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The high molecular weight of chitin, as a biopolymer, challenges its extraction due to its insolubility in the solvents. Also, chitosan, as the N-deacetylated form of chitin, can be employed as a primary material for different industries. The low mechanical stability and poor plasticity of chitosan films, as a result of incompatible interaction between chitosan and the used solvent, have limited its industrialization. Deep eutectic solvents (DESs), as novel solvents, can solve the extraction difficulties of chitin, and the low mechanical stability and weak plasticity of chitosan films. Also, DESs can be considered for the different chitosan and chitin productions, including chitin nanocrystal and nanofiber, N,N,N-trimethyl-chitosan, chitosan-based imprinted structures, and DES-chitosan-based beads and monoliths. This review aims to focus on the preparation and characterization (chemistry and morphology) of DES-chitin-based and DES-chitosan-based structures to understand the influence of the incorporation of DESs into the chitin and chitosan structure., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study revealed that mixed chitin esters with long fatty and bulky acyl substituents were efficiently synthesized by acylation using acyl chlorides in the presence of pyridine and N,N-dimethyl-4-aminopyridine in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), at 100 °C for 24 h. A stearoyl group was selected as the first substituent, which was combined with different long fatty and bulky acyl groups as the second substituents. In addition to IR analysis of the products, which suggested progress of the acylation, 1 H NMR measurement was allowed for structural confirmation for high degrees of substitution (DSs) of the desired derivatives in CDCl 3 /CF 3 CO 2 H solvents. Crystalline structures and thermal property of the products were evaluated by powder X-ray diffraction and differential scanning calorimetry measurements, respectively. All the products showed film formability by casting from solutions in chloroform or chloroform/trifluoroacetic acid solvents. The occurrence of halogen exchange between acyl chlorides and AMIMBr in the present system was speculated to produce highly reactive acyl bromides in situ, which efficiently reacted with hydroxy groups in chitin to obtain high DS products., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Most polysaccharides used in polysaccharide-based block copolymers are attached to the second block through the reducing end, due to the few and highly polysaccharide specific non-reducing end (NRE) functionalisation methods available. Chitin oligomers, prepared by nitrous acid degradation of chitosan (A n M) can, however, be selectively oxidised by periodate since they only possess a single vicinal diol in the NRE residue. Here, we show that both aldehydes formed after oxidation are highly reactive towards bifunctional oxyamines and hydrazide linkers. Sub-stochiometric amounts of linkers resulted in conjugation of A n M oligomers through both chain termini to yield a discrete distribution of 'polymerised' oligomers. Such chitin-based block polymers were, in contrast to chitins of the same chain lengths, water-soluble. Oxidised A n M oligomers, functionalised at both termini can also enable the preparation of more complex block polysaccharides such as ABA- or ABC-type., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Chitin and chitosan have been extensively used as wound dressings because of their special functions to promote wound healing. However, there was little focus on the effects of the degree of acetylation (DA) on wound healing. In this work, the regenerated chitin nonwoven fabrics with DA values of 90, 71, 60, and 42% were prepared, and the morphology and physical performances of the fabrics were characterized. Moreover, the effects of DA of the chitin nonwoven fabrics on wound recovery were studied with a full-thickness skin defect model in rats. In vitro experiments indicated that the chitin nonwoven fabrics exhibited good biocompatibility and blood compatibility and a low blood-clotting index (BCI). In vivo experiments revealed that the chitin nonwoven fabrics could accelerate wound healing more effectively than gauze by promoting re-epithelialization and collagen deposition as well as by stimulating neovascularization. The results of the wound healing process showed that DA of the chitin nonwoven fabrics had a profound effect on promoting wound healing. Notably, the regenerated chitin nonwoven fabrics with 71% DA significantly improved the wound healing compared to the commercial wound dressing Algoplaque film. Therefore, the regenerated chitin nonwoven fabrics are promising candidates for wound healing.

Chitin, a polymer composed of β(1-4)-linked N-acetyl-glucosamine monomers, and its partially deacetylated analogue chitosan, are abundant biopolymers with outstanding mechanical as well as elastic properties. Their degradation products, chitooligosaccharides (COS), can trigger the innate immune response in humans and plants. Both material and biological properties are dependent on polymer length, acetylation, as well as the pH. Without well-defined samples, a complete molecular description of these factors is still missing. Automated glycan assembly (AGA) enabled rapid access to synthetic well-defined COS. Chitin-cellulose hybrid oligomers were prepared as important tools for a systematic structural analysis. Intramolecular interactions, identified by molecular dynamics simulations and NMR analysis, underscore the importance of the chitosan amino group for the stabilization of specific geometries., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Chitooligosaccharides has attracted increasing attention due to their diverse bioactivities and potential application. Previous studies on the bioactivity of chitooligosaccharides were mostly carried out using a mixture. The structure-function relationship of chitooligosaccharides is not clear. Recently, it is confirmed that chitooligosaccharides with different degrees of polymerization play different roles in many bioactivities. However, heterogeneous chitooligosaccharides with a single degree of polymerization is still a mixture of many uncertain sequences and it is difficult to determine which structure is responsible for biological effects. Therefore, an interesting and challenging field of studying chitooligosaccharides with heterogeneous sequences has emerged. Herein, we reviewed the current methods for preparing heterogeneous chitooligosaccharides, including chemical synthesis, separation techniques and enzymatic methods. Advances in the bioactivities of chitooligosaccharides with heterogeneous sequences are also reviewed., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this study, new complexes of Naringin and Chitooligosaccharide (Nari-COS) at different mole ratios (1:1, 1:5, 1:10) were prepared by spray-drying method so as to enhance the water solubility and weaken the bitterness of naringin. At the same time, the antioxidant and the antibacterial properties of this complex were evaluated. SEM, FTIR, 1 H NMR analysis confirmed the successful synthesis of Nari-COS formed through hydrogen bonds between the A, B rings of naringin and COS. Nari-COS exhibited significantly better water solubility, reduced bitterness, stronger antioxidant capacity, and enhanced antibacterial property in comparison to pure naringin, benefitting the extensive application of natural products in foods.

A mutant lager strain resistant to the cell wall-perturbing agent Congo red (CR) was isolated and the genetic alterations underlying CR resistance were investigated by whole genome sequencing. The parental lager strain was found to contain three distinct Saccharomyces cerevisiae (Sc)-type CHS6 (CHitin Synthase-related 6) alleles, two of which have one or two nonsense mutations in the open reading frame, leaving only one functional allele, whereas the functional allele was missing in the isolated CR-resistant strain. On the other hand, the Saccharomyces eubayanus-type CHS6 alleles shared by both the parental and mutant strains appeared to contribute poorly to chitin synthase-activating function. Therefore, the CR resistance of the mutant strain was attributable to the overall compromised activity of CHS6 gene products. The CR-resistant mutant cells exhibited less chitin production on the cell surface and smaller amounts of mannoprotein release into the medium. All these traits, in addition to the CR resistance, were complemented by the functional ScCHS6 gene. It is of great interest whether the frequent nonsense mutations found in ScCHS6 open reading frame in lager yeast strains are a consequence of the domestication process of lager yeast., (© The Author(s) 2020. Published by Oxford University Press on behalf of FEMS.)

Chito-oligosaccharides (CHOS) are homo- or hetero-oligomers of N -acetylglucosamine (GlcNAc, A) and d-glucosamine (GlcN, D). Production of well-defined CHOS-mixtures, or even pure CHOS, with specific lengths and sugar compositions, is of great interest since these oligosaccharides have interesting bioactivities. While direct chemical synthesis of CHOS is not straightforward, chemo-enzymatic approaches have shown some promise. We have used engineered glycoside hydrolases to catalyze oligomerization of activated DA building blocks through transglycosylation reactions. The building blocks were generated from readily available (GlcNAc) 2 - para -nitrophenol through deacetylation of the nonreducing end sugar with a recombinantly expressed deacetylase from Aspergillus niger ( An CDA9). This approach, using a previously described hyper-transglycosylating variant of ChiA from Serratia marcescens ( Sm ChiA) and a newly generated transglycosylating variant of Chitinase D from Serratia proteamaculans ( Sp ChiD), led to production of CHOS containing up to ten alternating D and A units [(DA) 2 , (DA) 3 , (DA) 4 , and (DA) 5 ]. The most abundant compounds were purified and characterized. Finally, we demonstrate that (DA) 3 generated in this study may serve as a specific inhibitor of the human chitotriosidase. Inhibition of this enzyme has been suggested as a therapeutic strategy against systemic sclerosis.

Chitosan is an antimicrobial, biodegradable and biocompatible natural polymer, commercially derived from the partial deacetylation of chitin. Currently modified chitosan has occupied a major part of scientific research. Modified chitosan has excellent biotic characteristics like biodegradation, antibacterial, immunological, metal-binding and metal adsorption capacity and wound-healing ability. Chitosan is an excellent candidate for drug delivery, food packaging and wastewater treatment and is also used as a supporting object for cell culture, gene delivery and tissue engineering. Modification of pure chitosan via grafting improves the native properties of chitosan. Chitosan grafted copolymers exhibit high significance and are extensively used in numerous fields. In this review, modifications of chitosan through several graft copolymerization techniques such as free radical, radiation, and enzymatic were reported and the properties of grafted chitosan were discussed. This review also discussed the applications of grafted chitosan in the fields of drug delivery, food packaging, antimicrobial, and metal adsorption as well as dye removal., (Copyright © 2020. Published by Elsevier B.V.)

Chitooligosaccharides (COS) are derived from chitosan, which can be used as nutraceuticals and functional foods. Because of their various biological activities, COS are widely used in the food, medicine, agriculture, and other fields. COS were prepared by chitosanase  from Pseudoalteromonas sp. SY39 and their anti-obesity activity was researched in mice in this study. The effects of hydrolysis time, temperature, the ratio of enzyme to chitosan, and pH on the productivity of COS were discussed. Preparation process of COS was established in a 5-L fermenter. COS were characterized and their anti-obesity activity was studied in animal experiments. The results showed that COS could effectively reduce serum lipid levels and obesity in mice, and have a good anti-obesity activity. The preparation technology and remarkable anti-obesity activity of COS further expand their applications in the food and pharmaceutical industries.

We developed a rapid and precise method to determine the fraction of acetylation (F A ) of unknown chitosan samples using a combination of enzymatic sample hydrolysis, isotopic labeling, and HILIC-ESI-MS analysis. Chitosans are β-(1,4)-linked, partially N-acetylated and linear polyglucosamines representing an interesting group of functional biopolymers with a broad range of applications. For a better understanding of their structure-function relationships, it is key to have sensitive, accurate structural analysis tools available to determine parameters like the degree of polymerization (DP), fraction of acetylation (F A ), or pattern of acetylation (P A ). Here, we describe an improved enzymatic/mass spectrometric method for F A analysis of chitosan polymers. In contrast to the original chitinosanase-based mass spectrometric fingerprinting analysis of F A , the new method is independent of the P A and the intermolecular variation in F A (Đ FA ) of the chitosan sample. This allows accurate analysis of heterogeneously de-N-acetylated samples representing the majority of commercially available chitosans., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The main objective of this work to explore new safe antiviral agents against hepatitis A virus (HAV), norovirus (NoV) and Coxsackievirus B4 (CoxB4) infections. In this context, we have successfully prepared new polyquaternary phosphonium oligochitosans (PQPOC 1,2 ) to use them as natural synergistic in-situ bioreductants of silver ions into nanosilver and stabilizing agent for these nanosilver to fabricate PQPOCs-AgNPs nano-biocomposites (NBC1,2). The antiviral performance of the PQPOCs and NBCs against FCV, HAV, and CoxB4 reflects great virucidal activities for NBCs as compared with PQPOCs with maximum viral reduction% (41.42, 80.62, and 84.04%) for NBC1 against FCV, HAV, and CoxB4, respectively. Furthermore, the antiviral activity of NBC1 is concentration- / pH-dependent where NBC1 acquired its maximum antiviral at [NBC1] = 200 μL/mL and pH 4. Based upon these facts, we could attribute the enhanced virucidal efficacy of NBC1: (i) binding of AgNPs to the virions active sites. (ii) Electrostatic interaction between the positive brushes of PQPOC and negative targets of viruses. (iii) Inducing ribonuclease catalyzed by CS to degrade the viral RNA and consequently prevents its transcription and translation., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A simple, convenient and inexpensive method for the preparation of magnetic chitin composite, in which magnetite particles are densely covered with the polysaccharide shell has been developed. Two-step procedure for magnetic chitin preparation includes: (i) adsorption of chitosan onto magnetite particles and (ii) N-selective acetylation of chitosan to produce magnetic chitin. The composite combines the magnetic properties of magnetite and the adsorption properties of chitin. The synthesized magnetic chitin is an efficient adsorbent of β-d-GlcNAc-specific lectins and lysozyme. The adsorption capacity of magnetic chitin for wheat germ (Triticum vulgaris) and potato (Solanum tuberosum) lectins was in the range of 67-86 mg g -1 of the adsorbent. Magnetic chitin showed the high capacity for enzyme-lysozyme. Synthesized adsorbent is environmentally friendly and recyclable. Magnetic chitin may be used as a promising multi-purpose adsorbent of pollutants of organic or inorganic nature., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Chitin nanocrystal (ChiNC) was fabricated based on p-toluenesulfonic acid -choline chloride deep eutectic solvent treatment. The obtained ChiNC was about 12-44 nm in width and 206-399 nm in length. The crystalline structure and the functional groups of ChiNC were maintained during the preparation process. Moreover, porcine pancreas lipase (PPL) was successfully immobilized onto the ChiNC to form the immobilized PPL (PPL@ChiNC). The resulting PPL@ChiNC has enzyme loading and activity recovery of 35.6 mg/g and 82.5%, respectively. The thermal stability, pH and temperature adaptabilities of PPL@ChiNC was improved, comparing with free PPL. The demonstrated DES treatment process was efficient for ChiNC preparation and the as-prepared ChiNC exhibited great potentials in biocatalysis and biomedical field., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Chitin is the second abundant polysaccharide after cellulose, and has been demonstrated to possess various applications in the fields of the biomaterials, water treatment, etc. Here, mechanically strong chitin films were successfully fabricated from chitin solution in NaOH/urea aqueous system with cooling by chemical crosslinking with epichlorohydrin (ECH). The results indicated that tensile strength and elongation at break of the chitin film prepared by using the weight ratio of ECH to chitin solution of 6:100 enhanced significantly to achieve 139 MPa and 43%, respectively, showing highly strong strength and elongation. The cell assay results confirmed that the chitin films were non-toxicity. Water vapor transmittance rate testing indicated that the chitin films had better breathable properties than commercial product. The robust chitin films with high transmittance, biocompatibility and breathability have great potentials in the wide applications such as biomedical, food packaging, wound healing, garments fields, etc., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The development of physical approaches and green technologies to construct novel chitin materials is essential for the exquisite utilization of the renewable and valuable resource of chitin. In the present study, chitin nanogels were simply fabricated from a chitin solution dissolved in 8% NaOH/4% urea aqueous solvent by high speed stirring. The mechanical stirring generated in situ heat that induced the regeneration of chitin chains and ensured good dispersion of the nanogels. The prepared nanogels were composed of spherical nanoparticles of size 20 to 30 nm with some aggregates. The formation of chitin nanogels was confirmed to be a physical process without using organic solvent or chemical crosslinking. Rheological tests revealed a shear thinning behavior of the nanogels and injectable hydrogels were developed accordingly. The chitin nanogels showed no toxicity to L929 cells and cell attachment on the surface of the nanogel was observed. Further, monodispersed cationic nanogels and anionic nanogels were facilely obtained by deacetylating and TEMPO-mediated oxidizing chitin nanogels, and demonstrated different antibacterial properties.

ChiEn3 from Coprinopsis cinerea was characterized as an exo-acting chitinase with a processivity. ChiEn3 hydrolyzed only soluble chitin and exhibited a hyperhydrolytic activity toward 85% deacetylated chitosan which was 33.6-fold higher than its hydrolytic activity toward glycol chitin. Its maximum hydrolytic activity was observed at 60 °C and retained 66.2% of hydrolytic activity after 60 min incubation at 60 °C. Commercial 85% deacetylated chitosan was degraded by ChiEn3 to a series of COSs with a DP of 2-20 in which COSs with a DP of 3-6 were dominant, whereas, lab-prepared chitosan (F A  = 0.65) was degraded by ChiEn3 to COSs with a DP of 2-10 in which the AA dimer was dominant. DPPH-radical-scavenging activity of ChiEn3-digested products of 85% deacetylated chitosan was 3.32-fold higher than that of undigested 85% deacetylated chitosan. Therefore, ChiEn3 shows a valuable advantage for application to the preparation of COSs from commercial 85% deacetylated chitosan., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A carboxylate chitooligomer (C-COS) containing carboxyl groups attached to chitooligomer (COS) molecules has been prepared by laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) system, which is a green-chemistry method. Several experiments were designed to evaluate inhibition effects on melanin and mechanisms of C-COS. The results indicated that C-COS exhibited more distinct anti-melanogenic effects compared to COS. C-COS inhibits melanin production with tyrosine (Tyr) and DOPA as the substrate of melanin formation, and the inhibition rates are, respectively, 89.07% and 84.45%, which reach 1.4-2 times those of COS. UV-vis spectroscopy was used to elucidate the interaction mechanism between C-COS and tyrosinase (TYR). It is C-COS chelating with metal Cu ions in tyrosinase (TYR) that decreases the enzyme activity. Half-maximal inhibitory concentrations (IC 50 ) of C-COS were calculated as 13.49 and 4.07 mg/mL for monophenolase (cresolase) and diphenolase (catecholase), respectively., (Copyright © 2018. Published by Elsevier Ltd.)

Introduction of linolenic acid (LNA) and methoxy poly (ethylene glycol) (MPEG) to the backbone of oligochitosan (CS) afforded LNA-modified MPEG-CS conjugate (MPEG-CS-LNA). Amphotericin B-loaded MPEG-CS-LNA micelles (AmB-M) were prepared via dialysis method with 82.27 ± 1.96% of drug encapsulation efficiency and 10.52 ± 0.22% of drug loading capacity. The AmB-M enhanced AmB's water-solubility to 1.64 mg/mL, being 1640-folds higher than native AmB. The AmB-M obviously reduced hemolytic effect and renal toxicity of AmB when compared to marketed AmB injection (AmB-I). Its antifungal activity against Candida albicans was equivalent to AmB-I although AmB's release from AmB-M was significantly retarded. According to fluorescence microscopy test, the unchanged activity should be attributed to enhanced fungal cellular uptake of AmB-M caused by combined inducement of LNA and CS. The pharmacokinetic studies demonstrated that AmB-M also improved the pharmacokinetic parameters of AmB with AmB-I as control. Conclusively, developed LNA-modified MPEG-CS micellar system could be a viable alternative to the current toxic commercial AmB-I as a highly efficacious drug delivery system., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Chitooligosaccharides (CHOS) have gained increasing attention because of their important biological activities. Enhancing the efficiency of CHOS production essentially requires screening of novel chitosanase with unique characteristics. Therefore, a rapid and efficient one-step affinity purification procedure plays important roles in screening native chitosanases. In this study, we report the design and synthesis of affinity resin for efficient purification of native chitosanases without any tags, using chitodisaccharides (CHDS) as an affinity ligand, to couple with Sepharose 6B via a spacer, cyanuric chloride. Based on the CHDS-modified affinity resin, a one-step affinity purification method was developed and optimized, and then applied to purify three typical glycoside hydrolase (GH) families: 46, 75, and 80 chitosanase. The three purified chitosanases were homogeneous with purities of greater than 95% and bioactivity recovery of more than 40%. Moreover, we also developed a rapid and efficient affinity purification procedure, in which tag-free chitosanase could be directly purified from supernatant of bacterial culture. The purified chitosanases samples using such a procedure had apparent homogeneity, with more than 90% purity and 10⁻50% yield. The novel purification methods established in this work can be applied to purify native chitosanases in various scales, such as laboratory and industrial scales.

Chitin synthesis inhibitors (CSIs), as alternatives to conventional insecticides, have been in worldwide demand in recent years. However, little attention has been paid to the potential ecological safety and health risks of CSIs, especially their abilities to interfere with nonsexual hormone receptors such as hypoxia-inducible factor 1α (HIF-1α). In this work, we conducted a systematic study regarding the influence of CSIs on HIF-1α-related liver cancer cell metastasis. The dual-luciferase reporter gene assay revealed that two of fourteen CSIs exhibited dose-response HIF-1α agonistic activities at noncytotoxic concentrations with relative luciferase activity (RLA) values of 25.6% for diflubenzuron (DFB) and 20.9% for triflumuron (TFM). Following this result, in vitro bioassays demonstrated that both DFB and TFM stimulated HepG2 cell migration and invasion. This action was associated with the varied expression levels of genes involved in epithelial-to-mesenchymal transition (EMT) activation and extracellular matrix (ECM) degradation, such as the upregulation of fibronectin (FN1) and matrix metalloproteinase-2 (MMP-2) and the suppression of E-cadherin (E-cad) and tissue inhibitor of metalloproteinases-2 (TIMP-2). Moreover, changes in these EMT and ECM phenotype markers were dramatically blocked by a HIF-1α inhibitor (KC7F2), which further verified the involvement of HIF-1α in CSI-induced HepG2 cell metastasis. For the first time, our findings reveal that CSIs play crucial roles in promoting the metastasis of human liver cancer cells and that HIF-1α is potentially responsible for these changes., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Bacterial strain NYT501, which we previously isolated from soil, was identified as Stenotrophomonas maltophilia, and it was confirmed that this strain produces an intracellular β-N-acetylhexosaminidase exhibiting transglycosylation activity. Several properties of this enzyme were characterized using a partially purified enzyme preparation. Using N,N'-diacetylchitobiose (GlcNAc) 2 and N,N',N″-triacetylchitotriose (GlcNAc) 3 as substrates and dried cells of this bacterium as a whole-cell catalyst, chitin oligosaccharides of higher degrees of polymerization were synthesized. (GlcNAc) 3 was generated from (GlcNAc) 2 as the major transglycosylation product, and a certain amount of purified sample of the trisaccharide was obtained. By contrast, in the case of the reaction using (GlcNAc) 3 as a substrate, the yield of higher-degree polymerization oligosaccharides was comparatively low.

Natural and synthetic chitin films, obtained from the same source were produced and their physicochemical properties were examined comparatively. Firstly, natural chitin film was obtained from elytra of an insect (Oryctes nasicornis L.) and purity of the obtained chitin film (degree of acetylation: 79±2%) was demonstrated by solid state 13 C nuclear magnetic resonance ( 13 C NMR). Then, the synthetic film was produced by dissolving of natural chitin film in LiCl-DMAc. The obtained natural and synthetic films were characterized by AFM, TGA, DSC, FTIR, mechanical properties, light transmission and contact angle. The analyses result demonstrated that natural chitin film lost very important properties such as high thermal stability, transparency, nanofibrous nature, tensile strength, Young's modulus and hydrophobicity after transforming the synthetic film., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study characterizes chitin extracted from bio-sources of snail and periwinkle using varied combinations of acid and alkali concentrations. A three level factorial design of experiment with alkali and acid concentrations was used. FTIR, XRD and SEM were used to investigate the structural changes after treatments. Results reveal that both alkali and acid concentrations significantly affect the development of the functional groups and their intensities in the extracted chitin. A certain combination of concentration of acid and alkali can be used to obtain chitin with high degree of order (Crystallinity Index (CrI)>0.9) and a degree of de-acetylation (DD>50%). This results in combined high crystallinity and degree of de-acetylation. The study also established that certain combination of acid and alkali concentrations could lead to alpha to beta transformation in chitin structure., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Some of the most abundant biomolecules on earth are the polysaccharides chitin and chitosan of which especially the oligomeric fractions have been extensively studied regarding their biological activities. However, most of these studies have not been able to assess the activity of a single, defined, partially acetylated chitosan oligosaccharide (paCOS). Instead, they have typically analyzed chemically produced, rather poorly characterized mixtures, at best with a single, defined degree of polymerization (DP) and a known average degree of acetylation (DA), as no pure and well-defined paCOS are currently available. We here present data on the enzymatic production of all 14 possible partially acetylated chitosan tetramers, out of which four were purified (>95%) regarding DP, DA, and pattern of acetylation (PA). We used bacterial, fungal, and viral chitin deacetylases (CDAs), either to partially deacetylate the chitin tetramer; or to partially re-N-acetylate the glucosamine tetramer. Both reactions proceeded with surprisingly strong and enzyme-specific regio-specificity. These pure and fully defined chitosans will allow to investigate the particular influence of DP, DA, and PA on the biological activities of chitosans, improving our basic understanding of their modes of action, e.g. their molecular perception by patter recognition receptors, but also increasing their usefulness in industrial applications.

Lipo-chitotetrasaccharide analogues where one central GlcNAc residue was replaced by a triazole unit have been synthesized from a derivative obtained by chitin depolymerization and a functionalized N-acetyl-glucosamine via the copper-catalyzed azide-alkyne cycloaddition. Their evaluation in a binding assay using LYR3, a putative lipo-chitooligosaccharide receptor in Medicago truncatula, shows a complete loss of binding.

Positive charges of chitooligomer (COS) enable COS to interact with negatively charged anionic groups on the cell surface resulting in an improvement in the biological activity of COS and its derivatives. In this study, 4-hydroxybenzaldehyde-COS (HB-COS) was synthesized and investigated for its abilities against H 2 O 2 -induced oxidative stress in microglia BV-2 cells. Under oxidative stress, HB-COS significantly attenuated reactive oxygen species (ROS) generation and DNA oxidation, and upregulated the protein levels of antioxidative enzymes. HB-COS is therefore proposed as a potential protective agent against neuronal damage., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The bioactivities of chitooligosaccharides are markedly influenced by the degree of acetylation, degree of polymerization or molecular weight and pattern of acetylation. Thus, it is crucial to identify reproducible processes that will give rise to well-defined chitooligosaccharides and establish methods for their posterior physicochemical characterization in order to advance in the knowledge of their bioactivity. Chitooligosaccharides were prepared by two different processes. The first used chitosanase enzymatic hydrolysis and the second consisted of a two-step procedure based on chemical hydrolysis followed by chitosanase hydrolysis. Chitooligosaccharides produced in the second process were composed of 63 % of fully deacetylated sequences and inhibited the growth of Escherichia coli and Listeria monocytogenes. Better antibacterial activity was found for those obtained in the first process composed of 27 % of fully deacetylated sequences. Therefore, a low percentage of free amino groups and the presence of acetylated sequences are necessary in these molecules to exert good antibacterial capacity., (Copyright © 2016. Published by Elsevier Ltd.)

The synthesis of chitosan (Chs) and chitin (Chi) copolymer and grafting of acrylamide (AAm) onto the synthesized copolymer have been carried out by chemical methods. The grafted copolymer was characterized by FTIR, SEM and XRD. The extracellular cutinase of Aspergillus sp. RL2Ct (E.C. 3.1.1.3) was purified to 4.46 fold with 16.1% yield using acetone precipitation and DEAE sepharose ion exchange chromatography. It was immobilized by adsorption on the grafted copolymer. The immobilized enzyme was found to be more stable then the free enzyme and has a good binding efficiency (78.8%) with the grafted copolymer. The kinetic parameters K M and V max for free and immobilized cutinase were found to be 0.55mM and 1410μmolmin -1 mg -1 protein, 2.99mM and 996μmolmin -1 mg -1 protein, respectively. The immobilized cutinase was recycled 64 times without considerable loss of activity. The matrix (Chs-co-Chi-g-poly(AAm)) prepared and cutinase immobilized on the matrix have potential applications in enzyme immobilization and organic synthesis respectively., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Chitin and chitosan are attractive biopolymers with enormous structural possibilities for chemical modification, creating platforms for new chemical entities with a broad scope of applications, ranging from material science to medicine. During the last few years, incredible efforts have been dedicated to the regioselective modification of these biopolymers paving the way for improved properties and tailored activities. Herein, the most recent advances in chitin/chitosan regioselective modification, reaction conditions, selectivity, and the impact on its applications are highlighted. Moreover, the recent focus on chitooligosaccharides, their regioselective and chemoselective functionalization, as well as their role in biological studies, including molecular recognition with several biological targets are also covered., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Manganese dioxide (MnO 2 )-chitin-hybrid material was prepared by a facile "one-pot" synthesis method. MnO 2 -chitin hybrid was used for the effective removal of methylene blue (MB) from liquid solution as model for wastewater treatment. The hybrid obtained was characterized by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The effect of pH and temperature were studied. MnO 2 -chitin hybrid showed high performance for oxidative decolorization and removal of MB. Typically, 25mL of MB (20mg/L) can be completely decolorized in 2.5min with 8.5mg of the MnO 2 -chitin hybrid. The hybrid material exhibited excellent recyclability and durability with the degradation value of 99% for MB after ten consecutive cycles., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Chitin is a carbohydrate polymer with unique pharmacological and immunological properties, however, because of its unwieldy chemistry, the synthesis of discreet sized sub-micron particles has not been well reported. This work describes a facile and flexible method to fabricate biocompatible chitin and dibutyrylchitin sub-micron particles. This technique is based on an oil-in-water emulsification/evaporation method and involves the hydrophobization of chitin by the addition of labile butyryl groups onto chitin, disrupting intermolecular hydrogen bonds and enabling solubility in the organic solvent used as the oil phase during fabrication. The subsequent removal of butyryl groups post-fabrication through alkaline saponification regenerates native chitin while keeping particles morphology intact. Examples of encapsulation of hydrophobic dyes and nanocrystals are demonstrated, specifically using iron oxide nanocrystals and coumarin 6. The prepared particles had diameters between 300-400nm for dibutyrylchitin and 500-600nm for chitin and were highly cytocompatible. Moreover, they were able to encapsulate high amounts of iron oxide nanocrystals and were able to label mammalian cells., Statement of Significance: We describe a technique to prepare sub-micron particles of highly acetylated chitin (>90%) and dibutyrylchitin and demonstrate their utility as carriers for imaging. Chitin is a polysaccharide capable of stimulating the immune system, a property that depends on the acetamide groups, but its insolubility limits its use. No method for sub-micron particle preparation with highly acetylated chitins have been published. The only approach for the preparation of sub-micron particles uses low acetylation chitins. Dibutyrylchitin, a soluble chitin derivative, was used to prepare particles by oil in water emulsification. Butyryl groups were then removed, forming chitin particles. These particles could be suitable for encapsulation of hydrophobic payloads for drug delivery and cell imaging, as well as, adjuvants for vaccines., (Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Water-soluble quaternized chitins (QCs) were homogeneously synthesized by reacting chitin with (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHPTAC) in 8wt% NaOH/4wt% urea aqueous solutions. The chemical structure and solution properties of the quaternized chitins were characterized by (1)H NMR, FT-IR, elemental analysis, dynamic light scattering (DLS) and zeta potential measurements. The results demonstrated that the water-soluble QCs, with a degree of substitution (DS) values of 0.27-0.54, could be obtained by varying the concentration of chitin, the molar ratio of CHPTAC to chitin unit, and the reaction time at room temperature (25°C). Two QCs (DS=0.36 and 0.54) were selected and studied as gene carriers. Agarose gel retardation assay revealed that both QCs could condense DNA efficiently when N/P ratio>3. The results of particle size and zeta potential indicated that both QCs had a good ability of condensing plasmid DNA into compact nanoparticles with the size of 100-200nm and zeta potential of +18 to +36mV. Compared to polyethylenimine (PEI, 25kDa), the QCs exhibited outstanding low cytotoxicity. Transfection efficiencies of the QCs/DNA complexes were measured using pGL-3 encoding luciferase as the foreign DNA, and the QCs/DNA complexes showed effective transfection efficiencies in 293T cells. These results revealed that the QCs prepared in NaOH/urea aqueous solutions could be used as promising non-viral gene carriers owing to their excellent characteristics., (Copyright © 2016. Published by Elsevier Ltd.)

The aim of our research activity was to obtain a biocompatible nanostructured composite based on naturally derived biopolymers (chitin and sodium alginate) loaded with commercial antibiotics (either Cefuroxime or Cefepime) with dual functions, namely promoting wound healing and assuring the local delivery of the loaded antibiotic. Compositional, structural, and morphological evaluations were performed by using the thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and fourier transform infrared spectroscopy (FTIR) analytical techniques. In order to quantitatively and qualitatively evaluate the biocompatibility of the obtained composites, we performed the tetrazolium-salt (MTT) and agar diffusion in vitro assays on the L929 cell line. The evaluation of antimicrobial potential was evaluated by the viable cell count assay on strains belonging to two clinically relevant bacterial species (i.e., Escherichia coli and Staphylococcus aureus).

Homogenous modification of natural chitin offers the advantage of fair structure control. In this work, novel carboxymethyl chitins (CMCHs) with broad range of degree of substitution (DS: 0.035 to 0.74), high degree of acetylation (DA) and little de-polymerization were synthesized homogeneously in aqueous NaOH/urea solution. The simultaneous determination of DA, DS and carboxymethylation fraction at C3 and C6 for these CMCHs was achieved by proton NMR in acidic deuterated aqueous solution for the first time. Due to the good homogeneity, the prepared CMCH-4 with lower DS of carboxymethylation exhibited, for the first time to our knowledge, dual thermo- and pH-sensitive properties. The nontoxic thermo-sensitive polymer systems gel at body temperature (37 °C) in physiological condition, which is very useful as injectable hydrogels for drug delivery and tissue engineering., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The relationship between two aminopolysaccharide stereoisomers, namely α-(1→4)- and β-(1→4)-linked (N-acetyl)-D-glucosamine polymers, is of significant interest within the field of polysaccharide science, as they correspond to amino analogs of the representative abundant natural polysaccharides, viz. amylose and cellulose. While the latter glucosamine polymer is the basis of well-known natural polysaccharides, chitin and chitosan (linear polysaccharides composed of β-(1→4)-linked N-acetyl-D-glucosamine and D-glucosamine), to the best of our knowledge, the former (α-(1→4)-linked) has not been observed in nature. For the purpose of these studies, the synthesis of such non-natural aminopolysaccharides was performed by the thermostable α-glucan phosphorylase (from Aquifex aeolicus VF5)-catalyzed enzymatic polymerization of α-D-glucosamine 1-phosphate (GlcN-1-P), via successive α-glucosaminylations, in ammonia buffer containing Mg(2+) ions, resulting in the production of the α-(1→4)-linked D-glucosamine polymers, corresponding to the structure of the chitosan stereoisomer. Subsequent N-acetylation of the products gave the aminopolysaccharides, corresponding to the chitin stereoisomer.

Present study illustrates the preparation of chitin nanofibrils (CNF) reinforced carrageenan nanocomposite films by the solution-casting technique. CNF was prepared by acid hydrolysis of chitin, followed by high speed homogenization and sonication. FTIR result demonstrated that the chemical structure of chitin had not changed after acid hydrolysis. However, the crystalinity of CNF was found to be higher than chitin. The crystallite size of chitin and CNF was 4.73 and 6.27 nm, respectively. The char content at 600 °C of chitin (19.2%) was lower than the CNF (25%). The carrageenan/CNF composite films were smooth and flexible and the CNF was dispersed uniformly in the carrageenan polymer matrix. The tensile strength and modulus of carrageenan film were increased significantly (p<0.05) after CNF reinforcement with up to 5 wt%, however, elongation at break, water vapor permeability, and transparency decreased slightly. Carrageenan/CNF nanocomposite films showed strong antibacterial activity against a Gram-positive food-borne pathogen, Listeria monocytogenes., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

This review presents an analysis of the literature data over the last decade in order to reveal the relationship between the structure and composition of chitin/chitosan oligomers and their antitumor activity. Oligosaccharides consisting of N-acetylglucosamine and/or glucosamine units connected to each other by β-1,4-O-glycoside bond are generally called chitooligosaccharides. Homochitooligosaccharides are the oligomers of N-acetylglucosamine (AGA) or glucosamine (GA). Heterooligosaccharides are a mixture of various oligomers differing in the degree of polymerization (DP), acetylation (DA), or deacetylation (DD), as well as in the location of N-acetyl residues in the oligomer chain. Heterochitooligomers with a polymerization degree of no more than 10 are usually water soluble. The solubility of chitooligosaccharides with a DP of more than 10 depends on the DA and pH of a solution. The pharmaceutical and food industries, as well as scientists engaged in basic research, are interested in the use of heterochitooligosaccharides. This is explained by their unique properties, such as good water solubility; minimal toxicity; biocompatibility; the ability to penetrate cell membranes, resulting in a high degree of absorption (unlike chitin and chitosan); and their biological activity. Therefore, in the last decade, researchers have focused their attention on studying the relationship of the structure of oligosaccharides and their specific activity, such as antitumor, antimicrobial, antioxidant, immunemodulatory, and other activities. This is shown by the number of publications, which has doubled compared to the number in 2001.

A highly hydrophobic and oleophilic chitin sponge was synthesized, for the first time, via a freeze-dried method and then by using a thermal chemical vapor deposition of methyltrichlorosilane (MTCS) at different relative humidity. Fourier-transform infrared, energy-dispersive X-ray spectra, and scanning electron microscopy confirmed that the silanization occurred on the pore wall surface of the chitin sponge. The MTCS-coated chitin sponge had interconnected open-cell structures with the average pore size from 20 to 50 μm, and the MTCS nanofilaments immobilized on the chitin matrix, leading to the high hydrophobicity, as a result of the existence of a solid/air composite rough surface. Cyclic compression test indicated that the hydrophobic chitin sponges exhibited excellent elasticity and high mechanical durability. The sponges could efficiently collect organics both on the surface and bottom from the water with the highest 58 times of their own weight absorption capacities through the combination of the particular wettability and great porosity. Furthermore, the biodegradation kinetics of the chitin sponge forecasted that the chitin could be completely biodegraded within 32 days by the microorganisms in the soil. This work provided a new pathway to prepare the chitin-based materials for highly effective removal of oil from water, showing potential application in the pollutant remediation field.

High strength chitin/poly(vinyl alcohol) (PVA) composite hydrogels (RCP) were constructed by adding PVA into chitin dissolved in a NaOH/urea aqueous solution, and then by cross-linking with epichlorohydrin (ECH) and freezing-thawing process. The RCP hydrogels were characterized by field emission scanning electron microscopy, FTIR, differential scanning calorimetry, solid-state (13)C NMR, wide-angle X-ray diffraction, and compressive test. The results revealed that the repeated freezing/thawing cycles induced the bicrosslinked networks consisted of chitin and PVA crystals in the composite gels. Interestingly, a jellyfish gel-like structure occurred in the RCP75 gel with 25 wt % PVA content in which the amorphous and crystalline PVA were immobilized tightly in the chitin matrix through hydrogen bonding interaction. The freezing/thawing cycles played an important role in the formation of the layered porous PVA networks and the tight combining of PVA with the pore wall of chitin. The mechanical properties of RCP75 were much higher than the other RCP gels, and the compressive strength was 20× higher than that of pure chitin gels, as a result of broadly dispersing stress caused by the orderly multilayered networks. Furthermore, the cell culture tests indicated that the chitin/PVA composite hydrogels exhibited excellent biocompatibility and safety, showing potential applications in the field of tissue engineering.

Cyto-compatible, 80nm sized chitin/PLGA composite nanogels (chit/PLGA-comp NGs) were prepared by regeneration method and characterized. The multifaceted chit/PLGA-comp NGs were surface modified with Au, Fe3O4, CdTe/ZnTe-QDs and umbelliferone, respectively. 185nm sized Au-chit/PLGA-comp NGs, 170nm sized QD-chit/PLGA-comp-NGs and 160nm sized Fe3O4-chit/PLGA-comp-NGs showed RF heating. The QD-chit/PLGA-comp-NGs and 180nm sized umb-chit/PLGA-comp-NGs were well uptaken by Escherichia coli, Staphylococcus aureus and Candida albicans. The chit/PLGA-comp NGs could be useful for microbial monitoring and RF application for cancer therapy. The preliminary data showed that multifaceted chit/PLGA-comp-NGs could be useful for hyperthermia for cancer treatment and microbial labelling and imaging., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Deep eutectic solvents (DESs) consisting of the mixtures of choline halide (chloride/bromide)-urea and choline chloride-thiourea were used as solvents to prepare α-chitin nanofibers (CNFs). CNFs of diameter 20-30 nm could be obtained using the DESs comprising of the mixture of choline chloride and thiourea (CCT 1:2); however, NFs could not be obtained using the DESs having urea (CCU 1:2) as hydrogen bond donor. The physicochemical properties of thus obtained NFs were compared with those obtained using a couple of imidazolium based ionic liquids namely, 1-butyl-3-methylimidazolium hydrogen sulphate [(Bmim)HSO4] and 1-methylimidazolium hydrogen sulphate [(Hmim)HSO4] as well as choline based bio-ILs namely, choline hydrogen sulphate [(Chol)HSO4] and choline acrylate. The CNFs obtained using the DES as a solvent were used to prepare calcium alginate bio-nanocomposite gel beads having enhanced elasticity in comparison to Ca-alginate beads. The bio-nanocomposite gel beads thus obtained were used to study slow release of 5-fluorouracil, an anticancer drug., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Nowadays, chitin and chitosan are produced from the shells of crabs and shrimps, and bone plate of squid in laboratory to industrial scale. Production of chitosan involved deproteinization, demineralization, and deacetylation. The characteristics of chitin and chitosan mainly depend on production processes and conditions. The characteristics of these biopolymers such as appearance of polymer, turbidity of polymer solution, degree of deacetylation, and molecular weight are of major importance on applications of these polymers. This chapter addresses the production processes and conditions to produce chitin, chitosan, and chito-oligosaccharide and methods for characterization of chitin, chitosan, and chito-oligosaccharide., (© 2014 Elsevier Inc. All rights reserved.)

Light scattering studies indicate that oligochitosan (short-chain chitosan) solutions contain aggregates at pH values below the critical pH of phase separation, while at or above this point the gel phase coexists with the aggregate solution. This work demonstrates for the first time that the presence of D-glucosamine in an oligochitosan solution shifts the critical pH to a higher value and improves the oligochitosan antibacterial activity against Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermis in neutral and slightly alkaline aqueous media. By comparing the results of light scattering studies and antimicrobial assays one can conclude that the antimicrobial activity of oligochitosan is dependent on its unimolecular form, not its supramolecular structures. The widening of the homogeneity region of an oligochitosan solution could lead to promising biomedical applications., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Chitin is a biopolymer found in cell walls of various fungi and skeletal structures of numerous invertebrates. The occurrence of chitin within calcium- and silica-containing biominerals has inspired development of chitin-based hybrids and composites in vitro with specific physico-chemical and material properties. We show here for the first time that the two-dimensional α-chitin scaffolds isolated from the skeletons of marine demosponge Ianthella basta can be effectively silicified by the two-step method with the use of Stöber silica micro- and nanodispersions under Extreme Biomimetic conditions. The chitin-silica composites obtained at 120 °C were characterized by the presence of spherical SiO2 particles homogeneously distributed over the chitin fibers, which probably follows from the compatibility of Si-OH groups to the hydroxyl groups of chitin. The biocomposites obtained were characterized by various analytical techniques such as energy dispersive spectrometry, scanning electron microscopy, thermogravimetric/differential thermal analyses as well as X-ray photoelectron spectroscopy, Fourier transform infrared and Raman spectroscopy to determine possible interactions between silica and chitin molecule. The results presented proved that the character and course of the in vitro chitin silicification in Stöber dispersions depended considerably on the degree of hydrolysis of the SiO2 precursor., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The nanoparticles of oligochitosan-water soluble tragacanth (OCH-WST) as novel gene carriers have been prepared and their transfection efficiency has been investigated on Hela and HepG2 cell lines. Different OCH:WST weight ratios were prepared to obtain particles with low size distribution and high surface charge, and also in range of below 200 nm. Nanoparticles with 132.5 ± 6.77 nm size, polydispersity index 1.92 ± 0.061, surface charge 30.45 ± 1.84 and spherical morphology, have been chosen as gene carrier. Nanoparticle-DNA complexes (nanoplexes) showed better transfection efficiency in both Hela and HepG2 cells than chitosan polyplexes, with 1.26 × 10(6) versus 9.05 × 10(5) and 7.76 × 10(5) versus 2.16 × 10(5), respectively. Higher transfection efficiency of nanoplexes could be attributed to their weaker complexation. Decreasing of transfection in presence of galactose in HepG2 cells, indicated receptor mediated endocytosis of nanoplexes. These properties all together, make OCH-WST nanoparticles as potential gene carrier for active gene delivery into cells containing sugar receptors., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Selective modification of chitosan has been achieved by incorporating ethylene-1,2-diamine molecule in a regioselective manner using N-phthaloylchitosan and chloro-6-deoxy N-phthaloylchitosan as precursors. The present modification results in additional nitrogen centres which function as potential binding sites during adsorption of metal ions. The derivative ethylene-1,2-diamine-6-deoxy-chitosan and its pthaloylated precursor have been evaluated for divalent metal ion removal. The former is found to have higher capacity for adsorption due to the presence of additional NH₂ group. The samples exhibited highest affinity for Cu and least for Zn. About 80% of the adsorbed metal ions could be stripped in a solution of pH 1.2. The interaction between acidic metal centres and basic nitrogen centres on surface of the adsorbent appears to govern adsorption. Intrachain and interchain co-ordinate bonding involving NH and NH₂ groups is proposed to be the mechanism of formation of metal-adsorbent complex. The adsorption process is described by Langmuir model., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Coupling of chitin whisker (CTWK) or water-soluble chitosan (WSCS) with magnetic nanoparticles (MAG) via a covalent linkage by using a silane coupling agent in an aqueous system is proposed. The use of the silane coupling agent glycidoxypropyltrimethoxy, having a trimethoxy silane as well as an epoxide functionality, allows one step coupling between CTWK or WSCS and MAG. The MAG derivatives obtained are well dispersed and their colloidal aqueous solutions can be stabilized for days. An external magnetic field initiates alignment of nano-rod structured CTWK-MAG in the direction of the magnetic field. The uniqueness of these two materials is that CTWK-MAG shows solvent polarity responsiveness whereas WSCS-MAG performs pH responsiveness. A model application study on DNA extraction confirms that WSCS-MAG with positively charged at pH 7 and with high surface area performs more Escherichia coli extraction ability for two times as compared to CTWK-MAG., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)

In this work, we developed 120-150 nm sized nickel nanoparticles loaded chitin nanogels (Ni-Chitin NGs) by regeneration chemistry approach to investigate and determine its cytocompatibility and antibacterial activity against Staphylococcus aureus. The nickel nanoparticles were prepared by hydrothermal method. The prepared Ni-Chitin NGs were well characterized by SEM, FTIR, TG/DTA/DTG and XRD and the in vitro cytocompatibility was tested on A549 and L929 cells which showed that they are completely non-toxic. Ni-Chitin NGs showed better toxicity to the bacterial strains when compared to previous study with other nanoparticles using serial dilution method. The rhodamine labeled-Ni-Chitin NGs showed cellular localization on both L929 and A549 cells without perturbing their cellular constituents. These studies showed that the Ni-Chitin NGs could be used for various applications in biomedical filed., (Copyright © 2013 Elsevier Ltd. All rights reserved.)