Degradation Of Chitosan Research Articles

Gamma radiation degradation of chitosan for application in growth promotion and induction of stress tolerance in potato (Solanum tuberosum L.)

Oligo-chitosan (82.20 kDa) was prepared from chitosan (337.73 kDa) by application of 100 kGy γ-irradiation. UV–vis spectroscopy, FTIR, XRD, DSC and TGA analyses showed typical properties of chitosan with slight variations after γ-irradiation. Degree of deacetylation of chitosan and oligo-chitosan was 82%, while 1,1-diphenyl-2-picrylhydrzyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity were 10.01 ± 0.18 and 43.30 ± 3.75 μMTE/mL and 13.64 ± 0.16 and 79.93 ± 4.44 μMTE/mL, respectively. Chitosan and oligo-chitosan was applied as foliar spray on potato plants to analyze growth promoting and stress tolerance inducing effects. Improvement in shoot height and number of nodes was observed after foliar spray of chitosan and oligo-chitosan at 50–75 mg/L. Furthermore, membrane stability index and malondialdehyde reduced while chlorophyll, carotenoids, proline, reducing and total sugars, enhanced considerably. The antioxidant and defense enzymes CAT, POD, SOD, chitinase and chitosanase showed prominent increment. Overall results indicated that chitosan (75 mg/L) and oligo-chitosan (50 mg/L) can augment plant growth and induce defense mechanism for drought stress tolerance in potato.

Effect of carboxyl content on the physicochemical properties and intramolecular water distribution of 6‐carboxyl chitooligomer prepared by laccase‐TEMPO

ABSTRACT6‐carboxyl chitooligomer was prepared by degradation of chitosan with H2O2 followed by catalytic oxidation in the laccase‐2,2,6,6‐Tetramethylpiperidine‐1‐oxyl (TEMPO) system. The TEMPO was used as a single variable to alter the content of introduced carboxyl groups. The resulting oxidation products were analyzed by ion chromatography, scanning electron microscopy, and 1H low‐field NMR. Moisture absorption‐retention ability, antioxidation, and thermal stability also were characterized. The results showed that the carboxyl content in the molecules increased with increasing TEMPO. With the addition of 8% TEMPO (mass fraction relative to chitooligomers), the carboxyl content and the oxidation degree of the product reached 4.90 mmol/g and 96.53%, respectively. Under these conditions, it also had the highest ABTS radical cation scavenging ability of 85.47% and improved thermal stability. When the amount of TEMPO was reduced to 2%, the oxidation product had a degree of oxidation of ~50% and showed a unique molecular structure and supreme moisture absorption‐retention ability. A higher associated water content was observed inside the molecules where more bound water was locked in the process of moisture absorption. Furthermore, the physicochemical properties of 6‐carboxyl chitooligomer were much higher than chitooligomer and oligomeric sodium hyaluronate (HA‐Oligo). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47509.

Purification and Characterization of A New Cold-Adapted and Thermo-Tolerant Chitosanase from Marine Bacterium Pseudoalteromonas sp. SY39.

Chitosanases play an important role in chitosan degradation, forming enzymatic degradation products with several biological activities. Although many chitosanases have been discovered and studied, the enzymes with special characteristics are still rather rare. In this study, a new chitosanase, CsnM, with an apparent molecular weight of 28 kDa was purified from the marine bacterium Pseudoalteromonas sp. SY39. CsnM is a cold-adapted enzyme, which shows highest activity at 40 °C and exhibits 30.6% and 49.4% of its maximal activity at 10 and 15 °C, respectively. CsnM is also a thermo-tolerant enzyme that recovers 95.2%, 89.1% and 88.1% of its initial activity after boiling for 5, 10 and 20 min, respectively. Additionally, CsnM is an endo-type chitosanase that yields chitodisaccharide as the main product (69.9% of the total product). It’s cold-adaptation, thermo-tolerance and high chitodisaccharide yield make CsnM a superior candidate for biotechnological application to produce chitooligosaccharides.

Thermal and kinetics of the degradation of chitosan with different deacetylation degrees under oxidizing atmosphere

The degradation process of chitosan with degrees of deacetylation (DD) varying from 54 to 84% was investigated by thermogravimetric analysis at different heating rates under air atmosphere. The chitosan with DD of 54% presented the highest thermal stability and slower changes in its structure as the temperature was increased, according to the infrared spectroscopy analyses.The activation energies (Ea) of the degradation process were estimated by the Flynn-Wall-Ozawa and the Vyazovkin isoconversional methods, obtaining values between 90 and 319 kJ/mol. The 3R-Gaussian distributed activation energy (3R-Gaussian DAEM) model was applied and adjusted successfully to the experimental data. In addition, DAEM model allowed to determine the Ea associated to each degradation reaction stage of chitosan (between 163–346.3 kJ/mol), in contrast to isoconversional methods. Consequently, the 3R-Gaussian DAEM model is a suitable option to describe the kinetics of chitosan degradation process.

Cytotoxicity against cancer cells of chitosan oligosaccharides prepared from chitosan powder degraded by electrical discharge plasma

Chitosan oligosaccharides, which obtain from degradation of chitosan, possess some interesting molecular weight-dependent biological properties, especially anticancer activity. Therefore, the conversion of chitosan to chitosan oligosaccharides with specific molecular weight has been continuously investigated in order to find effective strategies that can achieve both economic feasibility and environmental concerns. In this study, a novel process was developed to heterogeneously degrade chitosan powder by highly active species generated by electrical discharge plasma in a dilute salt solution (0.02 M) without the addition of other chemicals. The degradation rate obtained from the proposed process was comparable to that obtained from some other methods with the addition of acids and oxidizing agents. Separation of the water-soluble degraded products containing chitosan oligosaccharides from the reaction solution was simply done by filtration. The obtained chitosan oligosaccharides were further evaluated for an influence of their molecular weights on cytotoxicity against cancer cells and the selectivity toward cancer and normal cells.

Biocompatibility and in vivo degradation of chitosan based hydrogels as potential drug carrier

Carboxymethyl chitosan-graft-polylactide (CMCS-PLA) and carboxymethyl chitosan (CMCS) hydrogels were prepared by using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) as crosslinking agent and catalyst at room temperature. The biocompatibility of the hydrogels was evaluated with the aim of assessing their potential as drug carrier. Various aspects of biocompatibility were considered, including MTT assay, agar diffusion test, release of lactate dehydrogenase (LDH), hemolytic test, plasma recalcification time (PRT), and dynamic clotting time. MTT assay showed that the cytotoxicity level of both hydrogels to L-929 cells was 0 or 1. The LDH release of CMCS and CMCS-PLA was 26 and 29%, respectively, which is slightly higher than that of the negative control (21%) and much lower than that of the negative control (87%). The hemolysis ratio of CMCS and CMCS-PLA was 1.4 and 1.7%, respectively, suggesting outstanding anti-hemolysis properties of both materials. The PRT value of CMCS and CMCS-PLA was higher by 77 and 99% than the value of the positive control. All the results revealed that the hydrogels present good cytocompatibility and hemocompatibility in vitro. In vivo degradation and tissue compatibility were evaluated by subcutaneous injection in the dorsal area of rats. CMCS and CMCS-PLA hydrogels were completely degraded and the inflammatory response also completely disappeared around hydrogels after 19 days in vivo. It is thus concluded that hydrogels formed of CMCS and CMCS-PLA with outstanding biocompatibility are promising as potential drug carrier.

Consequences of chitosan decomposition by nitrous acid: Approach to non-branched oligochitosan oxime

It is well known that chitosan degradation by nitrous acid leads to oligochitosan (oligoCHIt–ahm) bearing reactive 2,5-anhydromannose (3,4-dihydroxy-5-hydroxymethyl-tetrahydrofuran-2-aldehyde) units at the new reducing ends of macromolecules. Standard protocol requires reduction of oligoCHIt–ahm with NaBH4 to corresponding oligoCHIt–hml bearing unreactive hydroxymethyl group instead of reactive aldehyde group. For the first time, HP SEC as well as UV and CD spectroscopy methods have revealed that the reduction leads to an indefinite side modification and the formation of a branched oligoCHIt-hml with increased molecular weight. Here, it is shown that the branching and modification can be prevented by means of the simple and reproducible reaction of oligoCHIt–ahm with hydroxylamine that allows preparation of a stable linear oligochitosan oxime, oligoCHIt–oxm. Cytotoxicity tests show that oligoCHIt–ahm, oligoCHIt–hml and oligoCHIt–oxm are non-toxic at concentration below 2.5 mg/ml, and the cytotoxicity is concentration dependent and decreases in the order oligoCHIt–ahm > oligoCHIt–hml > oligoCHIt–oxm at higher concentrations both before and after long shelf-storage. The elaborated approach and cytotoxicity data give an opportunity to use the non-branched oligoCHIt–oxm for biomedical applications.

Spectral, Thermal and Morphological Characterization of Biodegradable Graphene Oxide-Chitosan Nanocomposites

Graphene oxide (GO) was chemically synthesized from natural graphite by modified Hummers method. The graphene oxide-chitosan (GO-CHI) nanocomposites were synthesized by simple solution-mixing and evaporation method using ultrasonication. The samples were characterized using FTIR, UV-Vis spectroscopy, TG/DTA, DSC, SEM, TEM and AFM. The FTIR spectrum suggested that interactions existed between CHI and GO as evidenced by the downshift of the C=O stretching vibration of the amide group at 1653 cm⁻¹. UV-Vis spectra shows a bathochromic shift in bands of GO in the nanocomposite. The optical analysis of the GO and GO-CHI nanocomposites gave a direct energy band gap of 1.02 eV and 1.08 eV respectively indicating the highly conducting nature of the synthesized nanocomposite. Thermal stability was studied through TG/DTA which showed an enhancement in degradation temperature of chitosan from 175.4 °C to 302.5 °C in the composite and DSC studies showed an endothermic peak at 94.55 °C which is due to the loss of physisorbed water from the surface of the CHI matrix and an exothermic peak at 302.11 °C due to degradation and deacetylation of chitosan indicating high thermal stability of the composite. SEM micrograph of the nanocomposite showed the presence of the biopolymer chitosan with its porous, rough, granular morphology and the GO with its layered morphology. TEM image of the nanocomposite showed the particle size to be 20 nm and it also showed the presence of exfoliated GO as a fibrous network on the surface of the chitosan matrix. AFM study shows the value of the RMS coefficient for the nanocomposite as 40 nm indicating the formation of composite in the nano dimension. It also revealed the presence of rough surface thus indicating the presence of large number of active sites.<div><br></div>

D-Glucosamine production from chitosan hydrolyzation over a glucose-derived solid acid catalyst.

A glucose-based solid acid catalyst (GSA) was synthesized by hydrothermal carbonization and its physicochemical properties were explored by various characterization techniques including IR, TG and SEM. In addition, its catalytic performance towards d-glucosamine formation from the hydrolysis of chitosan was extensively investigated to determine the effects of reaction parameters, such as reaction temperature, time and mass ratio of catalyst and reactants. The experimental results revealed that the yield of targeted product d-glucosamine could reach as high as 98.1% under optimal conditions (temperature: 110 °C; time: 6 h). After six catalytic cycles, no evident deactivation was observed, suggesting the satisfactory stability of the investigated solid acid catalyst. This might provide insight on the development of suitable catalyst systems for d-glucosamine formation to replace homogeneous catalysts.

Antioxidant Activity of Chitosan Hydrolysates Derived by Microwave-assisted Irradiation

Degradation of chitosan by free radical cleavage at 90℃ in the presence of ammonium persulfate was performed. Typically, high molecular weight chitosan was dissolved in 2% acetic acid and then submitted to the Microwave-assisted and room temperature using different time. The in vitro quantification analysis and antioxidant activity of self-assembled and hydrolyzed chitosan was evaluated and compared as radical scavengers against 1,1- diphenyl-2-picrylhydrazyl radicals (DPPHㆍ), 2,2’- Azinobis (3-ethylbenzothiazoline-6-sulfonic acid) di-ammonium salt (ABTS), and ferric reducing antioxidant power (FRAP) using established methods and the effect of microwave and room temperature on the antioxidant activity of these molecular weight chitosan is discussed. Our data suggested the different type chitosan hydrolysates could be effectively employed as natural antioxidant materials for the various applications such as cosmeceutical and other potent industry products.

Lysozyme-Induced Degradation of Chitosan: The Characterisation of Degraded Chitosan Scaffolds

Up till now, chitosan has confirmed its versatile application in skin, cartilage and bone tissue engineering, as well as in drug delivery applications. This study is focused on enzymatic degradation of porous chitosan structures usually designed for mentioned purposes. In vitro degradation was monitored during four weeks of incubation at physiological temperature and in two different media, phosphate buffer saline solution and water. The scaffolds were characterised before and after enzymatic degradation using scanning electron microscopy and infrared spectroscopy with Fourier transformations (FTIR). According to the gravimetric analysis, higher weight loss of chitosan scaffolds was observed in buffered medium with respect to the water. The results implied that the total weight loss obtained in buffer involves physical dissolution of chitosan and lysozyme cleavage of glycoside bond. Importantly, FTIR identification of chitosan scaffolds after enzymatic degradation indicated the absence of lysozyme activity in water, indicating that weight loss is a result of the chitosan dissolution. This finding greatly impacts design of degradation experiments and characterisation of degradation behaviour of chitosan-based materials utilised as implants or drug delivery systems.

Effect of heat in chitosan dissolution and addition of KI on the enhancement of ionic conductivity

This work focuses on the effect of chitosan-based carbohydrate polymer electrolytes (CHPE) that were prepared by the application of heat in chitosan dissolution. Furthermore, various wt% of potassium iodide (KI) that was incorporated into this heat-applied chitosan (KI-HAC) were investigated. Electrochemical impedance spectroscopy (EIS) shows that the pure HAC has the room temperature ionic conductivity of 5.57 × 10−4 S/cm. The conductivity enhanced from 5.57 × 10−4 S/cm to 6.39 × 10−4 S/cm on the addition of 0.3 wt% of KI and further enhanced to 2.07 × 10−2 S/cm on the increment of KI from 0.3 to 1.8 wt%. The conductivity enhancement in chitosan was found due to the formation of amino glucosyl carboxonium ions (AGCI) and is due to the effect of heat in chitosan dissolution. XRD affirms the reduction in crystallinity. SEM analysis shows the spherical morphology for pure chitosan, porous morphology for HAC, and KI-HAC. FTIR confirms the degradation of chitosan and the formation of AGCI. Dielectric study, dielectric tan loss study, and dielectric modulus study confirm the results obtained by EIS. The results are authenticating that the conductivity enhancement in CHPE is not only due the addition of inorganic salt but also due to the chitosan which plays the role in conductivity enhancement. Dye-sensitized solar cell using HAC and KI-HAC shows efficiency of 1.25 and 1.62% at 1 sun condition.

Green Synthesis of 5‐Hydroxymethylfurfural from Chitosan Biomass Catalyzed by Benzimidazole‐Based Ionic Liquids

Abstract5‐Hydroxymethylfurfural (5‐HMF) is one of the most important platform chemicals in biorefinery, which could be further converted into bio‐fuels. In this work, an effective and green route for 5‐HMF production from chitosan biomass in a dimethylsulfoxide (DMSO)/water mixed solvent using acidic ionic liquids as the catalysts is reported. Several ionic liquids were successfully synthesized and used as catalysts for the degradation of chitosan. Benzimidazolium chloride ([Hbim]Cl) exhibited the best catalytic activity. We achieved a maximum 5‐HMF yield of 34.9 mol% in 10 wt% DMSO‐water mixed solvent. Moreover, the catalyst could be easily recycled and reused at least five times without a significant loss of activity. Our investigation involved the use of recycled catalysts and crustacean waste as the starting material, which makes the process “green” and sustainable.

Influence of Early-Stage Hydrolysis on Tensile Fracture Behavior of HAp/PLA Composites Interface-Controlled by Reaction Control Utilizing Photodissociable Protecting Groups

In this study, the change in the tensile fracture behavior of HAp/PLA composites, interface-controlled using pectin and chitosan, was evaluated for the case of the early-stage hydrolysis. Here, the reaction between the HAp particles and modification polymers was controlled using o-nitrobenzyl alcohol. Tensile tests after immersion in a pseudo biological environment indicated that the interface-control method employed in this study improved the fracture properties of HAp/PLA composites significantly, inducing the large plastic deformation. In addition, the effects of early-stage hydrolysis on fracture behavior and mechanism are discussed from the viewpoint of interfacial structures for the interface-controlled HAp/PLA composites. Observations of fracture morphologies and surfaces suggest that the interface-control employed in this study successfully improved interfacial bonding, enabling the effective usage of the deformability of the PLA matrix. The interface-control method employed in this study also maximized the fracture strain through the combination of improved interfacial bonding and an increase in the ductility of the PLA matrix after a 2-week immersion. Test results also suggest that the cancelation induced by the degradation of chitosan accelerated the degradation of the PLA matrix after a longer immersion.

Effect of foliar application of oligochitosan with different molecular weight on growth promotion and fruit yield enhancement of chili plant

Oligochitosan (OC) is effective biostimulant on growth promotion and elicitation against disease infection for plants. However, the range of OC molecular weight that exhibits the most effective activity is not fully understood and requires further investigation. In this study, OCs with different weight average molecular weight (Mw) were prepared by gamma Co-60 irradiation degradation of chitosan in solution and the effect on growth promotion and enhancement of fruit yield of chili plant (Capsicum frutescens L.) by foliar application of OCs particularly with Mw of 7.8, 5.0, and 2.5 kDa was investigated. Chili plants, cultivated in a greenhouse were sprayed with OC concentration of 50 mg/L for three times. Results indicated that among treatments, OC with 2.5 kDa proved to be the best, which increased the shoot fresh weight by 71.5%, shoot dry weight by 184%, total chlorophyll content by 12%, and fruit fresh weight by 49.8% for the control. Thus, OC with low Mw (2.5 kDa) that can be suitably produced on large scale by gamma Co-60 ray irradiation degradation of chitosan solution is potentially promising to apply as a biostimulant to enhance chili fruit yield significantly.

Preperation of nanochitosan from radiation degraded oligochitosan for shelf life extension of strawberry

Oligochitosans (OCT) were prepared from chitosan (CTS) by gamma irradiation technique. The parameters affecting to the chitosan degradation were studied. And then, OCT nanoparticles wereformed using the method of tripolyphosphate (TPP) cross-linking. Effect of concentration and molecular weight of OCT, concentration of TPP on particle size of the formed OCT nanoparticles were also studied. The formation of OCT nanoparticles was verified by Fourier transform infrared (FT-IR) spectrometer and differential scanning calorimeter (DSC), the morphology was observed using scanning electron microscope (SEM), and the characteristics (particle size and zeta potential) of OCT nanoparticles were also studied. The effect of OCT nanoparticles on strawberry presevation was carried out using the coating method. Results showed that an increase in radiation dose resulted in a decrease of chitosan molecular weight. The OCT with molecular weight of approximately 7.7 kDa was obtained by the synergistic effect of hydrogen peroxide (5 %, v/v) and gamma ray at dose of 30 kGy. The smaller OCT nanoparticles was obtained with a lower molecular weight of OCT. The results of FTIR, DSC indicated the success in the formation of OCT nanoparticles with the particle size approximately 129.9 nm, with the spherical shape. The application of OCT nanoparticles on strawberry has prolonged the preservation times approximately 2.5 times higher comp

Microwave‐assisted degradation of chitosan with hydrogen peroxide treatment using Box‐Behnken design for enhanced antibacterial activity

SummaryLow molecular mass (MM) chitosan with high degree of deacetylation (DDA) has excellent bioactivity including antioxidant, antibacterial and encapsulation properties. In this work, to reduce the MM of chitosan, microwave‐assisted heating treatment (MAHT) conditions were investigated using three factors at three levels Box‐Behnken design (BBD). Microwave heating (MH) time, H2O2 concentration and solid‐to‐liquid ratio significantly affected the DDA and MM of chitosan. The antibacterial activities of chitosan before and after degradation were investigated based on minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The results showed that a second‐order polynomial equation fitted the observed values using multiple regression analysis and had a high coefficient of determination (R2 = 0.9591 and 0.9161 for the DDA and MM of chitosan, respectively). An optimisation study was performed using Derringer's desirability function methodology, and the optimal conditions were 80‐s MH time, 1.5% H2O2 concentration and 1:40 solid‐to‐liquid ratio. The MIC and MBC of chitosan before and after degradation against Escherichia coli and Salmonella typhimurium were 0.031 and 0.063 mg mL−1, and 0.25 and 0.125 mg mL−1, respectively. The optimised DDA and MM of chitosan were 90.58 ± 2.04% and 124.25 ± 14.36 kDa, respectively, which significantly reduces the use of oxidant reagent.

Kinetic study of thermal degradation of chitosan as a function of deacetylation degree

Thermal degradation of chitosan with varying deacetylation degree (DD) ranging between 50 and 85% was analyzed by dynamic thermogravimetric analysis at different heating rates. The present study focused on the temperature range between 500 and 800K, above water evaporation. Thermal degradation showed a main degradation stage in this temperature interval with a second stage that appeared in the weight derivative curves as a shoulder in the high temperature side of the main peak with increasing intensity as the DD decreased. The Kissinger and isoconversional Ozawa-Flynn-Wall models were employed to evaluate the Ea of both thermal degradation processes. Different kinetic models were tested to computer simulate the thermogravimetric traces calculating the model parameters with a non-linear least squares fitting routine. The Sestack-Berggren model allowed reproducing accurately the overlapping of the two degradation mechanisms and calculating the mass fraction lost in each of them revealing the coupling between the two degradation mechanisms.

Enhanced degradation of chitosan by applying plasma treatment in combination with oxidizing agents for potential use as an anticancer agent

Solution plasma (SP) treatment in combination with oxidizing agents, i.e., hydrogen peroxide (H2O2), potassium persulfate (K2S2O8) and sodium nitrite (NaNO2) were adopted to chitosan degradation in order to achieve fast degradation rate, low chemicals used and high yield of low-molecular-weight chitosan and chitooligosaccharide (COS). Among the studied oxidizing agents, H2O2 was found to be the best choice in terms of appreciable molecular weight reduction without major change in chemical structure of the degraded products of chitosan. By the combination with SP treatment, dilute solution of H2O2 (4–60mM) was required for effective degradation of chitosan. The combination of SP treatment and dilute solution of H2O2 (60mM) resulted in the great reduction of molecular weight of chitosan and water-soluble chitosan was obtained as a major product. The resulting water-soluble chitosan was precipitated to obtain COS. An inhibitory effect against cervical cancer cell line (HeLa cells) of COS was also examined.

Chitosan degradation products facilitate peripheral nerve regeneration by improving macrophage-constructed microenvironments.

Chitosan-based artificial nerve grafts have been widely employed to repair peripheral nerve defects. Our previous study has shown that chitosan constructed nerve graft not only provides suitable scaffolds for nerve regeneration, its degradation products, chitooligosaccharides (COS), also promote nerve repair. However, the involved mechanisms are still not fully elucidated. In the present study, we observed that pro-inflammatory cytokines, as well as macrophage infiltration, were transiently up-regulated in the injured sciatic nerves which were bridged with silicon tubes filled with COS. Based upon transcriptome analysis, the axis of miR-327/CCL2 in Schwann cells (SCs) was identified as a potential target of COS. The following experiments have confirmed that COS stimulate CCL2 expression by down-regulating miR-327 in SCs. Consequently, the resulting CCL2 induces macrophage migration at injury sites to re-construct microenvironments and thus facilitates nerve regeneration. Collectively, our data provide a theoretical basis for the clinical application of chitosan-based grafts in peripheral nerve regeneration.