Preparative methods of phosphorylated chitin and chitosan--an overview

Biomaterials such as chitin, chitosan and their derivatives have a significant and rapid development in recent years. Chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However, the applications of chitin and chitosan are limited due to its insolubility in most of the solvents. The chemical modification of chitin and chitosan are keen interest because of these modifications would not change the fundamental skeleton of chitin and chitosan but would keep the original physicochemical and biochemical properties. They would also bring new or improved properties. The chemical modification of chitin and chitosan by phosphorylation is expected to be biocompatible and is able to promote tissue regeneration. In view of rapidly growing interest in chitin and chitosan and their chemical modified derivatives, we are here focusing the recent developments on preparation of phosphorylated chitin and chitosan in different methods.     

Dyeing and antimicrobial characteristics of chitosan treated wool fabrics with henna dye

Chitosan, a naturally available biopolymer which is now increasingly being used as a functional finish on textile substrates to impart antimicrobial characteristics and increase dye uptake of fabrics was applied on wool fabrics. Henna a natural dye with proven bactericidal properties was applied on wool fabrics along with chitosan to impart antimicrobial characteristics. The effect of chitosan application on the dyeing properties of wool fabrics was studied by measuring the K/S values of the treated substrates at various concentrations of chitosan and the dye. The antimicrobial properties of chitosan and natural dyes both when applied independently and collectively on fabrics were assessed. The results proved that the chitosan treated wool fabrics showed increase dye uptake of fabrics. The treated fabrics were found to be antimicrobial and the chitosan treatment enhances the antimicrobial characteristics of the dyes. Fastness properties of the applied finish to washing, rubbing and perspiration have also been discussed.     

A biomimetic chitosan composite with improved mechanical properties in wet conditions

Chitosan is one of the most widely used structural polymers for biomedical applications because it has many favorable properties. However, one of the most critical drawbacks regarding the use of chitosan as a biomedical material is its poor mechanical properties in wet conditions. Here, we designed a method to improve the mechanical properties of chitosan in wet conditions and minimized the swelling behavior of chitosan film due to water adsorption by mimicking the sclerotization of insect cuticles and squid beaks, that is, catechol‐meditated crosslinking. The biomimetic chitosan composite film was prepared by mixing chitosan with l ‐3,4‐dihydroxyphenylalanine (DOPA) as a catecholic crosslinker and sodium periodate as an oxidant. The catechol‐meditated crosslinking provided a sevenfold enhancement in the stiffness in wet conditions compared to pure chitosan films and reduced the swelling behavior of the chitosan film. This strategy expands the possible applications for the use of chitosan composites as load‐bearing biomaterials. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 505–512, 2013     

Chitosan functional properties

Chitosan is a partially deacetylated polymer of N-acetyl glucosamine. It is essentially a natural, water-soluble, derivative of cellulose with unique properties. Chitosan is usually prepared from chitin (2 acetamido-2-deoxy β-1,4-D-glucan) and chitin has been found in a wide range of natural sources (crustaceans, fungi, insects, annelids, molluscs, coelenterata etc.) However chitosan is only manufactured from crustaceans (crab and crayfish) primarily because a large amount of the crustacean exoskeleton is available as a by product of food processing. Squid pens (a waste byproduct of New Zealand squid processing) are a novel, renewable source of chitin and chitosan. Squid pens are currently regarded as waste and so the raw material is relatively cheap. This study was intended to assess the functional properties of squid pen chitosan. Chitosan was extracted from squid pens and assessed for composition, rheology, flocculation, film formation and antimicrobial properties. Crustacean chitosans were also assessed for comparison. Squid chitosan was colourless, had a low ash content and had significantly improved thickening and suspending properties. The flocculation capacity of squid chitosan was low in comparison with the crustacean sourced chitosans. However it should be possible to increase the flocculation capacity of squid pen chitosan by decreasing the degree of acetylation. Films made with squid chitosan were more elastic than crustacean chitosan with improved functional properties. This high quality chitosan could prove particularly suitable for medical/analytical applications. This revised version was published online in November 2006 with corrections to the Cover Date.     

Functionalization of Titanium with Chitosan via Silanation: Evaluation of Biological and Mechanical Performances

Complications in dentistry and orthopaedic surgery are mainly induced by peri-implant bacterial infections and current implant devices do not prevent such infections. The coating of antibacterial molecules such as chitosan on its surface would give the implant bioactive properties. The major challenge of this type of coating is the attachment of chitosan to a metal substrate. In this study, we propose to investigate the functionalization of titanium with chitosan via a silanation. Firstly, the surface chemistry and mechanical properties of such coating were evaluated. We also verified if the coated chitosan retained its biocompatibility with the peri-implant cells, as well as its antibacterial properties. FTIR and Tof-SIMS analyses confirmed the presence of chitosan on the titanium surface. This coating showed great scratch resistance and was strongly adhesive to the substrate. These mechanical properties were consistent with an implantology application. The Chitosan-coated surfaces showed strong inhibition of Actinomyces naeslundii growth; they nonetheless showed a non significant inhibition against Porphyromonas gingivalis after 32 hours in liquid media. The chitosan-coating also demonstrated good biocompatibility to NIH3T3 fibroblasts. Thus this method of covalent coating provides a biocompatible material with improved bioactive properties. These results proved that covalent coating of chitosan has significant potential in biomedical device implantation.     

Antifungal properties of Schiff bases of chitosan, N-substituted chitosan and quaternized chitosan

Schiff bases of chitosan, N-substituted chitosan, and quaternized chitosan were synthesized and their antifungal properties were analyzed against Botrytis cinerea Pers. (B. cinerea pers.) and Colletotrichum lagenarium (Pass) Ell.et halst (C. lagenarium (Pass) Ell.et halst) based on the method of D. Jasso de Rodríguez and co-workers. The results showed that quaternized chitosan had better inhibitory properties than chitosan, Schiff bases of chitosan, and N-substituted chitosan.     

Preparation and characterization on mechanical and antibacterial properties of chitsoan/cellulose blends

Polysaccharides-based membranes of chitosan and cellulose blends were prepared using trifluoroacetic acid as a co-solvent. Morphology and mechanical property of prepared membranes were studied by Instron and dynamic mechanical thermal analysis. The mechanical and dynamic mechanical thermal properties of the cellulose/chitosan blends appear to be dominated by cellulose, suggests that cellulose/chitosan blends were not well miscible. It is believed that the intermolecular hydrogen bonding of cellulose is supposed to be break down to form cellulose–chitosan hydrogen bonding; however, the intra-molecular and intra-strand hydrogen bonds hold the network flat. The reduced water vapor transpiration rate through the chitosan/cellulose membranes indicates that the membranes used as a wound dressing may prevent wound from excessive dehydration. The chitosan/cellulose blend membranes demonstrate effective antimicrobial capability against Escherichia coli and Staphylococcus aureus, as examined by the antimicrobial test. These results indicate that the chitosan/cellulose blend membranes may be suitable to be used as a wound dressing with antibacterial properties.     

Sulfated chitin and chitosan as novel biomaterials

Chitin and chitosan are known to be natural polymers and they are non-toxic, biodegradable and biocompatible. Chemical modification of chitin and chitosan with sulfate to generate new bifunctional materials is of interest because the modification would not change the fundamental skeleton of chitin and chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. The sulfated chitin and chitosan have a variety of applications, such as, adsorbing metal ions, drug delivery systems, blood compatibility, and antibacterial field. The purpose of this review is to take a closer look about the different synthetic methods and potential applications of sulfated chitin and chitosan. Based on current research and existing products, some new and futuristic approaches in this context area are discussed in detail. From the studies reviewed, we concluded that sulfated chitin and chitosan are promising materials for biomedical applications.     

Growth of human mesenchymal stem cells (MSCs) on films of enzymatically modified chitosan

Mesenchymal stem cells (MSCs) are known to be an attractive cell source for tissue engineering and regenerative medicine. One of the main limiting steps for clinical use or biotechnological purposes is the expansion step. The research of compatible biomaterials for MSCs expansion is recently regarded as an attractive topic. The aim of this study was to create new functional biomaterial for MSCs expansion by evaluating the impact of chitosan derivative films modified by enzymatic approach. First, chitosan particles were enzymatically modified with ferulic acid (FA) or ethyl ferulate (EF) under an eco‐friendly procedure. Then, films of chitosan and its modified derivatives were prepared and evaluated by physicochemical and biological properties. Results showed that the enzymatic grafting of FA or EF onto chitosan significantly increased hydrophobic and antioxidant properties of chitosan films. The MSCs cell viability on chitosan derivative films also increased depending on the film thickness and the quantity of grafted phenols. Furthermore, the cytotoxicity test showed the absence of toxic effect of chitosan derivative films towards MSCs cells. Cell morphology showed a well attached and spread phenotype of MSCs cells on chitosan derivative films. On the other hand, due to the higher phenol content of FA‐chitosan films, their hydrophobic, antioxidant properties and cell adhesion were improved in comparison with those of EF‐chitosan films. Finally, this enzymatic process can be considered as a promising process to favor MSCs cell growth as well as to create useful biomaterials for biomedical applications especially for tissue engineering. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:491–500, 2016     

Alginate-chitosan complex coacervation for cell encapsulation: effect on mechanical properties and on long-term viability

The use of chitosan in complexation with alginate appears to be a promising strategy for cell microencapsulation, due to the biocompatibility of both polymers and the high mechanical properties attributed by the use of chitosan. The present work focuses on the optimization and characterization of the alginate-chitosan system to achieve long-term cell encapsulation. Microcapsules were prepared from four types of chitosan using one- and two-stage encapsulation procedures. The effect of reaction time and pH on long-term cell viability and mechanical properties of the microcapsules was evaluated. Using the single-stage encapsulation procedure led to increase of at least fourfold in viability compared with the two-stage procedure. Among the four types of chitosan, the use of high molecular weight (MW) chitosan glutamate and low MW chitosan chloride provided high viability levels as well as good mechanical properties, i.e., more than 93% intact capsules. The high viability levels were found to be independent of the reaction conditions when using high MW chitosan. However, when using low MW chitosan, better viability levels (195%) were obtained when using a pH of 6 and a reaction time of 30 min. An alginate-chitosan cell encapsulation system was devised to achieve high cell viability levels as well as to improve mechanical properties, thus holding great potential for future clinical application.     

Preparation of N-vanillyl chitosan and 4-hydroxybenzyl chitosan and their physico-mechanical, optical, barrier, and antimicrobial properties

Chitosan derivatives such as N-vanillyl chitosan and 4-hydroxybenzyl chitosan were prepared by reacting chitosan with 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxybenzaldehyde. Amino groups on chitosan reacts with these aldehydes to form a Schiff base intermediate, which is later on converted into N-alkyl chitosans by reduction with sodium cyanoborohydride. The chemical reaction was monitored by ¹H NMR spectroscopy and the absence of aldehydic proton at 9.83 ppm in NMR spectra was observed for both the modified chitosan derivatives confirming the reaction. Modified chitosan films were later prepared by solution casting method and their physico-mechanical, barrier, optical and thermal properties were studied. The results clearly indicated significant change in tensile strength, water vapour transmission rate, and haze properties of modified chitosans. Modified chitosan films were also studied for their antimicrobial activity against Aspergillus flavus. The results showed a marked reduction of aflatoxins produced by the fungus in the presence of the N-vanillyl chitosan and 4-hydroxybenzyl chitosan film discs to 98.9% and non-detectable levels, respectively.     

Cytotoxic activities of chitosan nanoparticles and copper-loaded nanoparticles

Chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions and copper ion sorption. In this study, the cytotoxic activities of the chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles was investigated and a relationship between physiochemical properties and activity is suggested. The chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles elicited dose-dependent inhibitory effects on the proliferation of tumor cell lines.     

Novel chitosan-based films cross-linked by genipin with improved physical properties

Novel cross-linked chitosan-based films were prepared using the solution casting technique. A naturally occurring and nontoxic cross-linking agent, genipin, was used to form the chitosan and chitosan/poly(ethylene oxide) (PEO) blend networks, where two types of PEO were used, one with a molecular weight of 20 000 g/mol (HPEO) and the other of 600 g/mol (LPEO). Genipin is used in traditional Chinese medicine and extracted from gardenia fruit. Importantly, it overcomes the problem of physiological toxicity inherent in the use of some common synthetic chemicals as cross-linking agents. The mechanical properties and the stability in water of cross-linked and un-crosslinked chitosan and chitosan/PEO blend films were investigated. It was shown that, compared to the transparent yellow, un-cross-linked chitosan/PEO blend films, the genipin-cross-linked chitosan-based film, blue in color, was more elastic, was more stable, and had better mechanical properties. Genipin-cross-linking produced chitosan networks that were insoluble in acidic and alkaline solutions but were able to swell in these aqueous media. The swelling characteristics of the films exhibit sensitivity to the environmental pH and temperature. The surface properties of the films were also examined by contact angle measurements using water and mixtures of water/ethanol. The results showed that, with the one exception of cross-linked pure chitosan in 100% water, the cross-linked chitosan and chitosan/PEO blends were more hydrophobic than un-crosslinked ones.     

Coliphages inactivation using chitosan derivatives

The effect of chitosan fragments with different degrees of polymerization and the chemical derivatives of chitosan differing in the number of amino groups and total molecule charge on phages T2, T4, and T7 was studied. The interaction of chitosan with bacteriophage particles inactivated them to the extent dependent on the chemical properties of chitosan and its concentration. Phage T2 was found to be most susceptible to inactivation by chitosan. The polycationic nature of chitosan plays an important role in the inactivation of phages. It is assumed that the abnormal rearrangement of the basal plate of phages, the loss of long tail fibers, and probably, modification of the receptor-recognizing phage proteins may be responsible for the inactivation of coliphages by chitosan.     

Inactivation of coliphages by chitosan derivatives

The effect of chitosan fragments with different degrees of polymerization and the chemical derivatives of chitosan differing in the number of amino groups and total molecule charge on phages T2, T4, and T7 was studied. The interaction of chitosan with bacteriophage particles inactivated them to the extent dependent on the chemical properties of chitosan and its concentration. Phage T2 was found to be most susceptible to inactivation by chitosan. The polycationic nature of chitosan plays an important role in the inactivation of phages. It is assumed that the abnormal rearrangement of the basal plate of phages, the loss of long tail fibers, and, probably, modification of the receptor-recognizing phage proteins may be responsible for the inactivation of coliphages by chitosan.     

Blending chitosan with polycaprolactone: effects on physicochemical and antibacterial properties

Chitosan is a well sought-after polysaccharide in biomedical applications and has been blended with various macromolecules to mitigate undesirable properties. However, the effects of blending on the unique antibacterial activity of chitosan as well as changes in fatigue and degradation properties are not well understood. The aim of this work was to evaluate the anti-bacterial properties and changes in physicochemical properties of chitosan upon blending with synthetic polyester poly(epsilon-caprolactone) (PCL). Chitosan and PCL were homogeneously dissolved in varying mass ratios in a unique 77% acetic acid in water mixture and processed into uniform membranes. When subjected to uniaxial cyclical loading in wet conditions, these membranes sustained 10 cycles of predetermined loads up to 1 MPa without break. Chitosan was anti-adhesive to Gram-positive Streptococcus mutans and Gram-negative Actinobacillus actinomycetemcomitans bacteria. Presence of PCL compromised the antibacterial property of chitosan. Four-week degradation studies in PBS/lysozyme at 37 degrees C showed initial weight loss due to chitosan after which no significant changes were observed. Molecular interactions between chitosan and PCL were investigated using Fourier transform infrared spectroscopy (FTIR) which showed no chemical bond formations in the prepared blends. Investigation by wide-angle X-ray diffraction (WAXD) indicated that the crystal structure of individual polymers was unchanged in the blends. Dynamic mechanical and thermal analysis (DMTA) indicated that the crystallinity of PCL was suppressed and its storage modulus increased with the addition of chitosan. Analysis of surface topography by atomic force microscopy (AFM) showed a significant increase in roughness of all blends relative to chitosan. Observed differences in biological and anti-bacterial properties of blends could be primarily attributed to surface topographical changes.     

壳聚糖调节植物生长发育及诱发植物抗病性研究进展

综述了壳聚糖在调节植物生长发育和诱导植物抗病性方面所起的重要作用及其可能的作用机制。壳聚糖对植物氨同化关键酶具有明显的生理调节功能,可以提高植物同化NH4 的能力,有利于蛋白质的生物合成与积累,改善植物的营养品质及园艺性状;并能迅速激发植物的防卫反应,启动植物的防御系统,有效地提高植物的抗病性。同时通过壳聚糖结合蛋白的分离、纯化及其生化特性的研究为进一步确定壳聚糖的作用机制奠定了基础。     

Adhesion and growth of HUVEC endothelial cells on films of enzymatically functionalized chitosan with phenolic compounds

Human Umbilical Vein Endothelial Cell (HUVEC) growth on chitosan films and its enzymatically functionalized derivatives films with ferulic acid (FA) and ethyl ferulate (EF) was assessed by evaluating cell adhesion, morphology and cell viability. The results indicated that chitosan derivative films improved protein adsorption properties compared to chitosan films. The HUVEC cell morphology showed well attachment and spread phenotype on chitosan derivative films compared to those growing on chitosan films which did not spread and remained round. Evaluation of cell viability revealed improvement of cell adhesion on chitosan derivative films compared to chitosan film depending on the quantity of oxidized phenols grafted on chitosan. In addition, FA-/EF-chitosan films allowed almost similar cell adhesion. Furthermore, cell adhesion was increased with the film thickness. These results suggested that the oxidized phenols grafting on chitosan is a promising process to enhance cell adhesion, growth and creating useful functional biomaterials.     

Preparation and application of nanochitosan to finishing treatment with anti-microbial and anti-shrinking properties

In this study, we used low-molecular-weight chitosan (LWCS) to prepare nanochitosan (NCH) and applied this material to wool fabric finishing treatment. The diameters and zeta potential of the nanochitosan decreased as the value of the molecular weight of chitosan decreased. Additionally, the wool fabric was treated with various types of chitosan. The anti-bacterial and shrink-proofing properties of the treated fabric are ranked as following: NCH > LWCS > chitosan. The former two properties also increased as the concentration of nanochitosan increased. In addition, the nanochitosan-treated wool fabric possesses better anti-bacterial and shrink-proofing properties after washing for 20 times.     

Progress of Study on Chitosan in Regulating Plants’Growth and Eliciting Plants’Defense Responses

Important effect of chitosan on regulating plant growth , eliciting plant resistance to disease and it’s possible operating mechanism are reviewed . Chitosan shows evidence physiological effect on the key enzymes of ammonia assimilation and enhances the amination capacity in plant, which is in favor of biology synthesize and accumulation of protein . Thus , chitosan improves nutrition quality and horticulture properties of plant . Moreover , chitosan rapidly stimulates plant defense responses , then startups defensive system and elevates resistance to disease . To a further understanding of the mechanism of chitosan on plant , we have isolated and determined some biochemical properties of a chitosan-bingding protein .