Optimal gamma-ray dose and irradiation conditions for producing low-molecular-weight chitosan that retains its chemical structure

Application of depolymerized chitosan in crop production: A review

Currently, chitosan (CHT) is well known for its uses, particularly in veterinary and agricultural fields. However, chitosan's uses suffer greatly due to its extremely solid crystalline structure, it is insoluble at pH levels above or equal to 7. This has sped up the process of derivatizing and depolymerizing it into low molecular weight chitosan (LMWCHT). As a result of its diverse physicochemical as well as biological features which include antibacterial activity, non-toxicity, and biodegradability, LMWCHT has evolved into new biomaterials with extremely complex functions. The most important physicochemical and biological property is antibacterial, which has some degree of industrialization today. CHT and LMWCHT have potential due to the antibacterial and plant resistance-inducing properties when applied in crop production. This study has highlighted the many advantages of chitosan derivatives as well as the most recent studies on low molecular weight chitosan applications in crop development.

Potential Medical Applications of Chitooligosaccharides

Chitooligosaccharides, also known as chitosan oligomers or chitooligomers, are made up of chitosan with a degree of polymerization (DP) that is less than 20 and an average molecular weight (MW) that is lower than 3.9 kDa. COS can be produced through enzymatic conversions using chitinases, physical and chemical applications, or a combination of these strategies. COS is of significant interest for pharmacological and medical applications due to its increased water solubility and non-toxicity, with a wide range of bioactivities, including antibacterial, anti-inflammatory, anti-obesity, neuroprotective, anticancer, and antioxidant effects. This review aims to outline the recent advances and potential applications of COS in various diseases and conditions based on the available literature, mainly from preclinical research. The prospects of further in vivo studies and translational research on COS in the medical field are highlighted.

Effect of Gamma Irradiation on the PLA-Based Blends and Biocomposites Containing Rosemary Ethanolic Extract and Chitosan

The irradiation of polymeric materials with ionizing radiation (γ-rays, X-rays, accelerated electrons, ion beams, etc.) may lead to disproportion, hydrogen abstraction, arrangements, degradation, and/or the formation of new bonds. The purpose of this paper is to evaluate the effect of gamma irradiation on some new poly(lactic acid) (PLA)-based blends and biocomposites, which is crucial when they are used for food packaging or medical purposes. The polymeric blends and biocomposites based on PLA and rosemary ethanolic extract (R) and poly(ethylene glycol) (PEG) (20 wt%) plasticized PLA, chitosan (CS) (3–6 wt%) and R (0.5 wt%) biocomposites were subjected to gamma irradiation treatment using three low γ-doses of 10, 20, and 30 kGy. The effect of irradiation was evaluated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), thermogravimetry (TG), chemiluminescence method (CL), migration studies, and antibacterial activity tests. It was found that in comparison with neat PLA, the gamma irradiation in the oxidative conditions of the PLA-based blends and biocomposites, causes modifications in the structure, morphology, and thermal properties of the materials depending on irradiation dose and the presence of natural additives such as rosemary and chitosan. It was established that under a gamma-irradiation treatment with dose of 10–20 kGy, the PLA materials showed minor changes in structure and properties being suitable for application in packaging and in addition after irradiation with such doses their antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium is improved.

Low molecular weight sulfated chitosan isolation, characterization and anti-tuberculosis activity derived from Sepioteuthis lessoniana

The research focused on tuberculosis as it is one of the world's most serious health problems. The extracted chitin from the gladius of Sepioteuthis lessoniana converted into Chitosan (CH). The purified and freeze-dried CH was refined as Sulfated Chitosan (SCH). The SCH was converted into low molecular weight of SCH with various doses of Gamma Irradiation (GIR). Fluorescence characteristics of GIR-SCH and elemental analysis were confirmed. The structure and molecular weights of GIR-SCH were determined with FT-IR, NMR and MALDI-TOF/Mass Spectroscopy. 100 Gy of GIR-SCH significantly showed the minimum inhibitory concentration (MIC) against Mycobacterium smegmatis. The MIC against M. smegmatis was not affected by the varied sulfate levels in the identical molecular weight GIR-SCH. However, the lowest molecular weight GIR-SCH displayed a significantly MIC against M. smegmatis. In docking analysis, the 6ZT3 ligand had the lowest binding energy of -1.57 kcal/Mol indicating a superior binding interaction with GIR-SCH. The effect of molecular weight reduction by GIR on the anti-tuberculosis capacity of GIR SCH was investigated in this study which had antimicrobial implications.

Low-energy electron beam sterilization of solid alginate and chitosan, and their polyelectrolyte complexes

Polysaccharidic scaffolds hold great hope in regenerative medicine, however their sterilization still remains challenging since conventional methods are deleterious. Recently, electron beams (EB) have raised interest as emerging sterilization techniques. In this context, the aim of this work was to study the impact of EB irradiations on polysaccharidic macroporous scaffolds. The effects of continuous and pulsed low energy EB were examined on polysaccharidic or on polyelectrolyte complexes (PEC) scaffolds by SEC-MALLS, FTIR and EPR. Then the scaffolds' physicochemical properties: swelling, architecture and compressive modulus were investigated. Finally, sterility and in vitro biocompatibility of irradiated scaffolds were evaluated to validate the effectiveness of our approach. Continuous beam irradiations appear less deleterious on alginate and chitosan chains, but the use of a pulsed beam limits the time of irradiation and better preserve the architecture of PEC scaffolds. This work paves the way for low energy EB tailor-made sterilization of sensitive porous scaffolds.

Photoactive and antioxidant nanochitosan dots/biocellulose hydrogels for wound healing treatment

Bacterial infection and their resistance to known antibiotics delays wound healing. In this study, nanochitosan dots (nChiD) produced by gamma irradiation have been encapsulated in bacterial cellulose (BC) polymer matrix to study the antibacterial potentials of these nanocomposites and their possible usage in wound healing treatment (scratch assay). Detailed analyses show that nChiDs have disc-like shape and average diameter in the range of 40 to 60 nm depending of the applied dose. All nChiDs as well as BC-nChiD nanocomposites emit green photoluminescence independently on the excitation wavelengths. The new designed nanocomposites do not have a cytotoxic effect; antioxidant analysis shows their moderate radical scavenging activity whereas antibacterial properties show significant growth inhibition of strains mostly found in difficult-to-heal wounds. The obtained results confirm that new designed BC-nChiD nanocomposites might be potential agent in wound healing treatment.

Structural Characterization and Antioxidant Potential of Chitosan by γ-Irradiation from the Carapace of Horseshoe Crab

Natural product extraction is ingenuity that permits the mass manufacturing of specific products in a cost-effective manner. With the aim of obtaining an alternative chitosan supply, the carapace of dead horseshoe crabs seemed feasible. This sparked an investigation of the structural changes and antioxidant capacity of horseshoe crab chitosan (HCH) by γ-irradiation using 60Co source. Chitosan was extracted from the horseshoe crab (Tachypleus gigas; Müller) carapace using heterogeneous chemical N-deacetylation of chitin, followed by the irradiation of HCH using 60Co at a dose-dependent rate of 10 kGy/hour. The average molecular weight was determined by the viscosimetric method. Regarding the chemical properties, the crystal-like structures obtained from γ-irradiated chitosan powders were determined using Fourier transfer infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses. The change in chitosan structure was evident with dose-dependent rates between 10 and 20 kGy/hour. The antioxidant properties of horseshoe crab-derived chitosan were evaluated in vitro. The 20 kGy γ-irradiation applied to chitosan changed the structure and reduced the molecular weight, providing sufficient degradation for an increase in antioxidant activity. Our findings indicate that horseshoe crab chitosan can be employed for both scald-wound healing and long-term food preservation due to its buffer-like and radical ion scavenging ability.

Enzymatic Modification of Native Chitin and Conversion to Specialty Chemical Products

: Chitin is one of the most abundant biomolecules on earth, occurring in crustacean shells and cell walls of fungi. While the polysaccharide is threatening to pollute coastal ecosystems in the form of accumulating shell-waste, it has the potential to be converted into highly profitable derivatives with applications in medicine, biotechnology, and wastewater treatment, among others. Traditionally this is still mostly done by the employment of aggressive chemicals, yielding low quality while producing toxic by-products. In the last decades, the enzymatic conversion of chitin has been on the rise, albeit still not on the same level of cost-effectiveness compared to the traditional methods due to its multi-step character. Another severe drawback of the biotechnological approach is the highly ordered structure of chitin, which renders it nigh impossible for most glycosidic hydrolases to act upon. So far, only the Auxiliary Activity 10 family (AA10), including lytic polysaccharide monooxygenases (LPMOs), is known to hydrolyse native recalcitrant chitin, which spares the expensive first step of chemical or mechanical pre-treatment to enlarge the substrate surface. The main advantages of enzymatic conversion of chitin over conventional chemical methods are the biocompability and, more strikingly, the higher product specificity, product quality, and yield of the process. Products with a higher Mw due to no unspecific depolymerisation besides an exactly defined degree and pattern of acetylation can be yielded. This provides a new toolset of thousands of new chitin and chitosan derivatives, as the physio-chemical properties can be modified according to the desired application. This review aims to provide an overview of the biotechnological tools currently at hand, as well as challenges and crucial steps to achieve the long-term goal of enzymatic conversion of native chitin into specialty chemical products.

Graft copolymerization of acrylamide on chitosan-co-chitin and its application for immobilization of Aspergillus sp. RL2Ct cutinase

The synthesis of chitosan (Chs) and chitin (Chi) copolymer and grafting of acrylamide (AAm) onto the synthesized copolymer have been carried out by chemical methods. The grafted copolymer was characterized by FTIR, SEM and XRD. The extracellular cutinase of Aspergillus sp. RL2Ct (E.C. 3.1.1.3) was purified to 4.46 fold with 16.1% yield using acetone precipitation and DEAE sepharose ion exchange chromatography. It was immobilized by adsorption on the grafted copolymer. The immobilized enzyme was found to be more stable then the free enzyme and has a good binding efficiency (78.8%) with the grafted copolymer. The kinetic parameters K_M and V_max for free and immobilized cutinase were found to be 0.55mM and 1410μmolmin^-1mg^-1 protein, 2.99mM and 996μmolmin^-1mg^-1 protein, respectively. The immobilized cutinase was recycled 64 times without considerable loss of activity. The matrix (Chs-co-Chi-g-poly(AAm)) prepared and cutinase immobilized on the matrix have potential applications in enzyme immobilization and organic synthesis respectively.

Comparison of the properties of collagen-chitosan scaffolds after γ-ray irradiation and carbodiimide cross-linking

The property of collagen-chitosan porous scaffold varies according to cross-linking density and scaffold composition. This study was designed to compare the properties of collagen-chitosan porous scaffolds cross-linked with γ-irradiation and carbodiimide (CAR) for the first time. Eleven sets of collagen-chitosan scaffolds containing different concentrations of chitosan at a 5% increasing gradient were fabricated. Fourier transform infrared spectroscopy was performed to confirm the success of cross-linking in the scaffolds. The scaffold morphology was evaluated under scanning electron microscope (SEM). SEM revealed that chitosan was an indispensable material for the fabrication of γ-ray irradiation scaffold. The microstructure of γ-ray irradiation scaffold was less stable than those of alternative scaffolds. Based upon swelling ratio, porosity factor, and collagenase degradation, γ-ray irradiation scaffold was less stable than CAR and 25% proportion of chitosan scaffolds. Mechanical property determines the orientation in γ-irradiation and CAR scaffold. In vitro degradation test indicated that γ-irradiation and CAR cross-linking can elevate the scaffold biocompatibility. Compared with γ-ray irradiation, CAR cross-linked scaffold containing 25% chitosan can more significantly enhance the bio-stability and biocompatibility of collagen-chitosan scaffolds. CAR cross-linked scaffold may be the best choice for future tissue engineering.

Bioproduction of chitooligosaccharides: present and perspectives

Chitin and chitosan oligosaccharides (COS) have been traditionally obtained by chemical digestion with strong acids. In light of the difficulties associated with these traditional production processes, environmentally compatible and reproducible production alternatives are desirable. Unlike chemical digestion, biodegradation of chitin and chitosan by enzymes or microorganisms does not require the use of toxic chemicals or excessive amounts of wastewater. Enzyme preparations with chitinase, chitosanase, and lysozymeare primarily used to hydrolyze chitin and chitosan. Commercial preparations of cellulase, protease, lipase, and pepsin provide another opportunity for oligosaccharide production. In addition to their hydrolytic activities, the transglycosylation activity of chitinolytic enzymes might be exploited for the synthesis of desired chitin oligomers and their derivatives. Chitin deacetylase is also potentially useful for the preparation of oligosaccharides. Recently, direct production of oligosaccharides from chitin and crab shells by a combination of mechanochemical grinding and enzymatic hydrolysis has been reported. Together with these, other emerging technologies such as direct degradation of chitin from crustacean shells and microbial cell walls, enzymatic synthesis of COS from small building blocks, and protein engineering technology for chitin-related enzymes have been discussed as the most significant challenge for industrial application.

Bioproduction of chitooligosaccharides: present and perspectives

Chitin and chitosan oligosaccharides (COS) have been traditionally obtained by chemical digestion with strong acids. In light of the difficulties associated with these traditional production processes, environmentally compatible and reproducible production alternatives are desirable. Unlike chemical digestion, biodegradation of chitin and chitosan by enzymes or microorganisms does not require the use of toxic chemicals or excessive amounts of wastewater. Enzyme preparations with chitinase, chitosanase, and lysozymeare primarily used to hydrolyze chitin and chitosan. Commercial preparations of cellulase, protease, lipase, and pepsin provide another opportunity for oligosaccharide production. In addition to their hydrolytic activities, the transglycosylation activity of chitinolytic enzymes might be exploited for the synthesis of desired chitin oligomers and their derivatives. Chitin deacetylase is also potentially useful for the preparation of oligosaccharides. Recently, direct production of oligosaccharides from chitin and crab shells by a combination of mechanochemical grinding and enzymatic hydrolysis has been reported. Together with these, other emerging technologies such as direct degradation of chitin from crustacean shells and microbial cell walls, enzymatic synthesis of COS from small building blocks, and protein engineering technology for chitin-related enzymes have been discussed as the most significant challenge for industrial application.

Prevention of browning of depolymerized chitosan obtained by gamma irradiation

In this paper, effect of oxygen and pH on the browning of chitosan exposed to gamma radiation was investigated. It was found that oxygen and pH value could play important roles in the inhibiting browning of irradiated chitosan. When the pH value of chitosan solution was below 3.0, sufficient oxygen could inhibit browning of irradiated chitosan in aqueous solution. As a result of irradiation of chitosan solution (pH<3) with sufficient oxygen, the irradiated chitosan solutions obtained were colorless and pellucid. FT-IR, (13)C NMR, and UV-vis spectra confirmed that the irradiation in the presence of oxygen cannot result in chemical modification of irradiated chitosan. An effective technology was developed for the inhibition of browning of irradiated chitosan during depolymerization of chitosan by gamma irradiation.

Novel high-viscosity polyacrylamidated chitosan for neural tissue engineering: fabrication of anisotropic neurodurable scaffold via molecular disposition of persulfate-mediated polymer slicing and complexation

Macroporous polyacrylamide-grafted-chitosan scaffolds for neural tissue engineering were fabricated with varied synthetic and viscosity profiles. A novel approach and mechanism was utilized for polyacrylamide grafting onto chitosan using potassium persulfate (KPS) mediated degradation of both polymers under a thermally controlled environment. Commercially available high molecular mass polyacrylamide was used instead of the acrylamide monomer for graft copolymerization. This grafting strategy yielded an enhanced grafting efficiency (GE = 92%), grafting ratio (GR = 263%), intrinsic viscosity (IV = 5.231 dL/g) and viscometric average molecular mass (MW = 1.63 × 10⁶ Da) compared with known acrylamide that has a GE = 83%, GR = 178%, IV = 3.901 dL/g and MW = 1.22 × 10⁶ Da. Image processing analysis of SEM images of the newly grafted neurodurable scaffold was undertaken based on the polymer-pore threshold. Attenuated Total Reflectance-FTIR spectral analyses in conjugation with DSC were used for the characterization and comparison of the newly grafted copolymers. Static Lattice Atomistic Simulations were employed to investigate and elucidate the copolymeric assembly and reaction mechanism by exploring the spatial disposition of chitosan and polyacrylamide with respect to the reactional profile of potassium persulfate. Interestingly, potassium persulfate, a peroxide, was found to play a dual role initially degrading the polymers—“polymer slicing”—thereby initiating the formation of free radicals and subsequently leading to synthesis of the high molecular mass polyacrylamide-grafted-chitosan (PAAm-g-CHT)—“polymer complexation”. Furthermore, the applicability of the uniquely grafted scaffold for neural tissue engineering was evaluated via PC12 neuronal cell seeding. The novel PAAm-g-CHT exhibited superior neurocompatibility in terms of cell infiltration owing to the anisotropic porous architecture, high molecular mass mediated robustness, superior hydrophilicity as well as surface charge due to the acrylic chains. Additionally, these results suggested that the porous PAAm-g-CHT scaffold may act as a potential neural cell carrier.

Production of chitooligosaccharides and their potential applications in medicine

Chitooligosaccharides (CHOS) are homo- or heterooligomers of N-acetylglucosamine and D-glucosamine. CHOS can be produced using chitin or chitosan as a starting material, using enzymatic conversions, chemical methods or combinations thereof. Production of well-defined CHOS-mixtures, or even pure CHOS, is of great interest since these oligosaccharides are thought to have several interesting bioactivities. Understanding the mechanisms underlying these bioactivities is of major importance. However, so far in-depth knowledge on the mode-of-action of CHOS is scarce, one major reason being that most published studies are done with badly characterized heterogeneous mixtures of CHOS. Production of CHOS that are well-defined in terms of length, degree of N-acetylation, and sequence is not straightforward. Here we provide an overview of techniques that may be used to produce and characterize reasonably well-defined CHOS fractions. We also present possible medical applications of CHOS, including tumor growth inhibition and inhibition of T(H)2-induced inflammation in asthma, as well as use as a bone-strengthener in osteoporosis, a vector for gene delivery, an antibacterial agent, an antifungal agent, an anti-malaria agent, or a hemostatic agent in wound-dressings. By using well-defined CHOS-mixtures it will become possible to obtain a better understanding of the mechanisms underlying these bioactivities.

Alterations of human acellular tissue matrix by gamma irradiation: Histology, biomechanical property, stability,in vitro cell repopulation, and remodeling

AlloDerm, a processed acellular human tissue matrix, is used in a number of surgical applications for tissue repair and regeneration. In the present work, AlloDerm serves as a model system for studying gamma radiation-induced changes in tissue structure and stability as well as the effect of such changes on the cell-matrix interactions, including cell repopulation and matrix remodeling. AlloDerm tissue matrix was treated with 2-30 kGy gamma irradiation at room temperature. Gamma irradiation reduced the swelling of tissue matrix upon rehydration and caused significant structural modifications, including collagen condensation and hole formation in collagen fibres. The tensile strength of AlloDerm increased at low gamma dose but decreased with increasing gamma dosage. The elasticity of irradiated AlloDerm was reduced significantly. Calorimetric study showed that gamma irradiation destabilized the tissue matrix, resulting in greater susceptibility to proteolytic enzyme degradation. Although gamma irradiation did not affect in vitro proliferation of fibroblast cells, it promoted tissue degradation upon cell repopulation and influenced synthesis and deposition of new collagen.

One-pot synthesis in aqueous system for water-soluble chitosan-graft-poly(ethylene glycol) methyl ether

Chitosan is functionalized with poly(ethylene glycol) methyl ether (mPEG) at the amino and hydroxyl groups via a single step reaction in a homogeneous aqueous system. A chitosan aqueous solution obtained from the mixture of chitosan and hydroxybenzotriazole (HOBt) in water is a key factor in providing mild conditions to conjugate mPEG by using a carbodiimide conjugating agent. The reaction at ambient temperature for 24 h gives chitosan-g-mPEG with water solubility with mPEG content as high as 42%. This work demonstrates that a water-soluble chitosan-HOBt complex is an effective system for the preparation of chitosan derivatives via the aqueous system without the use of acids or organic solvents.