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Background: Bio-based materials, as the plentiful and renewable resources for natural constituents which are essential for biomedical and pharmaceutical applications, have not been exploited adequately yet. Chitosan is a naturally occurring polysaccharide obtained from chitin, which has recently attracted widespread attention owing to its excellent activity. This review shows the methods of extraction and modification of chitosan and provides recent progress of synthesis and use of chitosan-based materials in biological applications., Methods: By consulting the research literature of the last decade, the recent progresses of functional chitosan-based materials for biological applications were summarized and divided into the methods of extraction chitosan, the chemical modification of chitosan, chitosan-based materials for biological applications were described and discussed., Results: Chemical modification of chitosan broadens its applications, leading to developing numerous forms of chitosan-based materials with excellent properties. The excellent bioactivity of chitosan-based material enables it serves potential applications in biomedical fields., Conclusion: Chitosan-based materials not only exhibit the excellent activities of chitosan but also show other appealing performance of combined materials, even give the good synergistic properties of chitosan and its composite materials. Further studies are needed to define the ideal physicochemical properties of chitosan for each type of biomedical applications. The development of various functional chitosan-based materials for biological applications will be an important field of research, and this kind of material has important commercial value., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Edible packaging films play an important role in extending the shelf life of food products. In this work, the properties of cellulose nanofiber (CNF) reinforced hemicelluloses/chitosan-based edible films with xylooligosaccharides (XOS) have been evaluated. Results showed that the tensile strength (TS) of the film can be increased by 2.5 times with adding 5 wt% CNF. Incorporating 1.79-7.18% XOS into hemicelluloses-chitosan matrix only caused slightly higher water vapor permeability, and the composite films exhibited good hydrophobicity, thermal stability, and high transparency. The hemicelluloses/chitosan films with 1.79-5.38% XOS had higher TS (42.7-50.7 MPa) and lower oxygen permeability (OP, 4.95-5.06 cm 3  μm/m 2 ·day·kPa) than those containing 7.18% XOS. Additionally, ∼92.6% XOS in films can be released in simulated gastric fluid within 60 min. Overall, XOS (1.79-5.38%) with prebiotic properties can be added to films successfully to improve the functionality and the films were fit for food-packaging where high TS and low OP are required., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this study, we report a smart and green strategy to synthesize copper sulfide nanoparticles (CuS-NPs) for clinically translatable cancer treatment. For the first time, the preparation of CuS-NPs was developed by taking advantage of the copper-amine complex as the copper source and sodium sulfide as the sulfide source, in which the quaternized chitosan (QCS) was used as a biotemplate and stabilizing agent. The obtained QCS/CuS-NPs composites (CuS@QCS-NPs) were spherical and stable with an average diameter of 5.6 nm, and showed strong NIR absorbance for photothermal conversion. Moreover, in vitro and in vivo cancer theranostic capability of CuS@QCS-NPs without any biomodification was evaluated. The result reveals that after intratumoral (i.t.) injection of CuS@QCS-NPs with NIR laser irradiation (808 nm, 1.5 W/cm 2 , 5 min), the 4T1 mammary tumor growth could be effectively suppressed comparing with the other control groups, and there was no obvious lethal toxicity to liver function, kidney function, and vital organs. Such QCS-stabilized CuS-NPs may provide an alternative for clinical application of CuS-based photothermal therapy., (Copyright © 2018. Published by Elsevier B.V.)

Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Quaternized chitosan/organic montmorillonite (QCS/OMMT) nanocomposites were synthesized under microwave irradiation. XRD and TEM analyses confirmed that QCS intercalated into the interlayer of OMMT and clay layers distributed uniformly in QCS matrix. QCS/OMMT nanocomposites were used as retention and drainage-aid agents in pulp suspension, during which the interface behavior of positively charged QCS/OMMT nanocomposites on negatively charged cellulosic substrate and CaCO3 substrate was investigated. With the addition of QCS/OMMT nanocomposites, the particle size of cellulosic substrate increased, while the beating degree and the total residual carbohydrate concentration decreased. The results indicated that QCS/OMMT nanocomposite made a difference in paper making process through the charge patch interaction. Moreover, QCS/OMMT nanocomposites had a strong interaction with CaCO3, which was significant in fiber fines retention and paper production. When the mass ratio of QCS to OMMT was 8:1, the QCS/OMMT nanocomposite demonstrated the strongest retention and drainage-aid effect., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

β-Carotene (β-C) is a well-established natural antioxidant agent, but its poor water-solubility, low chemical stability and low bioavailability limit its application in food, pharmaceuticals and cosmetics industries. Thus it is critical to develop an efficient method to improve the water solubility and stability of β-C. In this research, amphiphilic chitosan-graft-poly (lactide) (CS-g-PLA) copolymer was synthesized via a homogeneous ring-opening polymerization (ROP) in ionic liquid. The obtained CS-g-PLA copolymer was able to self-assemble into about 14 nm micelles in water at low concentration, and β-C loaded micelles (β-C/M) had low β-C degradation after 15 days. The antioxidant properties of the β-C/M were investigated by the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method and ferric reducing antioxidant power (FRAP) method, respectively. Significantly improved antioxidant activity was observed for β-C/M in compare with free β-C. The aqueous dispersion of β-C/M has potential to be applied in the field of functional food and cosmetics., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A novel crosslinked hydrogel film was prepared from carboxymethylchitosan (CMCS) and carboxymethylcellulose (CMC) by ionical and covalent crosslinking with CaSO4 and genipin, respectively. The swelling ratio of the crosslinked CMCS/CMC hydrogel films was investigated at different pH solutions (1-9), and the results indicated that the crosslinked hydrogels had the swelling-deswelling properties with two primary peaks of swelling ratio at pH 3 and 7. The surface morphologies of the crosslinked hydrogels at different pH values provided evidences of the swelling-deswelling properties. The mechanical properties of the hydrogel films were also examined. The ionical and covalent crosslinking were found to have the primary impact on the toughness and max load, respectively, of the crosslinked hydrogels. The cells comparatively cultured on the crosslinked hydrogels and the negative and positive controls suggested the biocompatibility of the crosslinked CMCS/CMC films. This kind of hydrogel films have potential application in drug delivery vehicles and skin tissue engineering., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A facile method is reported to prepare Maillard reaction products (MRPs) from chitosan and xylan in co-solvent ionic liquid. UV absorbance and fluorescence changes were regarded as indicators of the occurrence of Maillard reaction. FT-IR, NMR, XRD and TG were used to investigate the structure of chitosan-xylan conjugate. The results revealed that when chitosan reacted with xylan in ionic liquid, the hydrogen bonds in chitosan were destroyed, the facts resulted in the formation of chitosan-xylan MRPs. Moreover, when the mass ratio of chitosan to xylan was 1:1, the Maillard reaction proceeded easily. In addition, relatively high antioxidant property was also noted for the chitosan-xylan conjugate with mass ratio 1:1. So the obtained chitosan-xylan MRP is a promising antioxidant agent for food industry., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A facile and green method to synthesize stable Ag nanoparticles (Ag NPs) with a narrow size distribution in water is reported. Water-soluble quaternized carboxymethyl chitosan (QCMC) with a surfactant-like structure was used as both a reducing and stabilizing agent under microwave irradiation via the modified Tollens reaction. In order to study the preparation mechanism, carboxymethyl chitosan (CMC) and quaternized chitosan (QCS) were compared as both reducing and stabilizing agents. Full characterization was performed using UV-vis, XRD, TEM, AAS, FT-IR, NMR and TGA. The results revealed that the prepared Ag NPs were mostly spherical with a small proportion being cylinders or cuboids; they were stable due to the package of the macromolecules; the diameters were 10.24 ± 3.13 nm. The Tollens reaction followed first order kinetics, and the Ea was 102.4 kJ mol(-1) for QCMC/Ag NP composite. During the growth of the Ag NPs, some quaternary ammonium groups and carboxymethyl groups were respectively oxidized to -CH2COCH3 and -CH3 groups, and the quaternary ammonium groups were more helpful for the growth of Ag NPs than the carboxymethyl groups. In addition, QCMC/Ag NP composite had much higher thermal stability than QCMC.

Microwave irradiation was used to intercalate quaternized carboxymethyl chitosan oligosaccharide (QCMCO) into the layer of rectorite (REC) to prepare QCMCO/REC (QCOR) nanocomposites in 70 min, which was much faster than conventional heating method of 48 h. The structures and morphology of QCOR nanocomposites were characterized by XRD, TEM, FT-IR and zeta potential analysis, the thermal behavior and antimicrobial activity of QCOR nanocomposites were also discussed. The results revealed that the interlayer distance of QCOR nanocomposites enlarged with the increase of QCMCO content, hydrogen bonding and electrostatic interaction between QCMCO and REC took place. As compared to QCMCO, the crystallinity of QCOR nanocomposites reduced, the thermal stability of QCOR nanocomposites improved, and the inhibitory activity of QCOR nanocomposites against microorganisms was stronger, the lowest minimum inhibition concentration was only 0.025% (w/v), the antimicrobial mechanism was discussed via TEM and SEM micrographs., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Drug-delivery systems, using natural drug carriers, have become increasingly important because of their nontoxicity and biodegradability. In this study, firstly, quaternized carboxymethyl chitosan (QCMC) was intercalated into the interlayer of organic montmorillonite (OMMT) to obtain the QCMC/OMMT nanocomposites, their structure, morphology, and thermal stability were investigated. Next, crosslinked alginate/QCMC/OMMT (AQCOM) microsphere was obtained by crosslinking with CaCl2, and the drug-controlled release behavior was evaluated with bovine serum albumin (BSA) as model drug. The results suggested that, carboxyl groups in alginate and QCMC crosslinked with Ca(2+), quaternary ammonium groups in QCMC or OMMT electrostatically interacted with carboxyl groups in alginate, and there was stable three-dimensional network in AQCOM microsphere. The swelling ratio of AQCOM microspheres decreased with the increase of OMMT content, the lowest one was only about 45% compared to the microsphere without OMMT of 197%. Besides, the in vitro release results for BSA indicated that the AQCOM microsphere displayed more excellent encapsulation and controlled release capacities than the microsphere without OMMT. The in vitro active cutaneous anaphylaxis test was carried out on Guinea pigs, which revealed that AQCOM microsphere did not cause anaphylaxis. Therefore, QCMC/OMMT nanocomposites from natural materials are considerably suitable to apply as drug-controlled release carriers.

Exfoliated quaternized carboxymethyl chitosan/rectorite (QCMC/REC) nanocomposite was prepared via microwave irradiation method for 70 min, which was performed in only water without any additional plasticizer. XRD, TEM, AFM, SEM and FTIR results revealed that when the mass ratio of QCMC to REC was no less than 4:1, the silicate layers of REC were completely exfoliated in QCMC matrix and were homogenous with QCMC, the surface of QCMC/REC nanobiocomposite was very smooth; two types of interactions of hydrogen bond and electrostatic attraction existed in the QCMC/REC nanobiocomposite. Thermal analysis indicated that QCMC/REC nanobiocomposite had higher thermal stability than only QCMC. Therefore, the microwave irradiation method appears to be a promising tool for preparing exfoliated biopolymer/layered silicate nanocomposites at a mild condition., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A fast and sensitive method based on fluorescent carboxymethyl chitosan/CdS quantum dots (CMCS-CdS QDs) composites was developed for specific detection of Staphylococcus aureus in food and the environment. Fluorescent CMCS-CdS QDs were prepared in aqueous solution through a green method. A human immunoglobulin (IgG) antibody was then bioconjugated to the QDs in the presence of 1-ethyl-3-(3)-dimethylaminopropyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to make a novel type of mono-dispersed water-soluble fluorescent bioprobes. The fluorescent bioprobes were employed to identify S. aureus by incubating them with the bacteria for a certain time and observing the marked cells under fluorescence microscopy after removing free fluorescent QDs. Fluorescence microscopy images showed the S. aureus cells were successfully recognized by the bioprobes. Several other bacteria commonly found in environment such as Escherichia coli and Bacillus subtilis were also incubated with the bioprobes to test their specificity. It was found that the novel QDs-CMCS-IgG bioprobes had specific identification to S. aureus cells. Fluorescence measurement using a luminescence spectrometer could be applied to quantify S. aureus cells. The fluorescence intensity of the samples at 600 nm was proportional to the cell concentration in the range of 10(3)-10(7) cfu/ml, and the detection limit was as low as 900 cfu/ml. Considering the simplicity and cost-efficiency of this method, its application in the identification and quantification of bacteria in clinical, food and environmental samples is anticipated., (© Koninklijke Brill NV, Leiden, 2011)

Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells. [ABSTRACT FROM AUTHOR]

The optimal conditions for synthesizing quaternized chitosan (QCS) via microwave irradiation were explored. The microwave temperature, time, power, mole ratio between chitosan and 2,3-epoxypropyltrimethyl ammonium chloride (ETA), volume ratio between isopropanol and water, and pH value of the reaction system were studied to evaluate the effect on the degree of substitution (DS). The structure of QCS was characterized by means of FT-IR, NMR, XPS and XRD. TGA and DTG were used to measure its thermal stability. At last, QCS acted as a reducing and stabilizing agent to greenly synthesize gold nanoparticles without adding any other chemical reagent. [ABSTRACT FROM AUTHOR]

Using microwave irradiation as an intercalation method, quaternized chitosan/organo– montmorillonite (QCS/OMMT) nanocomposites were prepared rapidly by intercalating quaternized chitosan into the interlayer of organo–montmorillonite. The structure and morphology of QCS/OMMT nanocomposites were characterized by XRD and TEM, the effects of weight average molecular weight (Mw) of QCS and degree of quaternization (DQ) in QCS on the intercalation, crystallinity and thermal stability of QCS/OMMT nanocomposites were explored. The result showed that the completely exfoliated QCS/OMMT nanocomposites were obtained when the mass ratio of QCS to OMMT was 4:1, in this case, it was found that with the increase ofDQandMwof QCS, the interlayer distance of clay was enlarged gradually, but the crystallinity of QCS/OMMT nanocomposites was destroyed; the thermal stability of QCS/OMMT nanocomposites was lower with the increasingDQin QCS and the decreasingMwof QCS. The study will guide the practical application of chitosan-based layered silicate nanocomposites. [ABSTRACT FROM AUTHOR]

Homogeneous acetylation of chitosan was carried out with acetyl chloride in 1-allyl-3-methylimidozolium chloride (AmimCl) ionic liquid. The dissolution process of chitosan in AmimCl was observed by polarized optical microscopy. The optimal reaction conditions were achieved by screening the effect of temperature, reaction time, and acylating reagents on recovery yield of acetylated chitosan and degree of substitution, which was determined by infrared (IR) spectra analysis using baseline method. The acetylated chitosan could be separated easily by water precipitation followed by filtration. The acetylation process was further confirmed by IR spectra and scanning electron microscopy, and the crystal structure was changed after the acetylation detected by X-ray diffraction spectroscopy. Compared with traditional acetylation of chitosan, the homogeneous system, mild conditions, and simply workup make this methodology more accessible to the demand of sustainable green biomass chemistry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Drug-delivery systems, using natural drug carriers, have become increasingly important because of their nontoxicity and biodegradability. In this study, firstly, quaternized carboxy-methyl chitosan (QCMC) was intercalated into the interlayer of organic montmorillonite (OMMT) to obtain the QCMC/OMMT nanocomposites, their structure, morphology, and thermal stability were investigated. Next, crosslinked alginate/QCMC/OMMT (AQCOM) microsphere was obtained by crosslinking with CaCl2, and the drug-controlled release behavior was evaluated with bovine serum albumin (BSA) as model drug. The results suggested that, carboxyl groups in alginate and QCMC crosslinked with Ca2+, quaternary ammonium groups in QCMC or OMMT electrostatically interacted with carboxyl groups in alginate, and there was stable three-dimensional network in AQCOM microsphere. The swelling ratio of AQCOM microspheres decreased with the increase of OMMT content, the lowest one was only about 45% compared to the microsphere without OMMT of 197%. Besides, the in vitro release results for BSA indicated that the AQCOM microsphere displayed more excellent encapsulation and controlled release capacities than the microsphere without OMMT. The in vitro active cutaneous anaphylaxis test was carried out on Guinea pigs, which revealed that AQCOM microsphere did not cause anaphylaxis. Therefore, QCMC/OMMT nanocomposites from natural materials are considerably suitable to apply as drug-controlled release carriers. [ABSTRACT FROM AUTHOR]

A novel cellulose- click-chitosan polymer was prepared successfully in three steps: (1) propargyl cellulose with degrees of substitution (DS) from 0.25 to 1.24 was synthesized by etherification of bamboo Phyllostachys bambusoide cellulose with propargyl chloride in DMA/LiCl in the presence of NaH. The regioselectivity of propargylation on anhydrous glucose unit determined by GC-MS was in the order of 2 >> 6 > 3; (2) the functional azide groups were introduced onto the chitosan chains by reacting chitosan with 4-azidobenzoic acid in [Amim]Cl/DMF and the DS ranged from 0.02 to 0.46; (3) thus, the cellulose- click-chitosan polymer was obtained via click reaction, that is, the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction, between the terminal alkyne groups of cellulose and the azide groups on the chitosan backbone at room temperature. The successful binding of cellulose and chitosan was confirmed and characterized by FTIR and CP/MAS 13C NMR spectroscopy. TGA analyses indicated that the cellulose- click-chitosan polymer had a higher thermal stability than that of cellulose and chitosan as well as cellulose-chitosan complex. More interestingly, some hollow tubes with near millimeter length were also observed by SEM. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Controllable synthesis of self-associating lauroyl-grafted chitosan with high molecular weight was realized in ionic liquid reacting media. The obtained lauroyl chitosan with different grafting degrees was characterized by FT-IR and 1H-NMR spectra. The chitosan derivatives were able to self-assemble into spherical polymeric micelles in water. The onset of micellization or critical micelle concentration (CMC) was estimated by fluorescence spectroscopy. The hydrodynamic diameters of various lauroyl chitosan micelles, determined by dynamic light scattering, were in the range of 122–295 nm. The morphology of the micelles was observed by scanning electron microscopy. The self-assembly behavior and the size of the assembled micelles of lauroyl chitosan were affected by the grafting degree of lauroyl groups. Generally, higher grafting degree resulted in lower CMC and smaller micelle size. These lauroyl chitosan nano-micelles may have potential applications in biological and medical fields. [ABSTRACT FROM AUTHOR]

In order to determine the effect of quaternary ammonium groups and carboxymethyl groups of chitosan on antioxidant activity, nine quaternized carboxymethyl chitosan oligosaccharides (QCMCOs) were prepared from chitosan with chloroacetic acid and 2,3-epoxypropyltrimethyl ammoniumchloride as the modifying agent under microwave irradiation. The structures of QCMCOs were characterized by FT-IR, NMR, XRD and their Mw were detected by gel permeation chromatography (GPC). The thermal stability was evaluated by thermal gravimetric analysis (TGA), and their antioxidant activities were investigated including scavenging activity of superoxide and hydroxyl radical, reducing power and metal chelating ability. The results revealed that the introduction of quaternary ammonium groups and carboxymethyl groups decreased the crystallinity and the thermal stability of chitosan oligosaccharide (COS), and their antioxidant activities were closely related to the degree of substitution of quaternary ammonium groups and the carboxymethyl groups. This study provides important guidelines for developing new antioxidant agents. [ABSTRACT FROM PUBLISHER]

A novel promising polyampholyte, being water–soluble quaternized carboxymethyl chitosan (QCM–chitosan), can be prepared by grafting carboxymethyl groups and quaternary ammonium groups on chitosan. Traditionally, QCM–chitosan was obtained by a conventional heating method in organic solvent for a lengthy time. The present study was to prepare QCM–chitosan rapidly under microwave irradiation for 70 min; the whole preparation proceeded in water without any organic solvent. Firstly, chitosan was carboxymethylated, and sequentially carboxymethyl chitosan (CM-chitosan) was quaternized to obtain QCM–chitosan. QCM–chitosan's structure was characterized. GPC-LLS were used to analyze its weight – average molecular weight (Mw ), and the degree of substitution (DS) was determined by titration. The thermal stability of QCM–chitosan was measured by TGA. The results proved that QCM–chitosan was synthesized. The maximum degree of substitution (DS) of carboxymethyl groups and quaternary ammonium groups under the optimum reaction condition was 0.82 and 0.48, respectively. Compared to chitosan, the thermal stability of QCM–chitosan decreased because of disintegration of intermolecular hydrogen bonding and partial breaking of the molecular structure, moreover, as DS of quaternary ammonium and carboxymethyl groups increased, QCM-chitosan showed lower thermal stability. In summary, the microwave irradiation method is a rapid and environmentally friendly process to synthesize soluble chitosan derivatives. [ABSTRACT FROM AUTHOR]

A fast and sensitive method based on fluorescent carboxymethyl chitosan/CdS quantum dots (CMCS-CdS QDs) composites was developed for specific detection of Staphylococcus aureus in food and the environment. Fluorescent CMCS-CdS QDs were prepared in aqueous solution through a green method. A human immunoglobulin (IgG) antibody was then bioconjugated to the QDs in the presence of 1-ethyl-3-(3)-dimethylaminopropyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to make a novel type of mono-dispersed water-soluble fluorescent bioprobes. The fluorescent bioprobes were employed to identify S. aureus by incubating them with the bacteria for a certain time and observing the marked cells under fluorescence microscopy after removing free fluorescent QDs. Fluorescence microscopy images showed the S. aureus cells were successfully recognized by the bioprobes. Several other bacteria commonly found in environment such as Escherichia coli and Bacillus subtilis were also incubated with the bioprobes to test their specificity. It was found that the novel QDs-CMCS-IgG bioprobes had specific identification to S. aureus cells. Fluorescence measurement using a luminescence spectrometer could be applied to quantify S. aureus cells. The fluorescence intensity of the samples at 600 nm was proportional to the cell concentration in the range of 103-107 cfu/ml, and the detection limit was as low as 900 cfu/ml. Considering the simplicity and cost-efficiency of this method, its application in the identification and quantification of bacteria in clinical, food and environmental samples is anticipated. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (Ag NPs) were synthesized greenly into the lamellar space of rectorite (REC) with quaternized carboxymethyl chitosan (QCMC), meanwhile quaternized carboxymethyl chitosan/rectorite/silver bionanocomposite was obtained. Results showed that QCMC and rectorite acted as reducing agent and solid support for Ag NPs, respectively. Exfoliated rectorite (REC) and organic rectorite (OREC) were obtained, simultaneously Ag NPs were formed on their interlayer and external surface. With the confinement effect of rectorite, the average diameters of Ag NPs changed from 45 nm to 22 nm, along with the change in size distributions from 30–65 nm to 18–28 nm, and their shapes changed from sphere to oval. The obtained quaternized carboxymethyl chitosan/rectorite/silver bionanocomposites were made into beads (∼1 mm) to catalyze the reduction of 4-nitrophenol (4-NP), the catalytic rate followed the order: the beads with OREC > those with REC > those without rectorite. The beads with quaternized carboxymethyl chitosan/rectorite/silver bionanocomposites without any treatments still performed well for four consecutive catalytic experiments. Using rectorite to stabilize Ag NPs and get smaller Ag NPs with narrower size distribution may extend the synthesis strategy of other nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Quaternized carboxymethyl chitosan (QCMC) was intercalated into the interlayer of rectorite (REC) to prepare QCMC/REC nanocomposite. XRD and TEM results revealed that REC was well dispersed in the polymer matrix and obtained the largest interlayer distance when the mass ratio of QCMC to REC was 2:1. FTIR, NMR and zeta-potential analyses showed that the intercalation of QCMC did not destroy the structure of REC layer, but there were hydrogen-bonding and electrostatic interactions between QCMC and REC. Quaternized chitosan (HTCC)/REC nanocomposite was prepared and studied in parallel. The comparative analysis of the two biopolymer/clay nanocomposites indicated that the free volume and positive charge density of biopolymers were important factors that affected the intercalation of biopolymer into clay. At last, thermal analysis indicated that QCMC/REC nanocomposites had obviously higher thermal stability in comparison with QCMC. This study shows that the combination with clay materials is a functional way to expand the possible application of QCMC as drug controlled-release carriers, antimicrobial agent and pulp-cap. [Copyright &y& Elsevier]

Copper oxide functionalized chitosan hybrid hydrogels for highly efficient photocatalytic-reforming of biomass-based monosaccharides to lactic acid. [Display omitted] • The CuO@CS-H had lower bandgaps, excellent stability, and alkalinity. • The photocatalyst can efficiently synthesize lactic acid in weak base system. • The photocatalyst has universality for synthesis of lactic acid from biomass-based monosaccharides. • Good yield of lactic acid was observed from two-thousand-fold scale-up experiment. Much attention has been focused on the photocatalytic-reforming of biomass to produce high-value chemicals due to their unique merits. In this study, we report a freezing-thawing strategy for the preparation of an alkaline CuO-chitosan hybrid hydrogel (CuO@CS-H). The synergism between CuO and alkaline chitosan hydrogel led to a highly efficient photocatalytic-reforming of xylose to lactic acid under a weak alkaline system, and the highest lactic acid yield is 81.6 %. The retained lactic acid yield was about 91.2 % after being used nine times. The reaction system is universal for the production of lactic acid from biomass-derived pentoses and hexoses, and O 2 − plays a major role in the synthesis of lactic acid. Industrial production of lactic acid via the as-proposed system was shown to be feasible according to a two-thousand-fold scale-up experiment. This work initiates a novel strategy of photocatalytic synthesis of lactic acid from biomass-based monosaccharides. [ABSTRACT FROM AUTHOR]

• Glycerol had the best plasticizing effect among the three plasticizers. • Addition of CNF can improve the TS of the films significantly. • Both high TS and TB were achieved in the films containing 20–30% glycerol. In this work, the properties of the plasticized hemicelluloses/chitosan-based edible films reinforced by cellulose nanofiber (CNF) have been evaluated. Results showed that the tensile strength (TS) of the film increased by 2.3 times with adding 5% CNF. As compared with unplasticized film, the films containing 10–40% plasticizers (glycerol, xylitol, sorbitol) showed slightly higher water vapor permeability, oxygen permeability, transparency, solubility, and lower contact angle. Among the three types of plasticized films, glycerol-plasticized films exhibited the highest tensile strain at break (TB, 7.80–18.53%), while the sorbitol-plasticized films exhibited the highest TS (23.14–48.96 MPa). However, there were no substantial differences in the three types of plasticized films except TS and TB. Overall, the films containing 20–30% glycerol with high TS (31.02–38.56 MPa) and TB (10.07–15.98%) were suitable for food-packaging applications where high mechanical strength and flexibility are required. [ABSTRACT FROM AUTHOR]