Synthesis,Characterization and Antioxidant Activity of Quaternized Carboxymethyl Chitosan Oligosaccharides

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.     

Revealing the Nano‐Level Molecular Packing in Chitosan–NiO Nanocomposite by Using Positron Annihilation Spectroscopy and Small‐Angle X‐ray Scattering

Chitosan–NiO nanocomposite (CNC) is shown to be a potential dielectric material with promising properties. CNCs containing NiO nanoparticles (0.2, 0.6, 1, 2, 5 wt %) are prepared through chemical methods. The inclusion of NiO nanoparticles in the chitosan matrix is confirmed by scanning electron microscopy (SEM) and X‐ray diffraction. The morphology of the NiO nanoparticles and the nanocomposites is investigated by transmission electron microscopy and SEM, respectively. Positron annihilation lifetime spectroscopy (PALS) and the coincidence Doppler broadening (CDB) technique are used to quantify the free volume and molecular packing in the nanocomposites. The triplet‐state positronium lifetime and the corresponding intensity show the changes in nanohole size, density, and size distribution as a function of NiO loading. Small‐angle X‐ray scattering indicates that the NiO aggregates are identical in all the CNCs. The momentum density distribution obtained from CDB measurements excludes the possibility of a contribution of vacant spaces (pores) available in NiO aggregates to the free volume of nanocomposites upon determination by using PALS. The results show systematic variation in free‐volume properties and nano‐level molecular packing as a function of NiO loading, which is presumed to play a vital role in determining the various properties of the nanocomposites.     

Novel Potential Application of Chitosan Oligosaccharide for Attenuation of Renal Cyst Growth in the Treatment of Polycystic Kidney Disease

Chitosan oligosaccharide (COS), a natural polymer derived from chitosan, exerts several biological activities including anti-inflammation, anti-tumor, anti-metabolic syndrome, and drug delivery enhancer. Since COS is vastly distributed to kidney and eliminated in urine, it may have a potential advantage as the therapeutics of kidney diseases. Polycystic kidney disease (PKD) is a common genetic disorder characterized by multiple fluid-filled cysts, replacing normal renal parenchyma and leading to impaired renal function and end-stage renal disease (ESRD). The effective treatment for PKD still needs to be further elucidated. Interestingly, AMP-activated protein kinase (AMPK) has been proposed as a drug target for PKD. This study aimed to investigate the effect of COS on renal cyst enlargement and its underlying mechanisms. We found that COS at the concentrations of 50 and 100 µg/mL decreased renal cyst growth without cytotoxicity, as measured by MTT assay. Immunoblotting analysis showed that COS at 100 µg/mL activated AMPK, and this effect was abolished by STO-609, a calcium/calmodulin-dependent protein kinase kinase beta (CaMKKβ) inhibitor. Moreover, COS elevated the level of intracellular calcium. These results suggest that COS inhibits cyst progression by activation of AMPK via CaMKKβ. Therefore, COS may hold the potential for pharmaceutical application in PKD.     

Chitosan and Lecithin Ameliorate Osteoarthritis Symptoms Induced by Monoiodoacetate in a Rat Model

The present work aimed to assess the chondroprotective influence of chitosan and lecithin in a monoiodoacetate (MIA)-induced experimental osteoarthritis (OA) model. Forty male rats weighing 180–200 g were randomly distributed among the following five experimental groups (eight per group): control, MIA-induced OA, MIA-induced OA + chitosan, MIA-induced OA + lecithin, and MIA-induced OA + chitosan + lecithin. The levels of TNF-α, IL6, RF, ROS, and CRP, as well as mitochondrial markers such as mitochondrial swelling, cytochrome C oxidase (complex IV), MMP, and serum oxidative/antioxidant status (MDA level) (MPO and XO activities) were elevated in MIA-induced OA. Also, SDH (complex II) activity in addition to the levels of ATP, glutathione (GSH), and thiol was markedly diminished in the MIA-induced OA group compared to in control rats. These findings show that mitochondrial function is associated with OA pathophysiology and suggest that chitosan and lecithin could be promising potential ameliorative agents in OA animal models. Lecithin was more effective than chitosan in ameliorating all of the abovementioned parameters.     

Development of Reasonably Stable Chitosan Based Proton Exchange Membranes for a Glucose Oxidase Based Enzymatic Biofuel Cell

Chitosan based reasonably stable membranes were prepared as polymeric electrolyte and separator for enzymatic fuel cell applications. Glucose oxidase (GOx) bioanode centered biofuel cell with the developed chitosan membranes performed much better in stability with high current densities than that of the biofuel cell utilizing a 125 μ‐thick perfluorosulfonic acid‐type membrane (i. e. Nafion® 115). Proposed chitosan membrane structural stability was enhanced by employing cellulosic support materials and chemical crosslinking. The effects of pH, buffer type, buffer concentration, temperature on the manufactured chitosan membranes along with the biofuel cell system were investigated. The biofuel cell operation parameters were optimized for the current density and stability aspects and more than 3 mA cm^?2 current density was acquired from the cell at optimum conditions. Operational half‐life of the chitosan membrane was found as higher than the half‐life of the GOx immobilized bioanode. Therefore, this result indicates that chitosan membrane structural stability was not a limiting issue for the biofuel cell lifespan.     

A Laccase/Chitosan‐Lambda‐Carrageenan Based Voltammetric Biosensor for Phenolic Compound Detection

In this contribution, a new concept of voltammetric catechol biosensor, based on the encapsulation of laccase (LAC) in a chitosan+lambda‐carrageenan (CHIT+CAR) polyelectrolyte complex (PEC) employing a simple coacervation process is presented. Chitosan (CHIT) was prepared from α‐chitin extracted from shrimp shells and lambda‐carrageenan (CAR) was extracted from red algae, both polysaccharides and PEC being characterized using FTIR spectrometry and electrochemistry. Cyclic voltammetry was utilized to determine the analytical features of the laccase (LAC) biosensor for catechol detection. The linear range was from 10^?20 M to 10^?14 M with a sensitivity of 1.55 mA/p[catechol] and a limit of detection of 3×10^?21 M.The laccase biosensor exhibits good repeatability (RSD 2.38 %) and stability (four weeks). The developed biosensor was tested by applying it to the evaluation of the total polyphenolic content in natural oil samples.     

Mannose functionalized chitosan nanosystems for enhanced antimicrobial activity against multidrug resistant pathogens

Escalating antimicrobial resistance is causing a major threat to the public health. Failure of traditional antibiotics urges the development of alternative therapeutics, which include biopolymeric nanosystems with intrinsic antimicrobial potential. In the present study, mannose functionalized chitosan nanosystems (M-CNS) were fabricated through reductive amination of chitosan with mannose and further its ionic gelation. Changes in zeta potential and characteristic peaks in FTIR spectra revealed surface functionalization of chitosan with mannose. Zeta-sizer studies disclosed relatively higher size (180 ± 5 nm) of mannosylated CNS as compared to CNS (162 ± 7 nm). Inversely, the zeta-potential was reduced from +32.2 mV to +25.4 mV for M-CNS. Scanning electron microscopy verified the slight increase in size for M-CNS. Antimicrobial evaluation of designed nanosystems as alternative antibacterial agent was assessed by time-kill, polystyrene adherence and antibiofilm assays against both Gram-positive and Gram-negative pathogens. Results indicated that mannose functionalized CNS inhibited the growth of resistant Escherichia coli and Listeria monocytogenes, while demonstrating anti-adherence and biofilm disruption activity. Furthermore, highly resistant Pseudomonas aeruginosa and Staphylococcus aureus were also susceptible against M-CNS. This study unveiled the potential of M-CNS against pathogenic, multidrug resistant, biofilm forming bacteria; thus, making them an ideal candidate for developing alternative-medicines to cure the emerging resistant infections.     

壳聚糖-Fe(Ⅲ)复合凝胶球去除磷酸根的影响因素与吸附机理

为改善当前环境水体中的磷污染现状,利用溶胶-滴定-真空冷冻干燥法制备了壳聚糖-铁(CS-Fe)复合凝胶球去除水中磷酸根。 对CS-Fe凝胶球的形貌结构进行了表征,研究了材料对磷酸根的吸附影响因素,并探索了反应机理。 结果表明,CS-Fe对磷酸根的吸附为自发、吸热、熵增过程;吸附过程符合拟一级动力学方程,吸附平衡时间为50 min;根据Langmuir模型计算最大吸附量为23.97 mg/g,脱附效率大于90%。 傅里叶红外光谱(FT-IR)、扫描电子显微镜-能量散射谱(SEM-EDS)、Zeta电势分析、X射线光电子能谱(XPS)等证明,CS-Fe形成利于磷酸根快速吸附的蜂窝状结构;吸附机理包含静电吸附和离子交换过程。 该吸附剂将金属化合物的吸附性能与壳聚糖大分子利于构建多孔材料的特点相结合,改善了吸附效果,球状材料更利于回收,避免二次污染,具有良好应用前景。     

Potential of glucose measurement in soil and food sample using low molecular weight O-(2-hydroxyl)propyl-3-trimethylammonium chitosan chloride nanoparticle-glucose oxidase immobilised on a natural fibre membrane

Low, medium and high molecular weights O-(2-hydroxyl)propyl-3-trimethylammonium chitosan chloride nanoparticles (L-, M- and H-O-HTCC NP) have been synthesised and used to immobilise glucose oxidase on eggshell membranes for glucose biosensing. Among these O-HTCC NP-based biosensors, L-O-HTCC NP provides the highest sensitivity to glucose with a linear response of 0.012–0.60 mM and a detection limit of 12 μM (S/N = 3). The effect of L-O-HTCC NP and enzyme loading ratio, pH, temperature and phosphate buffer concentration on the sensitivity of the biosensor was studied in detail. The biosensor exhibits fast response time (40 s), good repeatability (3.0%, n = 10) and storage stability (95% of initial sensitivity after 1-year storage). Common interferents including acetic acid, DL-α-alanine, L-ascorbic acid, butyric acid, citric acid, DL-cysteine, ethanol, folic acid, glycine, lactic acid, lactose, propionic acid, sodium benzoate and sucrose do not cause significant interference on the L-O-HTCC NP biosensor. The recoveries 88.3%–102% and 102%–116% and relative standard deviations (RSDs) 3.90%–5.56% and 1.25%–3.00% are respectively, for the soil and food sample analyses. The proposed biosensor method has been applied to determine glucose in soil and food samples with good accuracy and recovery, inferring that it has potential for detection and quantification of diversified samples of different matrices. Finally, it has successfully monitored the changes of glucose contents in soil samples at various incubation times, demonstrating its potential use in environmental and geochemical analysis.