Showing papers on "Chitin published in 2017"

Chitin and Chitosan: Structure, Properties and Applications in Biomedical Engineering

Abstract: Chitin and its deacetylated derivative chitosan are natural polymers composed of randomly distributed β-(1-4)-linked d-glucosamine (deacetylated unit) and N-acetyl-d-glucosamine (acetylated unit). Biopolymers like chitin and chitosan exhibit diverse properties that open up a wide-ranging of applications in various sectors especially in biomedical science. The latest advances in the biomedical research are important emerging trends that hold a great promise in wound-healing management products. Chitin and chitosan are considered as useful biocompatible materials to be used in a medical device to treat, augment or replace any tissue, organ, or function of the body. A body of recent studies suggests that chitosan and its derivatives are promising candidates for supporting materials in tissue engineering applications. This review article is mainly focused on the contemporary research on chitin and chitosan towards their applications in numerous biomedical fields namely tissue engineering, artificial kidney, skin, bone, cartilage, liver, nerve, tendon, wound-healing, burn treatment and some other useful purposes.

Preparation and Characterization of Chitosan Obtained from Shells of Shrimp (Litopenaeus vannamei Boone)

Abstract: The main source of commercial chitosan is the extensive deacetylation of its parent polymer chitin It is present in green algae, the cell walls or fungi and in the exoskeleton of crustaceans A novel procedure for preparing chitosan from shrimp shells was developed The procedure involves two 10-minutes bleaching steps with ethanol after the usual demineralization and deproteinization processes Before deacetylation, chitin was immersed in 125 M NaOH, cooled down and kept frozen for 24 h The obtained chitosan was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV, X-ray diffraction (XRD) and viscosimetry Samples of white chitosan with acetylation degrees below 9 % were obtained, as determined by FTIR and UV-first derivative spectroscopy The change in the morphology of samples was followed by SEM The ash content of chitosan samples were all below 0063 % Chitosan was soluble in 1 % acetic acid with insoluble contents of 062 % or less XRD patterns exhibited the characteristic peaks of chitosan centered at 10 and 20 degrees in 2 θ The molecular weight of chitosan was between 23 and 28 × 10 5 g/mol It is concluded that the procedure developed in the present work allowed obtaining chitosans with physical and chemical properties suitable for pharmaceutical applications

Antimicrobial properties of chitosan nanoparticles: Mode of action and factors affecting activity

Abstract: The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan for biomedical applications. The presence of primary amine groups in repeating units of chitosan grants it several properties like antibacterial activity, antitumor activity and so on. Chitosan forms nanoparticles spontaneously on the addition of polyanion tripolyphosphate which has greater antimicrobial activity than parent chitosan. In the present study, chitosan nanoparticles (ChNP) were prepared by the ionic gelation method. The physiochemical characteristics of nanoparticles were analyzed using XRD, SEM, FTIR. The antibacterial activity of chitosan nanoparticles against medical pathogens Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa was evaluated by calculation of minimum inhibitory concentration (MIC) and compared with chitosan and chitin activity. The mode of action and factors affecting antibacterial activity were also analyzed. ChNP compounds exhibited superior antimicrobial activity against all microorganisms in comparison with chitosan and chitin. The antibiofilm activity was studied using crystal violet assay and growth on congo red agar. The study is thus a good demonstration of the applicability of chitosan nanoparticles as an effective antimicrobial agent with antibiofilm activity as well.

Current Status and New Perspectives on Chitin and Chitosan as Functional Biopolymers

Abstract: The natural biopolymer chitin and its deacetylated product chitosan are found abundantly in nature as structural building blocks and are used in all sectors of human activities like materials science, nutrition, health care, and energy Far from being fully recognized, these polymers are able to open opportunities for completely novel applications due to their exceptional properties which an economic value is intrinsically entrapped On a commercial scale, chitosan is mainly obtained from crustacean shells rather than from the fungal and insect sources Significant efforts have been devoted to commercialize chitosan extracted from fungal and insect sources to completely replace crustacean-derived chitosan However, the traditional chitin extraction processes are laden with many disadvantages The present review discusses the potential bioextraction of chitosan from fungal, insect, and crustacean as well as its superior physico-chemical properties The different aspects of fungal, insects, and crustacean chitosan extraction methods and various parameters having an effect on the yield of chitin and chitosan are discussed in detail In addition, this review also deals with essential attributes of chitosan for high value-added applications in different fields and highlighted new perspectives on the production of chitin and deacetylated chitosan from different sources with the concomitant reduction of the environmental impact

Chitin and chitosan: biopolymers for wound management

Abstract: Chitin and chitosan are biopolymers with excellent bioactive properties, such as biodegradability, non-toxicity, biocompatibility, haemostatic activity and antimicrobial activity. A wide variety of biomedical applications for chitin and chitin derivatives have been reported, including wound-healing applications. They are reported to promote rapid dermal regeneration and accelerate wound healing. A number of dressing materials based on chitin and chitosan have been developed for the treatment of wounds. Chitin and chitosan with beneficial intrinsic properties and high potential for wound healing are attractive biopolymers for wound management. This review presents an overview of properties, biomedical applications and the role of these biopolymers in wound care.

Extraction and physicochemical characterization of chitin and chitosan isolated from house cricket.

Abstract: Chitin ranks next to cellulose as the most important bio-polysaccharide which can primarily be extracted from crustacean shells. However, the emergence of new areas of the application of chitin and its derivatives are on the increase and there is growing demand for new chitin sources. In this study, therefore, an attempt was made to extract chitin from the house cricket (Brachytrupes portentosus) by a chemical method. The physicochemical properties of chitin and chitosan extracted from crickets were compared with commercial chitin and chitosan extracted from shrimps, in terms of proximate analysis in particular, of their ash and moisture content. Also, infrared spectroscopy, x-ray diffraction (XRD), scanning electron microscopy and elemental analysis were conducted. The chitin and chitosan yield of the house cricket ranges over 4.3%-7.1% and 2.4%-5.8% respectively. Chitin and chitosan from crickets compares favourably with those extracted from shrimps, and were found to exhibit some similarities. The result shows that cricket and shrimp chitin and chitosan have the same degree of acetylation and degree of deacetylation of 108.1% and 80.5% respectively, following Fourier transform infrared spectroscopy. The characteristic XRD strong/sharp peaks of 9.4 and 19.4° for α-chitin are common for both cricket and shrimp chitin. The percentage ash content of chitin and chitosan extracted from B. portentosus is 1%, which is lower than that obtained from shrimp products. Therefore, cricket chitin and chitosan can be said to be of better quality and of purer form than commercially produced chitin and chitosan from shrimp. Based on the quality of the product, chitin and chitosan isolated from B. portentosus can replace commercial chitin and chitosan in terms of utilization and applications. Therefore, B. portentosus is a promising alternative source of chitin and chitosan.

Solubility of Chitin: Solvents, Solution Behaviors and Their Related Mechanisms

Abstract: Chitin is a natural polysaccharides having a unique molecular arrangement of 2-(acetylamino)-2-deoxy-d-glucose, it possesses multifunctional properties and is suitable for various applications mainly in pharmaceutical, biomedical food, textiles and packaging fields. Therefore, being considered as a superior material for a sustainable future of industrial development, chitin perfectly meets up the demands with diversified functionalities in applications, excellent biocompatibility and biodegradability. Non-toxicity to human and environment (air, water and soil) is a great opportunity for this revolutionary, innovative and sustainable material. Moreover, antibacterial potency and low immunogenicity of chitin have broadened the aspects of research and development on structurefunction relationship toward biological tissues and activities. Despite abundance, low cost and availability, many experimental data from potential studies, reproducibility problems of chitin solubility measurement still limit the development of products and access to the market in large volume. Batch-to-batch variability, non-precise characterization and randomly distributed acetyl groups of chitin structure eventually results in a bad reproducibility of chitin solubility. Therefore, the chapter aims to organize the information of chitin structure at molecular level and correlate solubility with chitin structure. Moreover, the dissolution mechanism and solution behaviors in different solvents will be discussed in this chapter.

Extremely Strong and Transparent Chitin Films: A High-Efficiency, Energy-Saving, and “Green” Route Using an Aqueous KOH/Urea Solution

Abstract: Crystalline polysaccharides are useful for important and rapidly growing applications ranging from advanced energy storage, green electronics, and catalyst or enzyme supports to tissue engineering and biological devices. However, the potential value of chitin in such applications is currently neglected because of its poor swellability, reactivity, and solubility in most commonly used solvents. Here, a high-efficiency, energy-saving, and “green” route for the fabrication of extremely strong and transparent chitin films is described in which chitin is dissolved in an aqueous KOH/urea solution and neutralized in aqueous ethanol solution. The neutralization temperature, ethanol concentration, and chitin solution deacetylation time are critical parameters for the self-assembly of chitin chains and for tuning the morphology and aggregate structures of the resulting chitin hydrogels and films. Moreover, the drawing orientation can produce extremely strong and tough chitin films with a tensile strength, Young's modulus, and work of fracture of 226 MPa, 7.2 GPa, and 20.3 MJ m−3, respectively. The method developed here should contribute to the utilization of seafood waste and, thereby, to the sustainable use of marine resources.

Adsorption of crystal violet dye onto a mesoporous ZSM-5 zeolite synthetized using chitin as template

Abstract: Hypothesis ZSM-5 zeolite is an efficient adsorbent for several compounds. However, is a microporous material, and consequently, is little efficient for large dye molecules. In order to make ZSM-5 zeolite a mesoporous material with ability to adsorb dyes, the use of chitin (low-cost biopolymer) as template in the synthesis route can be an alternative. Experiments ZSM-5 zeolites were synthetized using a nucleating gel as structure-directing agent for the material formation, followed by the chitin insertion (or not), homogenization and hydrothermal treatment. The obtained zeolites (ZSM-5 and chitin/ZSM-5) from these different methods were characterized. The potential of ZSM-5 and chitin/ZSM-5 zeolites to adsorb crystal violet dye (CV) was evaluated in batch mode, considering the effects of adsorbent dosage and pH. Equilibrium, thermodynamic and kinetic studies were also performed. Findings The use of chitin in the synthesis route provided the following improvements on the ZSM-5 structure: (i) the mesopores volume increased from 0.027 (ZSM-5) to 0.142 cm 3 g −1 (chitin/ZSM-5); (ii) the pore diameter increased from 1.97 (ZSM-5) to 22.49 nm (chitin/ZSM-5); (iii) the porosity was increased and the crystallinity was decreased. For both, ZSM-5 and chitin/ZSM-5, the CV adsorption was favored with adsorbent dosage of 2.0 g L −1 and pH of 7.5. The pseudo-second order model was suitable to represent the adsorption kinetics and, the Langmuir model was adequate to represent the equilibrium. The maximum adsorption capacity increased from 141.8 (ZSM-5) to 1217.3 mg g −1 (chitin/ZSM-5). The adsorption was spontaneous, favorable and endothermic.

Catalytic Conversion of Structural Carbohydrates and Lignin to Chemicals

Abstract: Lignocellulose and chitin are the two most abundant renewable sources of organic carbon available as alternative for chemical and fuel synthesis. Catalytic conversion of these composite polymers to monomers is a multifaceted challenge. Lignocellulose and chitin are inherently unreactive toward chemical attacks as they serve the function of structural materials in plants and animals. A combination of pretreatment and catalytic reaction is necessary to convert these materials into useful small molecules. These upstream reactions involving depolymerization of polymers are the roadblock for realizing future chemicals production based on biomass. In this chapter, we first discuss the pretreatment technologies currently available for lignocellulose and their relevance for catalytic conversion. Catalytic pathways for depolymerization of cellulose, hemicellulose, and lignin are then discussed, highlighting important reactions and mechanism. An analogy is derived between mechanism of cellulose hydrolysis using enzymes and heterogeneous carbon catalysts containing acidic functional groups. Finally, the use of chitin as a renewable carbon source is discussed. The chemical structure of chitin is described along with its origin from crab shells and availability. Recent advances in conversion of chitin to N-acetylglucosamine and its derivatives are described.

Recyclable Universal Solvents for Chitin to Chitosan with Various Degrees of Acetylation and Construction of Robust Hydrogels

Abstract: Chitin and chitosan are enticing natural polymers derived from seafood wastes, and their applications mostly depend on the degree of acetylation (DA). For their efficient utilization, a series of universal solvents for the direct dissolution from chitin to chitosan with various DA ranged from 5 to 94% were designed, and robust hydrogels were constructed from their solution via a physical regeneration, for the first time. The NMR results demonstrated that K+ of KOH interacted easily with C═O group to break the NH...O═C intermolecular hydrogen bonds of chitin, whereas Li+ of LiOH could bound with NH2 group to promote the destruction of NH...O6 hydrogen bonds of chitosan. Thus, a series of LiOH/KOH/urea aqueous solutions with weight ratios of LiOH to KOH from 0 to 2.5 were developed to directly dissolve these biomacromolecules with DAs ranging from 5 to 94%. Subsequently, a series of coagulants were also exploited for the regeneration of these chitin/chitosan solutions to construct the robust hydrogels with ...

Engineering strategies for chitin nanofibers.

Abstract: Chitin nanofibers are key components in several structural biological materials. Chitin nanofibers are often part of a hierarchical structure formed by chitin molecules assembled into larger nano- and microfibers, aligned, and assembled into a twisted plywood structure. As a result, structural biological materials often couple lightweight with exceptional mechanical properties. These biological materials are an inspiration for engineered biomimetic composites that incorporate chitin nanofibers. Here, we review engineering approaches to obtain chitin nanofibers and their applications.

Distribution and diversity of enzymes for polysaccharide degradation in fungi

Abstract: Fungi are important polysaccharide degraders in the environment and for biotechnology. Here, the increasing number of sequenced fungal genomes allowed for systematic identification of genes and proteins involved in polysaccharide degradation in 218 fungi. Globally, 9,003 sequences for glycoside hydrolases and lytic polysaccharide mono-oxygenases targeting cellulose, xylan, and chitin, were identified. Although abundant in most lineages, the distribution of these enzymes is variable even between organisms from the same genus. However, most fungi are generalists possessing several enzymes for polysaccharide deconstruction. Most identified enzymes were small proteins with simple domain organization or eventually consisted of one catalytic domain associated with a non-catalytic accessory domain. Thus unlike bacteria, fungi's ability to degrade polysaccharides relies on apparent redundancy in functional traits and the high frequency of lytic polysaccharide mono-oxygenases, as well as other physiological adaptation such as hyphal growth. Globally, this study provides a comprehensive framework to further identify enzymes for polysaccharide deconstruction in fungal genomes and will help identify new strains and enzymes with potential for biotechnological application.

Short-Chain Chitin Oligomers: Promoters of Plant Growth

Abstract: Chitin is the second most abundant biopolymer in nature after cellulose, and it forms an integral part of insect exoskeletons, crustacean shells, krill and the cell walls of fungal spores, where it is present as a high-molecular-weight molecule. In this study, we showed that a chitin oligosaccharide of lower molecular weight (tetramer) induced genes in Arabidopsis that are principally related to vegetative growth, development and carbon and nitrogen metabolism. Based on plant responses to this chitin tetramer, a low-molecular-weight chitin mix (CHL) enriched to 92% with dimers (2mer), trimers (3mer) and tetramers (4mer) was produced for potential use in biotechnological processes. Compared with untreated plants, CHL-treated plants had increased in vitro fresh weight (10%), radicle length (25%) and total carbon and nitrogen content (6% and 8%, respectively). Our data show that low-molecular-weight forms of chitin might play a role in nature as bio-stimulators of plant growth, and they are also a known direct source of carbon and nitrogen for soil biomass. The biochemical properties of the CHL mix might make it useful as a non-contaminating bio-stimulant of plant growth and a soil restorer for greenhouses and fields.

Chitin-induced and CHITIN ELICITOR RECEPTOR KINASE1 (CERK1) phosphorylation-dependent endocytosis of Arabidopsis thaliana LYSIN MOTIF-CONTAINING RECEPTOR-LIKE KINASE5 (LYK5).

Abstract: Summary To detect potential pathogens, plants perceive the fungal polysaccharide chitin through receptor complexes containing lysin motif receptor-like kinases (LysM-RLKs). To investigate the ligand-induced spatial dynamics of chitin receptor components, we studied the subcellular behaviour of two Arabidopsis thaliana LysM-RLKs involved in chitin signalling, CHITIN ELICITOR RECEPTOR KINASE1 (CERK1) and LYSIN MOTIF-CONTAINING RECEPTOR-LIKE KINASE5. We performed standard and quantitative confocal laser scanning microscopy on stably transformed A. thaliana plants expressing fluorescently tagged CERK1 and LYK5 from their native promoters. Microscopy approaches were complemented by biochemical analyses in plants and in vitro. Both CERK1 and LYK5 localized to the plasma membrane and showed constitutive endomembrane trafficking. After chitin treatment, however, CERK1 remained at the plasma membrane while LYK5 relocalized into mobile intracellular vesicles. Detailed analyses revealed that chitin perception transiently induced the internalization of LYK5 into late endocytic compartments. Plants that lacked CERK1 or expressed an enzymatically inactive CERK1 variant did not exhibit chitin-induced endocytosis of LYK5. CERK1 could phosphorylate LYK5 in vitro and chitin treatment induced CERK1-dependent phosphorylation of LYK5 in planta. Our results suggest that chitin-induced phosphorylation by CERK1 triggers LYK5 internalization. Thus, our work identifies phosphorylation as a key regulatory step in endocytosis of plant RLKs and also provides evidence for receptor complex dissociation after ligand perception.