Electrophoretic extraction and analysis of DNA from chitosan or poly-l-lysine-coated alginate beads

Alginate beads containing entrapped DNA were produced using both external and internal calcium sources, and coated with chitosan or poly-l-lysine membranes. The beads were assayed with DNase nuclease to determine formulation conditions offering the highest level of DNA protection fromnucleic acid hydrolysis, simulating gastrointestinal exposure. A method was developed to extract and assay intracapsular DNA through a modified agarose electrophoresis system. Both external and internally gelled beads were permeable to DNase (M_w=31 kDa), indicated by the absence of DNA after nuclease exposure. At low levels of DNase exposure, coated high guluronic content alginate beads offered a higher level of DNA protection compared with coated beads with low guluronic alginate. No apparent correlation was found with chitosan membrane molecular weight and degree of deacetylation; however, increasing poly-l-lysine molecular weight appeared to increase DNase exclusion from beads. At elevated levels of DNase exposure, DNA hydrolysis was evident within all coated beads with the exception of those coated with the highest molecular weight poly-l-lysine (M_w=197.1 kDa), which provided almost total nuclease protection. Optimal combination then for DNA protection from nucleases is a high guluronic alginate core, coated with high molecular weight poly-l-lysine.     

海藻酸钠的疏水改性及在药物控释中的应用

海藻酸盐是一种由β-D-甘露糖酸盐(M)和α-L-古罗糖酸盐(G)连接而成的天然高分子,广泛存在于各类棕色海藻中,可与多价阳离子形成凝胶,成胶条件温和,该凝胶在生物体内以酶解方式生成甘露糖醛酸和葡萄糖醛酸,对机体无毒性、无免疫原性,适合作为释放或包埋药物、蛋白质与细胞的微胶囊.     

海藻酸盐-壳聚糖复合微/纳米凝胶研究进展

综述了海藻酸盐-壳聚糖复合微/纳米凝胶研究进展.指出海藻酸盐与壳聚糖的生物相容性、黏附性和降解性良好,以其为原料制备微/纳米凝胶具有方法简便安全、对药物包载效果好等优点,且与常规尺寸凝胶相比分散性和透过性较好.两者复合制备微/纳米凝胶主要采用一步交联、两步交联、自组装等方法,与单一组分凝胶相比优势明显,在药物输送等领域具有良好的应用前景.     

海藻酸钠-壳聚糖-桑椹红微囊的制备

以海藻酸钠-壳聚糖为复合囊材采用锐孔法制备桑椹红微囊,探讨了海藻酸钠浓度、壳聚糖浓度、Ca Cl2浓度、桑椹红浓度、针头孔径、下滴高度、温度、转速等因素对微囊包封率的影响。确定了最佳制备工艺条件为海藻酸钠浓度4.0%、壳聚糖浓度2.5%、氯化钙浓度2.0%、桑椹红浓度0.50%、针头孔径0.390mm、下滴高度4cm、温度为20℃、转速为300r·min-1。制得的微囊药物含量为11.28%,包封率为88.93%。     

Modification of collagen-chitosan membrane by oxidation sodium alginate and in vivo/ in vitro evaluation for wound dressing application

Collagen-chitosan (COL-CS) membranes materials without a cross-linking agent have poor mechanical properties. In this paper, COL-CS membranes were modified by a novel naturally-derived crosslinker, alginate dialdehyde (ADA) with different oxidation degree, and the COL-CS-ADA films were obtained. COL-CS-ADA films were characterized by Fourier transform attenuation total reflection infrared spectroscopy (ATR-FTIR), differential calorimetric scanning (DSC), thermogravimetric analysis (TG), tensile testing, and cross-link density testing. The modification of ADA exhibited positive effects on mechanical properties, the thermal stability of COL-CS membranes. The cross-linking degree between ADA and COL-CS membranes increased significantly with an increase in the oxidation degree. COL-CS-ADA films showed no cytotoxicity toward L929 fibroblasts and had good biocompatibility. The animal experiments showed that COL-CS-ADA film could promote wound healing.     

Uniform chitosan microspheres for potential application to colon-specific drug delivery

Uniform chitosan microspheres have been fabricated and weakly crosslinked for potential applications in colon-specific drug delivery. The effects of microsphere size, crosslinking density and electrostatic interactions between the drug and chitosan on drug release were studied, employing model drugs of different acidities. When the drug was basic, all chitosan spheres exhibited 100% release within 30 min. As the acidity of the drug increased, the release slowed down and depended on the crosslinking density and microsphere size. The release of weakly acidic drug was most suppressed for large spheres (35-38 microm), while the small spheres (23-25 microm) with higher crosslinking exhibited the most retention of highly acidic drug, indicating that they are a promising candidate for colon-specific delivery.     

不同交联剂含量对戊二醛交联壳聚糖膜结构与性 能影响的研究

仔细研究壳聚糖膜的结晶度、溶胀度及其对二价铜离子的吸附量与交联剂戊二醛含量(特别是在戊二醛含量较低时)的关系。结果发现膜的结晶度、溶胀度以及对铜离子的吸附量均在戊二醛摩尔分数为0.25%时达到极大值。结晶度的增大可归结于轻度交联能使壳聚糖分子链在成膜时排列更为有序;而溶胀度和对铜离子吸附量的增加则可认为是交联能使壳聚糖中原先被氢键作用所束缚的氨基获得了自由。     

Stable encapsulation of active enzyme by application of multilayer nanofilm coatings to alginate microspheres

In an effort to improve the stability for long-term biosensor use, layer-by-layer self-assembly was explored as a potential technique to provide a diffusion barrier to encapsulated glucose oxidase inside alginate microspheres (<5 microm), fabricated using an emulsification technique. The total loss of encapsulated enzyme was reduced to less than 25 and 15% with the application of single PAH/PSS and crosslinked PAH/PAA coatings, respectively, in comparison to at least a 45% loss observed with uncoated and PDDA/PSS-coated microspheres. Furthermore, it was found that enzyme within PAH/PSS- and crosslinked PAH/PAA-coated spheres retained more than 84 and 60% of initial activity, respectively, after three months, whereas uncoated and PDDA/PSS-coated microspheres retained less than 20%.     

Ionically crosslinked alginate/carboxymethyl chitin beads for oral delivery of protein drugs

Complex beads composed of alginate and carboxymethyl chitin (CMCT) were prepared by dropping aqueous alginate-CMCT into an iron(III) solution. The structure and morphology of the beads were characterized by IR spectroscopy and scanning electron microscopy (SEM). IR confirmed electrostatic interactions between iron(III) and the carboxyl groups of alginate as well as CMCT, and the binding model was suggested as a three-dimensional structure. SEM revealed that CMCT had a porous morphology while alginate and their complex beads had a core-layer structure. The swelling behavior, encapsulation efficiency, and release behavior of bovine serum albumin (BSA) from the beads at different pHs were investigated. The BSA encapsulation efficiency was fairly high (>90%). It was found that CMCT disintegrated at pH 1.2 and alginate eroded at pH 7.4 while the complex beads could effectively retain BSA in acid (>85%) and reduce the BSA release at pH 7.4. The results suggested that the iron(III)-alginate-CMCT bead could be a suitable polymeric carrier for site-specific protein drug delivery in the intestine.     

O-羧甲基黄原酸壳聚糖合成及应用研究

以壳聚糖(CS)为原料,先制备出O-羧甲基壳聚糖(OCMC),再和二硫化碳在碱性条件下合成O-羧甲基黄原酸壳聚糖(CXCS)。通过产物的含硫量对碱浓度、投料比和反应时间等因素进行了优化,采用固体13CNMR和SEM表征其结构。结果表明,合成CXCS的最佳条件为碱浓度10%,投料比1∶1,室温反应3h,产品的含硫量达10.22%。最后研究了CXCS对水溶液镉离子的吸附性能,结果表明CXCS具有优异的吸附性能,其最大吸附量可达288.5 mg/g,是壳聚糖吸附量的2.65倍。红外分析结果表明吸附主要依靠结构中的羧基和黄原酸基团。     

交联黄原酸壳聚糖对铅离子的吸附研究

以壳聚糖为原料,通过交联和黄原酸化反应制备出交联黄原酸壳聚糖,采用FT-IR和XRD表征了其结构,并探讨壳聚糖及交联黄原酸壳聚糖对Pb2+的吸附性能。研究了初始溶液pH值、温度以及吸附时间等因素对Pb2+吸附量的影响。结果表明,在Pb2+起始浓度0.01 M,起始溶液pH=5,室温25℃吸附2h条件下,壳聚糖和交联黄原酸壳聚糖对铅离子的吸附量分别为126.8 mg/g和238.9 mg/g,交联黄原酸壳聚糖吸附能力为壳聚糖的1.89倍。     

Preparation of magnetic chitosan microspheres and its applications in wastewater treatment

The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mechanisms have been discussed. Supported by the Key Natural Science Foundation of China (Grant No. 50633030)     

壳聚糖纳米微球对牛血清蛋白的包封和缓释效果研究

壳聚糖(chitosan,CS)是甲壳素脱乙酰化的产物,是由葡萄糖结构单元组成的直链多糖。CS作为一种带正电荷的天然多糖,本身具有无毒、无刺激性、无致敏性、无致突变的性质,降解产物为低分子壳寡糖和葡萄糖胺,具有良好的生物相容性和生物降解性[1-2]。CS本身具有的特性,引起了人们的     

Dialdehyde starch‐crosslinked chitosan films and their antimicrobial effects

For improved mechanical and water‐swelling properties of chitosan films, a series of transparent films were prepared with dialdehyde starch as a crosslinking agent. Fourier transform infrared and X‐ray analysis results demonstrated that the formation of Schiff's base disturbed the crystallization of chitosan. The mechanical properties and water‐swelling properties of the films were significantly improved. The best values of the tensile strength and breaking elongation were 113.1 MPa and 27.0%, respectively, when the dialdehyde starch content was 5%. All the crosslinked films still retained obvious antimicrobial effects toward S. aureus and E. coli, and they showed potential for biomedical applications. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 993–997, 2003     

Radiation grafting of ionically crosslinked alginate/chitosan beads with acrylic acid for lead sorption

Radiation-induced grafting of acrylic acid onto alginate/chitosan beads was performed in solution at a dose rate of 20.6 Gy/min of Co-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted and un-grafted beads was performed by FTIR spectroscopy and the swelling measurements at different pHs was studied. It is found that as the pH value increases the swelling degree increases up to pH 6 but with further increase in pH value the swelling decreases. Also, it is noticed that the grafting yield increased with increase the irradiation dose. Both un-grafted and grafted alginate/chitosan beads were examined as sorbents for the removal of Pb ions from aqueous solutions. The sorption behavior of the sorbents was examined through pH, and equilibrium measurements. Grafted alginate/chitosan beads presented higher sorption capacity for Pb ions than un-grafted beads.     

The cooperative binding behavior of sodium dodecyl sulfate to crosslinked chitosan films

The binding behavior of sodium dodecyl sulfate (SDS) to cationic chitosan, in the form of a swollen crosslinked film is described. Chitosan films were crosslinked with epichlorohydrin. Binding isotherms were determined potentiometrically. The binding isotherms of the crosslinked chitosan was compared to the binding isotherms of chitosan in free solution. As expected, a more highly cooperative binding phenomena is observed, than for cationic chitosan in free solution. The collapse of the gel occurs at a binding fraction greater than 0.6. The collapsed cationic chitosan/SDS complex is described. The presence of hydrophobic regions within the chitosan-SDS complex was demonstrated with the oleophilic dyes C.I. Disperse Yellow 23 and C.I. Solvent Green 3. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3755–3765, 1997     

Effect of anionic surfactant on alginate‐chitosan polyelectrolyte multilayer thickness

Alginate and chitosan are among the most common biopolyelectrolytes. Surfactants can be included in alginate and chitosan formulations in order to improve their physical and functional properties. In the present study, the effect of the anionic surfactant sodium dodecyl sulfate (SDS) on alginate‐chitosan polyelectrolyte multilayer (PEM) films is reported for the first time. Layer‐by‐layer deposition technique was employed to prepare the PEM samples and the samples were characterized by ellipsometry, X‐ray reflectivity, atomic force microscopy, and quartz crystal microbalance with dissipation. Incorporation of SDS into PEM formulations increased the film thickness and an increased adsorption behavior between alginate and chitosan layers are observed. Since the concentration of SDS was below its critical micelle concentration, no micelle formation was expected and hydrophobic‐hydrophobic interaction between alginate and SDS might be the main reason. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1798–1803     

Transport properties of chitosan membranes: Influence of crosslinking

A chitosan film with acetylation degree close to 2% was crosslinked with glutaraldehyde. The consequences of this chemical modification were studied on the polymer gas and water transport properties. The crystalline domains were not affected by the crosslinking reaction and the modification of the amorphous phase did not induce variation of the gas permeability at anhydrous state. A crosslinking of 5 h, leading to a theoretical amine conversion of 60% in the amorphous phase induced only small changes of the polymer water sorption capacity at relative pressures less than 0.5. The main modification of the transport properties induced by this treatment occurred at a relative pressure equal to one with a significant reduction of the water sorption and water permeation and with the impossibility to measure the gas permeability coefficient in these conditions due to the brittleness of the membrane. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1521–1529, 2000     

磁性壳聚糖微球的制备和应用

磁性壳聚糖微球是通过一定的方法用壳聚糖将磁性材料包埋而形成的磁性微球,其内核为纳米级的磁性金属微粒,外层为壳聚糖.壳聚糖含有大量的氨基和羟基,使其具有特定的理化性质,由此奠定了壳聚糖的许多生物学特性及加工特性的基础.另一方面,其磁性内核使磁性壳聚糖微球具有很好的顺磁性,利用外加磁场可以很方便地进行分离.因此磁性壳聚糖在固定化酶、污水处理、食品工业和生物医药等方面具有广泛的用途,磁性壳聚糖的制备及应用的相关研究也越来越受到重视.本文作者对磁性壳聚糖微球的制备和应用进行评述.     

Effect of method of preparation and process variables on controlled release of insoluble drug from chitosan microspheres

An inexpensive and simple method was adopted for the preparation of chitosan microspheres, crosslinked with glutaraldehyde (GA), for the controlled release of an insoluble drug‐ibuprofen, which is a commonly used NSAID (non‐steroidal anti‐inflammatory drug). The chitosan microspheres were prepared by different methods and varying the process conditions such as rate of stirring, concentration of crosslinking agent, and drug:polymer ratio in order to optimize these process variables on microsphere size, size distribution, degree of swelling, drug entrapment efficiency, and release rates. The absence of any chemical interaction between drug, polymer, and the crosslinking agent was confirmed by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analyses (TGA) techniques. The microspheres were characterized by optical microscopy, which indicated that the particles were in the size range of 30–200 µm and scanning electron microscopy (SEM) studies revealed a smooth surface and spherical shape of microspheres. The microsphere size/size distributions were increased with the decreased stirring rates as well as GA concentration in the suspension medium. Decreasing the concentration of crosslinker increased the swelling ratio whereas extended crosslinking exhibited lowered entrapment efficiency. The in vitro drug release was controlled and extended up to 10 hr. Copyright © 2007 John Wiley & Sons, Ltd.