Networks based on chitosan and oxidized cyclodextrin—II. Structural and catalytic features of a copper (II)-loaded network

Chitosan is well known for its binding properties toward transition metal ions. We prepared a chemical hydrogel based on chitosan using as cross-linking agent a polyfunctionalized β-cyclodextrin and studied the structural and catalytic features of this hydrogel loaded with copper(II) ions in aqueous medium. Stability of the complex and its structural characteristics were determined by isothermal microcalorimetry and EPR spectroscopy, respectively. Kinetics of the oxidation of (d, l)-adrenaline and of l-adrenaline catalyzed by copper (II) bound to the matrix was monitored with a Clark-type O^-₂ sensitive electrode. The advantages of working with a heterogeneous system are coupled with the preservation of both structural and catalytic features of copper(II) site in the matrix with respect to copper(II) ions bound to chitosan derivatives in solution.     

Effect of Different Composition on Particle Size Chitosan-PMAA-PNIPAM Hydrogel

Chitosan-based (chitosan-poly(methacrylic acid)-poly(N-isopropylacrylamide) [Cs-PMAA-PNIPAM] copolymer hydrogels were synthesized by free radical emulsion polymerization to study the effect of different composition of monomer on hydrogel particle size. Chitosan usually applied for medical use such as drug delivery due to its biodegradability, bio-compatibility, and non-toxicity properties. Co-polymerized chitosan with MAA and NIPAM is an improvement of chitosan gel to be more responsive to the environment of human body included different pH, temperature, ionic strength, electric field, and enzyme activities. Small size of the particles is particularly important to ensure the particles reach the target site especially as a drug delivery. A full factorial experimental design (2³) was employed to identify which factors influenced most on the particle size. The design considered three factors which is amount of MAA, NIPAM and N,N’-Methylenebisacrylamide (MBA) while particle size are chosen as the responses of the variation on each composition. Particle size distribution was measured by laser diffractionin wet condition. From the design of experiment, NIPAM shows the main factor affected the particle size. However combination of the others factors also contributed on the whole size of the hydrogel.     

Recent Applications of Dual-Stimuli Responsive Chitosan Hydrogel Nanocomposites as Drug Delivery Tools

Polysaccharides are a versatile class of macromolecules that are involved in many biological interactions critical to life. They can be further modified for added functionality. Once derivatized, these polymers can exhibit new chemical properties that can be further optimized for applications in drug delivery, wound healing, sensor development and others. Chitosan, derived from the N-deacetylation of chitin, is one example of a polysaccharide that has been functionalized and used as a major component of polysaccharide biomaterials. In this brief review, we focus on one aspect of chitosan’s utility, namely we discuss recent advances in dual-responsive chitosan hydrogel nanomaterials.     

Improved Antimicrobial Potency through Synergistic Action of Chitosan Microparticles and Low Electric Field

Techniques to inhibit gram-negative bacteria such as Shiga toxin-producing Escherichia coli are valuable as the prevalence of large-scale industrial food preparation increases the likelihood of contamination. Chitosan, the deacetylated derivative of chitin, has been demonstrated to inhibit bacteria growth in acidic environments, but is significantly less effective in preventing bacteria grown at pH?>7.0. Pulsed electric fields, constituting another method of bacteria inhibition, are difficult to generate at sufficient strength due to the high electric potentials required. This study utilizes adsorption of particulate chitosan in a very low electric field for an increased inhibition of gram-negative bacteria in neutral or alkaline pH conditions. Chitosan microparticles are demonstrated to flocculate E. coli, inhibit growth, and exhibit increased efficacy when combined with a low voltage electric field applied over 2-min intervals. Using sustained pulses of approximately 100?V/cm, it is demonstrated that bacteria viability is reduced by several orders of magnitude. The degree of bacterial inhibition is increased when chitosan microparticles are introduced to the system prior to imposing a small electric field.     

The Effects of Demineralization Process on Diameter,Tensile Properties and Biodegradation of Chitosan Fiber

Chitosan fiber is one of the potential fibers that can be used as absorbable monofilament suture in biomedical application. In chitosan synthesis, aside from deproteination and deacetylation, demineralization is a crucial step where the major minerals within crustacean shells are removed. This demineralization process is carried out with two parameters, i.e. time and temperature. This research studies the influence of demineralization time on the diameter, tensile properties and biodegradability of chitosan fibers. Chitosan was synthesized from shrimp shells using 1 × 2 h and 3 × 2 h demineralization process. Chitosan fibers were produced by means of wet spinning. The chemical properties of chitosan fibers were characterized by means of Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diffractometry (XRD) technique. Physical properties characterization was carried out to measure the fibers’ diameter, density and viscosity. Tensile properties were evaluated by means of tensile test. The results were compared to standard of absorbable suture from the United States Pharmacopoeia (USP). Furthermore, in vitro degradation testing was also performed for analyzing biodegradation properties. Chitosan fibers were successfully made with diameter and maximum tensile force of chitosan fibers in a range of 364 - 460 μm and 5.6 - 8.3 N, respectively. The results of this research pointed that adding demineralization time would increase the diameter of chitosan fiber. However, the degradation occurred in prolonged demineralization process broke the bonds within the fiber which lead to a decrease in fiber's density. It is due to the degradation of chitosan occurred during extended demineralization process, which leads to degree of crystallinity reduction. Extensive demineralization process has been found to lower fibers’ tensile strength from 80.4 MPa to 38.4 MPa (52.2%), but increase their biodegradability by 17% and maximum elongation from 6.9% to 16.2% (136%). Despite that extensive demineralization process lowered chitosan fiber's tensile strength, both fibers made could still fit the standard for synthetic absorbable suture from USP number 0 and 1.     

Perspectives on composite films of chitosan-based natural products (Ginger,Curcumin, and Cinnamon) as biomaterials for wound dressing

Natural materials are gaining popularity in wound healing and food applications, and they have the potential to alleviate the major environmental problems generated via traditional materials. Biomaterials based on Chitosan incorporated with natural products (Ginger, Curcumin, and Cinnamon) have been fabricated by solvent casting method. The antimicrobial characterization of the prepared samples were also investigated using in vitro antimicrobial studies using Gram-positive microorganism [Micrococcus luteus, Staphylococcus aureus, and Staphylococcus epidermidis], Gram-negative microorganism [Pseudomonas aeruginosa], and pathogenic [Candida albicans]. XRD patterns confirmed the complexation between chitosan and other natural products and this indicate the change in structural of chitosan. The shifting and disappearing of bands in FTIR-ATR and changing in fingerprints in FTIR spectra indicate the homogeneity and interaction between chitosan and the other. Optical properties such as absorption, absorption coefficient, Urbach tail and band gap calculation confirmed that Ginger, Curcumin and Cinnamon interact with chitosan and induces localized state between valence and conduction band. The mechanical properties also studied and revealed that Chitosan/Ginger has the best mechanical characteristic compared the other samples. In addition, the shifting toward higher wavelength for chitosan/Ginger may be utilized to generate electron–hole pairs, which is important for antimicrobial activities, and this confirmed from antimicrobial analysis that Chitosan/Ginger give high antimicrobial activity toward Gram-positive microorganism and suggest it for wound dressing application.     

Critical review of radiation processing of hydrogel and polysaccharide

Radiation processing of an aqueous solution of polymer initiated by OH radicals formed by radiolysis of water is applied for preparation of hydrogel wound dressing and plant growth promoter. Recently, Fenton reagent that generates OH radicals was successfully applied to synthesize PVP hydrogel. The Fenton reaction also can be applied to the depolymerization of chitosan. These progresses in the syntheses of hydrogel and oligo-chitosan by radiation and non-radiation methods such as hydrolysis, oxidative degradation, photolysis, sonolysis and degradation by microwave are reviewed to survey a possibility to reduce the costs of production. Radiation synthesized hydrogel should target value-added medical products because only radiation can crosslink and sterilize simultaneously. Oligo-chitosan can be produced economically by irradiation of solid chitin by Fenton reagent, if necessary.     

Electrorheology of chitosan polysaccharide suspensions in soybean oil

Chitosan, a biodegradable polysaccharide composed of primarily d -glucosamine repeating units, was adopted as a dry-base electrorheological fluid using soybean oil as a suspending medium. The electrorheological properties were examined under various applied electric field strengths. We found that natural organic polymers such as chitosan possessing amino polar groups induce electrorheological behavior, and the yield stress, τ_y, of chitosan increases with the electric field strength, E , according to a power-law form, τ_y∝ E ^α, which is consistent with the conduction model.     

Protective,Biostimulating, and Eliciting Effects of Chitosan and Its Derivatives on Crop Plants

Chitosan is a biodegradable and biocompatible polysaccharide obtained by partial deacetylation of chitin. This polymer has been gaining increasing popularity due to its natural origin, favorable physicochemical properties, and multidirectional bioactivity. In agriculture, the greatest hopes are raised by the possibility of using chitosan as a biostimulant, a plant protection product, an elicitor, or an agent to increase the storage stability of plant raw materials. The most important properties of chitosan include induction of plant defense mechanisms and regulation of metabolic processes. Additionally, it has antifungal, antibacterial, antiviral, and antioxidant activity. The effectiveness of chitosan interactions is determined by its origin, deacetylation degree and acetylation pattern, molecular weight, type of chemical modifications, pH, concentration, and solubility. There is a need to conduct research on alternative sources of chitosan, extraction methods, optimization of physicochemical properties, and commercial implementation of scientific progress outcomes in this field. Moreover, studies are necessary to assess the bioactivity and toxicity of chitosan nanoparticles and chitosan conjugates with other substances and to evaluate the consequences of the large-scale use thereof. This review presents the unique properties of chitosan and its derivatives that have the greatest importance for plant production and yield quality as well as the benefits and limitations of their application.     

Recent Developments in Chitosan-Based Micro/Nanofibers for Sustainable Food Packaging,Smart Textiles,Cosmeceuticals, and Biomedical Applications

Chitosan has many useful intrinsic properties (e.g., non-toxicity, antibacterial properties, and biodegradability) and can be processed into high-surface-area nanofiber constructs for a broad range of sustainable research and commercial applications. These nanofibers can be further functionalized with bioactive agents. In the food industry, for example, edible films can be formed from chitosan-based composite fibers filled with nanoparticles, exhibiting excellent antioxidant and antimicrobial properties for a variety of products. Processing ‘pure’ chitosan into nanofibers can be challenging due to its cationic nature and high crystallinity; therefore, chitosan is often modified or blended with other materials to improve its processability and tailor its performance to specific needs. Chitosan can be blended with a variety of natural and synthetic polymers and processed into fibers while maintaining many of its intrinsic properties that are important for textile, cosmeceutical, and biomedical applications. The abundance of amine groups in the chemical structure of chitosan allows for facile modification (e.g., into soluble derivatives) and the binding of negatively charged domains. In particular, high-surface-area chitosan nanofibers are effective in binding negatively charged biomolecules. Recent developments of chitosan-based nanofibers with biological activities for various applications in biomedical, food packaging, and textiles are discussed herein.     

Acetylation and molecular mass effects on barrier and mechanical properties of shortfin squid chitosan membranes

Chitosan samples with different N-deacetylation levels were obtained from β-chitin under heterogeneous alkali conditions. Oxidative depolymerisation was performed to attain low-acetylated chitosan samples with different molecular mass. Water vapour permeability, membrane swelling and tensile mechanical properties were analysed in plasticized self-supporting chitosan membranes. The main purpose was to describe unambigously the effect of the biopolymer molecular mass and acetylation degree on these properties. Commercially available chitosan samples derived from α-chitin were also studied for comparison. The equilibrium degree of swelling in water and the water vapour permeability increase by increasing the molecular mass or the degree of acetylation. Regarding the effect on the mechanical properties, generally harder and tougher membranes were obtained for chitosans with higher molecular mass or lower acetylation degree. These observations are tentatively explained based on the different structural characteristics of the polymer and can lead to a better understanding of the tools necessary to tailor a specific type of chitosan membrane.     

Acetate chitosan with CaCO3 doping form tough hydrogel for hemostasis and wound healing

In recent years, chitosan has been applied for wound management due to its properties of biocompatibility, biodegradability, antimicrobial activity, and low immunogenicity. But the poor water solubility in neutral pH limited its further application in clinical wound healing. To overcome this problem, acetate chitosan was developed and approved as commercial products for wound healing. However, the acidity of acetate chitosan was potentially allergenic, and the poor mechanical properties of its formed hydrogels also hindered the therapeutic efficacy in wound care. In this study, CaCO₃ was simply doped into acetate chitosan to form the wound dressing. After absorbing water, the H⁺ of acetate chitosan reacted with CaCO₃ to release Ca²⁺, resulting in acidity decreased. The production of Ca²⁺ and residue of CaCO₃ cross‐linked with chitosan to form a tough hydrogel by electrostatic interaction. The physical characteristics, swelling, mechanical testing, and blood clotting were evaluated. The results in vitro demonstrated that after doping CaCO₃ into acetate chitosan, the mechanical properties and blood clotting of the formed hydrogel were increased. Then, the evaluation of hydrogels in vivo revealed that it can also accelerate the wound healing by promoting re‐epithelization and collagen deposition. This simple way by doping CaCO₃ into acetate chitosan can increase wound healing, and it can also broad the application of acetate chitosan in clinical use.     

Modified chitosan III,superabsorbency, salt‐ and pH‐sensitivity of smart ampholytic hydrogels from chitosan‐g‐PAN

Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric‐initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan‐g‐PAN product was then hydrolyzed to yield a novel smart hydrogel (H‐chitoPAN) with superabsorbing properties. The influence of add‐on values as well as temperature and time of hydrolysis of the initial chitosan‐g‐PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH‐sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a wide range (pH 2–13). The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. Superabsorbency, pH‐ and salt‐sensitivity of the chitosan‐based hydrogel was briefly compared with the classical starch‐based superabsorbent, H‐SPAN. The pH‐reversibility and on–off switching behavior of the intelligent H‐chitoPAN hydrogels makes them good candidates for considering as potential drug carries. Copyright © 2004 John Wiley & Sons, Ltd.     

壳聚糖及其衍生物作为疫苗佐剂的研究进展

疫苗佐剂能够增强机体对抗原的免疫应答反应或改变免疫应答反应类型,延长疫苗在体内作用时间,提高疫苗效力。壳聚糖能有效地将疫苗递送到靶抗原递呈细胞或组织,激活抗原提呈细胞,诱导产生免疫应答,促进Th1/Th2应答反应的平衡,因此,壳聚糖作为疫苗佐剂具有一定的潜力。为了解决壳聚糖在中性和碱性溶液中溶解性差,以及进一步提高其黏膜黏附性和靶向性等问题,通过对壳聚糖进行化学改性,生成一系列壳聚糖衍生物,提高其佐剂性能。本论文就近年来有关壳聚糖及其衍生物作为疫苗佐剂和递送系统在疫苗中的应用进行了综述,总结并提出了壳聚糖及其衍生物在疫苗佐剂应用领域所面临的问题以及其未来的发展方向,使读者对其有全面的了解。     

壳聚糖的结构特性及其衍生物的应用

壳聚糖由甲壳素经脱乙酰基而得,又称为可溶性甲壳素。壳聚糖的结构特征使其具有了独特的物理化学性质和生物活性。本文介绍了壳聚糖的结构特性、重要的化学性质及衍生物的应用。     

Radiation resistance of chitin and chitosan applied in the chromatography of radioactive solutions

Chitin and chitosan were irradiated in acidic solutions containing a decontaminating soap. It has been shown that these powders suspended in aqueous media do not undergo radiolysis, as their I.R. spectra are not altered, and there is no radiolysis product in the solution, except for the case of nitric acid at lowpH where some chitosan is present in dissolved form. These polymers therefore exhibit very good radiation resistance, in spite of the fact that the monomers undergo very rapid radiolysis.⁶⁰Co radiations up to 50 000 krad were used. Under these conditions, chitosan does not lose its collection capacity for most of the metal ions of interest in the nuclear field, including cobalt, that can be collected from decontaminating soap solutions with a volume reduction of 10.     

Preparation of alginate coated chitosan hydrogel beads by thermosensitive internal gelation technique

Chitosan hydrogel beads were successfully prepared by the method of thermosensitive internal gelation technique. The prepared beads were spherical, smooth-surfaced and non-aggregated with a diameter of 1.7–2.1 mm. The diameters of beads can be controlled and have a correlation with the initial drop size, the concentration of CaCl₂, alginate and the time of solidification. The bead is comprised of three parts, which are chitosan/glycerophosphate (CS/GP) hydrogel core, chitosan-alginate (CS/SA) gel layer in the middle and calcium-alginate gelatin capsules in outer layer. Swelling studies indicate that the beads can be stable in simulated gastric fluid. But the beads shrink sharply when removed to simulated intestinal fluid. Drug release behavior showed that release of ornidazole in the beads is much slower than in the CS/GP hydrogel.     

Bioactive polymeric formulations for wound healing

Ricinoleic acid (RA) has potential to promote wound healing because of its analgesic and anti‐inflammatory properties. This study investigates the synthesis and characterization of RA liposomes infused in a hydrogel for topical application. Lecithin liposomes containing RA were prepared and incorporated into a chitosan solution and were subsequently cross‐linked with di‐aldehyde β‐cyclodextrin (Di‐β‐CD). Chitosan/Di‐β‐CD concentrations and reaction temperatures were varied to alter gelation time, water content, and mechanical properties of the hydrogel in an effort to obtain a wide range of RA release profiles. Hydrogel cross‐linking was confirmed by spectroscopy, and liposome and carrier hydrogel morphology via microscopy. Chitosan, Di‐β‐CD, and liposome concentrations within the formulation affected the extent of matrix swelling, mechanical strength, and pore and overall morphology. Higher cross‐linking density of the hydrogel led to lower water uptake and slower release rate of RA. Optimized formulations resulted in a burst release of RA followed by a steady release pattern accounting for 80% of the encapsulated RA over a period of 48 hours. However, RA concentrations above 0.1 mg/mL were found to be cytotoxic to fibroblast cultures in vitro because of the oily nature of RA. These formulations promoted wound healing when used to treat full thickness skin wounds (2 cm²) in Wister male rats. The wound contraction rates were significantly higher compared to a commercially available topical cream after a time period of 21 days. Histopathological analysis of the RA‐liposomal chitosan hydrogel group showed that the epidermis, dermis, and subcutaneous skin layers displayed an accelerated yet normal healing compared to control group.     

Chitosan for coagulation/flocculation processes - An eco-friendly approach

Chitosan is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin, a biopolymer extracted from shellfish sources. Chitosan exhibits a variety of physico-chemical and biological properties resulting in numerous applications in fields such as cosmetics, biomedical engineering, pharmaceuticals, ophthalmology, biotechnology, agriculture, textiles, oenology, food processing and nutrition. This amino-biopolymer has also received a great deal of attention in the last decades in water treatment processes for the removal of particulate and dissolved contaminants. In particular, the development of chitosan-based materials as useful coagulants and flocculants is an expanding field in the area of water and wastewater treatment. Their coagulation and flocculation properties can be used to remove particulate inorganic or organic suspensions, and also dissolved organic substances. This paper gives an overview of the main results obtained in the treatment of various suspensions and solutions. The effects of the characteristics of the chitosan used and the conditions in solution on the coagulation/flocculation performance are also discussed.     

Chitosan-based nanocomposites for medical applications

Chitosan as a biobased polymer is gaining increasing attention due to its extraordinary physico-chemical characteristics and properties. While a primary use of chitosan has been in horticultural and agricultural applications for plant defense and to increase crop yield, recent research reports display various new utilizations in the field of advanced biomedical devices, targeted drug delivery, and as bioimaging sensors. Chitosan possesses multiple characteristics such as antimicrobial properties, stimuli-responsiveness, tunable mechanical strength, biocompatibility, biodegradability, and water-solubility. Further, chitosan can be processed into nanoparticles, nano-vehicles, nanocapsules, scaffolds, fiber meshes, and 3D printed scaffolds for a variety of applications. In recent times, nanoparticles incorporated in chitosan matrices have been identified to show superior biological activity, as cells tend to proliferate/differentiate faster when they interact with nanocomposites rather than bulk or micron size substrates/scaffolds. The present article intents to cover chitosan-based nanocomposites used for regenerative medicine, wound dressings, drug delivery, and biosensing applications.