The presence of nitrate and other redox-active anionic contaminants in terrestrial ecosystems poses a significant risk to humans and other forms of life on Earth. The purpose of the present study was to test a potential in situ system, using poly-(D) glucosamine (chitosan) adsorbed to mineral surfaces under redox-active conditions in order to degrade nitrate to lower oxidation states. Chitosan is a linear polysaccharide derived from the chitin found in the shells of shrimp and other shellfish. Five different loadings of chitosan (0, 0.075, 0.25, 0.50, and 1.0 g/L; labeled C0, C1, C2, C3, and C4, respectively) were adsorbed to ferruginous smectite (SWa-1) to form chitosan-SWa-1 composites (CSC) in the pH range 5.8–4. The CSC was then reduced by Na2S2O4 in a citrate-bicarbonate buffered dispersion and washed free of excess salts under inert-atmosphere conditions. Upon addition of the nitrate, the solution pH remained slightly acidic, ranging from 5.5 to 4.7. Samples were analyzed for Fe(II) content, reacted with a NaNO3 solution, and then re-analyzed for structural Fe(II) content. Supernatant solutions were analyzed for nitrate, nitrite, and ammonium. In samples C1 to C4, extensive concentrations of nitrite were observed in the supernatants with a corresponding increase in the reoxidation of structural Fe(II), proving that a coupled redox reaction had occurred between the nitrate and the structural Fe in the clay mineral. The most efficient loading, defined as the largest percentage of adsorbed nitrate reduced to nitrite, occurred in sample C1. The total amount of nitrate reduced and Fe(II) reoxidized followed the trend 0 = C0 < C2 < C3 < C4 ≈ C1. Chitosan showed the potential to reverse the surface charge of constituent clay minerals, thereby enabling the CSC to remove nitrate anions from aqueous mineral systems via redox reactions with structural Fe(II) in clay minerals.

Chitosan (CTS) modified montmorillonite (Mnt) composites (CTS-Mnt), which have been widely reported for the adsorption of heavy-metal ions and biological dyes, have not been applied to the field of mycotoxin adsorption. The current study was focused on the preparation of CTS-Mnt by calcination as a mycotoxin adsorbent for the efficient removal of aflatoxin B1 (AFB1). The CTS-Mnt samples obtained were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption analysis. The CTS-Mnt samples prepared at various calcination temperatures exhibited varying structural configurations, surface hydrophobicities, and texture properties. The results revealed that stable CTS-Mnt speciments, obtained at <350°C, displayed superior adsorption capacity for AFB1 from a simulated gastrointestinal tract, increasing from 0.51 mg/g of raw Mnt to 4.97 mg/g. With increased calcination temperature, the effect of pH on the adsorption process of AFB1 becomes negligible. This study demonstrates that the novel CTS-Mnt has tremendous potential as an AFB1 adsorbent.

Obesity is often introduced as one of the metabolic disorders caused by imbalance between energy consumption and metabolisable energy intake. Experts in the field considered obesity as one of the robust risk factors for the lifestyle-associated diseases. The present research examined interventional effects of marine chitosan (CS), swimming training (ST) and combination of CS and ST (CS + ST) in the mice fed with high-fat diets (HFD). In this study, sample size was considered more than three in groups. Forty mice were randomly divided into five groups (n 8 per group) including control group (received the standard diet), HFD group (received high-fat food with 20 % fat), HFD + CS group (treated with high-fat food with 5 % CS), HFD + ST group (treated with HFD and ST) and HFD + CS + ST group (treated with high-fat food with 5 % CS and ST). After 8 weeks, the blood glucose, oxidative stress (OS) and lipid profile were measured. The results showed that CS + ST group has more effects in the control of body weight with the increased concentration of HDL-cholesterol, OS inhibition via enhancing the body antioxidant capacity in comparison with the ST or CS alone in HFD-fed mice. Moreover, lipid profile was improved in CS + ST-treated mice compared with HFD-treated mice, and OS inhibition correlated with the greater activities of the antioxidant enzyme enhances the lipid oxidation, cholesterol and fatty acid homoeostasis. The results suggested that a dietary intervention with a combined ST and CS can be a feasible supplementary for human prevention of obesity.

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the main pests of fruit, worldwide, and the use of population suppression method with low environmental impact is an increasingly strong requirement of the consumer market. The aim of this study was to evaluate the effect of mineral and natural films on the physical–chemical properties of grapes (Vitis vinifera L.), cultivar Itália, and oviposition behaviour of C. capitata. Fruits were immersed in suspensions (100 and 200 g L−1) of mineral (kaolin Surround®WP, kaolin 607, kaolin 608, kaolin 611 and talc) and natural films (chitosan, cassava starch, potato starch and guar gum 5.0 g L−1) and distilled water (control). After drying, fruits were exposed to C. capitata pairs of males and females for 24 h in choice and non-choice tests; the number of punctures with and without eggs, eggs per fruit and behavioural response of fly to treated and untreated fruits were recorded. Results obtained in this study are promising, given the scientific evidence that films of mineral particles such as kaolin (Surround®, 607, 608 and 611) changed the firmness, luminosity, chroma and hue angle of grapes and reduced the oviposition of C. capitata. In addition, our results also showed that natural polymers do not deter C. capitata females, but rather seem to stimulate oviposition.

An 8-week feeding experiment was conducted to investigate and confront the putative functions of chitosan (CTS) and chitooligosaccharide (COS) in the growth and homoeostasis of distal intestine in juvenile turbots fed diets containing soyabean meal (SBM). Three isolipidic and isonitrogenous diets were formulated by supplemented basal diet (based on a 400 g/kg SBM) with 7·5 g/kg CTS or with 2·0 g/kg COS. Our results indicated that both CTS and COS supplementation could significantly improve (i) the growth performance and feed efficiency ratio; (ii) antioxidant activity driven by metabolic enzymes (i.e. catalase, glutathione reductase, glutathione peroxidase and superoxide dismutase); (iii) glutathione levels; (iv) acid phosphatase and lysozyme activity and (v) IgM content. As a result, these two particular prebiotics were able to significantly attenuate the histological alterations due to local inflammation as well as to decrease the transcriptional levels of proinflammatory cytokines (i.e. IL-1β, IL-8 and TNF-α) and major pathway effectors (i.e. activator protein-1 (AP-1), NF-кB, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase and extracellular regulated kinase). High-throughput sequencing data indicated that dietary CTS and COS could significantly decrease the diversity of intestinal bacteria but elevate the relative abundances of Bacillus, Lactobacillus and Pseudomonas genera. Altogether, these findings suggest that CTS and COS can improve growth of turbot, enhance intestinal immune and anti-oxidant systems and promote the balance of intestinal microbiota. The protective effects, elicited by these two prebiotics, against SBM-induced inflammation could be attributed to their roles in alleviating the overexpression of inflammatory cytokines by possibly down-regulating NF-кB, AP-1 and/or mitogen-activated protein kinases pathways.

The present study was conducted to test the hypothesis that dietary supplementation with a nano chitosan–zinc complex (CP–Zn, 100 mg/kg Zn) could alleviate weaning stress in piglets challenged with enterotoxigenic Escherichia coli K88 by improving growth performance and intestinal antioxidant capacity. The in vivo effects of CP–Zn on growth performance variables (including gastrointestinal digestion and absorption functions and the levels of key proteins related to muscle growth) and the antioxidant capacity of the small intestine (SI) were evaluated in seventy-two weaned piglets. The porcine jejunal epithelial cell line IPEC-J2 was used to further investigate the antioxidant mechanism of CP–Zn in vitro. The results showed that CP–Zn supplementation increased the jejunal villus height and decreased the diarrhoea rate in weaned piglets. CP–Zn supplementation also improved growth performance (average daily gain and average daily feed intake), increased the activity of carbohydrate digestion-related enzymes (amylase, maltase, sucrase and lactase) and the mRNA expression levels of nutrient transporters (Na+-dependent glucose transporter 1, glucose transporter type 2, peptide transporter 1 and excitatory amino acid carrier 1) in the jejunum and up-regulated the expression levels of mammalian target of rapamycin (mTOR) pathway-related proteins (insulin receptor substrate 1, phospho-mTOR and phospho-p70S6K) in muscle. In addition, CP–Zn supplementation increased glutathione content, enhanced total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-px) activity, and reduced malondialdehyde (MDA) content in the jejunum. Furthermore, CP–Zn decreased the content of MDA and reactive oxygen species, enhanced the activity of T-SOD and GSH-px and up-regulated the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway-related proteins (Nrf2, NAD(P)H:quinone oxidoreductase 1 and haeme oxygenase 1) in lipopolysaccharide-stimulated IPEC-J2 cells. Collectively, these findings indicate that CP–Zn supplementation can improve growth performance and the antioxidant capacity of the SI in piglets, thus alleviating weaning stress.

Dietary chitosan (CS) supplementation could improve the growth rate, small intestinal morphology, nutrients apparent digestibility and digestive enzyme activities in pigs, broiler chickens, rats and fish, whereas no data has been reported about the effect of CS on the growing Huoyan geese. Therefore, this study was designed to investigate the effects of CS on growth rate, small intestinal morphology, nutrients apparent utilization and digestive enzyme activities of growing Huoyan geese. Three hundred and twenty (28 days of age, gender balance) Huoyan geese were randomly divided into control, CS100, CS200 and CS400 groups (based on BW) with 20 geese per pen and 4 replicates pen per group, and the feeding experiment lasted for 4 weeks. The 4 diets contained 0, 100, 200 and 400 mg CS per kg feed, respectively. The results showed that CS200 groups had higher average daily gain, final BW, apparent utilization of DM and CP, and lower feed/gain ratio compared with the control group (P < 0.05). Meanwhile, CS100 and CS200 groups had higher villus height, villus height/crypt depth ratio and lower crypt depth in duodenum and jejunum than those in the control group (P < 0.05). The geese in CS100 and CS200 groups had higher villus height, villus height/crypt depth ratio and lower crypt depth of ileum compared with those in control and CS400 groups (P < 0.05). In addition, compared with the control group, CS200 group has higher trypsin activities and lower lipase activities in duodenal, jejunal and ileal contents (P < 0.05). The results suggested that addition of 200 mg/kg CS had positive effects on growth rate, small intestinal morphology, nutrients apparent utilization and digestive enzyme activities of growing Huoyan geese.

Chitosan is one of the most versatile biopolymers available with established properties such as antimicrobial, antitumor, anti-inflammatory, mucoadhesive, and more. It has been in biomedical research for long, but still the bench-to-bedside translation is hampered because of viscosity and solubility issues. The only commercial application of chitosan has been in hemostatic dressings. Chitosan oligosaccharide (COS), on the other hand, is highly promising in a similar research area where chitosan's limitations come into the way. COS is highly soluble in water, and its viscosity is very less than that of the parent chitosan. Although COS retains properties very similar to those of chitosan, there has been minuscule volume of research on this water-soluble chitosan. COS has been successfully used as a drug delivery vehicle in various research. COS has also shown to have osteogenic ability. It has been used as a coating on experimental orthopedic implants because of its antibacterial properties. As of now, COS is not a much-explored biopolymer, although it could be an important biopolymer for its capacity in biomedical research. This article reviews various properties and reports of COS relevant for biomedical applications.

Chitosan has attracted significant attention in the past decade because of its potential applications in water engineering, the food and nutrition technology, the textile and paper industries, and drug delivery. Recently, a particularly interesting application of chitosan has been proposed in transparent flexible electronic devices, including memristors and transistors. In this work, the resistive switching (RS) effect of chitosan thin films in a capacitor-like structure with Ag and Al as alternative top electrodes was studied. Both the devices showed a bistable RS effect under an external electric field with a high endurance of 102. The electrical conduction and RS mechanisms of chitosan-based devices were investigated. The trap-controlled space charge–limited current was responsible for electrical transport at the low-resistance state of both devices, while direct tunneling and Schottky emission at the high-resistance state were related to Ag/chitosan/fluorine-doped tin oxide (FTO) and Al/chitosan/FTO, respectively. The RS mechanism of the Ag/chitosan/FTO device was attributed to the formation and dissociation of Ag filaments through the dielectric layer, whereas the change in the barrier height at the Al and chitosan interface under an external electric field could control the RS mechanism of the Al/chitosan/FTO device.

Superparamagnetic iron oxide nanoparticles are well known for biomedical applications. The particle size, morphology, surface area, and functionalization are the key parameters that affect their bioactivity properties. Inline to this, the superparamagnetic Fe3O4 nanoparticles were prepared via chemical coprecipitation method with an average particle size of 6 ± 3 nm. The particles were surface-functionalized with chitosan and in-house prepared reduced graphene oxide (rGO) to obtain chitosan-coated Fe3O4 nanoparticles (C-Fe3O4) and rGO-Fe3O4 nanocomposites (G-Fe3O4), respectively. Upon functionalization, the physicochemical properties of the materials were characterized thoroughly using X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer, Raman Spectroscopy, and thermal gravimetric analysis. Furthermore, they have subjected to cytotoxicity assay, agar two-fold broth dilution test, and disc diffusion assay experiments for the determination of cytotoxicity and antibacterial activities. The effect of surface functionalization on their bioactivity was investigated thoroughly. The surface functionalization with chitosan and rGO has enhanced the bioactivity of the Fe3O4 nanoparticles.

The solvent-casting method was used to synthesize a silver–zeolite–chitosan (AgZ-Ch) composite from Philippine natural zeolites. X-ray diffraction, ultraviolet–visible (UV-Vis) spectroscopy, optical emission spectroscopy (OES), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) were used to investigate the different properties of the composite before and after plasma treatment. The major phase of the zeolite is Na-clinoptilolite with trace amounts of mordenite, feldspar and quartz. UV-Vis and OES analyses confirmed the presence of Ag and zeolite on the chitosan matrix. The decrease in the transmittance signal at 290 nm and the emission spectra of the discharge showed the presence of Ag I, Al I and Si I signals at 705–852 nm. The TGA and DTG curves revealed the thermal stability of the natural zeolites after ion exchange and after incorporation in the chitosan matrix, where the onset of degradation was observed to occur above ~37°C, the human body temperature. Bacterial count showed minimal growth of colonies on all samples, both pristine and plasma-treated, suggesting that the surface of the composites does not influence bacterial habitation. The fabricated composites meet the minimum requirements for biomedical application such as thermal stability with respect to the average human body temperature and absence of bacteria.

Giardia lamblia (G. lamblia) is the most widely known protozoan parasite that causes human gastrointestinal infection worldwide. Some natural compounds exhibited pivotal effects against different infectious diseases. In this research, the antigiardial activity and cytotoxicity of fungal chitosan, nano-chitosan, Rhamnus cathartica (R. cathartica) and emodin were evaluated in Balb/c mice. Genotyping of G. lamblia was assessed by PCR-RFLP technique. Different concentrations of mentioned compounds were used to check their antigiardial and cytotoxicity effects on human intestinal epithelial cells (HT-29) after 24, 48 and 72 h. The G. lamblia strain used in the current work was genotyped and revealed as an AII assemblage. All the concentration showed acceptable activity against G. lamblia cysts and trophozoites in comparison to the negative and positive controls (furazolidone and metronidazole) in vitro (P < 0.05). Giardia lamblia cysts were susceptible after treatment in all experiments in vivo in comparison to negative control (P < 0.05). Approximately, in most of the concentration, nano-chitosan and emodin were more effective than chitosan and R. cathartica, respectively (P < 0.05). The effects of exposure times in antigiardial and cytotoxicity effects were not statistically significant (P > 0.05). The maximum mortality rate (100%) was achieved at 100 and 50 µg kg−1 concentrations after 48 and 72 h of exposure time, respectively. Our results provide significant information about the new antigiardial agent and proposed the nano-chitosan and emodin for the development of new drugs against G. lamblia in the future.

Hemostasis, a process which causes bleeding to stop, can be enhanced using chitosan; but the detailed mechanism is unclear. Red blood cells (RBCs) adhere to chitosan because of their opposite charges, but the adhesion force is small, 3.83 pN as measured here using an optical tweezer, such that the direct adhesion cannot be the sole cause for hemostasis. However, it was observed in this study that layer structures of aggregated RBCs were formed next to chitosan objects in both static and flowing environments, but not formed next to cotton and rayon yarns. The layer structure is the clue for the initiation of hemostatsis. Through the supporting measurements of zeta potentials of RBCs and pH's using blood-chitosan mixtures, it is proposed here that the formation of the RBC layer structure next to chitosan objects is due to the reduction of repulsive electric double layer force between RBCs, because of the association of H+ deprotonated from chitosan with COO− on RBC membrane, under the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. The results are beneficial for designing effective chitosan-based wound dressings, and also for general biomedical applications.

Adsorption of the polycation chitosan on montmorillonite was studied at different pH values from 4.5 to 6.5 and at temperatures of 25, 50 and 75ºC. The amount of chitosan adsorbed increased with temperature, indicating that temperature is a decisive factor. At pH 5.0 and 25ºC the amount adsorbed was 1.18 molc kg–1, whereas it was 1.5 times higher (1.79 molc kg–1) at 75ºC. The uptake of chitosan increased significantly at higher pH. This can be attributed to the decrease in the degree of protonation. Surface charge and X-ray diffraction measurements indicate that most of the chitosan is adsorbed in the interlayer, where mono- and bilayer structures are formed.

The kinetics of chitosan adsorption also depend on temperature and pH. At ⩾ 50ºC, the adsorption mechanism of chitosan on montmorillonite is closest to the intraparticle diffusion model, whereas at lower temperature (25ºC) the adsorption process is closer to the pseudo-second order model. The pH of the solution affects the protonation degree of chitosan and the mode of adsorption on montmorillonite, but not the adsorption rate.

For chitosan-montmorillonite prepared at pH 5.0 and 75ºC, the effective anion exchange capacity (AEC) was found to be 80% (0.36 molc kg–1) of the calculated value. The relatively large AEC and the location of most of the anion exchange sites in the interlayer make chitosan-montmorillonite an interesting prospect as an adsorbent for water-purification procedures.

This study investigated the potential of halloysite nanotubes (HNTs) to improve the sustained release properties of chitosan (CS) microparticles cross-linked ionically with tripolyphosphate (TPP). Composite CS-HNTs microparticles were obtained by a simple and eco-friendly procedure based on a coaxial extrusion technique. Prior to encapsulation, a water-soluble model drug, verapamil hydrochloride (VH), was adsorbed successfully on HNTs. The microparticles were characterized by optical microscopy, Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis/ thermogravimetric analysis (DTA/TG) and evaluated for encapsulation efficiency and drug-release properties. The composite particles had a slightly deformed spherical shape and micrometric size with average perimeters ranging from 485.4 ± 13.3 to 492.4 ± 11.9 μm. The results of FTIR spectroscopy confirmed non-covalent interactions between CS and HNTs within composite particle structures. The DTA and TG studies revealed increased thermal stability of the composite particles in comparison to the CS-TPP particles. Drug adsorption on HNTs prior to encapsulation led to an increase in encapsulation efficiency from 19.6 ± 2.9 to 84.3 ± 1.9%. In contrast to the rapid release of encapsulated model drug from CS-TPP microparticles, the composite CS-HNTs microparticles released drug in a sustained manner, showing the best fit to the Bhaskar model. The results presented here imply that HNTs could be used to improve morphology, encapsulation efficiency and sustained drug-release properties of CS microparticles cross-linked ionically with TPP.

As a unique tubular nanoclay, halloysite nanotubes (HNTs) have recently attracted significant research attention. The HNTs have outer diameters of ∼50 nm, inner lumens of ∼20 nm and are 200–1000 nm long. They are biocompatible nanomaterials and widely available in nature, which makes them good candidates for application in biomedicine. Compared with other types of nanoparticles such as polymer nanoparticles and carbon nanotubes, the drawbacks associated with HNTs include brittleness, difficulty with fabrication, low fracture strength, high density and inadequate biocompatibility. Preparation of polysaccharide-HNT composites offer a means to overcome these shortcomings. Halloysite nanotubes can be incorporated easily into polysaccharides via solution mixing, such as with chitosan (CS), sodium alginate, cellulose, pectin and amylose, for forming composite films, porous scaffolds or hydrogels. The interfacial interactions, such as electrostatic attraction and hydrogen bonding, between HNTs and the polysaccharides are critical for improvement of the properties. Morphology results show that HNTs are dispersed uniformly in the composites. The mechanical strength and Young's modulus of the composites in both the dry and wet states are enhanced by HNTs and the HNTs can also increase the storage modulus, glass-transition temperature and thermal stability of the composites. Cytocompatibility results demonstrate that the polysaccharide-HNT composites have low cytotoxicity even for HNT loading >80%. Therefore, the polysaccharide-HNT composites show great potential for biomedical applications, e.g. as tissue engineering scaffold materials, wound-dressing materials, drug-delivery carriers, and cell-isolation surfaces.

The rheological behavior of composites made with high-density polyethylene (HDPE) and chitosan was studied. Composites were prepared by melt processing in a laboratory internal mixer. Maleic anhydride grafted HDPE (PE-g-MA) was used as compatibilizer to enhance the dispersion of chitosan in the HDPE matrix. Different percentages of chitosan and compatibilizer (up to a maximum of 25 phr) were added into HDPE to prepare composites. Characterization of the composites with parallel plate rheometer and laboratory internal mixer revealed that the presence of chitosan increases the complex viscosity, loss modulus, storage modulus and the torque (i.e., melt viscosity), and the combination chitosan/compatibilizer has a similar, if slighter, effect. At higher filler levels it is clear that the PE-g-MA affected the microstructure of the compounds, possibly increasing matrix–filler interactions and acting as an effective compatibilizer.

Chitin nanowhiskers were obtained with the purpose to be used as astaxanthin protectors against the photo and thermal degradation. These nanostructures were generated by a freezing/thawing procedure using two stirring methods: mechanical and sonication, which were named as FTM and FTS respectively. Morphological and spectroscopic studies were carried out on chitin nanowhiskers by scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Through a SEM analysis, chitin fibers were found uniformly spaced and oriented with the width ranged from of 20-40 nm. Furthermore, the nanowhiskers obtained by FTM showed long and flattened structures and bundles of homogeneous sizes, which have the capacity of being sites of stress concentration. In contrast, by FTS, the nanowhiskers showed coarse fibers exhibiting numerous peaks. By comparing the two methods is appreciated that FTS method provides more surface area, giving more sites for functionalization. Fourier transform infrared spectroscopy (FTIR) allowed the determination of free movement of functional groups on the surface of samples obtained by FTM and FTS methods. Significant differences of signals in the spectra indicate that there were more unassociated amides in the nanowhiskers obtained by FTS than by FTM.

A number of systems based on synthetic molecules, among them cationic liposomes and poly(ethylene imine)-based polymers, have been proposed as delivery vehicles for nucleic acids. Some of these systems have even reached the market, ensuring efficient and transient transfection levels in a variety of cell types. However, toxicity issues have limited their application in vivo. In this context, chitosan, a biocompatible and biodegradable polysaccharide, has been proposed as a promising alternative for the delivery of nucleic acid-based molecules. Here we present an overview of the state of the art of chitosan-based vectors for nucleic acid delivery and the most recent data on the in vivo testing of the proposed systems. We additionally express our view on the barriers that might be hampering the translation of this knowledge into clinical practice and the challenges that need to be fulfilled for these promising vehicles to reach patients.