Chitosan Samples Research Articles

Accurate Determination of the Degree of Deacetylation of Chitosan Using UPLC–MS/MS

The mole fraction of deacetylated monomeric units in chitosan (CS) molecules is referred to as CS’s degree of deacetylation (DD). In this study, 35 characteristic ions of CS were detected using liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS/MS). The relative response intensity of 35 characteristic ion pairs using a single charge in nine CS samples with varying DDs was analyzed using 30 analytical methods. There was a good linear relationship between the relative response intensity of the characteristic ion pairs determined using ultrahigh performance (UP) LC–MS/MS and the DD of CS. The UPLC–MS/MS method for determining the DD of CS was unaffected by the sample concentration. The detection instrument has a wide range of application parameters with different voltages, high temperatures, and gas flow conditions. This study established a detection method for the DD of CS with high sensitivity, fast analysis, accuracy, stability, and durability.

Influence of Deacetylation Degree of Chitosan on the Anticorrosive Properties of Carbon Steel Coatings

AbstractThis study outlines the improvement on anticorrosion behavior of chitosan‐based sol‐gel coatings on carbon steel surface obtained for high deacetylation degree values of this natural biopolymer. Important economic losses in major industries represent a problem due to corrosion of metals in aggressive medium, such as carbon steel, which is widely used due to its hardness, durability, ductility, low cost, handiness. Therefore, non‐toxic, cost‐effective, and eco‐friendly strategies are needed to protect metallic surface of steel. Against this background, the anticorrosion coating performance of chitosan, from three different commercial sources, as a single component, on carbon steel in chloride solutions is investigated using electrochemical impedance spectroscopy technique. The present study is performed to evaluate the corrosion protective abilities of chitosan in order to determine the relationship with its deacetylation degree (DDA), evaluated by potentiometric titration, a simple and reliable method. Depending on the DDA, the experimental results indicate that there is a remarkable difference between different chitosan samples regarding the value of the charge transfer resistance of coating on steel.

Chitosan-based Nanosystems as Drug Carriers

The formation and application of polymeric nanomaterials is great demandin science, industry, biotechnology, and medicine due to the possibility ofachieving a significant improvement in the physicochemical, mechanical,and barrier properties of polymers and using them as drug carriers andfillers, which is especially promising for biodegradable polymers such aschitosan and their derivatives. The article presents methods for creatingpolymer nanostructures based on polysaccharides and, in particular,chitosan. Obtaining nanostructured samples of chitosan using theapproaches of chemical transformation and modification of polysaccharidesis an urgent scientific problem, the solution of which makes it possible toobtain new polymer systems of great practical interest. The medical aspectsof the use of polymer carriers based on chitosan for the treatment of variousdiseases are discussed. The unique specificity of the properties of chitosanand nanomaterials derived from it, with the properties inherent in thisnatural polymer, can serve as a promising future, especially in the field ofmedicine.

A facile approach for the determination of degree of deacetylation of chitosan using acid-base titration

Several spectroscopic techniques such as nuclear magnetic resonance (NMR), UV-visible, Fourier transform infrared (FT-IR), etc. have been already used for the determination of degree of deacetylation (DD) of chitosan. These techniques involve the interpretation of spectral data apart from sample preparation for obtaining DD of chitosan. In addition, inaccurate interpretation of data sometimes misleads researchers to get an exact value of DD of chitosan. Among them, NMR is an excellent technique for the estimation of DD of chitosan but expensive and not found easily in every research laboratory. On the other hand, titrimetric methods have been employed by many researchers for determining the DD of chitosan but these existing methods involve many complex calculations, which do not always give accurate results. Moreover, few of the acid-base titration methods are little complicated for execution. Therefore, in this present study, we adopted a very handy and simple acid-base titration method with a new approach and proposed a new equation facilitating the ease of calculation that is not reported elsewhere for the determination of DD value by observing the net volume of NaOH consumed for the complete neutralization of protonated amino groups (-NH3+) of chitosan describing the novelty of the work. All the DD values (77.04 ± 1.36; 81.71 ± 1.73; 91.68 ± 1.42 for CS1, CS2, and CS3 respectively) obtained for various chitosan samples were in good agreement with the reported DD values (>75%, >80%, and >85% for CS1, CS2, and CS3 respectively) mentioned in the specifications of chitosan samples supplied by the manufacturer. Finally, the experimental DD values were further validated with the DD values (77.39%, 81.64%, and 90.5% for CS1, CS2, and CS3 respectively) obtained from the interpretation of 13C-NMR spectral data and all the experimental DD values were consistent with the DD values as calculated based on NMR spectra.

Use of phosphorylated chitosan/alumina nanoadditives for polymer performance improvement

In this research, a new generation of ternary nanocomposites based on poly(ethylene terephthalate) (PET), phosphorylated chitosan and surface modified alumina nanoparticles were fabricated in four steps. The phosphorylation process was targeted for the insertion of phosphorus moieties as a flame retardant agent in the final PET nanocomposite. Likewise, environmentally friendly nano-alumina was used for PET matrix to improve the thermal properties of PET in collaboration with organic anchored phosphorus moieties. Alternatively, the presence of bio-safe modified alumina nanoparticles in combination with phosphorylated chitosan simultaneously improved the antibacterial activity and thermal properties of the PET matrix. Furthermore, the effects of the phosphorylated chitosan and alumina nanoparticles on the morphology and thermal properties of nanocomposites were inspected by different approaches. The structure and distribution of the nanoscale particles in PET were analyzed by scanning electron microscopy. In addition, differential scanning calorimetry and thermogravimetric analyses were used for the in-depth evaluation of the thermal properties of prepared nanocomposites. Prepared nanocomposites showed better growth inhibition activities against Escherichia coli bacteria compared to the PET and PET/phosphorylated chitosan samples. Also, the thermal characteristics of prepared nanocomposites were considerably improved.

Indirect Additive Manufacturing: A Valid Approach to Modulate Sorption/Release Profile of Molecules from Chitosan Hydrogels.

This work studied the influence of hydrogel’s physical properties (geometry and hierarchical roughness) on the in vitro sorption/release profiles of molecules. To achieve this goal, chitosan (CS) solutions were cast in 3D-printed (3DP) molds presenting intricate shapes (cubic and half-spherical with/without macro surface roughness) and further immersed in alkaline solutions of NaOH and NaCl. The resulting physically crosslinked hydrogels were mechanically stable in aqueous environments and successfully presented the shapes and geometries imparted by the 3DP molds. Sorption and release profiles were evaluated using methyl orange (MO) and paracetamol (PMOL) as model molecules, respectively. Results revealed that distinct MO sorption/PMOL release profiles were obtained according to the sample’s shape and presence/absence of hierarchical roughness. MO sorption capacity of CS samples presented both dependencies of hierarchical surface and geometry parameters. Hence, cubic samples without a hierarchical surface presented the highest (up to 1.2 × greater) dye removal capacity. Moreover, PMOL release measurements were more dependent on the surface area of hydrogels, where semi-spherical samples with hierarchical roughness presented the fastest (~1.13 × faster) drug delivery profiles. This work demonstrates that indirect 3DP (via fused filament fabrication (FFF) technology) could be a simple strategy to obtain hydrogels with distinct sorption/release profiles.

Effects of deacetylation degree, molecular weight, and preparation method on wet‐adhesive and rheological properties of chitosan as food‐grade adhesive

In this study, the impacts of deacetylation degree and molecular weight on the rheological and adhesive properties of chitosan (CS) including shear viscosity, initial viscosity, and peel strength of tobacco leaves have been studied. The effect of different dissolution solvents such as acetic acid (HAC) and lactic acid (HL) on chitosan adhesives was also investigated. The results revealed that the adhesive properties increased first and then decreased with the increase of deacetylation degree, while chitosan with higher molecular weight showed higher initial adhesiveness and peel strength values. Chitosan sample III with a medium deacetylation degree of 80.5% showed the best adhesion properties with an excellent ability to reduce the total mold and yeast on the surface of tobacco leaves. Sample HL-CS-III showed a lower initial adhesiveness value but a higher peel strength value than sample HAC-CS-III due to its more viscous nature. Overall, chitosan showed great potential to be used as adhesives for cigar wrapping and other food applications. Novelty impact statement The adhesive properties of chitosan molecules with different molecular weights and degrees of deacetylation values are compared. Chitosan with a larger molecular weight and medium deacetylation degree shows maximum initial adhesiveness and peel strength to tobacco leaf. Chitosan dissolved in lactic acid had a higher peel strength value and better mechanical resistance than acetic acid-dissolved chitosan adhesive.

Estudio Fisicoquímico de Quitina y Quitosana obtenidas a partir del exoesqueleto de camarón café (Farfantepenaeus californiensis)

This work describes the obtention of chitin and chitosan from the brown shrimp exoskeleton (Farfentepenaeus californiensis), which is collected from the Gulf of California. The chitin isolation process was carried out by a consecutive treatment that includes demineralization and deproteinization. On the other hand, the preparation of chitosan was conducted through alkaline hydrolysis, and the product was purified by using a membrane filters series to homogenize the size of the macromolecular chains. According to the methodology, the yield of chitin and chitosan was around 34 % and 20 % (dry weight), respectively. The materials were characterized by FTIR spectroscopy and thermogravimetric analysis. Also, the chitosan sample was analyzed by proximal test, viscometric-average molecular weight, and deacetylation degree. The products exhibited chemical structure and physicochemical properties comparable to biopolymers isolated from similar sources reported in the literature. Chitosan was found to have a degree of acetylation of 15.87 % (by 1H-NMR analysis) and Mv=170 kDa. The results suggest that the chitinous waste from the Sea of Cortes coast can be considered a promising source for the preparation of chitosan and used for several applications in the region.

Qualitative and quantitative discrimination of major elements in Chitosan (natural polymer) using laser induced breakdown spectroscopy

In this work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for qualitative and quantitative analysis of Chitosan samples (natural polymer). For qualitative analysis, plasma parameters are determined, while for quantitative analysis, the initial concentration of chitosan samples is calculated. It developed a plasma plume using a second harmonic (532 nm) laser pulses, which makes the Q-Switched Nd: YAG laser compatible with delay generators and computing electronics. The component elements and their corresponding concentrations are calculated based on the strongest emission lines of the element using the line intensity ratio method and the calibration-free LIBS approach. The results obtained by both methods are compared for the effectiveness of the algorithm.In the chitosan monomer (C6H11NO4)n, four major elements (hydrogen, carbon, nitrogen and oxygen) were detected and their quantities were calculated. In addition to investigating the physical behavior of plasma in the interaction of laser beams with materials, the plasma parameters (electron number density and plasma temperature) are determined by stark-broadening profile fitting and Boltzmann plot method, respectively. The results obtained show that the LIBS can be exploited for quantitative and standard analysis of industrial grade materials for better results in applications.

Thermal Stability of Fluorescent Chitosan Modified with Heterocyclic Aromatic Dyes.

Fluorescent biopolymer derivatives are increasingly used in biology and medicine, but their resistance to heat and UV radiation, which are sterilizing agents, is relatively unknown. In this work, chitosan (CS) modified by three different heterocyclic aromatic dyes based on benzimidazole, benzothiazole, and benzoxazole (assigned as IBm, BTh, and BOx) has been studied. The thermal properties of these CS derivatives have been determined using the Thermogravimetric Analysis coupled with the Fourier Transform Infrared spectroscopy of volatile degradation products. The influence of UV radiation on the thermal resistance of modified, fluorescent chitosan samples was also investigated. Based on the temperature onset as well as the decomposition temperatures at a maximal rate, IBm was found to be more thermally stable than BOx and BTh. However, this dye gave off the most volatile products (mainly water, ammonia, carbon oxides, and carbonyl/ether compounds). The substitution of dyes for chitosan changes its thermal stability slightly. Characteristic decomposition temperatures in modified CS vary by a few degrees (<10 °C) from the virgin sample. Considering the temperatures of the main decomposition stage, CS-BOx turned out to be the most stable. The UV irradiation of chitosan derivatives leads to minor changes in the thermal parameters and a decrease in the number of volatile degradation products. It was concluded that the obtained CS derivatives are characterized by good resistance to heat and UV irradiation, which extends the possibilities of using these innovative materials.

Biological Characterization of Different Samples of Chitin and Chitosan for their Application on Biomedical Field

In this study, the degree of acetylation (DA) and degree of deacetylation (DDA) were determined by Fourier Transform Infrared Spectroscopy (FT-IR) analysis, and their viability was evaluated by the cytocompatibility test with L132 epithelial cells, from samples of chitin and chitosan extracted of Cryphiops caementarius. FT-IR measurements resulted in the successful determination of DA and DDA. Particularly the results showed that, the chitosan CHT-C has the highest DDA (93%), while viability tests employed to determine the cytotoxicity of chitin and chitosan showed that the cell survival rate of CH-C and CHT-C are 130% and 75% respectively while commercial CHT has a rate of 80% approximately, demonstrating that the CH-C (chitin) a favorable behavior against L132 cell.

Antibacterial and Antifungal Properties of Modified Chitosan Nonwovens.

Chitosan acquires bacteriostatic properties via protonation of its amino groups. However, much of the literature assumes that chitosan itself inhibits the growth of bacteria. This article presents a comparative study of chitosan nonwovens modified with various acids, including acetic, propionic, butyric, and valeric organic acids, as well as hydrochloric acid. The aim was to determine which acid salts influence the antibacterial and antifungal activity of chitosan-based materials. Two methods were used to modify (formation of ammonium salts) the chitosan nonwovens: First, acid vapors (gassing process) were used to find which salt of chitosan had the best antibacterial properties. Based on the results, the most effective acid was prepared in a solution in ethanol. The influence of the acid concentration in ethanol, the time of treatment of chitosan materials with acid solution, and the rinsing process of modified nonwovens on the antimicrobial activity of the modified materials was investigated. The modified materials were subjected to microbiological tests. Each of the modified materials was placed in bacterial inoculum. The cultures were tested on agar to observe their microbial activity. Toxicity to human red blood cells was also investigated. A reduction in the number of bacterial cells was observed for the S. aureus strain with chitosan salt modified with 10% acetic acid in ethanol. The antibacterial activity of the chitosan salts increased with the percentage of acid salts formed on the surface of the solid material (decreasing numbers of bacterial colonies or no growth). No reduction in growth was observed for the E. coli strain. The chitosan samples were either inactive or completely eliminated the bacterial cells. Antimicrobial activity was observed for chitosan salts with hydrochloric acid and acetic acid. Finally, 1H-NMR spectroscopy and FTIR spectroscopy were used to confirm the incorporation of the acid groups to the amino groups of chitosan.

Sustainable Biocomposites for Structural Applications with Environmental Affinity.

In this work, we report a facile preparation of biocomposites using a chitosan matrix that is reinforced with morphed graphene in amounts from 1 to 5 wt % C. The composites are processed by milling and conventional sintering. The morphed graphene additions show clear improvements in mechanical properties, having a direct correlation with temperature in particular for 180 °C. Higher temperatures are detrimental to chitosan and the properties drop because chitosan degrades. Mechanical properties in the composite such as yield strength and compressive strength increase between 40 and 50% with respect to the pure chitosan samples. The Young's modulus presents a drop of approximately 10%, but the fracture toughness increases up to 3.5 fold. The properties of our sustainable composites are comparable to those seen in polymers such as polyethylene, polypropylene, nylon, and poly(methyl methacrylate), among other commodity or single use plastics. The enhancement in the mechanical properties is attributed to the morphed graphene embedded chitosan matrix that generates a network of intergranular "anchors" that hold the chitosan crystals in place, preventing failure. The composites can be molded into near-net-shape products, machined, or shaped using various methods including laser lithography. These studies demonstrate the feasibility of fabricating biocomposites with different architectures and sizes for disposable structural components. Both chitosan and the composites are compostable and biodegradable with the potential to sustain plant growth when discarded. In addition, morphed graphene and chitosan are produced from byproducts or waste, which may result in a negative carbon footprint on the environment.

Evaluating Non-Conventional Chitosan Sources for Controlled Release of Risperidone.

In this work, two chitosan samples from cuttlebone and squid pen are produced and characterized. We studied the formation of thermoresponsive hydrogels with β-glycerol phosphate and found proper formulations that form the hydrogels at 37 °C. Gel formation depended on the chitosan source being possible to produce the thermoresponsive hydrogels at chitosan concentration of 1% with cuttlebone chitosan but 1.5% was needed for squid pen. For the first time, these non-commercial chitosan sources have been used in combination with β-glycerol phosphate to prepare risperidone formulations for controlled drug delivery. Three types of formulations for risperidone-controlled release have been developed, in-situ gelling formulations, hydrogels and xerogels. The release profiles show that in-situ gelling formulations and particularly hydrogels allow an extended control release of risperidone while xerogels are not appropriate formulations for this end since risperidone was completely released in 48 h.

Influence of Temperature and Polymer Concentration on the Nonlinear Response of Highly Acetylated Chitosan-Genipin Hydrogels.

Strain hardening, i.e., the nonlinear elastic response of materials under load, is a physiological response of biological tissues to mechanical stimulation. It has recently been shown to play a central role in regulating cell fate. In this paper, we investigate the effect of temperature and polymer concentrations on the strain hardening of covalent hydrogels composed of pH-neutral soluble chitosans crosslinked with genipin. A series of highly acetylated chitosans with a fraction of acetylated units, FA, in the range of 0.4–0.6 was synthesized by the homogeneous re-N-acetylation of a partially acetylated chitosan or the heterogeneous deacetylation of chitin. A chitosan sample with an FA = 0.44 was used to prepare hydrogels with genipin as a crosslinker at a neutral pH. Time and frequency sweep experiments were then performed to obtain information on the gelling kinetics and mechanical response of the resulting hydrogels under small amplitude oscillatory shear. While the shear modulus depends on the chitosan concentration and is almost independent of the gel temperature, we show that the extent of hardening can be modulated when the gelling temperature is varied and is almost independent of the experimental conditions used to build the hydrogels (ex situ or in situ gelation). The overall effect is attributed to a subtle balance between the physical (weak) entanglements and covalent (strong) crosslinks that determine the mechanical response of highly acetylated chitosan hydrogels at large deformations.

Superamphiphilic Chitosan Cryogels for Continuous Flow Separation of Oil-In-Water Emulsions.

Chitosan is a typical hydrophilic biomass building block widely used in material science and engineering. However, its intrinsic amphiphilicity has been seldom noted so far. Herein, a series of glutaraldehyde-crosslinked chitosan cryogels with superamphiphilicity are fabricated at moderately frozen conditions through a freezing–thawing process. The micron-sized porous cryogel samples display a 0° contact angle toward both water and oil, 0° water contact angle under oil, and over 120° oil contact angle underwater. By comparing the wetting behavior of the tablet compressed by pure chitosan powders, the superamphiphilicity of the chitosan sample is proven to be independent on crosslinkers. This special wettability endows the chitosan cryogels with high separation efficiency for various surfactant-stabilized oil-in-water emulsions under continuous flow mode driven by gravity as well as a peristaltic pump.

Exploring new marine bacterial species, Alcaligenes faecalis Alca F2018 valued for bioconversion of shrimp chitin to chitosan for concomitant biotechnological applications

The exploitation of chitinous materials seems to be an infinite treasure. To this end, using shellfish waste as the sole carbon/nitrogen source solves environmental challenges while lowering microbial chitinase production costs. Bioconversion of shellfish chitin wastes such as shrimp shells has recently been investigated for the production of enzymes and bioactive materials in order to maximize the utilization of chitin-containing seafood processing wastes. In this study, the bioconversion of chitin to chitosan by Alcaligenes faecalis Alca F2018 revealed the highest chitin deacetylase (CDA) activity of 40.6 U/μg. The resulted low Km and high Vmax values explain the high affinity of the purified CDA to the p-nitroacetanilide substrate. CDA with a molecular weight of 66 KDa was purified from F2018 strain, with a 14.5% yield. FT-IR revealed distinct chitosan peaks and XRD revealed that chitosan samples had lower crystallinity than chitin. TGA analysis revealed that the recovered chitosan samples were more thermally stable. The deacetylation degree percentages of the produced chitosan are in the same range as that of the commercial chitosan, suggesting the promising potential of A. faecalis Alca F2018 to utilize shrimp shells in their raw form in the fermentation media based on its CDA enzyme activity.

Immobilization of Catalase onto Polylysine Modified Chitosan Polymer

In this study, chitosan polymer was modified in two different ways and used for the immobilization of bovine liver catalase (CAT). First, it was activated with glutaraldehyde (GAL), and then covalently immobilized covalently onto the support via lysine amino acid residue in CAT. In the second modification, GAL-activated chitosan was interacted with polylysine (pLYS), then reactivated with GAL and used in CAT immobilization. Samples of bare chitosan (Chi), GAL-activated (ChiGAL), polylysine-modified (ChiGAL-pLYS), reactivated with GAL (ChiGAL-pLYSGAL) and CAT-immobilized chitosan (ChiGAL -CAT and ChiGAL-pLYSGAL-CAT) were all characterized by FTIR. The enzymatic activities of Free CAT, ChiGAL -CAT and ChiGAL-pLYSGAL-CAT samples were investigated at different pH and temperatures and the values with the highest activity were determined. In addition, the effect of substrate concentration on activity under optimal conditions was investigated. Optimum pH values of Free CAT, ChiGAL-CAT and ChiGAL-pLYSGAL-CAT samples were 7.5, 7.0 and 7.0, respectively; temperature values were determined as 25, 30 and 35 C, respectively. After immobilization, the Vmax values of the enzymes decreased, the Km values increased, and the efficiency of catalase immobilized to the polylysine modified support was found to be higher. It was observed that after 20 repeatedly use in the column reactor, ChiGAL-CAT and ChiGAL-pLYSGAL-CAT enzymes retained 88 % and 76 % of their initial activities, respectively.

Optimisation of conditions for deacetylation of chitin-containing raw materials

The paper describes the differences between chitosan and chitin, and reviews works by foreign scientists on obtaining chitosan from various raw materials. Methods of modifying chitosan and obtaining combined sorbents have been analysed. It has been studied whether chitosan is applicable in the technology of wines and alcoholic beverages as a sorbent. The purpose of the study was determining the optimal conditions of the deacetylation stage to obtain chitosan with the best sorption properties from Aspergillus niger biomass. A three-factor experiment has been carried out. It involved obtaining 27 samples of chitosan using sequential four-step acid-base hydrolysis under various conditions of the deacetylation stage. The deacetylation process was optimised under alkaline conditions depending on the alkali concentration, processing temperature, and exposure. For each of the samples obtained, the adsorption activity, specific surface area, and distribution coefficient in the sorbent–sorbate system have been determined. The degrees of deacetylation of all chitosan samples have been determined by potentiometric titration. The study has resulted in determining the optimal conditions for the deacetylation stage: processing temperature 110–130°C, sodium hydroxide concentration 27–36 g/dm3, exposure 45 to 65 minutes. The sample deacetylated at the temperature 120 °C, alkali concentration 30 g/dm3, and exposure 45 minutes has shown the best adsorption activity values: the adsorption activity for methyl orange 347.96 mg/g, the specific surface area of the sorbent samples 0.52·105 m2/g, the distribution coefficient in the sorbent–sorbate system 3.29·10-3 ml/g. This sample had the highest degree of deacetylation, 43.6%. The sample has been analysed using IR spectroscopy, and its main characteristic frequencies have been studied. It has been concluded that the sample obtained was equivalent to the reference chitosan

Elucidation of substituent distribution states for carboxymethyl chitosan by detailed NMR analysis

A series of carboxymethyl chitosan (CMCh) samples with a wide degree of substitution (0.65–2.03) was prepared by multi-step carboxymethylation of chitosan using a 2-propanol/aqueous sodium hydroxide solution mixture as the solvent and monochloroacetic acid as the etherification reagent. Two-dimensional NMR correlation maps of the direct and long-range coupled 1H and 13C spin pairs of the CMCh samples allowed complete assignment of the 1H and 13C chemical shifts of eight anhydroglucosamine units (AGUs) comprising CMCh chains, namely un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted AGUs. Line-shape analysis of the anomeric carbon resonance in the quantitative 13C NMR spectra determined the mole fractions of these AGUs. Plots of the mole fractions against the change in the degree of substitution clarified the detailed substitution state at the 2-amino and 3-/6‑hydroxyl groups of chitosan and the transition of the monomer fractions during the change from the unsubstituted to the fully substituted state. Therefore, the method estimating the mole fractions of the eight AGUs in CMCh is expected to be an effective and powerful tool for elucidating functionalities from a structural perspective.