and chloride ions. After structural characterization by FTIR and ¹H NMR, the antifungal and antioxidant activities were measured. Results indicated that glyoxylate bearing Schiff base could improve the bioactivity of TMCI and HACC obviously. Specifically, anionic TMCI with Schiff base of amino pyridines possessed best antioxidant activity >92.40% at 1.6 mg/mL against DPPH radicals. Meanwhile, they showed antifungal activity >84.88% at 1.0 mg/mL against G. cingulate. Furthermore, the cytotoxicity was evaluated, and all samples showed good cell viability >80.14% at 1000 μg/mL.

Efficient removal of Pb(II) using modified chitosan Schiff base@Fe/NiFe

A novel modified chitosan Schiff base@Fe₂O₃-NiFe₂O₄ (CsSB@Fe/NiFe) was prepared and characterized using FT-IR, XRD, SEM, EDX, TGA, DSC and VSM. FT-IR and XRD results confirm that the nanoparticles of Fe/NiFe distributed throughout the surface of CS-OH and successfully prepared CsSB@Fe/NiFe. SEM image shows that the Fe/NiFe nanoparticles were assembled in the surface and inside of CS-OH. Coercivity (H_c) of CsSB@Fe/NiFe is ≈ 110 Oe, indicated that it was kind of soft-magnetic materials with saturation magnetization (M_s) of 6.45 emu/g. In addition, CsSB@Fe/NiFe was further explored as an new sorbent for the removal of Pb(II) ion from aqueous solution and the influence of various important parameters such as solution pH, contact time, dosage of adsorbent and initial Pb(II) concentration were studied and optimized. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 0.05 g, initial Pb(II) concentration of 75 ppm and contact time of 120 min. The maximum Pb(II) removal percentage was found to be 97%. Also, CsSB@Fe/NiFe shows about 88% Pb(II) removal after five adsorption-desorption cycles. The results suggested that the sorption of Pb(II) onto CsSB@Fe/NiFe was feasible and spontaneous.

Preparation of new bio-based chitosan/Fe2O3/NiFe2O4 as an efficient removal of methyl green from aqueous solution

Modified chitosan with various functional groups has high potential as an efficient adsorbent in removing water pollution. In this study, new magnetic adsorbent, bio-based chitosan/Fe₂O₃/NiFe₂O₄, was successfully prepared by green chemistry route involving mixing of chitosan as core moiety and Fe₂O₃/NiFe₂O₄ nanocomposite, and slow evaporation of solvent. Synthesized chitosan/Fe₂O₃/NiFe₂O₄ was characterized by FT-IR, TGA, XRD, VSM and FE-SEM. The FT-IR and XRD results confirmed that the successful preparation of chitosan/Fe₂O₃/NiFe₂O₄. Uniform dispersion of Fe₂O₃/NiFe₂O₄ nanoparticles with low aggregation was confirmed by FE-SEM. The as-prepared magnetic chitosan/Fe₂O₃/NiFe₂O₄ was developed as solid phase adsorbent to remove methyl green (MG) dye from aqueous solutions. Several important parameters such as contact time, pH, temperature and adsorbent dosage were investigated systematically. The high and fast MG dye removal (≈ 80%) occurs after 30 min. The optimal conditions for MG removal was recorded at pH = 8, contact time of 60 min, adsorbent dosage of 0.2 g and 25 °C and displayed a high MG dye removal percentage of 96.51% and adsorption capacity of 77.22 mg/g.

New chitosan Schiff base and its nanocomposite: Removal of methyl green from aqueous solution and its antibacterial activities

New chitosan Schiff base (CS-NB) and its CS-NB-NiFe nanocomposite have been prepared and characterized by FTIR spectroscopy, XRD, SEM and DSC. FT-IR spectra and XRD patterns revealed the preparation of chitosan Schiff base CS-NB and its CS-NB-NiFe nanocomposite. DSC demonstrated the endo and exothermic correspondence the evaporation of solvent and decomposition of pyranose ring, respectively. Antibacterial activities was evaluated for the as-prepared compounds against two Gram-positive (Staphylococcus aureus and Bacillus cereus) and two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and the results shows that the antibacterial activities of the compounds are found to be stronger than that of chitosan. The order of antibacterial effect according to inhibitory zone around is as follows: S. aureus > E. coli > B. cereus > P. aeruginosa. In addition, the removal of methyl green (MG) dye using CS-NB and its CS-NB-NiFe nanocomposite were analyzed and results showed that the compounds can be effectively used to remove of MG from aqueous solution. Results show that the percentage removal of MG by nanocomposite is higher than Schiff base.

The Fe3O4@apple seed starch core-shell structure decorated In(III): A green biocatalyst for the one-pot multicomponent synthesis of pyrazole-fused isocoumarins derivatives under solvent-free conditions

In current decades, the fabrication and design of magnetic biocatalysts have been advancing as green catalysts. Hence, in this paper, we use the apple seed starch to create indium(III) immobilized on Fe₃O₄@apple seed starch core-shell magnetic nanocatalyst (Fe₃O₄@apple seed starch-In(III)). The prepared catalyst was identified and evaluated with several analysis techniques. The application of this catalyst in the synthesis of isochromeno[4,3-c]pyrazole-5(1H)-one derivates under solvent-free conditions was a new approach with high efficiency. Due to the magnetic nature of the catalyst, the catalyst separation from the reaction medium is easy, and it is reusable for five runs without significant change in catalytic activity. The fabrication of this catalyst is based on green chemistry principles and is more economical and stable than other catalysts in the synthesis of pyrazole-fused isocoumarins heterocyclic compounds.

Edible Materials in Tissue Regeneration

Edible materials have attracted increasing attention because of their excellent properties including availability, biocompatibility, biological activity, and biodegradability. Natural polysaccharides, phenolic compounds, and proteins are widely used in tissue regeneration. To better characterize their healing effect, this review article describes the applications of edible materials in tissue regeneration including wound healing and bone tissue regeneration. As an introduction to the topic, their sources and main bioactive properties are discussed. Then, the mechanism by which they facilitate wound healing based on their hemostasis, antibacterial, anti-inflammatory, and antioxidant properties is systematically investigated. Moreover, a more comprehensive discussion is presented on the approaches by which edible materials can be used as scaffolds or agents for the provision of the components of natural bones for regulating the level of osteogenesis-related cytokines to enhance bone repair. Finally, the prospects of edible materials for tissue regeneration are discussed.