香草醛交联壳聚糖载药微球的性能及其成球机理分析

以壳聚糖溶液为水相、液体石蜡为油相形成油包水型乳液, 以香草醛为交联剂, 采用乳化交联法制得壳聚糖微球. 结合IR光谱和XRD测试, 分析了壳聚糖交联固化成球的机理: 壳聚糖和香草醛之间所发生的Schiff碱反应和氢键的形成以及缩醛化反应, 以此为基础共同形成交联结构从而使壳聚糖交联固化成球. 探讨了交联后壳聚糖微球结晶度降低的原因: 壳聚糖固化时分子链未充分进行有序的结晶排列, 交联后的壳聚糖结构较复杂, 从而破坏了原壳聚糖分子的规整性. 选用盐酸小檗碱为模型药物, 制备了香草醛交联的壳聚糖载药微球, SEM结果显示, 载药微球表面致密且球形度好, 微球粒径在5-15 μm之间. 此外, 采用分光光度计对载药微球的载药率、药物包封率和药物体外释放性质进行了测试和分析, 结果表明载药微球缓释效果明显.     

Surface fabrication of hollow microspheres from N-methylated chitosan cross-linked with glutaraldehyde

We have successfully prepared biocompatible and biodegradable hollow microspheres with sizes between 2 and 5 mum using cyclohexane droplets as a template and the N-methylated chitosan (NMC) cross-linked with glutaraldehyde (GA) as the shell. The structure, morphology, and formation process of the hollow microspheres were characterized by FT-IR, (1)H and (13)C NMR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed that the microspheres exhibited a very smooth and hollow structure. This work confirmed that the hollow microspheres were accomplished by fabricating on the basis of chemical cross-linking on the surface of the emulsion droplets and by removing cyclohexane as core. The results from SEM and TEM indicated that the emulsion droplets covered with cross-linked NMC in the oil-in-water system aggregated together to form a precipitate of microspheres by coagulating with acetone. Moreover, the cross-linked NMC on the surface of the microspheres continuously cured to form the tight shell, whereas the inner area became a cavity with increase of the aging time, leading to the hollow microspheres. In addition, an anti-infective drug, ofloxacin (Floxin), encapsulated in the microspheres more rapidly released to reach 90 wt % at pH 7.4 within 8 h than at pH 1.2.     

The influence of chitosan on in vitro properties of Eudragit RS microspheres

Eudragit RS microspheres containing chitosan hydrochloride were prepared by the solvent evaporation method using acetone/liquid paraffin solvent system and their properties were compared with Eudragit RS microspheres without chitosan, prepared in our previous study. Different stirring rates were applied (400-1200 rpm) and drug content, Higuchi dissolution rate constant, surface and structure characteristics of the microspheres were determined for each size fraction. An increase in average particle size with a reduction of stirring rate appeared in limited interval in both series. The average particle size of microspheres without chitosan, prepared at the same stirring rate, was smaller. Pipemidic acid content increased with increasing fraction particle size, but not with increasing stirring rate as it was observed for microspheres without chitosan. We presume that high pipemidic acid content in larger microspheres is a consequence of cumulation of undissolved pipemidic acid particles in larger droplets during microspheres preparation procedure. Pipemidic acid release was faster from microspheres with chitosan and no correlation between Higuchi dissolution rate constant and stirring rate or fraction particle size was found, though it existed in the system without chitosan. Structure and surface characteristics of microspheres observed by scanning electron microscope (SEM) were not changed significantly by incorporation of chitosan. But in contrast with microspheres without chitosan, the surface of chitosan microspheres was more porous after three hours of dissolution. It is supposed that the influence of particle size fraction and stirring rate on release characteristics is expressed to a great extent through porosity and indirectly through total effective surface area, but the incorporation of highly soluble component i.e. chitosan salt hides these effects on drug release. In conclusion, changes in biopharmaceutical properties due to varying stirring rate and fraction particle size exhibited the same direction as those reported for the microspheres without chitosan, although they are less expressed because of increased experimental variability, likely caused by chitosan.     

磁性壳聚糖微球的制备及对Cr(Ⅵ)的吸附性能研究

用壳聚糖包埋磁流体,用戊二醛交联制成磁性壳聚糖微球,并用红外光谱表征其结构。用制备的磁性壳聚糖微球吸附Cr(Ⅵ)离子,考察了其对Cr(Ⅵ)离子的吸附性能;探讨了吸附时间、溶液pH值、吸附剂用量、温度、Cr(Ⅵ)起始浓度以及其他离子存在对Cr(Ⅵ)离子去除率的影响。实验结果表明,磁性壳聚糖微球吸附Cr(Ⅵ)离子的最佳条件为:吸附平衡时间40 min,最佳吸附pH值6左右,磁性壳聚糖微球用量10 mg,温度升高有利于提高磁性壳聚糖微球的吸附效率,Cr(Ⅵ)离子起始质量浓度为12μg/mL,无机盐的存在引起磁性壳聚糖微球的吸附性能降低。并且考察了吸附剂的再生性能,实验结果表明磁性壳聚糖微球具有良好的重复使用性。     

Release characteristics of cisplatin chitosan microspheres and effect of containing chitin

To increase cisplatin (CDDP) content, to suppress burst effect during the initial phase of drug release, and to improve the capacity of the system for sustained release, we prepared various types of CDDP chitosan microspheres incorporating chitin and investigated the content of CDDP and its in vitro release kinetics from these microspheres. The results of this study showed that the CDDP content increased with increasing chitosan concentration and that the incorporation of chitin in the carrier matrix produced a more pronounced increase in drug content. The addition of chitin also led to inhibition of the initial burst effect. The rate of CDDP release reduced with increasing concentration of chitosan: that is, the 50% CDDP release time was about 0.5 h with the microspheres prepared with 1.0% of chitosan and about 4.5 h with those prepared with 5.0% of chitosan, indicating about nine-fold prolongation. The addition of chitin further resulted in retardation of the rate of CDDP release. Meanwhile, our chitosan microspheres were shown to undergo enzymatic degradation by lysozymes.     

淫羊藿苷壳聚糖/明胶微球的制备及其体外释放研究

本试验以壳聚糖、明胶为载药基质,以中药淫羊藿苷为模拟药物,通过乳化交联的方法制备淫羊藿苷/壳聚糖/明胶微球。考察微球的理化特性,建立持续流动释放系统,检测了微球的体外释放特性和影响因素。微球的理化特性受工艺条件如搅拌速度、乳化剂用量、交联剂用量等因素影响。微球的体外释放速率与微球的粒径、交联度负相关,与载药量正相关。试验结果表明,壳聚糖、明胶可作为缓释微球的载体基质,微球制备工艺简单稳定,微球的释放速率可控,淫羊藿苷/壳聚糖/明胶微球是一种良好的药物释放体系。     

Colon specific chitosan microspheres for chronotherapy of chronic stable angina

In the present work, chitosan microspheres with a mean diameter between 6.32 μm and 9.44 μm, were produced by emulsion cross-linking of chitosan, and tested for chronotherapy of chronic stable angina. Aiming at developing a suitable colon specific strategy, diltiazem hydrochloride (DTZ) was encapsulated in the microspheres, following Eudragit S-100 coating by solvent evaporation technique, exploiting the advantages of microbiological properties of chitosan and pH dependent solubility of Eudragit S-100. Different microsphere formulations were prepared varying the ratio DTZ:chitosan (1:2 to 1:10), stirring speed (1000-2000 rpm), and the concentration of emulsifier Span 80 (0.5-1.5% (w/v)). The effect of these variables on the particle size and encapsulation parameters (production yield (PY), loading capacity (LC), encapsulation efficiency (EE)) was evaluated to develop an optimized formulation. In vitro release study of non-coated chitosan microspheres in simulated gastrointestinal (GI) fluid exhibited a burst release pattern in the first hour, whereas Eudragit S-100 coating allowed producing systems of controlled release diffusion fitting to the Higuchi model, and thus suitable for colon-specific drug delivery. DSC analysis indicated that DTZ was dispersed within the microspheres matrix. Scanning electron microscopy revealed that the microspheres were spherical and had a smooth surface. Chitosan biodegradability was proven by the enhanced release rate of DTZ in presence of rat caecal contents.     

离子凝胶反应法制备壳聚糖/N,O-羧甲基壳聚糖微球

以一氯乙酸与壳聚糖反应形成N,O-羧甲基壳聚糖两性聚电解质,分光光度法测定其等电点IEP=2．86。以此两性聚电解质与壳聚糖可以在一定条件下形成微球,光学显微镜和电子显微镜测试表明,控制两种聚电解质配比可以制备不同粒径大小的微球,而超声功率对微球粒径的影响较小。红外光谱测试表明微球中N,O-羧甲基壳聚糖羧基以羧酸根形式存在,分光光度与电导法联合测定表明两种聚电解质以离子凝胶作用形成微球,其最佳制备条件为IEP（CM-CHITOSAN）〈pH〈pKa（CS）,在此较宽的pH值范围内微球可稳定存在。     

Influence of ultraviolet-irradiated oxygen on depolymerization of chitosan

In the present paper, the depolymerization of chitosan was carried out by the ultraviolet-irradiated oxygen treatment. Influence of reaction conditions on depolymerization of chitosan was investigated. The chemical structure of the depolymerized chitosan was characterized by FT-IR and ¹³C NMR spectra. The FT-IR and ¹³C NMR spectra suggested that there was no obvious modification of chemical structure of the depolymerized chitosan. The X-ray diffraction analysis showed that crystalline structure of chitosan can be destroyed by ultraviolet-irradiated oxygen. The use of depolymerization of chitosan by ultraviolet-irradiated oxygen treatment can be a convenient, timesaving, and cost-efficient method for replacing the expensive and time-consuming enzymatic or chemical methods that are currently used to depolymerize chitosan.     

Preparation and release characteristics of cisplatin albumin microspheres containing chitin and treated with chitosan

Cisplatin (CDDP) containing albumin microspheres and microcapsules incorporating biodegradable macromolecules, chitin and chitosan, were prepared, and their CDDP content and releasing ability and susceptibility to various enzymes were examined. Chitin was incorporated during preparation of the microspheres, while chitosan was used to treat preformed microspheres. CDDP content was remarkably increased by chitin; when chitin was incorporated at a concentration of 1.5%, the CDDP content of the microspheres was found to be 16.2% (1.8 times that with no addition of chitin). CDDP release was suppressed by chitin and chitosan. The 50% CDDP release time was about 1.5 h when no chitin was added, but about 16 h was required when chitin was incorporated into the microspheres at a concentration of 1.5%. Chitin and chitosan suppressed the decomposition by protease. The microspheres treated with 70% deacetylated chitosan showed the greatest susceptibility to lysozyme. In conclusion, CDDP release can be controlled by the use of chitin or chitosan, and the microspheres should show no immunogenicity in vivo because of their susceptibility to lysozyme.     

Preparation and Drug Release of PVA Composite Nanofibers Loaded Chitosan Microsphere

In this paper, we reported the fabrication of poly(vinyl alcohol)-chitosan (PVA-CS) microspheres composite nanofibers by electrospinning technique. The chitosan microspheres were firstly prepared by electrospray with the solution of chitosan and combretastatin A4. The morphology and size distribution of chitosan microspheres were analyzed by scanning electron microscopy. The influencing factors including the concentrations of both PVA and CS microspheres were studied. The physical properties of the composite nanofibers were characterized by X-ray diffraction (XRD). The drug release rate, MTT toxicity test, and cell culture were also investigated in detail. Results indicate that the chitosan microsphere-loaded composite nanofibers can be prepared when the PVA concentration is 120 mg/mL. The continuity of the nanofibers was influenced by the concentration of CS microspheres. The characteristic peaks of CS or PVA were not observed in the diffractograms after the CS and PVA were processed using the high-voltage electrostatic technique. In addition, the drug release rate showed that nanofibers induce an obvious slow-release effect. Composite nanofibers were non-toxic to fibroblasts cells, and the fibroblasts cells could proliferate on the nanofiber mat.     

Acetaminophen particle design using chitosan and a spray-drying technique

In this study matrices were prepared from particles of poorly water-soluble drugs such as acetaminophen (Act) to determine the drug release rate from these matrix particles. The matrix particles were prepared by incorporating drugs into chitosan powder (Cht, carrier) using a spray-drying method. The formation of composite particles was confirmed by scanning electron microscopic (SEM) analysis. The matrix particles prepared by spray-drying were spherical with a smooth surface. The crystallinity of acetaminophen in the composite particles was evaluated by powder X-ray diffraction and differential scanning calorimetry (DSC). The degree of crystallinity of acetaminophen in the matrix particles decreased with a reduction in the weight ratio of acetaminophen relative to the carrier. These results indicate that a solid dispersion of acetaminophen in chitosan forms matrix particles. The interaction between acetaminophen and chitosan was also investigated by FT-IR analysis. FT-IR spectroscopy of the acetaminophen solid dispersion suggested that the carbonyl group of acetaminophen and the amino group of chitosan formed a hydrogen bond. There were some differences at pH levels of 1.2 and 6.8 in the release of acetaminophen from the physical mixture compared to the matrix particles. At pH 1.2, the release from the matrix particles (Act : Cht=1 : 5) was more sustained than from the physical mixtures. The 70% release time, T70, of acetaminophen from the matrix particles (Act : Cht=1 : 5) increased in pH 1.2 fluid by about 9-fold and in pH 6.8 fluid by about 5-fold compared to crystalline acetaminophen. These results suggest that matrix particles prepared by spray-drying are useful as a sustained release preparation.     

Development and validation of an RP-HPLC method to quantitate acyclovir in cross-linked chitosan microspheres produced by spray drying

An accurate, simple, reproducible, and sensitive liquid chromatographic method is developed and validated to quantitate acyclovir (ACV) in cross-linked chitosan microspheres produced by spray drying. The analysis is carried out using a reversed-phase C18 column with UV-vis detection at 254 nm. The mobile phase is diluted with pure water and acetonitrile (95:5 v/v) at a flow-rate of 0.8 mL/min. The parameters used in the validation process are: linearity, range, quantitation limit, detection limit, accuracy, specificity precision, and ruggedness. The retention time of acyclovir is approximately 3.5 min with symmetrical peaks. The linearity in the range of 1-10 microg/mL presents a correlation coefficient of 0.9999. The chitosan and the tripolyphosphate in the formulation do not interfere with the analysis, and the recovery is quantitative. Results are satisfactory, and the method proves to be suitable to quantitate ACV in cross-linked chitosan microspheres.     

Chitosan Cross-Linked Films for Drug Delivery Application

This work evaluated such a cross-linked chitosan based controlled release device to be later used for sustained drug release. Cross linking was required to control chitosan swelling/deswelling rate. Hexamethylene 1,6-Bis (aminocarboxysulfonate), a bisulfite blocked diisocyanate obtained by the reaction of 1,6 Hexamethylene Diisocyanate and Sodium bisulfite, was used as cross linking agent. Two films formulations were tested: 30 and 50% cross-linked, and they were prepared by solvent evaporation technique. Chitosan cross-linked films were characterized for cross linkage by FTIR, for hydrophilicity by Contact Angle and for swelling behavior by Gravimetric method. Cross linking reaction was confirmed by FTIR. Moreover, cross linking increased the hydrophilic character of cross-linked films and suppressed swelling. However, 30% cross-linked film swollen less than the 50% one, while 50% cross-linked film swollen less than chitosan film itself. This behavior was attributed to the hydrophilic character of the cross linking agent and to the polymeric network formation by cross linking.     

壳聚糖微球负载的己二胺型聚酰胺-胺树状大分子的制备及对胆红素的吸附

通过反相悬浮反应制备了戊二醛交联的壳聚糖微球。以所制备的壳聚糖微球为载体,合成了己二胺型低代数聚酰胺-胺（Polyamidoamine,简称PAMAM）树枝状大分子（Genaration≤3）。考察了该微球在生理条件下对水溶液中胆红素的吸附行为,以及溶液的pH值,离子强度,温度,胆红素初始浓度,牛血清白蛋白等因素对吸附的影响。结果表明,吸附剂对胆红素具有良好的吸附性能,CS-G2.0,CS-G3.0,CS-G1.0,CS-G0和CS微球的平衡吸附率分别为94.61%,93.44%,92.97%,86.47%,52.38%,CS-G1.0-G3.0微球在0.5h吸附率已经超过70%,1h基本接近平衡,对胆红素的吸附量高达42.78mg/g。     

Vitamin A and vitamin E interaction behavior on chitosan microspheres

Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications due to its biocompatibility, high charge density, and non-toxicity. In this study, chitosan microspheres were successfully prepared by an adapted method of coagulation/dispersion. The degree of deacetylation of chitosan powder was obtained by NMR ¹H and FTIR techniques. Chitosan powder and chitosan microspheres were characterized by BET surface area and scanning electron microscopy (SEM). The interactions among the chitosan microspheres and the vitamins A and E were characterized by FTIR. In order to evaluate the ability of interaction of vitamin A and vitamin E with the chitosan microspheres, the thermodynamic parameters were followed by calorimetric titration. Different experimental approaches were applied, such as adsorption isotherms, kinetics and thermodynamics studies. The obtained results showed that the interactions of chitosan microspheres with the vitamins were spontaneous, enthalpically and entropically favorable, indicating that the chitosan microspheres can be used with success in the controlled release of these vitamins.     

A study of embolizing materials for chemo-embolization therapy of hepatocellular carcinoma: embolic effect of cisplatin albumin microspheres using chitin and chitosan in dogs, and changes of cisplatin content in blood and tissue.

Hepatic artery of dogs was embolized with cisplatin (CDDP) albumin microspheres containing chitin and chitosan to investigate the in vivo CDDP release kinetics from CDDP albumin microspheres, the CDDP cumulative characteristics in the liver, and the influence of microsphere administration on hepatic tissue. Results showed that changes in blood CDDP content were dependent on CDDP albumin microsphere type and that release kinetics were better sustained when chitin was added to the microspheres or when the microspheres were treated with chitosan. In particular, the administration of CDDP in the chitin-containing CDDP chitosan albumin microspheres showed a blood CDDP content of approximately 0.26 micrograms Pt/ml 14 d after administration. The administration of chitin-containing or chitosan treated CDDP microspheres showed a CDDP content in the hepatic tissue of 0.14 to 0.23 micrograms Pt/g 28 d after administration. They also showed better control of CDDP release than those without chitin or chitosan treatment. No CDDP influence on hepatic tissue was observed. We conclude that, even in vivo, chitin and chitosan are effective embolic materials.     

壳聚糖微球用于LHRH拮抗剂类似物缓释体系的研究

研究壳聚糖微球对促黄体生成激素释放激素（ＬＨＲＨ）拮抗剂类似物（ＴＸ４６）的吸附与释放，考察了影响吸附与释放的因素，得到了各种不同微球对ＴＸ４６的吸附与释放平衡曲线，为ＬＨＲＨ拮抗剂用于生育控制及其它临床应用提供了初步的实验依据。     

Effect of molecular weight and degree of deacetylation on controlled release of isoniazid from chitosan microspheres

Glutaraldehyde cross‐linked chitosan microspheres for controlled release of isoniazid were prepared using chitosan of different molecular weights (MWs) and degrees of deacetylation (DDAs). Chitosan microspheres were characterized for their size, hydrophobocity, degree of swelling and loading of isoniazid. Hydrophobicity of chitosan microspheres increased on increasing the degree of cross‐linking and MW of chitosan. Chitosan microspheres with high degree of deacetylation (DDA) (75 wt%), high MW chitosan (2227 kg mol^?1), and with 12 wt% concentration of glutaraldehyde showed optimum loading and release of isoniazid. The isoniazid from chitosan microspheres was released in two steps, i.e. burst (%R_B) and controlled (%R_C) steps. The microspheres with low MW chitosan (260 kg mol^?1) and low DDA (48 wt%) showed prominent burst release of isoniazid, but microspheres with high MW chitosan (2227 kg mol^?1) and high DDA (75 wt%) have released more isoniazid in a controlled manner (60 wt%) at 37°C in a solution of pH 5.0 ± 0.1. The burst step of drug release (%R_B) has followed first order kinetics, whereas controlled step of drug release (%R_C) followed zero order kinetics. The burst step of drug release was Fickian and controlled step was non‐Fickian in nature. The diffusion constant (D) for isoniazid release was influenced by the properties of chitosan and degree of cross‐linking. Copyright © 2007 John Wiley & Sons, Ltd.     

Uniform chitosan hollow microspheres prepared with the sulfonated polystyrene particles templates

Biodegradable chitosan hollow microspheres have been fabricated by employing uniform sulfonated polystyrene (PS) particles as templates. The chitosan was adsorbed onto the surface of the sulfonated polystyrene templates through the electrostatic interaction between the sulfonic acid groups on the templates and the amino groups on the chitosan. Subsequently, the adsorbed chitosan was crosslinked by adding glutaraldehyde. After the removal of the sulfonated polystyrene core, chitosan hollow microspheres were obtained. The longer the sulfonation time used, the smaller the size of the hollow particles and the thicker the chitosan wall obtained. Fourier transform infrared spectrometry was used to characterize the component of the microspheres. The morphologies of the PS templates and the chitosan microspheres were observed by transmission electron microscopy and scanning electron microscopy. The controlled release behavior of the chitosan hollow microspheres was also primarily investigated.