Microencapsulation of DNA Within alginate microspheres and crosslinked chitosan membranes for in vivo application

Calf thymus DNA was microencapsulated within crosslinked chitosan membranes, or immobilized within chitosan-coated alginate microspheres. Microcapsules were prepared by interfacial polymerization of chitosan, and alginate microspheres formed by emulsification/ internal gelation. Diameters ranged from 20 to 500 Μm, depending on the formulation conditions. Encapsulated DNA was quantifiedin situ by direct spectrophotometry (260 nm) and ethidium bromide fluorimetry, and compared to DNA measurements on the fractions following disruption and dissolution of the microspheres. Approximately 84% of the DNA was released upon core dissolution and membrane disruption, with 12% membrane bound. The yield of encapsulation was 96%. Leakage of DNA from intact microspheres/capsules was not observed. DNA microcapsules and microspheres were recovered intact from rat feces following gavage and gastrointestinal transit. Higher recoveries (60%) and reduced shrinkage during transit were obtained with the alginate microspheres. DNA was recovered and purified from the microcapsules and microspheres by chromatography and differential precipitation with ethanol. This is the first report of microcapsules or microspheres containing biologically active material (DNA) being passed through the gastrointestinal tract, with the potential for substantial recovery.     

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     

Molecular modeling study on surface,thermal, mechanical and gas diffusion properties of chitosan

The motivation of this work is to provide reliable and accurate modeling studies of the physical (surface, thermal, mechanical and gas diffusion) properties of chitosan (CS) polymer. Our computational efforts have been devoted to make a comparison of the structural bulk properties of CS with similar type of polymers such as chitin and cellulose through cohesive energy density, solubility parameter, hydrogen bonding, and free volume distribution calculations. Atomistic modeling on CS polymer using molecular mechanics (MM) and molecular dynamics (MD) simulations has been carried out in three dimensionally periodic and effective two dimensionally periodic condensed phases. From the equilibrated structures, surface energies were computed. The equilibrium structure of the films shows an interior region of mass density close to the value in the bulk state. Various components of energetic interactions have been examined in detail to acquire a better insight into the interactions between bulk structure and the film surface. MD simulation (NPT ensemble) has also been used to obtain polymer specific volume as a function of temperature. It is demonstrated that these V–T curves can be used to locate the volumetric glass transition temperature (T_g) reliably. The mechanical properties of CS have been obtained using the strain deformation method. Diffusion coefficients of O₂, N₂, and CO₂ gas molecules at 300 K in CS have been estimated. The calculated properties of CS are comparable with the experimental values reported in the literature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1260–1270, 2007     

The preparation of nano‐scope chitosan‐oligomer copper complexes and their interaction with DNA

Water‐soluble low molecular weight chitosan of nanometer level and its copper complexes were prepared, and characterized by IR spectra, elemental analysis and gel permeation chromatography (GPC). The modes and mechanism of these copper complexes interaction with DNA were studied by a fluorescent probe method and electrophoresis analysis. It is suggested that there are electrostatic and intercalation modes of copper complexes interacting with DNA. At first, the cationic complex electrostaticly binds to the negatively charged phosphate backbone of DNA, and then a portion of the complex intercalates between the base pairs on the DNA duplex strand. Copyright © 2005 John Wiley & Sons, Ltd.     

壳聚糖衍生物的制备及其吸附性能

壳聚糖衍生物的制备及其吸附性能曲荣君，马千里，郑秀丽，孙言志（烟台师范学院化学系烟台２６４０２５）关键词壳聚精衍生物，制备，吸附壳聚糖（ＣＴＳ）是重金瞩离子的吸附剂￣［１，２］，由于壳聚精分子中的－ＮＨ＿２在ｐＨ较低的水溶液易形成而使ＣＴＳ溶于水，造...     

锌试剂分光光度法测定壳聚糖含量

利用锌试剂与壳聚糖在一定酸度条件下的特异性显色反应，即其复合物在465nm处吸光度与壳聚糖含量在0～O．04g／L范围内呈现良好的线性关系(R=0．996)，基于此建立了一种简便快速的分光光度法。平均回收率为99．68％。     

金在脱乙酰壳多糖化学修饰电极上的电化学行为及分析应用

用脱乙酰壳多糖化学修饰电极为工作电极，阳极溶出伏安法测定痕量金。在ｐＨ１～２的ＫＣｌ－ＨＣｌ底液中，起始电位０．２０Ｖ，终止电位１．３０Ｖ，富集时间５ｍｉｎ，以０．１Ｖ／ｓ扫速阳极溶出，峰电位在１．００Ｖ（ｖｓ．ＳＣＥ），Ａｕ（Ⅲ）浓度在０．１０ｍｇ／Ｌ～１０ｍｇ／Ｌ范围内与峰高呈线性关系。在富集１０ｍｉｎ时，可检测０．０２５ｍｇ／ＬＡｕ，大大提高了测定灵敏度，用于矿样测定，无需分离，结果满意。用紫外光谱和拉曼光谱研究了该法的电极过程机理。     

Thermal and mechanical properties of UV irradiated collagen/chitosan thin films

The thermal and mechanical properties of collagen/chitosan blends before and after UV irradiation have been investigated using thermal analysis and mechanical (Instron) techniques. Comparisons were made with the thermal and mechanical properties of both collagen and chitosan films. Air-dried collagen, chitosan and collagen/chitosan films were exposed to UV irradiation (wavelength 254 nm) for different time intervals. Thermal properties of collagen/chitosan blends depend on the composition of the blend and are not significantly altered by UV irradiation.Mechanical properties such as ultimate tensile strength and ultimate percentage of elongation were much better for collagen films than for collagen/chitosan films. The results have shown that the mechanical properties of the blends were greatly affected by the duration of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the blend. Increasing UV irradiation leads to an increase in Young's modulus of the collagen/chitosan blend.     

The significance of complex polysaccharides in personal care formulations

Complex polysaccharides have numerous pharmacological activities, such as antioxidant, antibacterial, antiviral, immunomodulating, anticoagulant and anticancer effects. In personal care products, these biopolymers are used as thickener and stabilizing agents or as moisturizing ingredients that could be beneficial to the skin. Various polysaccharides, such as glycosaminoglycans (GAGs), hyaluronic acid (HA), carrageenan, fucose, fucoidan, chitin, chitosan, etc., have applications in cosmeceutical industries. GAGs and HA incorporated in moisturizing creams strengthen the skin barrier by forming a protective layer which prevents transdermal water loss. Therefore, these polysaccharides have been formulated into potential cosmeceuticals and biopharmaceuticals.     

Effect of drug-loading methods on drug load, encapsulation efficiency and release properties of alginate/poly-L-arginine/chitosan ternary complex microcapsules

The drug-loaded alginate/poly-L-arginine/chitosan ternary complex microcapsules were prepared by mixing method, absorption method and the combined method of mixing and absorption, respectively. The effect of drug-loading methods on drug load, the encapsulation efficiency and the release properties of the complex microcapsules were investigated. The results showed that the absorption process is a dominating factor to greatly increase the drug load of Hb into microcapsules. Upon loading Hb into microcapsules by combined method of mixing and absorption, the drug load (19.9%) is up to the maximum value, and the encapsulation efficiency is 93.8%. Moreover, the drug release is a zero-order kinetics process for the ternary complex microcapsules made by mixing. For the complex microcapsules made by absorption, the drug release is a first-order kinetics. However, for the complex microcapsules made by combining the mixing and the absorption, the drug release obeys a first-order kinetics during the first eighteen hours, changing afterwards to a zero-order kinetics process. Effect of drug-loading methods on drug load and encapsulation efficiency of alginate/poly-L-arginine/chitosan ternary complex microcapsules.