Temperature shifts for extraction and purification of zygomycetes chitosan with dilute sulfuric Acid

The temperature-dependent hydrolysis and solubility of chitosan in sulfuric acid solutions offer the possibility for chitosan extraction from zygomycetes mycelia and separation from other cellular ingredients with high purity and high recovery. In this study, Rhizomucor pusillus biomass was initially extracted with 0.5 M NaOH at 120 °C for 20 min, leaving an alkali insoluble material (AIM) rich in chitosan. Then, the AIM was subjected to two steps treatment with 72 mM sulfuric acid at (i) room temperature for 10 min followed by (ii) 120 °C for 45 min. During the first step, phosphate of the AIM was released into the acid solution and separated from the chitosan-rich residue by centrifugation. In the second step, the residual AIM was re-suspended in fresh 72 mM sulfuric acid, heated at 120 °C and hot filtered, whereby chitosan was extracted and separated from the hot alkali and acid insoluble material (HAAIM). The chitosan was recovered from the acid solution by precipitation at lowered temperature and raised pH to 8-10. The treatment resulted in 0.34 g chitosan and 0.16 g HAAIM from each gram AIM. At the start, the AIM contained at least 17% phosphate, whereas after the purification, the corresponding phosphate content of the obtained chitosan was just 1%. The purity of this chitosan was higher than 83%. The AIM subjected directly to the treatment with hot sulfuric acid (at 120 °C for 45 min) resulted in a chitosan with a phosphate impurity of 18.5%.     

活性艳橙的脱色处理研究

探讨了分别使用粉煤灰和壳聚糖处理活性艳橙模拟废水的效果。结果表明：用粉煤灰吸附处理的工艺条件为室温下振荡2 h、振荡速度200 r/min、吸附剂用量0.01 g/mL、pH值约为7,此时最大脱色率为88%;用壳聚糖吸附处理的工艺条件为室温下振荡2 h、振荡速度200 r/min、吸附剂用量0.000 3 g/mL、pH值约为7,此时脱色率达97%以上。处理后的废水都达到了我国污水综合排放标准中的一级标准。     

硫铁矿废水制备铁黑颜料的工艺

采用湿法氧化沉淀法,通过调节反应溶液初始pH值(7～12)、反应温度(70～95℃)、反应时间(1～4.5h)和搅拌速度(50～250r/min),探索了硫铁矿废水制备铁黑颜料的工艺条件。结果表明:在pH值为9.5、反应温度为85℃、反应时间为2.5h、搅拌速度为150r/min的条件下,能制备得到较优的铁黑颜料。其经XRD、SEM及铁黑颜料技术指标检测分析,表明该铁黑颜料粒径在60nm左右,Fe3O4含量在95%以上,各项指标均能达到氧化铁黑颜料行业标准中一级品的要求。     

壳聚糖对水中磷的吸附处理研究

采用天然高分子聚合物壳聚糖对含磷废水进行吸附处理，考察了壳聚糖前处理的方式、处理时间、pH值、壳聚糖用量等条件对吸附率的影响，得出壳聚糖前处理最佳pH值为2．0；处理的水样pH值为6．0—6．2时，吸附磷的效果最好；最佳处理时间为40—50min，吸附率达到74．14％，吸附量为0．342mg／g。动态解吸，回收率可达91．84％。壳聚糖还可以进行再生，再生利用率为94．34％，同时还探讨了该方法在实际中的具体应用。     

Controlled release of Montelukast Sodium from pH-sensitive injectable hydrogels

pH sensitive hydrogels showed excellent drug release properties, with promise for other biomedical applications. Also, the impact of molecular weight (MW) and degree of deacetylation (DDA) of chitosan on the fabricated chitosan/poly (vinyl alcohol) (3:1 mol ratio) hydrogel with selective silane crosslinker amount was evaluated for controlled drug delivery. The FTIR spectroscopy confirmed the incorporated components and the developed interactions among the polymer chains. The hydrogel characteristics were expressed by their responsive behaviour in different environments (water, ionic media and pH). The hydrogel sample (CH1000) having chitosan with higher MW and DDA exhibited more thermal stability and bacterial growth inhibition against E.coli. All hydrogels exhibited maximum swelling at basic and neutral pH and less swelling was observed in acidic media. For drug release analysis performed in simulated gastric fluid, hydrogel showed controlled drug release in 2 h but it was more than 10%, consequently cannot be used for oral purpose. In simulated intestinal fluid, hydrogels exhibited more than 80% release within 90 min. This characteristic phenomenon at neutral pH empowered hydrogel appropriate towards injectable and targeted controlled release of applicable drug. It was concluded that the prepared hydrogel can be administered directly into the venous circulation through syringe and can be used with better results for biomedical applications.     

壳聚糖/活性炭纤维复合膜的制备及对甲基橙的吸附研究

通过化学交联法制备了纯壳聚糖膜和壳聚糖/活性炭纤维复合膜(质量比为1∶1.1);探讨时间、pH值、温度、甲基橙溶液初始浓度以及吸附剂用量对吸附甲基橙的影响。研究结果表明,最佳吸附时间为120 min,在pH为6.0,甲基橙初始浓度10 mg/L,温度为10℃时,膜对甲基橙的吸附效果最好,去除率达99.54%。     

Improved mechanical properties of chitosan fibers

A highly deacetylated chitosan from shrimp with a degree of deacetylation of 95 ± 3% was prepared and spun into a monofilament fiber using a solution of 5% by weight chitosan in 5% by volume aqueous acetic acid. Samples of the spun fibers were immersed in separate solutions containing phosphate ions and phthalate ions, and subsequently washed and dried. The various solutions ranged in pH from 4.12 to 7.75. The highest dry mechanical properties resulted from solutions containing phthalate ions between 4.5–5.5 pH, and from solutions containing phosphate ions at pH 5.4. Immersion time was varied between 1 and 60 min at 25.8°C, and temperature was varied between 25.8 and 70.0°C, in the phosphate ion solutions at a pH of 5.8. Dry mechanical properties were highest at 25.8°C and after 1 h of treatment. Chitosan films were subjected to similar treatments in phosphate and phthalate ion solutions. Fourier transform infrared data (FTIR) on the films suggest that some interaction is occurring between the phosphate ions and the amine group on the chitosan backbone. An additional experiment was performed whereby the same chitosan was used to prepare a dope of 4% by weight chitosan in 4% by volume aqueous acetic acid with 30% by volume methanol. This solution was spun into fibers, but was subjected to a “final draw” by increasing the speed of the winder. With increasing the final draw, denier and elongation‐at‐break decreased, while the other mechanical properties showed a marked increase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1721–1732, 1999     

Preparation of Pure PLLA,Pure Chitosan,and PLLA/Chitosan Blend Porous Tissue Engineering Scaffolds by Thermally Induced Phase Separation Method and Evaluation of the Corresponding Mechanical and Biological Properties

The aim of this work was to prepare the scaffolds of pure poly (L-lactic acid) 3% (w/v), pure chitosan 3% (w/v), and PLLA/chitosan blend (1:5) 3% (w/v) using TIPS method and investigate their properties and application in tissue engineering. An in vitro degradation study of scaffolds showed the addition of chitosan to PLLA not only increased its degradation rate, but also slowed down its pH value reduction. Addition of chitosan to PLLA increased hydrophilicity, porosity, compressive properties, and cell viability of the scaffolds. The results indicate that among all scaffolds, the most appropriate candidate for tissue engineering is PLLA/chitosan blend.     

溶液吸收结合铁碳微电解法降解模拟废气中二氯甲烷

采用管式反应器,以铁屑和活性炭为填料,溶液吸收结合铁碳微电解反应处理废气中二氯甲烷（DCM）。实验对比了采用铁屑、活性炭和铁屑-活性炭（Fe-C）混合填料3种条件下对DCM的去除效果,表明采用Fe-C混合填料的DCM去除率要高于单独采用铁屑或活性炭作为填料的情况,同时发现Fe-C体系组成的溶液的氧化还原电位（ORP）从反应开始急剧下降,与其他两种条件下有明显的区别;降低溶液初始pH能提高Fe-C体系DCM的脱氯和降解效果,在pH 1.5的条件下,Cl^-生成率达最大为2.85%。通过气相色谱仪对反应进出口气体的分析,发现反应后产物主要为甲烷。     

Cover: Macromol. Mater. Eng. 3/2005

Summary: A novel human hair protein hybrid fiber was developed by combining (i) the high‐efficiency extraction technique for preparing human hair proteins and (ii) the watery hybridization spinning method using gellan and chitosan. The resulting human hair protein‐gellan‐chitosan hybrid fibers are conveniently produced by simply mixing the 7–35 wt.‐% human hair protein‐1.0 wt.‐% gellan aqueous solution and the 1.0 wt.‐% chitosan‐0.15 M acetic acid solution at 50 °C, followed by pulling out to spin the human hair protein‐gellan‐chitosan ternary complex thus formed at the aqueous solution interface. By use of this simple procedure and ambient spinning condition, the human hair proteins were successfully incorporated into the fiber matrix of gellan‐chitosan, without any denaturation and degradation. The hybrid fiber can also be recognized as a new type of the regenerated human hair keratin fiber, because of its high purity and content of human hair keratin types I and II. Mechanical strength of the human hair protein‐gellan‐chitosan fiber varies from 108 to 153 MPa, depending on the contents of the human hair proteins. SEM observation revealed that the incorporated human hair proteins were found as the particles (1–10 μm) on the fiber surface. The type I and II keratins in the fiber matrices were rapidly biodegraded by chymotrypsin within 30 min, and the digested fragments slowly released from the fiber matrices. Thus, the human hair hybrid fiber is a very promising material to have a broad spectrum of applications as the engineering fibers, particularly for the medical uses, because the human hair proteins are easily available, biocompatible, and bioresorbable materials.

Gellan‐chitosan hybrid fiber (a), human hair protein‐gellan‐chitosan hybrid fiber (b).     

Synthesis and characterization of a novel pH-responsive nanocomposite hydrogel based on chitosan for targeted drug release

Over the last decade, nanocomposite hydrogels have been provided a new approach for the biomedical field. In this work, a novel pH-responsive nanocomposite hydrogel was fabricated using simultaneous in situ formation of magnetite iron oxide nanoparticles and hydrogel networks of poly(acrylic acid) grafted onto chitosan. The effects of various types of precursor molecules, pH, salt, and loading pressure were examined on the swelling properties of resulting nanocomposite hydrogels. The synthesized nanocomposite hydrogel was well characterized using different instruments. In vitro drug releasing behavior of doxorubicin was studied at pH 5.4 and 7.4. The drug release mechanism was investigated through different kinetic models. These experimental results open a new opportunity to make pH-responsive nanocomposite hydrogel devices for controlled delivery of drug.     

Preparation and properties of core–shell alginate–carboxymethylchitosan hydrogels

BACKGROUND: Hydrogels of alginate (ALG) with partially carboxymethylated chitosan (CMCHI) have been produced for drug delivery, based on the interactions between the negative groups and an ionic crosslinker. In the present work, CMCHI was used to evaluate the influence of amino groups that are positively charged at pH = 4 and 6 on the ALG–CMCHI core–shell hydrogel preparation. An ANOVA statistics tool was used to evaluate the effect of composition, pH and chitosan chemical nature on the morphology and swelling properties of the hydrogels in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). RESULTS: The ALG–CMCHI core–shell hydrogels presented smaller (ca 2.3 µm) and more homogeneous microparticles than those with unmodified chitosan (ca 5.5 µm). The ALG–CMCHI hydrogels showed higher thermal stability and lower degree of swelling in SGF (314%) compared to those with chitosan (708%), since in the former hydrogels the protective layers that surround the particles are negatively charged. CONCLUSION: CMCHI can replace chitosan in the production of core–shell hydrogels with improved properties since the negative charge surrounding the ALG–CMCHI particles favours a lower degree of swelling. The results point out a possible prevention of burst release in SGF, sustaining the swelling ability of the ALG–CMCHI core–shell hydrogels in SIF, promising appropriate drug release. Copyright © 2009 Society of Chemical Industry     

Preparation,characterization, and in vitro bioactivity of magnetic co-polymer [N,N-dimethylaminopropylacrylamide-co-1-allylimidazole] as a new nanocarrier for delivery of cefotaxime

In this research, new magnetic nanoparticles (MNPs) conjugated radical co-polymerization with N, N-dimethylaminopropylacrylamide (N, N-DMAPAAm) as a thermosensitive monomer and 1-allylimidazole (AI) as a cross-linker agent was prepared as a magnetic nanocomposite (MNC). The synthesized MNC were characterized by Fourier transform infrared spectroscopy, Elemental analysis (CHN), Field emission scanning electron microscopy, Vibrating Sample Magnetometer, and Thermo Gravimetric Analysis. Cefotaxime was selected as a model drug and was loaded into the synthesized polymer. The main factors of adsorption process such as pH, contact time, temperature, and eluent were evaluated and optimized. The mechanism of cefotaxime adsorption is explained by Langmuir isotherm. Also, in vitro cefotaxime delivery in the simulated gastric and intestinal fluids was investigated. The drug release profile revealed that about 30.35% of the adsorbed cefotaxime was released in the first 30 min. at pH =1.2 (simulated gastric fluid) and 62.65% was released during 15 h at pH =7.4 (simulated intestinal fluid).     

Supercritical CO2 impregnation of lactulose on chitosan: A comparison between scaffolds and microspheres form

Nowadays, the application of green chemistry principles in the production of new polymeric materials is receiving an increasing attention. In the present work, we have investigated the impregnation of chitosan with lactulose using supercritical fluids under various operating conditions, in order to improve the solubility of this natural polymer at neutral or basic pH. A comparison between chitosan scaffolds and microspheres is also presented; both chitosans were characterized using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and Fourier transform infrared spectroscopy (FTIR). The degree of impregnation was evaluated by quantitative gas chromatography (GC-FID) analysis and interactions chitosan-lactulose by ninhydrin method. The supercritical carbon dioxide impregnation proved to be feasible for both chitosan forms. The highest impregnation yield (8.6%) was obtained for chitosan scaffolds using the following impregnation parameters: continuous process, 60 min contact time, 14% (v/v) of co-solvent ethanol:water (95:5), depressurization rate equal to 3.3 bar/min, 100 bar of pressure and 100 °C. Under these conditions, Maillard reaction also occurred.     

γ‐Irradiation preparation of poly(acrylic acid)–chitosan hydrogels for in vitro drug release

Biocompatible and biodegradable pH‐responsive hydrogels based on poly(acrylic acid) and chitosan were prepared for controlled drug delivery. These interpolymeric hydrogels were synthesized by a γ‐irradiation polymerization technique. The degree of gelation was over 96% and increased as the chitosan or acrylic acid (AAc) content increased. The equilibrium swelling studies of hydrogels prepared under various conditions were carried out in an aqueous solution, and the pH sensitivity in a range of pH 1–12 was investigated. The AAc/chitosan hydrogels showed the highest water content when 30 vol % AAc and 0.1 wt % chitosan were irradiated with a 30 kGy dose of radiation. In addition, an increase of the degree of swelling with an increase in the pH was noticed and it had the highest value at pH 12. The drug 5‐fluorouracil was loaded into these hydrogels and the release studies were carried out in simulated gastric and intestinal fluids. The in vitro release profiles of the drugs showed that more than 90% of the loaded drugs were released in the first 1 h at intestinal pH and the rest of the drug was released slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3270–3277, 2003     

Preparation of poly(acrylic acid)–chitosan hydrogels by gamma irradiation and in vitro drug release

Biocompatible and biodegradable pH‐responsive hydrogels based on poly(acrylic acid) (AAc) and chitosan were prepared for controlled drug delivery. These interpolymeric hydrogels were synthesized by a gamma irradiation polymerization technique. The degree of gelation was over 96% and increased as the chitosan or acrylic acid content increased. The equilibrium swelling studies of hydrogels prepared in various conditions were carried out in an aqueous solution, and the pH sensitivity in the range of pH 1–12 was investigated. The AAc/chitosan hydrogels showed the highest water content when the 30 vol % AAc and 0.1 wt % chitosan were irradiated with a 30‐kGy radiation dose. Also, an increase of swelling degree with an increase in the pH was noticed and showed the highest value at pH 12. The drug, 5‐fluorouracil, was loaded into these hydrogels and the release studies were carried out in simulated gastric and intestinal fluids. The in vitro release profiles of the drugs showed that more than 90% of the loaded drugs were released in the first 1 h at the intestinal pH and the rest of the drug had been released slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3660–3667, 2003     

ECDP短纤维染色饱和值的测定

以亚甲基蓝染料对阳离子染料可染涤纶(ECDP)短纤维进行染色,讨论了在ECDP短纤维染色过程中,染浴的pH值、染色温度、保温时间、染料浓度等因素对纤维染色饱和值(Sf)的影响。结果表明:染浴的pH值控制在4.5～5.0,纤维入染温度为50℃,以2℃/min的速率升到80℃,再以0.5℃/min的速率升到100℃,在100℃时保温时间为120 min;染料相对纤维的质量分数为5%～9%时,测得ECDP短纤维的Sf为8.4。     

静电喷射技术制备可酸致突释给药的壳聚糖微颗粒

利用静电喷射技术,以西咪替丁作为模型药物,混有药物的壳聚糖水溶液作为喷射液,甲苯/正己醇的混合溶液作为接收液,成功制备得到可在酸性条件下溶解并突释给药的壳聚糖载药微颗粒。系统考察了交联剂含量对壳聚糖微颗粒的药物包封率以及载药量的影响,并研究了壳聚糖微颗粒在酸性条件下的溶解特性以及在体外的突释给药效果。结果表明,当交联剂质量分数为2%时,壳聚糖微颗粒的包封率及载药量最大,分别为80%和3.8%。由于对苯二甲醛与壳聚糖交联形成的Schiff-base结构,使得壳聚糖微颗粒能够在中性条件下保持结构完整,而在酸性条件下由于Schiff-base结构的不稳定性致使微颗粒迅速溶解。因此,体外释药实验结果显示,在pH = 2、37℃的模拟胃酸溶液中,1min内壳聚糖微颗粒即可达到最大释药效果,而在pH = 6.4、37℃的水溶液中,壳聚糖微颗粒可以较长时间保持稳定,药物释放缓慢。这种具有酸致突释释药性能的壳聚糖微粒载体在胃部给药系统方面有良好的应用前景。     

壳聚糖与羧甲基壳聚糖对铁离子的络合性能研究

考察了壳聚糖及羧甲基壳聚糖对Fe(Ⅱ)及Fe(Ⅲ)的络合性能,优化了壳聚糖及羧甲基壳聚糖与铁离子的络合条件,包括pH值、壳聚糖或羧甲基壳聚糖用量、铁离子的起始浓度、络合时间等.结果表明,壳聚糖及羧甲基壳聚糖载铁量多且能形成稳定性适度的络合物,有开发补铁剂的应用前景.     

耐低pH的氧化亚铁硫杆菌选育及其氧化硫酸亚铁的初步研究

低pH条件下高效氧化硫酸亚铁的氧化亚铁硫杆菌的选育是两步法生物浸出工艺应用的前提条件. 本文经定向培育和连续培养筛选得到pH为1.7~2.0条件下氧化硫酸亚铁的氧化亚铁硫杆菌驯化菌，其氧化硫酸亚铁的最适pH值由原来的2.0~3.0下降到1.7~2.0，在初始pH为1.7条件下培养48 h后，9K培养基中Fe2+氧化率从13.1%提高到85%. 动力学研究结果表明，该菌在250 ml摇瓶中装量100 ml、接种量10%、起始pH=1.7、温度31℃、转速120 r/min的优化条件下培养52 h后，9K培养基中Fe2+氧化率在98%以上，对数期的细菌比生长速率为0.0635 h-1,与出发菌株相近. 该菌有望用于两步法生物浸出矿物的新工艺.