Search

The effect of chitosan decoration on the transport of epigallocatechin (EGC)-encapsulated ferritin cage across the Caco-2 cells was investigated. After the encapsulation of EGC in apo-red bean (adzuki) ferritin (apoRBF), the EGC-loaded apoRBF nanoparticle (ER) was fabricated with an encapsulation ratio of 11.6% (w/w). The results indicated that different chitosan molecules (with molecular weights of 980, 4600, 46 000, and 210 000 Da) could attach onto the apoRBF via electrostatic interactions to form ER-chitosan complexes (ERCs) (ERCs980, ERCs4600, ERCs46000, and ERCs210000). ERCs980 and ERCs4600 retained the typical shell-like morphology of ferritin with a size distribution of 12 nm and showed weak negative zeta-potentials at pH 6.7, while ERCs46000 and ERCs210000 significantly aggregated. Furthermore, the transport of EGC in ERCs980 and ERCs4600 across the Caco-2 cells was enhanced by the transferrin receptor 1 (TfR-1)-mediated absorption pathway, demonstrating that chitosan molecules with low molecular weights of 980 and 4600 Da were beneficial to the absorption of EGC based on the ferritin cage. This study will facilitate the application of ferritin-chitosan materials for fabricating the core-shell platform for encapsulation and bioavailability enhancement of bioactive molecules.

Chitin deacetylation is required to make the cuticle rigid and compact through chitin chain crosslinking. Thus it is presumed that specialized proteins are required to bind deacetylated chitin chains together. However, deacetylated-chitin binding proteins have not ever been reported. In a previous work, six cuticular proteins analogous to peritrophin 3 (CPAP3s) were found to be abundant in the moulting fluid of Bombyx mori. In this study, these BmCPAP3s (BmCPAP3-A1, BmCPAP3-A2, BmCPAP3-B, BmCPAP3-C, BmCPAP3-D1 and BmCPAP3-D2) were cloned and expressed in Escherichia coli and purified using metal-chelating affinity chromatography. Their binding activities demonstrated that although all of the BmCPAP3s showed similar binding abilities toward crystalline chitin and colloidal chitin, they differed in their affinities toward partially and fully deacetylated chitin. Amongst them, BmCPAP3-D1 exhibited the highest binding activity toward deacetylated chitin. The gene expression pattern of BmCPAP3-D1 was similar to BmCPAP3-A1 and BmCPAP3-C at most stages except that it was dramatically upregulated at the beginning of the pupa to adult transition stage. This work is the first report of a chitin-binding protein, BmCPAP3-D1, which exhibits high binding affinity to deacetylated chitin.

Chitosan oligosaccharides longer than a hexamer have higher bioactivity than polymer or shorter oligosaccharides, such as the monomer or dimer. In our previous work, we generated Paenibacillus fukuinensis chitosanase-displaying yeast using yeast cell surface displaying system and demonstrated the catalytic base. Here we investigated the specific function of putative four amino acid residues Trp159, Trp228, Tyr311, and Phe406 engaged in substrate binding. Using this system, we generated chitosanase mutants in which the four amino acid residues were substituted with Ala and the chitosanase activity assay and HPLC analysis were performed. Based on these results, we demonstrated that Trp159 and Phe406 were critical for hydrolyzing both polymer and oligosaccharide, and Trp228 and Tyr311 were especially important for binding to oligosaccharide, such as the chitosan-hexamer, not to the chitosan polymer. From the results, we suggested the possibility of the effective strategy for designing useful mutants that produce chitosan oligosaccharides holding higher bioactivity.

Chitosan binding to DNA was studied in solutions of different ionic strength. Data were analyzed within the model of ion condensation and the thermodynamic theory of extended ligand binding to DNA. The combination of these approaches allowed us to assess the sterical and energy characteristics of chitosan binding to DNA and to find the dependence of chitosan binding constant on solution ionic strength.

The DNA-chitosan polyplexes have attracted for some years now the attention of physical-chemists and biologists for their potential use in gene therapy, however, the correlation between the physicochemical properties of these polyplexes with their transfection efficiency remains still unclear. In a recent paper we demonstrated by means of DLS that the DNA-chitosan complexation is favored at acidic conditions considering that fewer amounts of chitosan were required to compact the DNA. As a second study, in the present work we analyze the influence of chitosan valence on the complexation and transfection of DNA. Three chitosans of different molecular weights (three different valences) are characterized as gene carriers at 25°C and pH 5 over a wide range of chitosan-Nitrogen to DNA-Phosphate molar ratios, N/P, by means of conductometry, electrophoretic mobility, isothermal titration calorimetry (ITC), transmission electron microscopy (TEM), atomic force microscopy (AFM), and β-galactosidase and luciferase expression assays.

The magnetic chitosan nanoparticles of 13.5 nm were prepared as a magnetic nano-adsorbent by the carboxymethylation of chitosan and the followed binding on the surface of Fe 3 O 4 nanoparticles via carbodiimide activation. Their saturation magnetization, remanent magnetization, coercivity, and squareness were 62 emu/g, 1.8 emu/g, 6.0 Oe, and 0.029, respectively, reflecting their superparamagnetic property. The binding reaction of carboxymethyl chitosan on the surface of Fe 3 O 4 nanoparticles was much faster than the self-crosslinking of carboxymethyl chitosan, and the appropriate reaction time was 1 h. At low carboxymethyl chitosan concentrations, the binding efficiency could be as high as 100%. The maximum amount of chitosan bound on the Fe 3 O 4 nanoparticles was 4.92 wt%. In addition, magnetic chitosan nano-adsorbent was shown to be quite efficient for the fast removal of Co(II) ions at pH 3–7 and 20–45 °C. The maximum adsorption capacity for Co(II) ions occurred at pH 5.5, and the adsorption process was exothermic in nature with an enthalpy change of −12.04 kJ/mol. The equilibrium was achieved within 1 min, and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 27.5 mg/g (557 mg/g based on the weight of chitosan) and a Langmuir adsorption equilibrium constant of 0.034 l/mg at 25 °C. Such fast adsorption rate and high adsorption capacity could be attributed to the absence of internal diffusion resistance and the high specific surface area.

The functionality of halloysite (Hal) nanotubes as drug carriers can be improved by lumen enlargement and polymer modification. This study investigates the influence of selective acid etching on Hal functionalization with cationic biopolymer chitosan. Hal was subjected to lumen etching under mild conditions, loaded under vacuum with nonsteroidal antiinflammatory drug aceclofenac, and incubated in an acidic solution of chitosan. The functionality of pristine and etched Hal before and upon polymer functionalization was assessed by ζ-potential measurements, structural characterization (FT-IR, DSC and XRPD analysis), cell viability assay, drug loading and drug release studies. Acid etching increased specific surface area, pore volume and pore size of Hal, decreased ζ-potential and facilitated binding of the cationic polymer. XRPD and DSC analysis revealed crystalline structure of etched Hal. Successful chitosan binding and drug entrapment were further confirmed by FT-IR and DSC studies. XRPD showed surface polymer binding. DSC and FT-IR analyses confirmed the presence of the entrapped drug in its crystalline form. Drug loading was increased for ≈81% by selective lumen etching. Slight decrease of drug content occurred during chitosan functionalization due to aceclofenac diffusion in the polymer solution. The drug release was more sustained from etched Hal nanocomposites (up to ≈87% for 12 h) than from pristine Hal (up to ≈97% for 12 h) due to more intensive chitosan binding. High human fibroblast survival rates upon exposure to pristine and etched Hal before and after chitosan functionalization (>90% in the concentration of 1000 μg/mL) confirmed that both lumen etching under mild conditions and polymer functionalization had no significant effect on cytocompatibility. Based on these findings, selective lumen etching in combination with polycation modification appears to be a promising approach for improvement of Hal nanotubes functionality by increasing payload, polymer binding capacity, and sustained release properties with no significant effect on their cytocompatibility.

This work develops a simple and innovative test-strip to monitor antibiotics in aquaculture facilities by an equipment-free approach. It consists of a low-cost disposable cellulose paper that was chemically modified to produce a colour change when in contact with a given antibiotic. In brief, the cellulose substrate was subject to oxidation with periodate, followed by amination with chitosan binding and modification with Cu(II). The test strip was then dipped in the target solution and the intensity of the colour generated therein revealed the concentration of antibiotic present for concentrations higher than 0.5 mM. The higher the concentration in sulfadiazine (SDZ), the more intense the pink colour formed in the final solution, which was also turbid due to the insolubility of the formed product. This colour intensity also varied linearly with the logarithm of the SDZ concentration (from 0.5 to 5 mM), when plotted against the sum of the RGB coordinates extracted from digital pictures. The linear equation of this response was represented by (R+G+B)=256.1 log(SDZ, mol/L)362.0, with an R-squared of 0.9913. The test-strip was stable for at least 15 days and was selective in the presence of tetracycline and difloxacin, while the response to other members of the sulfadiazine family requires prior evaluation. Overall, the test-strips developed herein are inexpensive and provide valuable (semi-) quantitative data for monitoring SDZ in waters, a most valuable approach to control and reduce the level of antibiotics in fish tanks, which in turn may reduce the costs of fish production and the environmental concerns linked to this practice. Moreover, the test strip uses a cellulose substrate that has little environmental impact upon discard., The authors acknowledge funding from project PTDC/AAGTEC/5400/2014, POCI-01-0145-FEDER-016637 funded by European through FEDER (European Funding or Regional Development) via COMPETE2020—POCI (operational program for internationalization and competitively) and by national funding through the National Foundation for Science and Technology, I.P., info:eu-repo/semantics/publishedVersion

The interaction of endotoxin (lipopolysaccharide - LPS) with low molecular weight chitosan (5.5 kDa), its N-acylated derivative and chitoliposomes was studied using a gravimetric piezoelectric quartz crystal microbalance biosensor. The optimal conditions for the formation of a biolayer based on immobilized LPS on the resonator surface and its regeneration were elaborated. The association and dissociation rate constants for LPS binding to chitosans were determined and the affinity constants (Kaf) were calculated based on the data on changes in the oscillation frequency of the quartz crystal resonator. The Kaf values correlated with the ones obtained using other methods. The affinity of N-acylated chitosan binding to LPS was higher than that of the parent chitosan binding to LPS. Based on the results obtained, we suggest that water-soluble N-acylated derivatives of chitosan with low degree of substitution of amino groups could be useful compounds for endotoxin binding and neutralization.

Conjugations of DNA with chitosans 15 kD (ch-15), 100 kD (ch-100) and 200 kD (ch-200) were investigated in aqueous solution at pH 5.5-6.5. Multiple spectroscopic methods and atomic force microscopy (AFM) were used to locate the chitosan binding sites and the effect of polymer conjugation on DNA compaction and particle formation. Structural analysis showed that chitosan-DNA conjugation is mainly via electrostatic interactions through polymer cationic charged NH2 and negatively charged backbone phosphate groups. As polymer size increases major DNA compaction and particle formation occurs. At high chitosan concentration major DNA structural changes observed indicating a partial B to A-DNA conformational transition.

The application of bioactive lutein in the food industry is limited because of its poor water-solubility, instability, and low bioavailability. Nano-sized ferritin and chitosan provide a platform for fabricating shell–core system to encapsulate lutein. Herein, soybean seed ferritin (Glycine max) and chitosan stabilized lutein composites (FCLs) were fabricated by a unique reversible disassembly-reassembly character of apoferritin and ferritin–chitosan interaction. Results showed that lutein molecules were successfully encapsulated within the apoferritin with a molar ratio of 25.2 to 1 (lutein/ferritin), and the encapsulation efficiency and loading capacity were 16.8% and 2.50% (w/w), respectively. It was calculated that approximately 10 chitosan molecules were bound to a ferritin with a binding constant of 6.3 × 105 M−1, suggesting electrostatic interaction played an important role in ferritin–chitosan interaction. Results also indicated as much as 74.1% (w/w) of lutein was retained in FCLs after storage at 20 °C for 7 days. In addition, the photo- and heat-stability of lutein in FCLs were greatly improved as compared to free lutein. Furthermore, FCLs exhibited prolonged release of lutein in simulated gastrointestinal tract (GI) digestion as a result of ferritin coating and chitosan binding. Interestingly, food components exerted different effects in lutein release, EGCG, grape seed proanthocyanidin, and milk could inhibit while pectin could facilitate the release of lutein from FCLs. This work demonstrates an innovative strategy to solubilize, stabilize and control release of functional food nutrients.

A novel β-NaCaPO 4 containing borate glass-ceramic is prepared. Two porous glass-ceramic scaffolds are prepared by binding particles with the size of 200–300 μm by 5 wt.% sodium silicate solution and 2 wt.% chitosan solutions, respectively. The reaction of the scaffolds in the SBF solution is characterized by weight loss analysis, XRD, FTIR, and SEM. The same is done to the 45S5 glass scaffolds as comparison. XRD and FTIR indicate that the carbonate hydroxyapatite has formed more rapidly on the borate glass-ceramic scaffolds. The carbonated hydroxyapatite depositing on chitosan binding scaffolds has lower crystallization degree than that on sodium silicate binding scaffolds and is similar to that of the human bone, which makes the chitosan binding scaffolds a good potential prospect in the field of tissue engineering.

The main objective of this study was to obtain chitosan functionalized viscose fabric with improved antibacterial properties and washing durability. In this regard carboxyl and aldehyde groups, as binding points for irreversible chitosan attachment into/onto viscose fabric, were introduced by two different pretreatments: 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) oxidation and coating with TEMPO oxidized cellulose nanofibrils (TOCN). The Fourier transform infrared spectroscopy, elemental analysis, zeta potential measurements, scanning electron microscopy, breaking strength and antibacterial testing were used to evaluate the influence of these pretreatments on chitosan binding, but also on chemical, electrokinetic, morphological, mechanical and antibacterial properties of pretreated and chitosan functionalized viscose fabrics. Washing durability of chitosan functionalized viscose was monitored through changes in the chitosan content, electrokinetic and antibacterial properties after multiple washing. TOCN coating improves mechanical properties of fabric, while TEMPO oxidation deteriorates them. The results show that both pretreatments improve chitosan adsorption and thus antibacterial properties, which are highly durable to washing. After five washings, the chitosan functionalized pretreated viscose fabrics preserve their antibacterial activity against Staphylococcus aureus, while antibacterial activity against Escherichia coli was lost. TOCN coated and chitosan functionalized viscose fabric is a high value-added product with simultaneously improved antibacterial and mechanical properties, which may find application as medical textiles.

Oxygen and carbon dioxide plasma treatments were applied in order to study their influences on chitosan adhesion onto PET foils. Modification of the surface and the adsorption of chitosan were monitored by the determination of XPS spectra, titrations, zeta potential, contact angles, and AFM. The plasma treatment resulted in hydrophilization of the surface through the introduction of new polar oxygen-containing groups. The treatment also yielded binding-sites for amino groups of chitosan. This led to a decrease in accessible protonated amino groups after chitosan binding onto plasma-activated foils in comparison with the plasma-non-activated ones. Consequently, the layer of chitosan adsorbed after plasma treatment was less antimicrobially active in the case of O2-treated foils. Surprisingly, the layer of chitosan adsorbed after CO2 plasma treatments were, in general, more active as antimicrobial agents than those of the non-plasma treated PET surfaces.

Background and objectives A current public health issue is preventing post-surgical complications by designing antibacterial implants. To achieve this goal, in this study we evaluated the antibacterial activity of an animal-free chitosan grafted onto a titanium alloy. Methods Animal-free chitosan binding on the substrate was performed by covalent link via a two-step process using TriEthoxySilylPropyl Succinic Anhydride (TESPSA) as the coupling agent. All grafting steps were studied and validated by means of X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) analyses and Dynamic-mode Secondary Ion Mass Spectrometry (DSIMS). The antibacterial activity against Escherichia coli and Staphylococcus aureus strains of the developed coating was assessed using the number of colony forming units (CFU). Results XPS showed a significant increase in the C and N atomic percentages assigned to the presence of chitosan. A thick layer of polymer deposit was detected by ToF-SIMS and the results obtained by DSIMS measurements are in agreement with ToF-SIMS and XPS analyses and confirms that the coating synthesis was a success. The developed coating was active against both gram negative and gram positive tested bacteria. Conclusion The success of the chitosan immobilization was proven using the surface characterization techniques applied in this study. The coating was found to be effective against Escherichia coli and Staphylococcus aureus strains. © 2017 D'Almeida et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Binding of a highly de-N-acetylated chitosan to Japanese pheasant lysozyme (JPL), which differs from hen egg white lysozyme (HEWL) by nine amino acid substitutions (including Arg114-->His), was investigated by 1H-NMR spectroscopy. The profile of the one-dimensional spectrum of JPL is essentially identical to that of HEWL. Using two-dimensional spectra of JPL and HEWL, several aromatic and aliphatic proton resonances of JPL were assigned by comparison. When a highly de-N-acetylated chitosan (number-average degree of polymerization, about 18; degree of acetylation, 0.04), where the N-acetylated units are predominantly surrounded by de-N-acetylated units (a monoacetylated chitosan), was added to the JPL solution, the NMR signals were clearly affected in Trp28 C5H and Ile98 gammaCH, as in the case of binding to HEWL. The dissociation constant of the monoacetylated chitosan evaluated from the NMR signal responses was calculated to be 0.23+/-0.05 mm (-31.5 kJ/mol), which is similar to that of HEWL (0.11+/-0.02 mm, -33.3 kJ/mol). Thus, the Arg-->His substitution of the 114th amino acid, which participates in sugar residue binding at the right-sided subsite F, did not significantly affect the chitosan binding. In addition, the C2H signal of His114 of JPL was not affected by the chitosan binding. These results suggest that the monoacetylated chitosan binds to subsites E and F through the left-sided binding mode.

The stability and controlled release of certain active substances (such as flavors, drugs, enzymes, essential oils, etc.) can be achieved through encapsulation. Ionically cross-linked hydrogels such as alginate- or alginate-chitosan-CaCl2 beads were proposed as suitable materials for encapsulation systems (Deladino et al. 2008; Han et al. 2008). Alginate beads coated with chitosan were used for encapsulation and release of different proteins (Coppi and Iannuccelli 2009; Zhou et al. 2010). Direct interaction between them forms beads with improved mechanical properties associated with reinforcement of bead structure due to chitosan binding to free alginate sites by cooperative ionic bounds (Deladino et al. 2008).

THE LIQUID-CRYSTALLINE STATE OF DNA The Condensed State of the High-Molecular-Mass Double-Stranded DNA The DNA Condensation and Aggregation Polyphosphates as a Simplified DNA Model Models of High-Molecular-Mass DNA Condensation in Water-Polymeric Solutions Grosberg Model of High-Molecular-Mass DNA Condensation Liquid-Crystalline Phases of the Low-Molecular-Mass Double-Stranded DNA Molecules Ordering of Low-Molecular-Mass Double-Stranded DNAs Brief Concept of Types of Liquid-Crystalline Phases Liquid-Crystalline Phases of Low-Molecular-Mass Double-Stranded DNA Molecules Dispersions of Low-Molecular-Mass Double-Stranded DNA Molecules Low-Molecular-Mass Double-Stranded DNA Dispersions in Water-Polymer Solutions Formation of DNA Dispersions in PEG-Containing Solutions Circular Dichroism of Nucleic Acid Dispersions Circular Dichroism as a Method of Proof of Cholesteric Packing of Nucleic Acid Molecules in Dispersion Particles and Analysis of Their Properties Effect of Different Factors on Formation and Properties of CLCD Particles Parameter of Nucleic Acid Molecule Order in CLCD Particles Polymorphism of Liquid-Crystalline Structures Formed by (DNA-Polycation) Complexes Some Peculiarities of Interaction of DNA Molecules with Polycations Specificity of Chitosan Binding to DNA Formation of Dispersions of (DNA-Chitosan) Complexes CD Spectra of Dispersions Formed by (DNA-Chitosan) Complexes X-Ray Parameters of Phases Formed by (DNA-Chitosan) Complexes Dependence of Efficiency of CLCD Formation by (DNA-Chitosan) Complexes on Various Factors Peculiarities of Interaction of Chitosan Molecules with Nucleic Acids Attempt at a Theoretical Description of Interactions Occurring in the (DNA-Chitosan) Complexes and Resulting in the Formation of Liquid-Crystalline Dispersions with Different Optical Properties Liquid-Crystalline State of DNA Circular Molecules Phase Exclusion of Circular Molecules of Nucleic Acids Formation of Dispersions From Circular Superhelical DNA CD Spectra of Circular Superhelical DNA Dispersions Under Conditions That Modify Parameters of Their Secondary Structure Packing Density and Rearrangement of the Spatial Structure of Superhelical DNA Molecules in LCD Particles Topological Forms and Rearrangement of the Spatial Organization of Superhelical DNA Molecules in LCD Particles DNA LIQUID-CRYSTALLINE FORMS AND THEIR BIOLOGICAL ACTIVITY Liquid-Crystalline State of DNA in Biological Objects DNA and Biological Objects DNA Reactions under Conditions Causing Liquid-Crystalline Dispersions Molecular Crowding Condensation of DNA under the Effect of Chitosan in Conditions Causing Molecular Crowding Activity of Nucleolytic Enzymes Under Conditions of Molecular Crowding Activity of Proteolytic Enzymes under Conditions of Molecular Crowding DNA LIQUID-CRYSTALLINE DISPERSIONS IN NANOTECHNOLOGY AND BIOSENSORICS Nanoconstructions Based on Nucleic Acid Molecules The General Concept of Nanotechnology Biological Molecules as a Background for Nanodesign Two Strategies of Nanodesign Based on NA Molecules Biosensors Based on Nucleic Acids General Concept of Construction and Operation of Biosensors Double-Stranded DNA Molecule as Polyfunctional Biosensing Unit Content and Principle of Operation of an Optical Biosensor Based on DNA Liquid-Crystalline Dispersions DNA CLCD Particles as Sensing Units Sandwich-Type Biosensing Units Based on (DNA-Polycation) Liquid-Crystalline Dispersions DNA Nanoconstruction as a Sensing Unit (New Type of Biodetectors) Hydrogels Containing DNA NaCs as New "Film-Type Biodetectors Index

Previously, we reported properties of a glycosylase belonging to GH-8 glycosyl hydrolase (GH) and having both chitosanase and glucanase activities. This enzyme (D2), whose molecular mass (86 kDa) was the largest among the GH-8 group, has its catalytic domain at the N-terminal region, and discoidin domain (DD) at the C-terminal region. Although various chitosanases, chitinases and glucanases have been known, DD is unique to the D2 enzyme. Glucanase and chitinase, but not chitosanase, are known to have functional domain such as carbohydrate-binding module, besides catalytic domain. Accordingly, function of the DD of D2 chitosanase was analyzed, using zygomycete cell wall containing chitosan, glucan and chitin as the basic constituents. The DD specifically and tightly bound to chitosan, but did not participate in affinity for glucan and chitin. Deletion of the DD caused marked reduction in absorbability to cell wall and in hydrolytic activity toward chitosan and glucan. These results suggest that the DD is concerned in binding of the enzyme to cell wall and in effective digestion of the insoluble substrate, through hydrolysis of not only chitosan but also coexisting glucan. Thus, this is the first example of chitosan-binding domain among various carbohydrate-binding modules reported thus far.

Chitosan-related enzymes including chitosanases, exo-β-glucosaminidases, and enzymes having chitosan-binding modules recognize ligands through electrostatic interactions between the acidic amino acids in proteins and amino groups of chitosan polysaccharides. However, in GH8 chitosanases, several aromatic residues are also involved in substrate recognition through stacking interactions, and these enzymes consequently hydrolyze β-1,4-glucan as well as chitosan. The binding grooves of these chitosanases are extended and opened at both ends of the grooves, so that the enzymes can clamp a long chitosan polysaccharide. The association/dissociation of positively charged glucosamine residues to/from the binding pocket of a GH2 exo-β-glucosaminidase controls the p Ka of the catalytic acid, thereby maintaining the high catalytic potency of the enzyme. In contrast to chitosanases, chitosan-binding modules only accommodate a couple of glucosamine residues, predominantly recognizing the non-reducing end glucosamine residue of chitosan by electrostatic interactions and a hydrogen-bonding network. These structural findings on chitosan-related enzymes may contribute to future applications for the efficient conversion of the chitin/chitosan biomass.

Chitosan/fucoidan nanoparticles were created using two fucoidans from the Fucus evanescens algae. One of them was a regular fucoidan obtained for the first time from the alga harvested at the reproductive growth stage, using only standard extraction methods, without additional modifications. Its structure was established via NMR spectroscopy to consist of the repeating →3)-α-L-Fucp-(2,4SO3−)-(1 → 4)-α-L-Fucp-(2SO3−)-(1→ fragment. Such fragment also coustituted 55% of the other fucoidan's structure, however it also included long sequences of α-L-fucopyranose residues sulfated only at C2. The nanoparticles were re-dispersed in water and the influence of fucoidan/chitosan mass ratio on the nanoparticles' size and zeta potential was investigated. 3D models of the regular fucoidan and chitosan's sections were created and their molecular docking was performed, showing that either polymer could occupy the exterior of the complex, depending on their ratio. Thermodynamic parameters of fucoidan-chitosan binding process were accessed, with the results indicating that significant conformational changes of fucoidan and chitosan molecules take place during the interaction, presumably to allow for more effective binding.

Inspired by the fact that chitosan is a representative constituent of the ectocellular structure of Cryptococcus neoformans and a typical biomaterial for improving drug oral absorption, we designed an elegant and efficient C. neoformans-targeted drug delivery system via oral administration. A chitosan-binding peptide screened by phage display was used as the targeting moiety, followed by conjugation to the surface of poly(lactic- co-glycolic acid) nanoparticles as the drug carrier, which was then incubated with free chitosan. The noncovalently bound chitosan adheres to mucus layers and significantly enhances penetration of nanoparticles through the oral absorption barrier into circulation and then re-exposed the targeting ligand for later recognition of the fungal pathogen at the site of infection. After loading itraconazole as a model drug, our drug delivery system remarkably cleared lung infections of C. neoformans and increased survival of model mice. Currently, targeted drug delivery is mainly performed intravenously; however, the system described in our study may provide a universal means to facilitate drug targeting to specific tissues and disease sites by oral administration and may be especially powerful in the fight against increasingly severe fungal infections.

Dissolved natural or modified chitosans are used as the carriers of bioactive compounds which demands knowledge on how these macromolecules bind chemicals in solutions. This work examines binding of ionizable salicylic acid (SA), a medicine chemical and plant hormone, to chitosan and its derivative obtained by amine N alkylation with n-C6H13. Binding was studied at two pHs, below the chitosan's pKa, by performing dialysis with a 3500 Da cut-of membrane, followed by a spectrophotometric determination of SA concentrations in the membrane-separated compartments. SA-chitosan binding obeys reversible linear isotherms showing distinct preferences for SA to distribute from water to macromolecules with a coefficient reaching up to few hundreds (L kg−1), depending on pH and NaCl concentration. Both SA molecules and anions bind to dissolved chitosan. Although the SA anion-chitosan interactions tend to dominate, they can be suppressed by competing anions. Chitosan N-alkylation is associated with a modest decreasing effect on SA binding. For water-soluble formulations of bioactive substances, binding quantification may help to differentiate between the effects of concentration of chitosan-bound active chemicals and the ability of complexes to pass biological barriers.

Plant chitinase hydrolyzing β-1,4-glycosidic linkages of chitin are major enzymes acting in plant-microbe interactions and are involved in self-defense against fungal pathogens. Chitosanases from soil bacteria are also involved in plant defense by hydrolyzing chitosan components of the fungal cell wall. The crystal structures of these enzymes in complex with their substrates have been solved, and the mechanisms of substrate binding were elucidated at the atomic level. These findings enabled us to speculate on the enzyme targets under physiological conditions, leading us to define the physiological roles of the enzymes. The structures and functions of chitin/chitosan-binding modules appended to modular chitinases/chitosanases were analyzed by NMR and isothermal titration calorimetry (ITC), and the enzymes were found to form an appropriate modular organization to fulfill their roles in plant-microbe interactions.

The binding of bile acids to dietary fibers in the small intestine has been proposed as a mechanism for the reduction of blood cholesterol levels. In this study, isothermal titration calorimetry (ITC) was used to characterize the binding of sodium taurocholate (NaTC) to a cationic biopolymer (chitosan). The influence of ionic strength (0–150 mM NaCl) and temperature (10–40 °C) on the binding interactions was examined (pH 3, acetate buffer). At 30 °C, NaTC bound strongly to chitosan to form an insoluble complex that contained about 4×10−3 mol of NaTC per 1 g of chitosan at saturation. The presence of salt (0–150 mM NaCl, pH 3) decreased the critical micelle concentration (CMC) of NaTC (in both the absence and presence of chitosan), increased the minimum NaTC concentration required for binding to be observed, but had little influence on the amount of NaTC bound to chitosan at saturation. The enthalpy changes associated with micelle dissociation went from exothermic at low-holding temperatures (10 °C) to endothermic at higher holding temperatures (40 °C). Conversely, the enthalpy changes associated with NaTC–chitosan binding went from endothermic at low-holding temperatures (10 °C) to exothermic at higher holding temperatures (40 °C). The temperature dependence of these processes indicated the importance of changes in hydrophobic interactions within the systems. This study provides information that may lead to the rational design of chitosan-based ingredients or products with improved cholesterol lowering ability.

Chitosan has emerged as a promising material for biomedical applications. However, the effect of chitosan adsorption on the structure of model biomembrane is not known. In this study, atomic force microscopy (AFM) is employed to investigate the interaction between chitosan and mica-supported dipalmitoylphosphocholine (DPPC) bilayer. First, in situ AFM measurement indicates that nucleation of chitosan occurs around the membrane defects at the initial stage of chitosan incubation. Eventually, DPPC-chitosan binding and chitosan intermolecular association lead to chitosan aggregation on the membrane surface which is quantified by average height measurement and RMS roughness analysis. Lateral force microscopy (LFM) confirms that the adsorbed chitosan has distinct material properties. Furthermore, the trend of surface pressure-area isotherms supports the condensation of DPPC monolayer induced by chitosan in the aqueous subphase. Surface coverage and surface roughness analysis show that the extent of chitosan aggregation on the supported membrane is affected by the incubation time during long-term chitosan incubation.

The aim of this study was to analyze binding of chitosan and chitosan nanoparticles onto cellulose via oxidized cellulose. The ability of chitosan and chitosan nanoparticles to be adsorbed onto surfaces was determined by the use of the XPS spectroscopy which provided information about chemical composition of the fiber surface. On the other hand, the gravimetric method was also used by which the amount of chitosan and chitosan nanoparticles bounded onto surface was calculated based on the difference in masses before and after functionalization. The most important was to study the influence of aldehyde groups on the stability of chitosan binding onto cellulose. Thus, desorption of chitosan/chitosan nanoparticles from the fiber surfaces was evaluated by the presence of total nitrogen (TN) in desorption bath as well as by polyelectrolyte titrations. Together with these two methods, desorption was evaluated also by gravimetric method, where the extent of desorption was evaluated on the basis of the differences in the masses of fibers before and after desorption. It is concluded that the chitosan and chitosan nanoparticles are more efficiently bounded onto oxidized cellulose in comparison with the non-oxidized (reference) ones. Despite the binding of the positively-charged amino groups with the negative groups of cellulose and consequently smaller amount of available/residual protonated amino groups that are responsible for bioactivity, such functionalized fibers are still specifically antimicrobial.

Tailorable cationic chitosan/PLGA nanoparticles (CPNP) were used for the delivery of an antisense 2'-O-methyl-RNA (2OMR) directed against RNA template of human telomerase. Here, we describe the influence of the chitosan content on binding efficiency, complex stability, uptake in different human lung cell types and finally demonstrate the efficacy of this nanoplex system. CPNPs were prepared by the emulsion-solvent evaporation method using different amounts of chitosan and purified by preparative size exclusion chromatography. The characterization by photon correlation spectroscopy and zeta potential measurements showed a small increase in size and an increase of zeta potential with increasing amounts of chitosan. Binding efficiency and complex stability with 2OMR was high in water and correlated well with the chitosan content of particles but was weak in physiologically relevant media (PBS and RPMI cell culture medium). However, flow cytometry analysis showed that the uptake of 2OMR into A549 lung cancer cells was considerably higher in combination with nanoparticles and dependent on the amount of chitosan when compared to 2OMR alone. Confocal laser scanning microscopy revealed that the uptake into A549 cells is mediated via complexes of 2OMR and chitosan/PLGA nanoparticles despite the weak binding in cell culture medium. The nanoparticles were well tolerated and efficient in inhibiting telomerase activity.

Chitosan is a cationic biopolymer that has many potential applications in the food industry because of its unique nutritional and physicochemical properties. Many of these properties depend on its ability to interact with anionic surface-active molecules, such as surfactants, phospholipids, and bile acids. The purpose of this study was to examine the influence of pH (3 and 7), ionic strength (0-200 mM NaCl), and temperature (10-50 degrees C) on the interactions between a model anionic surfactant (sodium dodecyl sulfate, SDS) and chitosan using isothermal titration calorimetry, selective surfactant electrode, and turbidity measurements. At pH 3 and 30 degrees C, SDS bound strongly to chitosan to form an insoluble complex that contained about 4-5 mmol of SDS/1 g of chitosan at saturation. When SDS and chitosan were mixed at pH 7 they did not interact strongly, presumably because the biopolymer had lost most of its positive charge at this pH. However, when SDS and chitosan were mixed at pH 3 and then the solution was adjusted to pH 7, the SDS remained bound to the chitosan. The presence of NaCl (0-200 mM) in the solutions decreased the critical micelle concentration (cmc) of SDS (in both the absence and the presence of chitosan) but had little influence on the amount of SDS bound to chitosan at saturation. The cmc of SDS and the amount of SDS bound to the chitosan at saturation were largely independent of the holding temperature (10-40 degrees C). Nevertheless, the enthalpy changes associated with micelle dissociation were highly temperature-dependent, indicating the importance of hydrophobic interactions, whereas the enthalpy changes associated with SDS-chitosan binding were almost temperature-independent, indicating the dominant contribution of electrostatic interactions. This study provides information that may lead to the rational design of chitosan-based ingredients or products with specific nutritional and functional characteristics, for example, cholesterol lowering.