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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 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.

To reduce costs and improve practicability, an ion imprinted magnetic chitosan (IMCS) was synthesized through co-precipitation using steel pickling waste liquor and chitosan and Cu(II) as template ions, which was then characterized by TEM, SEM, EDX, FTIR, XRD and VSM. The batch experiments were carried out for its potential application and high selectivity of Cu(II) removal, which were observed due to the paramagnetic properties and coordination reactions in the imprinted cavities. Kinetic studies revealed that the adsorption process followed a pseudo second-order model and the equilibrium data fit perfectly with the Langmuir isotherm model. The maximum adsorption capacity was 109.89 mg g−1. Negative values for ΔH0 and ΔG0 indicated an exothermic and spontaneous adsorption process. The adsorption process was found to be a chemical reaction and coordination complexes were formed between the metal ions and the groups of chitosan binding mainly in the “bridge model”. Moreover, 0.2 mol L−1 HCl solution was considered as the most appropriate eluent for regeneration. It showed a great performance in the experiments for practical copper wastewater and the process was considerably cost-effective.

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.

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.

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.

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.

Optimization of the technological parameters affecting the mechanical properties and permeability of capsules is essential to produce capsules with improved properties for cell immobilization. In the present paper, the effect of different parameters on the technological properties of alginate/Ca2+/oligochitosan capsules has been investigated. The correct adjustment of the alginate concentration in the polymer matrix and the oligochitosan molar mass, concentration and coating time, have been found to be key parameters in obtaining porous and mechanically stable alginate/Ca2+/oligochitosan capsules. Results showed that an increase in the coating time and concentration of the alginate generated more stable capsules with a reduced membrane cut-off. Furthermore, we have established some correlations between capsule properties and the effectiveness of chitosan binding within the capsule's membrane. Data addressed herein could be a valid tool to fabricate optimized alginate/Ca2+/oligochitosan capsules with a potential for use in cell immobilization technology. Copyright © 2006 Society of Chemical Industry

To know the mechanism of ammonia assimilation in non-heading Chinese cabbage (Brassica campestrish L. ssp. chinensis (L.) Makino) leaves regulated by chitosan (CTS), a CTS-binding protein was isolated from non-heading Chinese cabbage leaves using the chitosan affinity chromatography approach and this CTS-binding protein was partially characterized. The profile of the 53.1 kDa purified protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was compared with the native molecular weight of 106.5 kDa, which indicated that the purified protein was a dimer with identical subunits. After isoelectric focusing, a band was obtained at pH 8.25. The agglutination test and periodic acid-Schiff staining further revealed that the protein was a glycoprotein with lectin activity. Moreover, the purified protein contained 17.4% (w/w) neutral carbohydrate and 82.56% (w/w) protein. The comparison of this protein and the 67 kDa CTS-binding protein isolated previously from Rubus culture tissue exhibited some differences in characterization. According to results of peptide mass fingerprinting analysis, the protein purified in the present study does not show any similarity with any protein in the protein data bank. Thus, it was deduced that the protein purified in the present study is a novel CTS-binding protein. (Managing editor: Li-Hui ZHAO)

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.