Chitosan Group Research Articles

A novel multifunctional composite film of oxidized dextran crosslinked chitosan and ε-polylysine incorporating protocatechuic acid and its application in meat packaging

Oxidized dextrans (ODex) with different oxidation degrees were prepared by periodate oxidation. Chitosan (CS) and ε-polylysine (PL) were crosslinked with ODex and incorporated with protocatechuic acid (PA) to enhance the properties of the chitosan-based films. FT-IR, XPS and XRD analysis showed that the aldehyde groups of ODex were covalently crosslinked with amino groups of CS and PL through Schiff base reaction, and PA interacted with the film components through non-covalent bonds. The results of SEM and AFM indicated that the film structure became denser with the addition of ODex. Increasing crosslinking degree resulted in deepened color and improved the UV-blocking ability of the films, which was caused by the increase of CN groups. Covalent crosslinking significantly reduced the moisture content, swelling degree and water solubility. The film with 50% ODex had the highest mechanical strength (31.72 MPa) and modulus of elasticity (885.54 MPa). The results of water vapor permeability, thermal properties and PA release experiments also indicated the crosslinking of the films by ODex. The incorporation of PA significantly improved the antioxidant activity of the films, but to some extent, the antibacterial activity of the films decreased due to the consumption of amino groups by crosslinking. In addition, application experiments suggested that crosslinked films could maintain the quality and freshness of chilled meat for a longer period than that of PE plastic films. The study suggested that the new crosslinked films might have good prospects as food packaging materials.

New Functionalized Chitosan with Thio-Thiadiazole Derivative with Enhanced Inhibition of Pathogenic Bacteria, Plant Threatening Fungi, and Improvement of Seed Germination

In this study, a new modified chitosan conjugate (Chito-TZ) was developed via amide coupling between the acid chloride derivative of the methylthio-thidiazole compound and the free primary amino groups of chitosan. The product was characterized using several instrumental investigations, including Fourier-transform infrared spectroscopy (FT-IR), 1H-Nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). XRD indicated that the crystalline pattern of chitosan was interrupted after chemical modification with the thiadiazole derivative. Broido’s model was used to determine the thermal activation energy Ea, and the results showed that the Ea for the first decomposition region of Chito-TZ is 24.70 KJ mol−1 lower than that required for chitosan (95.57 KJ mol−1), indicating the accelerating effect of the thiadiazole derivative on the thermal decomposition of Chito-TZ. The modified chitosan showed better antibacterial and antifungal activities than the non-modified chitosan; except for seed germination, chitosan was better. The Chito-TZ showed a low MIC value (25–50 µg mL−1) compared to Chito (50–100 µg mL−1). Moreover, the maximum inhibition percentages for plant-pathogenic fungi, Aspergillus niger, Fusarium oxysporum, and Fusarium solani, were attained at a concentration of 300 µg mL−1 with values of 35.4 ± 0.9–39.4 ± 1.7% for Chito and 45.2 ± 1.6–52.1 ± 1.3% for Chito-TZ. The highest germination percentages (%) of broad bean, shoot and root length and weight, and seed vigor index were obtained after Chito treatment with a concentration of 200 µg mL−1 compared to Chito-TZ.

The Effect of Chitosan and Polyvinyl Alcohol Combination on Physical Characteristics and Mechanical Properties of Chitosan-PVA-Aloe vera Film

Background: Wound is a condition where there is damage or disruption to the anatomical structure and function of the skin. Wounds that are not treated properly can lead to infection. As wound dressings, film dressings have many advantages such as being elastic, flexible, transparent, and can adapt to the wound shape. Film’s characteristics of are affected by the plasticizer and the polymer. Combination of chitosan and polyvinyl alcohol (PVA) is able to improve the mechanical properties of the film such as its swelling capacity, tensile strength, and elongation at break. Objective: This study aims to determine the effects of chitosan and PVA in various concentrations on the physical characteristics and mechanical properties of the film. Methods: Film was prepared by solvent casting method, using chitosan and alginate in various concentrations of 0% to 1.5%, 1.5% Aloe vera, and 6% propylene glycol. Films’ characteristics and mechanical properties were evaluated, such as swelling index, tensile strength, elongation at break, and Young’s modulus. Results: The result showed that chitosan and PVA polymers had a significant effect on the swelling index, tensile strength, elongation at break, and Young’s modulus. The effect of chitosan and PVA combination on the swelling index, tensile strength, and elongation at break is due to the hydrogen bonding between the hydroxyl group of PVA and the amine group of chitosan. Conclusion: The combination of chitosan and polyvinyl alcohol influenced the film's physical and mechanical properties. Film with chitosan and polyvinyl alcohol ratio of 1.5%:1.5% have best characteristics compared to others.

The Impact of the Molecular Weight of Degradation Products with Silicon from Porous Chitosan-Siloxane Hybrids on Neuronal Cell Behavior.

Silicon (Si) is an essential trace element in the human body and it exists in connective tissue as aqueous orthosilicic acid. Porous chitosan-3-glycidoxypropyltrimethoxysilane (GPTMS) hybrids can regenerate nerve tissue and recover sensor and motor functions. However, the structures and roles of the degradation products with Si extracted from the hybrids in nerve regeneration are not clear. In this study, we prepared porous chitosan-GPTMS hybrids with different amounts of GPTMS to amino groups of chitosan (chitosan:GPTMS = 1:0.5 and 1:1 molar ratios). The structures of the degradation products with Si from the hybrids were examined using time-of-flight mass spectrometry, and biological assessments were conducted in order to evaluate their potential use in the preparation of devices for nerve repair. Glial and motor cell lines and ex vivo explants of dorsal root ganglia were used in this study for evaluating their behavior in the presence of the different degradation products with Si. The structure of the degradation products with Si depended on the starting composition. The results showed that glial cell proliferation was lower in the medium with the higher-molecular-weight degradation products with Si. Moreover, motor cell line differentiation and the neurite outgrowth of dorsal root ganglion explants were improved with the lower-molecular-weight degradation products with Si. The results obtained could be useful for designing a new nerve regeneration scaffold including silicon components.

Investigating the Electrochemical Properties of Alkaloids Compound Derived from Catharanthus Roseus Extract

The Catharanthus roseus plant was extracted and converted to nanoparticles in this work. The Soxhlet method was used to extract alkaloid compounds from the Catharanthus roseus plant and converted them to the nanoscale. Chitosan polymer was used as a linking material and converted to Chitosan nanoparticles (CSNPs). The extracted alkaloids were linked with Chitosan nanoparticles by maleic anhydride to get the final product (CSNPs-Linker-alkaloids). The pure Chitosan, Chitosan nanoparticles, and CSNPs-Linker-alkaloids were characterized by X-ray diffractometer, and Fourier Transform Infrared spectroscopy. X-ray results show that all samples have an orthorhombic structure with crystallite size in nanodimensions. FTIR spectra prove that the P=O is the cross-linkage between chitosan and phosphate groups by ionic bond, which indicate that the Chitosan nanoparticle has been formed in the solution. FTIR spectrum for CSNPs - Linker - alkaloids appear a new distinct band at 1708.93 cm-1 which demonstrates the presence of C = O esterification. Atomic Force Microscope images of the Chitosan nanoparticles and CSNPs-Linker-alkaloids show that they have almost spherical shapes with average sizes of 90 and 92.6 nm respectively. The electroactive surface area of glassy carbon electrodes (GCE), extract plant, and Linker-alkaloids were calculated in KCl solution containing K3[Fe (CN)6]. The presence of CSNPs-Linker-alkaloids in modified glassy carbon electrodes about 3 times. The successful synthesis of organic nanoparticles from the Catharanthus roseus plant can be used safely in biosensors, environmental monitoring, and biomedical applications.

Evaluation of different sugars for glycation modifications of chitosan to improve its functionality for food preservation

The modification of chitosan's amino groups through the Maillard reaction (MR) presents a pioneering approach to enhance its functional and biological properties. The present study aimed to understand the association between sugar-specific glycation-induced modifications and Chitosan-based Maillard Reaction Products (CMRPs) functionality. CMRPs were prepared by treating chitosan (CHO) with different saccharides, namely fructose (Fru), galactose (Gal), glucose (Glc), lactose (Lac), maltose (Mal), and methylglyoxal (MGO) at 80 °C for 6 h. These CMRPs were characterized by assessing 1) glycation markers, 2) structural modifications, and 3) functional properties. CMRPs formation was higher in aldohexoses (Gal, Glc) as compared to ketohexose (Fru) and disaccharides (Mal and Lac). Notably, fructosamine content, carbonyl adducts, and β-amyloid aggregates were highest in Gal CMRPs (46 mM/mg, 52 mM/mg, 6 M/mg) and Glc CMRPs (45 mM/mg, 15 mM/mg, 3 M/mg). Furthermore, MR of chitosan with aldohexoses at 100 °C for 8 h accelerated CMRPs synthesis with improved emulsifying activity, surface hydrophobicity, antioxidant potential, and substantial gel formation. The thermogravimetric analysis assessed the thermal stability and residual weight, while field emission scanning electron microscopy revealed a compact, nonporous morphology compared to chitosan alone. FTIR and HPLC analysis confirmed the structural changes, primarily due to the binding of the carbonyl group of sugars with the NH2 group of chitosan. Differential scanning calorimetry of CMRPs indicated shifts in peak temperatures and endothermic transitions in terms of enthalpy. Overall, Glc CMRPs exhibited improved functional, thermal, antioxidant, and emulsifying properties indicating their potential application in food preservation and packaging.

Effect of Surface Modification with Na Lauryl Sulfate on The Water-Uptake and Release Properties of Na Tripolyphosphate-Cross Linked Chitosan Beads

In this study we evaluated the effect of Na Lauryl sulfate (SLS) on the water-uptake and release properties of Na Tripolyphosphate (TPP)-cross linked chitosan beads. Chitosan beads were prepared by dropping riboflavin-loaded, chitosan (CS) solution into a curing medium composed of either an aqueous solution of TPP, SLS or a combination of these solutes. The resultant beads were characterized in terms of their size, drug encapsulation efficiency, water uptake properties by gravimetry and image analysis. Drug release properties of the prepared beads were studied using USP Apparatus 1 in media with different pH and ionic strength. Composites (CS/TPP, CS/SLS, and CS/TPP/SLS) were also evaluated using DSC, FTIR and contact angle measurements. Encapsulation efficiency was found to be 93%, 93.2% and 93.1% for CS/TPP, CS/SLS, and CS/TPP/SLS beads respectively and did not show any dependence on the composition of the curing medium for riboflavin. FTIR data suggested the presence of electrostatic interactions between positively charged amine group of CS and the negatively charged TPP and SLS. Drug release from the prepared beads was prolonged with CS/SLS beads releasing the drug faster than CS/TPP beads. The slowest drug release was observed in the case of CS/TPP/SLS beads. Drug release from the different types of beads was pH-dependent with the fastest release observed in 0.1 N HCl. Gravimetric water uptake was highest for CS/SLS beads followed by CS/TPP and CS/TPP/SLS respectively. Swelling study using image analysis showed a similar trend to the gravimetric water uptake results. The drug release and water uptake results could be explained by the effect of SLS on the wettability of the beads and the ability of the release medium to hydrate them which was confirmed by the high contact angle between water and CS/TPP/SLS composites.

Evaluation of Osteogenic Potential of Fucoidan Containing Chitosan Hydrogel in the Treatment of Periodontal Intra-Bony Defects-A Randomized Clinical Trial.

Periodontal diseases significantly impact about half of the global population, and their treatment often encompasses relieving symptoms as well as regenerating the destroyed tissues. Revolutionary research in the management of periodontal disease includes biomaterials, a boon to re-generative dentistry owing to their excellent biological properties: non-toxicity, anti-inflammatory, biocompatibility, biodegradability, and adhesion. This study aimed to fabricate an injectable fucoidan containing chitosan hydrogel and prove its effectiveness in periodontal bone regeneration. The injectable hydrogel was prepared using the sol-gel method and was subjected to various physical, chemical, and biological characterizations to understand its efficacy in formation of new bone. The effectiveness of the developed hydrogel was assessed in periodontal bony defects to study the soft and hard tissue changes. A total of 40 periodontitis patients with bony defects were recruited and randomized into two groups to receive fucoidan-chitosan hydrogel and concentrated growth factor, respectively. Customized acrylic stents were used to guide the hydrogel placement into the defect site. Post-surgical changes in clinical parameters were assessed at 3, 6, and 9 months to appreciate the soft and hard tissue changes using repeated measures analysis of variance and Bonferroni's post hoc test. Significance was kept at 5%. The porosity, water uptake of the prepared hydrogel showed good efficacy, with particle size of the fucoidan containing chitosan hydrogel of 6.000 nm. The MG-63 osteoblasts cell line revealed biocompatibility, biodegradability and showed slow and sustained drug release, increased cell proliferation, and enhanced alkaline phosphatase secretion. Mineralization assay was greatest in the fucoidan containing chitosan hydrogel. Clinically, it exhibited significantly lower probing depth values and a higher mean improvement in clinical attachment level as compared to the concentrated growth factor (CGF) group at the end of 3 and 6 months (p < 0.05). The mean of the defect fills in the fucoidan containing chitosan group was 1.20 at the end of 9 months (p < 0.001) as compared with defect fills observed in the CGF group. The presence of fucoidan in the hydrogel significantly contributed to bone regeneration in humans, thus strengthening its potential in tissue engineering. Fucoidan-chitosan will be a promising biomaterial for bone tissue regeneration.

Preparation and properties of bio-based intumescent flame retardant containing chitosan functionalized ammonium polyphosphate for polyurethane

In this study, chitosan (CS) from fish waste was used to prepare bio-based environmentally friendly flame retardants. After the hydroxyl group (−OH) of CS and the ammonium group (NH4+) of ammonium polyphosphate (APP) underwent reactions, they were filtered and dried to obtain CS-APP. The amino group of CS-APP then reacted with the epoxy group of 4,4′-methylenebis(N,N-diglycidylaniline) (NDY) to form CS-APP-NDY. Isophorone diisocyanate, polyol, and 3-aminopropyltriethoxysilane reacted to form silicon polyurethane. CS-APP-NDY was then mixed with Si-PU to prepare polymer composites. To determine the structure, thermal properties, flame retardancy, and mechanical properties of the composites, Fourier-transform infrared spectroscopy, thermogravimetric analysis, limiting oxygen index (LOI), cone calorimetry, UL-94, thermal analysis-FTIR (TA-FTIR) spectroscopy, universal machine testing, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were performed. The TGA results revealed that, after the addition of CS-APP-NDY, char yield increased from 0.5 wt% to 25.8 wt%, and the thermal stability of pristine PU also improved. In addition, the LOI and UL-94 results indicated that, after the addition of CS-APP-NDY, the LOI increased from 18.2% to 26.3%, and the UL-94 level improved from “Fail” to V-1. Overall, these results indicated that the addition of CS-APP-NDY to pristine PU increased its flame-retarding performance.

Investigation of Bioactive Complexes of Chitosan and Green Coffee Bean or Artichoke Extracts.

The formation of water-insoluble complexes between chitosan (ChS) and caffeoylquinic acid (CQ) derivatives present in artichoke (AE) and green coffee bean (GCBE) extracts was investigated by the equilibrium adsorption method. The UPLC/HPLC analysis revealed that the phenolic compounds accounted for 8.1% and 74.6% of AE and GCBE respectively, and CQ derivatives were the predominant compounds. According to the applied Langmuir adsorption model, anionic compounds present in natural extracts were adsorbed onto the active centers of ChS, i.e., primary amino groups. The driving forces of adsorption were electrostatic interactions between cationic groups of ChS and anionic compounds of natural extracts. Chromatographic analysis revealed that not only CQ derivatives, but also other phenolic compounds of natural extracts were attached to ChS. The release of adsorbed compounds into different media as well as the bioactive properties of complexes were also studied. With the immobilization of bioactives onto ChS, increased and prolonged ABTS•+ radical scavenging activity and decreased antifungal activity against Fusarium graminearum and Botrytis cinerea were observed compared to those of ChS. The findings of the current study highlight that the adsorption approach could be used to successfully prepare water-insoluble complexes of ChS and components of natural extracts with prolonged antioxidant activity.

Preparation and Administration of a Controlled-Release Delivery System of Chitosan Hydrogel loaded with Methadone and Piroxicam in Experimental Defect of Tibial in Rats; Histopathological Evaluation

Purpose: In this study, a controlled-release drug delivery system loaded with piroxicam and methadone was synthesized and used subcutaneously in rats with experimental tibial defect, and healing were assessed histopathologically.&#x0D; Materials and Methods: For this purpose, 100 adult female rats were randomly divided into five equal groups; control group, chitosan group, piroxicam group, methadone group, and piroxicam-methadone group. The morphological structure of the synthesized drug systems was studied by scanning electron microscope. In addition, the structure of the hydrogels was investigated by Fourier transform infrared spectroscopy and while releasing the hydrogels' gelation time, the release of piroxicam and methadone from the hydrogels was evaluated in vitro.&#x0D; Results: Histological results of the 3rd day of the study showed the lowest extent and severity of inflammation in the chitosan, piroxicam, and piroxicam-methadone groups, while on the 7th day, tissue inflammation and the extent of bleeding were lower in the piroxicam, methadone, and piroxicam-methadone groups than in the other groups. Evaluation of new bone formation on day 21 showed that the chitosan, piroxicam, and methadone groups had better repair than the other groups.&#x0D; Conclusion: It seems that in the control group that did not receive any treatment intervention, following the experimental bone defect, the highest inflammatory response was observed in histological examination and finally the weakest bone repair. On the other hand, the presence of piroxicam, methadone, and chitosan in the piroxicam-methadone group (all of which have anti-inflammatory effects) also seems to have a negative effect on the repair.

Fabricating pectin and chitosan double layer coated liposomes to improve physicochemical stability of beta-carotene and alter its gastrointestinal fate

To improve storage stability and gastrointestinal (GI) stability of liposomes, pectin and chitosan double layer coated liposome (P-C-L) was proposed and optimized using electrostatic deposition technique. The physical-chemical properties and GI fate of the carrier were then investigated in comparison to that of chitosan coated liposomes (C-L) and un-coated liposomes (L). The results showed P-C-L was successfully prepared at 0.2 % chitosan and 0.06 % pectin. It was hydrogen bonds between the amino groups in chitosan and liposomal interfacial region, and the interaction between the carboxyl groups in pectin layer and amino groups in chitosan layer maintained the structure of P-C-L after absorption by electrostatic interaction. The double layer coatings could improve chemical stability of the encapsulated β-carotene (βC), as well as the thermal stability of liposomes. What's more, the permeability of liposomal bilayers and βC release mechanism in simulated GI fluids was changed by the polymer coating. P-C-L exhibited better controlled release for βC than C-L and L, and displayer beneficial effect on delivering bioactive agents passing through intensity tract. This may assistant developing more efficient delivery system for bioactive agent.

PH-responsive, stable, and biocompatible functional nanogels based on chitosan (CS)/poly methacrylic acid (PMAA) polymers: Synthesis and characterization

Nanogels are presently the subject of a great deal of research worldwide due to their intriguing properties, such as biodegradability, biocompatibility, non-toxicity, and small size. Nanogels have great potential in biomedical and pharmaceutical fields, particularly drug delivery systems, owing to their high loading capacity, control, and targeted drug delivery. The current study aims to synthesize pH-responsive, biocompatible, chemically and physically crosslinked chitosan/polymethacrylic acid (CS/PMAA) based nanogels. FTIR study confirms the respective functional groups of CS, PMAA, and nanogels. Moreover, SEM and DLS analyses affirmed the formation of nanogels, which are submicron in size (> 200 nm and < 200 nm for 30 and 60 min reaction times, respectively). The prepared nanogels have manifested excellent stability (+ 31.66 mV and −33.12 mV, for cationic and anionic nanogels, respectively) under zeta potential measurements. The nanogels owned good thermal stability as characterized by DSC, and XRD results depict the semicrystalline structure. Cytotoxicity of prepared nanogels against PBMC cells was evaluated after 4hrs of exposure, and the cell viability of > 80% was observed for all the concentrations (1–100 μg/mL) of nanogels. However, high concentrations demonstrated viability loss due to the toxicity effect of NH3+ ions binding to negatively charged cell membranes. The experimental results from this study offer counseling for designing and developing CS-based nanogels for the diversity of applications in the biomedical and pharmaceutical industries.

Near-infrared light-responsive Cu2O@CuFeS2-hydroxyapatite-chitosan based antibacterial coating on titanium bioimplant

Bacterial infection over the titanium (Ti) bioimplants has been challenging, and it warrants re-surgery, which subsequently affects human health. In the present work, Cu2O, CuFeS2, and Cu2O@CuFeS2 composite was synthesized and used as a photothermal agent and fabricated their coatings over Ti surface using chitosan (CS)-hydroxyapatite (HA) matrix for the improvement of antibacterial activity under near-infrared (NIR, λ = 808 nm) irradiation and evaluated corrosion properties. The composite, CuFeS2 micro-flower (CuFeS2 MF) incorporated with Cu2O nanoparticles in the porous structure, showed a wide optical absorption window in the NIR region, resulting in the photothermal conversion efficiency of ~39 % under NIR light irradiation. Electrochemical studies indicated a variation in corrosion behavior for the coated and uncoated Ti, and its passive region remains similar in phosphate buffer saline (PBS) solution. Further, the prepared coatings displayed an excellent coating adhesion property over Ti. With the external stimuli of NIR light irradiation, the Cu2O@CuFeS2 composite exhibited a high antibacterial efficacy against S. aureus (~98.5 %) and E. coli (~96 %). The combination of the photothermal effect (CuFeS2) and bactericidal effect of Cu2O via cell membrane damage and ROS generation was found to be the cell death mechanism. The cytotoxicity assay of Cu2O@CuFeS2 composite in the presence of L929 cells ascertained their cell viability by >80 % at the optimized conditions, indicating a negligible toxicity level. Notably, the produced coating of CS-HA-Cu2O@CuFeS2 showed better antibacterial efficacy against S. aureus (~88.4 %) and E. coli (~84 %) under NIR light irradiation compared to without light. The CS-HA matrix also contributed to a marginal antibacterial activity due to the interactions of the charged amine group of CS with the charged group of the bacterial cell membrane.

Chitosan with enhanced deprotonation for accelerated thermosensitive gelation with β-glycerophosphate

Chitosan (CS)/β-sodium glycerophosphate (β-GP) gels have low temperature sensitivity, which limits their biomedical application. The protonation and deprotonation of the CS amino groups are regulated by pH. It is possible to accelerate thermosensitive gelation by increasing the pH of the CS solution to maximize the degree of CS amino deprotonation and enhance hydrophobic interactions. In this study, a CS solution with a higher pH (HpHCS; pH 6.19, close to pKa 6.2) was obtained by means of the consumption of hydrogen ions using excessive chitosan. Raman spectroscopy showed that strong hydrogen bonds might exist in HpHCS. Gelation was accelerated significantly at 37 °C using HpHCS due to the decreased sol–gel transition temperature. Support vector machine and t-distributed stochastic neighbor embedding analyses confirmed that the gel derived from HpHCS was significantly different from that of the other groups. In addition, the HpHCS gel exhibited a low degradation rate and low cytotoxicity. Furthermore, a mathematical equation was established to predict the gelation time of HpHCS/β-GP at 37 °C. A better concentration of HpHCS for in vivo injection was obtained due to the shorter gelation time and lower viscosity. We found that human mesenchymal stem cells survived and proliferated in vitro in the HpHCS/β-GP hydrogel. Therefore, this study provides an optimized HpHCS solution with enhanced deprotonation for accelerated thermosensitive gelation with β-GP.

Adsorption Characterization of Cu(II) and Cd(II) by a Magnetite-Chitosan Composite: Kinetic, Thermodynamic and Equilibrium Studies.

Optimizing the use of magnetite-chitosan composites for heavy metal adsorption has been of great interest due to their environmental friendliness. To gain insights into their potential with green synthesis, this study analyzed one of these composites through X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. Adsorption properties were then explored via static experiments to evaluate the pH dependence, isotherms, kinetics, thermodynamics and regeneration adsorption of Cu(II) and Cd(II). Results disclosed that the optimum pH of adsorption was 5.0, the equilibrium time was about 10 min, and the capacity for Cu(II) and Cd(II) reached 26.28 and 18.67 mg/g, respectively. The adsorption amount of cations increased with temperature from 25 °C to 35 °C and decreased with further increase in temperature from 40 °C to 50 °C, which might be related to the unfolding of chitosan; the adsorption capacity was above 80% of the initial value after two regenerations and about 60% after five regenerations. The composite has a relatively rough outer surface, but its inner surface and porosity are not obvious; it has functional groups of magnetite and chitosan, and chitosan might dominate the adsorption. Consequently, this research proposes the value of maintaining green synthesis research to further optimize the composite system of heavy metal adsorption.

The role of primary amines in modified chitosan to enhance the aldol condensation of biomass-derived carbonyl compounds

Aldol condensation is a key step for converting the lignocellulosic platform compounds to fuel. The catalyst used in the aldol condensation requires the avoidance of the overactivation of aldehyde groups while fully activating ketone carbonyl groups. Herein, the modified chitosan (NaOH/CT-0.6) was applied for the efficient syntheses of single condensation product from biomass-derived furfural (FFR) and methyl isobutyl ketone (MIBK), achieving an 87.01% yield of C11 at 60 °C and 3 h. Catalyst characterization revealed that the exposure of –NH2 groups in chitosan after modification led to the formation of the imine with the CO groups of FFR. It was confirmed that the imine formation avoided the overactivation of aldehyde groups and improved cross-condensation product yield. Furthermore, the theoretical feasibility of the imine catalytic path was elucidated through DFT simulation and in situ DRIFTS analysis. Finally, the obtained condensation products were subjected to hydrodeoxygenation (HDO) over the 2 wt% Pd/Nb2O5, obtaining the hydrocarbon components suitable for bio-jet fuels. This work contributes significantly to the design of novel catalysts for aldol condensation reactions and the efficient conversion of biomass.

Bonding of chitosan and nanochitosan modified universal adhesive to dentin

ObjectivesTo evaluate Wettability, pH and Microtensile bond strength (immediate and after thermocycling) of a universal adhesive after incorporation of 0.5% and 1% bulk-chitosan or nanochitosan. MethodsAll-bond universal adhesive was used to obtain five groups according to the type of additive; CONTROL, CHITOSAN (0.5), CHITOSAN (1%), NANOCHITOSAN (0.5%) and NANOCHITOSAN (1%). Contact angle and pH of the adhesives were tested with n = 7 for each test. for Microtensile bond strength testing, premolars teeth (N = 50) were used; twenty-five teeth for immediate bond strength and the other twenty-five were tested after thermocycling. ResultsCONTROL and CHITOSAN (0.5%) groups showed significantly higher contact angle measurements (30.78 ± 3.71 and 27.77 ± 4.63 respectively) compared to all other groups. CONTROL group showed significantly higher pH value (3.17 ± 0.05), followed by NANOCHITOSAN (0.5%) and NANOCHITOSAN (1%) and the least pH values were for 0.5% CHITOSAN group and CHITOSAN (1%). Bond strength results revealed that NANOCHITOSAN (0.5%) and NANOCHITOSAN (1%) had the highest bond strength (52.99 ± 16.14, 55.80 ± 16.11). CONTROL, CHITOSAN (0.5%) and CHITOSAN (1%) had no significant difference. After thermocycling, NANOCHITOSAN (0.5%) and NANOCHITOSAN (1%) had the highest bond strength values (38.58 ± 7.01 and 40.07 ± 11.40), followed by CHITOSAN (0.5%) and CHITOSAN (1%), and the least bond strength value was obtained by the control group. Hybrid layer micrographs showed that NANOCHITOSAN (1%) has intense resin infiltration before and after aging compared to all other groups. ConclusionIncorporation of nanochitosan (0.5% and 1%) improved the universal adhesive microtensile bond strength and bond durability.

A sensitive DNA biosensor based on the distance dependent quenching of Silica@Ru(bpy)32+‐chitosan‐GO electrochemiluminescence by Ferrocene@Gold nanoparticles

AbstractA sensitive electrochemiluminescence (ECL) biosensor for the specific DNA sequence of hepatitis C virus (HCV) was developed based on the efficient quenching effect of the ferrocene cluster functionalized gold nanoparticles (Fc@AuNPs) on the ECL of electrodeposited silica@Ru(bpy)32+‐chitosan‐graphene oxide nanocomposite (SiO2@Ru−CS−GO). Graphene oxide (GO) can accelerate electron transfer rate, thus improving the ECL of Ru(bpy)32+ on electrode surface. The molecular beacons (MB) was fixed to SiO2@Ru−CS−GO by glutaraldehyde (GA) using the Schiff reaction between amino groups of chitosan (CS) and MB. The ECL of SiO2@Ru−CS−GO was depressed greatly by the Fc@AuNPs labelled at the end of MB, then, a stronger ECL was observed when the distance between Fc@AuNPs and SiO2@Ru−CS−GO increased after the hybridization of target DNA with MB. Under optimum conditions, the restored ECL intensity increased linearly with the target DNA concentration in the range of 1.0×10−16∼1.0×10−10 mol ⋅ L−1, and the limit of detection (LOD) is 1.4×10−17 mol ⋅ L−1. The proposed method exhibits acceptable stability and reproducibility. In general, the constructed HCV biosensor can be used for the sensitive detection of HCV in human serum, suggesting potential application prospects in bioanalysis.

Coprecipitation-based synchronous chlorantraniliprole encapsulation with chitosan: carrier-pesticide interactions and release behavior.

Controlled-release pesticide formulations have emerged as a promising approach towards sustainable pest control. Herein, an environment-friendly formulation of insecticide chlorantraniliprole (CAP) was fabricated through a simple approach of coprecipitation-based synchronous encapsulation by chitosan (CTS), with carrier-pesticide interaction mechanism and release behavior investigated. The resulting CAP/CTS controlled-release formulation (CCF) showed a good loading content of 28.1% and a high encapsulation efficiency of 75.6%. Instrument determination in combination with molecular dynamics (MD) simulations displayed that the primary interactions between CAP and CTS were physical adsorption and complicated hydrogen (H)-bonds, which formed dominantly between NH in amides [or nitrogen (N) in ring structures] of CAP and hydroxyl (or amino) groups of CTS, as well as oxygen (O) in CAP with hydrogen in CTS or H2 O molecules. The in vitro release tests exhibited obvious pH/temperature sensitivity, with release dynamics following the first-order or Ritger-Peppas model. As the temperature increased, the CAP release process of the Ritger-Peppas model changed from Case-II to anomalous transport, and ultimately to a Fickian diffusion mechanism. The control effect against Plutella xylostella larvae also was evaluated by toxicity tests, where comparable efficacy of CCF to the commercial suspension concentrate was obtained. The innovative, easy-to-prepare CCF can be used as a formulation with obvious pH/temperature sensitivity and good efficacy on target pests. This work contributes to the development of efficient and safe pesticide delivery systems, especially using the natural polymer materials as carriers. © 2023 Society of Chemical Industry.