Adsorption and Desorption Behaviors of Bovine Serum Albumin on Gelatin/Chitosan Sponge

Gelatin (Gel) and chitosan (CTS) have several biomedical applications because of their biodegradability and biocompatibility. Crosslinking of Gel and Gel/CTS systems was evaluated using N-acetyl-D-glucosamine (GlcNAc) formed into sponges by lyophilization. The prepared sponges were used to study the adsorption and desorption of fluorescein isothiocyanate (FITC) labeled bovine serum albumin (BSA) as a model instead of a growth factor. The effect of FITC-BSA concentration and temperature on the adsorption behavior of Gel/CTS sponges was investigated. The Langmuir adsorption isotherm model was used on the basis of the assumption that monolayer adsorption occurs on the surface;the results fit with the experiment data. The adsorption constants were 5.77 and 9.68 mL/mg for Gel and Gel/CTS sponges, respectively. The adsorption thermodynamic constants were found;adsorption onto sponges was an exothermic reaction. In particular, Gibbs free energy (ΔG) exhibited negative values in the range of 283 - 343 K for both Gel and Gel/CTS sponges, demonstrating the spontaneous nature of adsorption reaction. In addition, desorption behavior was evaluated for different concentrations and pH values of the FITC-BSA solution. The high adsorbed amounts of FITC-BSA on sponge resulted in high desorbed amounts in sponge, up to 55% from 3.5 mg/mL adsorbed concentration (around 1.5 mg from 3 mg adsorb amount). Desorption decreased following the buffer solution pH decrease, from 7.4 to 4 and 2 in Gel and Gel/CTS sponges, respectively. Based on the results of this preliminary study, these composite sponges could have significant application in biomedical materials.

Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur(Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice.One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide(CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and-50°C. The synthesized laminar CC-rGO composite is mixed with acetylene black(AB) and coated on a commercial polypropylene(PP) membrane, resulting in a separator(CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

Thermal Stability and Degradation of Chitosan Modified by Cinnamic Acid

The reaction of chitosan with cinnamic acid gave the corresponding N-cinnamoyl chitosan (NCC) polymer. The chem-ical structure of the modified polymer was characterized by IR, 1H-NMR and elemental analysis. Thermogravim- etric analysis reveals that the thermal stability of chitosan polymer is greater than NCC polymer. The activation energies of thermal degradation of chitosan and NCC polymers were determined using Arrhenius relationship. Thermal degradation of NCC polymer was studied and the products of degradation were identified by GC-MS technique. It seems that the mechanism of degradation of NCC polymer is characterized by elimination of low-molecular weight radicals. Combination of these radicals and random scission mechanism along the backbone chain are the main source of the degradation products.

N,N-Dilauryl Chitosan: Synthesis and Surface Pressure-area Isotherm

With sodium dodecyl sulfonate(SDS) as the phase transferring catalyst, N,N-Dilauryl chitosans with a high degree of alkyl group substitution were prepared and characterized by means of FTIR, 1H NMR and elemental analyses. The results indicate that the average degree of alkyl group substitution on the chitosan increases with decreasing the molecular weight of the chitosan. The fully N,N-dilaurylated chitosan was found to be dissolvable in chloroform. The collapsed pressures of the samples derived from chitosan with 3000, 5000 and 10000 dalton are 47.6, 48.2 and 51.0 mN/m, respectively. The surface area occupied by the monomer unit(glucosamine) of all those samples is 0.6 nm2.

Synthesis of N-Succinyl-chitosan(Suc-Chi) and Preparation of Oxymatrine(OM)/N-Succinyl-chitosannanoparticles

Oxymatrine （OM）/N-succinyl-chitosan （Suc-Chi, with a degree of substitution being 0. 32） was synthesized via the ring-opening reaction of succinic anhydride with chitosan in dimethyl sulfoxide. OM-loaded Suc-Chi nanoparticles were prepared by an ionotropic gelation process and OM was quantified via the HPLC method： The influences of the initial OM concentration on the nanoparticle characteristics and OM release behavior were evaluated. The nanoparticles were found to have a mean diameter within a range of 267-392 nm, a positive surface charge, and a zeta potential in the range of 19-27 inV. The formulation with an initial OM concentration of 100μg/mL provided the highest loaded capacity（0. 77% ） and the highest extent of the released OM （68% at 24 h）, suggesting the possibility to achieve a therapeutic dose. According to the data obtained, this Suc-Chi-based nanotechnology will open up new and interesting prospects for the development of new anticancer drugs.

Adsorption of Pharmaceutical Contaminants from Aqueous Solutions Using N,O-Carboxymethyl Chitosan/Polyethylene Oxide (PEO) Electrospun Nanofibers

Residues of pharmaceutical and direct metabolites discharged into the aquatic environment have become a challenge for wastewater treatment facilities due to their increase in concentration and their different physicochemical properties. These emerging contaminants are daily detected in surface water and wastewater discharged by municipalities. To remediate the contaminated water, various methods are currently used including primary, secondary, and tertiary advanced treatments. However, some economic and environmental limitations have forced the scientific community to develop alternative disinfection processes to purify wastewater. As such, the adsorption strategy represents a “green” low-cost and effective solution to remove pollutants from water. In this study, a nanomaterial made of N,O-carboxymethyl chitosan (N,O-CMCS) was prepared using chitosan (CS) and monochloroacetic acid under various conditions. N,O-CMCS electrospun was synthetized with the copolymer polyethylene oxide (PEO) to create nanofiber membranes showing a better specificity toward diversified contaminants depending on the pH of medium. The developed adsorbent was used to remove fluoxetine (FLX) from aqueous solutions. The new nanomaterial was characterised using FTIR, NMR, and SEM techniques. Sorption batch tests were carried out using high-performance liquid chromatography and ultraviolet diode array detector (HPLC-UV DAD) under controlled pH experimental conditions to determine the contaminant removal capacity of the nanomaterial. The promising adsorption results obtained with N,O-CMCS/PEO nanofibers are among the best ones obtained so far in comparison to other commercial and synthetized adsorbents tested for FLX’s adsorption. Kinetic experiments were also performed to investigate effects of contact times on the FLX adsorption. Experimental results were fitted to both common kinetic models pseudo-first and second order. The latter kinetic model described the best the sorption on surface. It revealed a possible chemisorption mechanism with electrostatic bounding for N,O-CMCS/PEO nanofibers.

Chitosan-catalyzed n-butyraldehyde self-condensation reaction mechanism and kinetics

The chitosan was found to possess an excellent catalytic performance in n-butyraldehyde selfcondensation to 2 E2 H.Under suitable conditions,the conversion of n-butyraldehyde,the yield and selectivity of 2 E2 H separately attained 96.0%,86.0%and 89.6%.The chitosan catalyst could be recovered and used for 5 times without a significant deactivation after being treated with ammonium hydroxide.In order to elucidate the reaction mechanism,the adsorption and desorption of n-butyraldehyde on the surface of chitosan were studied using in situ FT-IR spectroscopy analysis.The result showed that n-butyraldehyde interacts with\\NH2 group of chitosan to form an intermediate species with an enamine structure.Then the reaction process of n-butyraldehyde self-condensation was monitored by React-IR technique and it was found that n-butyraldehyde self-condensation to 2-ethyl-3-hydroxyhexanal followed by a dehydration reaction to 2-ethyl-2-hexenal.On this basis,chitosan-catalyzed n-butyraldehyde self-condensation reaction mechanism was speculated and its reaction kinetics was investigated.The self-condensation reaction follows auto-catalytic reaction characteristics and then the corresponding kinetic model was established.

A Study on Dynamics of Drug Release from N-alkyl Chitosan Derivative Membranes In Vitro

The diffusion coefficient of model drugs (Sodium benzoate, Lysozyme and Ribonuclease) through chitosan and N-alkyl chitosan membranes were measured by using ’lag time’ technique. The results indicate that the release mechanism for the drug with small molecular weight is predominantly of ’pore type’, and for the drug with high molecular weight is predominantly pf ’partition type’. The release of protein drug with higher hydrophobicity enhances as the size of N-alkyl group and its substitution degree of chitosan increase.

Preparation of Thermal-responsive Chitosan-graft-N-isopropyl- acrylamide Membranes via γ-Ray Irradiation

A novel thermo-sensitive switching membrane has been prepared by radiation-induced simultaneous grafting N-isopropylacrylamide （NIPAAm） onto chitosan membrane. Fourier transform infrared spectroscopy （FTIR） was used to identify the structure of the grafted membranes. The surface morphology of the grafted membrane was observed from scanning electron microscopy （SEM）. Pure water flux measurements showed that water flux of the grafted membrane decreased with the increase of temperature, while that of chitosan membrane was constant. It was proved that grafted membrane was sensitive to temperature.

基于丙烯酸-N-琥珀酰亚胺酯共聚物交联剂的壳聚糖水凝胶的生物相容性研究

壳聚糖作为一种天然的氨基多糖,拥有良好的生物相容性和资源可再生性,但是较差的力学性能限制了其更广泛的应用。本研究以丙烯酸、N-乙烯基吡咯烷酮和丙烯酸-N-琥珀酰亚胺酯为单体聚合得到三元共聚物大分子交联剂,然后将其与壳聚糖溶液混合后制备壳聚糖水凝胶。采用红外、热重、SEM等对合成的聚合物及壳聚糖凝胶的组成、形貌和热稳定性进行了表征。结果表明,丙烯酸-N-琥珀酰亚胺酯共聚物的数均分子量为111900,具有一定的水溶性,与壳聚糖形成的水凝胶有良好的力学性能、溶胀性能和水蒸气渗透速率。在PBS(pH=7.4)中交联的凝胶膜与酸性条件下制备的凝胶膜相比,热分解温度提高,水接触角变大,力学性能得到较大提升。细胞毒性实验表明壳聚糖凝胶有良好的生物相容性,人脂肪干细胞在壳聚糖凝胶膜上会形成细胞簇并分泌外泌体。将壳聚糖凝胶膜覆盖在脂肪干细胞上,细胞能正常生长并分泌外泌体。因此,壳聚糖凝胶具有负载外泌体后应用于皮肤敷料的潜力。

新型纳米非病毒基因输送体系PCL-PEG-chitosan的构建与特性

目的优化新型纳米非病毒载体聚己内酯(PCL)-聚乙二醇(PEG)-壳聚糖(chitosan)(PCL-PEG-chitosan)在体外与质粒的复合条件,并进行转染活性测定。方法在体外利用凝胶电泳方法确定非病毒载体与携带绿色荧光蛋白基因的质粒(pEGFP)复合的最小氮磷比。利用动态光散射粒径测量仪确定复合物在不同氮磷比、不同缓冲溶液体系下粒径的变化情况。将pEGFP与PCL-PEG-chitosan进行复合后转染293T细胞,荧光显微镜观察转染效率。结果凝胶电泳结果显示,非病毒载体PCL-PEG-chitosan与pEGFP复合的最小氮磷比为4:1,PCL-chitosan与pEGFP复合的最小氮磷比也为4:1,chitosan与pEGFP复合的最小氮磷比为1:1。动态光散射实验结果显示:非病毒载体PCL-PEG-chitosan与pEGFP复合而成的复合物的粒径随着氮磷比的增大而减小;在醋酸盐缓冲体系与DMEM缓冲体系中,复合物的粒径基本一致,相对稳定。荧光显微镜观察发现,经过接枝改性的纳米载体PCL-PEG-chitosan的转染效率有所提高。结论 PCL修饰可减弱chitosan对pEGFP的复合能力,提高最低复合氮磷比。经PCL和PEG修饰的纳米载体PCL-PEG-chitosan的细胞转染活性有所提高,但尚需进一步改进。

Synthesis of N-methylene phosphonic chitosan(NMPCS)and its potential as gene carder

N-Methylene phosphonic chitosan （NMPCS）, an amphiphilic macromolecule with powerful chelating ability of Ca^2＋ ions, was synthesized and characterized. The physicochernical properties of NMPCS and the interactions between NMPCS and plasmid DNA were investigated by FTIR, ^13C NMR, X-ray, agarose gel electrophoresis retardation assay, atomic force microscopy （AFM） and circular dichroism （CD）. The results suggest that at charge ratio 2：1 or above, DNA could be completely entrapped and spherical complexes with mean size of 80-210 nm were formed. Taking HeLa as host cell, luciferase expression mediated by NMPCS improved about 100 times compared to the expression mediated by chitosan.

Preparation of a Novel Calcium Phosphate Cement Using N-methylene Phosphonic Chitosan as a Gelling Agent

A modified chitosan （ N-methylene phosphonic Chitosan, NMPC） was synthesized to improve solubility and ability to bind calcium ion. The properties of the raw material chitosan and its derivative NMPC were characterised using FTIR , ^1H- NMR . The aim of this study was to enhance the compressive CPC by reinforcing with NMPC. A formulation consisting of CPC powder , buffer solution and gelling agent was used for preparation of the CPC. CPC powder coasisted of tetracalcium phosphate（ TTCP ） and dicalcium phosphate anhydrous （ DCPA ）. NMPC which acted as the gelling ageut was dissohed into KH2PO4-Na2 HPO4 buffer solution. Each specimen in the mold was sandciched between two fritted glass sides and kept for 24 hours. Compressive strengths were determined, the setting product was identified using X-ray diffraction and scanning electron microscopy was used to investigate the hydroxyapatite particles size and porosity. The experimental results showed that the dominating influence on the compressive strengths of CPC-AMPC was the HA panicle size, its uniformity and appropriate porosity.

Methods of <i>N</i>-acetylated chitosan scaffolds and its <i>In-vitro</i>biodegradation by lysozyme

Generally, the lysozyme degradation on chitosan (CTS) is slower than that of chitin (CT). The CTS can be fabricated in scaffold form but it is difficult to fabricate CT scaffold under mild conditions. The method for the preparation of scaffold from N-acetylated CTS (N-CTS) was investigated in this research. By using this method, the scaffolds could be fabricated chitosan to chitin with the degree of acetylation (DA) 18% - 70%. Among these scaffolds, the highest degradation of scaffold by lysozyme was observed on the N-CTS scaffold with DA 60%, which determined by examination of the reducing end contents in the degradation media and by measuring the weight loss of scaffolds. Moreover, the best condition for the degradation of N-CTS scaffold with DA70% by lysozyme was also investigated. The maximum degradation rate of the scaffold was observed on the treatment with lysozyme 500 mg/l of acetate buffer at pH 4.5, 37°C, 100 rpm and for 7 days.

Preparation and characterization of N-isopropylacrylamide/carboxymethylated chitosan hydrogel

Poly （N-isopropylacrylamide） （PNIPAAm）/carboxymethylated chitosan （CMCH） hydrogels were prepared by irradiating the aqueous solution mixture of NIPAAm and CMCH by 60 Co γ-ray.The effects of feed ratio of NIPAAm and CMCH,temperature,pH and ionic strength on the swelling ratio of PNIPAAm/CMCH hydrogels were studied.The results show that the addition of CMCH shifts the lower critical solution temperature （LCST） of the PNIPAAm hydrogel to higher temperature.The PNIPAAm/CMCH hydrogel displays not only pH-and thermo-sensitivity,but also ion-sensitivity.Differential scanning calorimetry （DSC） was applied for the determination of the LCST of the hydrogel.

Preparation and Compressive Strength of Calcium Phosphate Bone Cement Containing N,O-carboxymethyl Chitosan

N, O-carboxymethyl chitosan （ CMCTS ）, a kind of biodegradable organic substance, was added to calcium phosphate bone cement （CPC） to prodnce a composite more similar in composition to human bone. The compressive strength of the new material was inereased by 10 times compared with conventional CPC.

N-酰基壳聚糖的制备及取代度控制的研究

对壳聚糖于醋酸 /甲醇介质中的 N-乙酰、N-丙酰、N-丁酰、N-己酰化反应进行了研究 .结果表明 :壳聚糖的 N-酰基化反应在室温 1h内接近完全 ,N-酰基取代度 ( DS)取决于醋酸和甲醇浓度以及酸酐与氨基的摩尔比( R) ,对醋酸和甲醇浓度及酸酐与氨基摩尔比进行控制 ,可制得不同取代度的 N -酰基壳聚糖 ,较为合适的反应条件为 :Me OH浓度 80 % ( w/w)、Ac OH浓度 1% ( w/w)、酸酐与氨基摩尔比 0～ 3.

N-2-羟丙基三甲基氯化铵壳聚糖-茶多酚防龋齿漱口液的制备及评价

制备一种以N-2-羟丙基三甲基氯化铵壳聚糖(N-2-hydroxypropyl trimethyl ammonium chloride chitosan,N-2-HACC)为主要成分、对致龋菌—变异链球菌(Streptococcus mutans,S.mutans)生长有抑制作用的新型漱口液。从10种具有抑菌活性的天然产物中筛选出抑菌效果最佳的物质,确定新型漱口液的最优组成成分,通过细胞毒性试验、生物相容性试验、急性毒性试验和口腔黏膜刺激试验评价漱口液的生物安全性。确定抑菌效果最优的天然产物为N-2-HACC和茶多酚,N-2-HACC和茶多酚的最低抑菌浓度分别为0.625和0.750 mg·mL^(-1)。以N-2-HACC和茶多酚为主要成分,制备了一种新型漱口液,漱口液中含1.2 mg·mL^(-1)N-2-HACC和1.0 mg·mL^(-1)茶多酚。该漱口液能够抑制S.mutans的生长,无细胞毒性,具有良好的安全性和血液相容性,溶血率符合要求。

Preparation, Swelling and Antibacterial Behaviors of N-Succinyl Chitosan-g-Poly(Acrylic Acid-co-Acrylamide) Superabsorbent Hydrogels

Superabsorbent hydrogels were prepared successfully from N-succinyl chitosan grafted poly（acrylic acid-co-acrylamide）. The potassium persulfate（KPS）, N, N＇-methylenebisacrylamide（MBA） were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM） were used to confirm the porous network structure of superabsorbent hydrogel. The effects of reaction parameters on the swelling behaviors of the superabsorbent hydrogels were investigated. The results indicated that water absorbency increased first, and then decreased gradually with the increase in the contents of monomer（AA＋AM）, KPS, MBA or acrylamide. The product had excellent water absorbency of 1375 g/g in distilled water and 83 g/g in 0.9wt% NaCl solution. Simultaneously, the superabsorbent hydrogels were p H sensitive. The antibacterial activities of the hydrogels against Escherichia coli（E. coli） were improved effectively because of polyamidoamine（PAMAM） dendrimer absorbed in the hydrogels.

谷氨酸/N-琥珀酰化壳聚糖水凝胶的制备和性能

以琥珀酸酐、壳聚糖为原料制备水溶性的N-琥珀酰化壳聚糖(NSC),再以谷氨酸(GA)为交联剂,在室温条件下,一定质量的GA和NSC在水溶液中通过自组装制备了GA/NSC水凝胶,研究了GA/NSC水凝胶的稳定性和溶胀性能,运用红外光谱(IR)、差示扫描量热仪(DSC)、扫描电子镜(SEM)等对其结构进行了表征,并考察了GA/NSC水凝胶的细胞毒性。结果表明,GA/NSC水凝胶为pH响应的离子交联水凝胶,具有较好的溶胀性能及生物相容性。