Fabrication of chitosan microspheres for efficient adsorption of methyl orange

In this article, morphology, structure and size controllable chitosan microspheres with high mechanical strength were synthesized by microfluidic technology combining chemical crosslinking and used as an adsorbent for methyl orange. The synthesized adsorbents were characterized using scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR), and an Energy Dispersive Spectrometer(EDS). The effect of pH revealed that the adsorption process depended on pH and the pH variation of methyl orange solution after adsorption indicated that adsorption capacity was affected through the associated role of chitosan nature and pH variation. Experimental results suggested that the as-prepared chitosan microspheres were controlled within a narrow size distribution(coefficients of variation is 1.81%), whose adsorption capacity reached to 207 mg·g~(-1) and mechanical strength was suitable to resist forces. In addition, the adsorption isotherm was well fitted with the Langmuir model, and the adsorption kinetic was best described by the pseudo-second-order kinetic model.The high performance microfluidic-synthesized chitosan microspheres have promising potentials in the applications of removing dyes from wastewater.     

改性磁性壳聚糖微球的制备、表征及性能研究

以(NH4)2Fe(SO4)2.6H2O、NH4Fe(SO4)2.12H2O和壳聚糖为原料,经羟丙基化、胺基化,采用一步包埋法制备了一种新型的多胺基化磁性壳聚糖微球。通过正交实验法确定了磁性微球的最佳制备条件,即搅拌速度1200r/min,壳聚糖用量3.0g,环氧氯丙烷用量2.5mL,乙二胺用量2.5mL。并用IR、TG、XRD和SEM对其结构及形貌进行了表征。结果表明,Fe3O4磁性粒子已包埋了一层胺基化壳聚糖。磁性微球胺基含量为2.302mmol/g;呈较规则的球形,平均粒径为209nm,且具有顺磁性和良好的耐酸性。     

Composite magnetic chitosan microspheres: In situ preparation and characterization

A method for preparing magnetic crosslinked chitosan microparticles was developed. The chitosan (CS) encapsulated magnetic particles were produced in alkaline conditions by in situ oxidation of the ferrous ions initially dispersed uniformly within the polysaccharide matrix. The polymer was then crosslinked using glutaraldehyde (GLA). The products were characterized regarding their size distribution and surface charge (by laser diffraction analysis, ζ-potential measurement, and conductometric titration), morphology (TEM), and magnetic properties (magnetic susceptibility analysis). The fact that the particles contain both magnetic iron oxide and chitosan was confirmed by FTIR and thermogravimetric analysis. The synthesis parameters were optimized for obtaining stable magnetic microparticles bearing surface amino groups that can subsequently be used for heavy metal ion complexation. The composite particles obtained by the optimum procedure had an average diameter of 40 μm and a saturation magnetization of 24 emu/g, corresponding to about 47% magnetic iron oxide content.     

Synthesis and characterization of injectable chitosan cryogel microsphere scaffolds

Treatment of tissue defects involves invasive processes such as implanting the tissue engineered scaffold to the defected area. Injectable scaffolds are increasingly being developed to achieve tissue regeneration in a less invasive manner. In this study, injectable chitosan cryogels in the form of microspheres were synthesized combining the water in oil emulsification method with the crosslinking of microspheres during cryogelation. The effects of polymer ratio, crosslinker concentration, cryogelation temperature, and stirring speed on the resulting cryogels’ chemistry, pore morphology, microsphere size, swelling ratio, degree of crosslinking, and degradation rate were examined for a possible noninvasive tissue engineering application. Microspheres with optimized properties were developed with an average pore and particle size of 5.50?±?0.63 and 220.11?±?25.58?µm at a chitosan ratio of 1%, glutaraldehyde concentration of 3%, reaction temperature of ?16°C, and stirring rate of 1,000?rpm.     

Construction of pH-responsive drug delivery platform with calcium carbonate microspheres induced by chitosan gels

Construction of simple and convenient platforms for controlled delivery of anti-cancer drugs is of great importance for medical science and pharmaceutics. Here, chitosan (CS) gels were used to induce the growth of calcium carbonate (CaCO₃) microspheres, and the resulting CaCO₃ microspheres were well dispersed within the three-dimensional (3D) network framework of the CS gels. The synthesized CaCO₃/CS composites were then examined by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR) and X-ray diffractometry (XRD). Finally, the designed CaCO₃/CS composites were used for loading and controlled delivery of methotrexate (MTX), an anti-cancer drug. The encapsulation ratio of MTX calculated by UV–vis spectroscopy was approximately 78.8%. In addition, pH-responsive delivery of MTX from the CaCO₃/CS composites was successfully achieved due to the pH-sensitive property of CS, and the cumulative release of MTX could reach 93.3%, 86.6% and 77.6% at pH 8.5, 7.4 and 5.8, respectively.     

壳聚糖止血微球的制备优化及表征

以壳聚糖为原料,采用乳化交联技术制备壳聚糖止血微球。在单因素实验结果的基础上,采用响应面法优化壳聚糖止血微球的制备条件,通过体外凝血法对其止血活性进行评价。结果表明,最优制备工艺条件为:壳聚糖浓度1.4%,壳聚糖分子量600 k Da和戊二醛与壳聚糖质量比1∶1。在此条件下,微球平均溶胀率为346.56%,与理论预测相当吻合;止血微球具有良好的外观形貌,分散性好;红外分析表明,壳聚糖止血微球已经成功地进行了化学交联,具有稳定的空间结构;壳聚糖微球具有显著的促凝血活性,呈现剂量相关性。将为开发新型壳聚糖高效止血材料奠定基础。     

壳聚糖止血微球的制备优化及表征

以壳聚糖为原料,采用乳化交联技术制备壳聚糖止血微球。在单因素实验结果的基础上,采用响应面法优化壳聚糖止血微球的制备条件,通过体外凝血法对其止血活性进行评价。结果表明,最优制备工艺条件为:壳聚糖浓度1.4%,壳聚糖分子量600 k Da和戊二醛与壳聚糖质量比1∶1。在此条件下,微球平均溶胀率为346.56%,与理论预测相当吻合;止血微球具有良好的外观形貌,分散性好;红外分析表明,壳聚糖止血微球已经成功地进行了化学交联,具有稳定的空间结构;壳聚糖微球具有显著的促凝血活性,呈现剂量相关性。将为开发新型壳聚糖高效止血材料奠定基础。     

Preparation and characterization of inulin ester microspheres as drug carriers

Acetylated and succinoylated inulin were synthesized by reacting inulin with acetic anhydride and succinic anhydride. The modified inulin was characterized by FTIR, NMR, and potentiometric titration. The compositional dependence of their properties, such as solubility, pKa, and melting point, was investigated. The results reveal that the solubility of the inulin derivatives in pH 7.4 buffer solution increases with the succinyl content, varying from negligible for fully acetylated inulin to over 54% for fully succinoylated inulin, whereas the corresponding pKa of the inulin derivatives decreases with increasing succinyl content. In addition, the melting point is lowered by acetylation and/or succinoylation. The influence of pH and ionic strength on the solubility of inulin acetate succinate was also studied. The solubility increases dramatically as the pH value approaches that of the pKa. Interestingly, in pH 7.4 buffer solutions of varying ionic strength, a maximum solubility appears at an ionic strength of 0.15M. This is interpreted as a result of a balance of the ion exchange process and the double layer suppression. Microspheres of inulin acetate and inulin acetate succinate with and without drug were prepared by the solvent precipitation method. Cationic compounds, chlorhexidine and chymotripsin, were used as model drugs. The size and morphology of microspheres were determined by scanning electron microscope. The microspheres range in diameters from 0.5 to 4 μm for inulin acetate and inulin/chymotripsin microspheres, and from 90 to 130 μm for inulin acetate/chlorhexindine microspheres. The cross‐section of the microspheres exhibits a porous interior. Preliminary results show that the microspheres are able to release the incorporated drugs for an extended period of time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 833–840, 2000     

一种新型的硬模板法制备单分散壳聚糖中空微球

壳聚糖自发组装在未经修饰的模板聚苯乙烯微球表面,通过原位交联及模板移除,得到壳聚糖中空微球。采用扫描电子显微镜、透射电子显微镜和傅里叶变换红外光谱等手段对壳聚糖中空微球的结构和形貌进行表征。结果表明,在独特的热力学驱动力作用下,不须对模板微球进行任何的表面修饰,即可制得壳聚糖中空微球。另外,所得壳聚糖中空微球的形态可通过调整交联时间及醋酸溶液的浓度而得到改变。     

Synthesis and characterization of modified chitosan microspheres: Effect of the grafting ratio on the controlled release of nifedipine through microspheres

The grafting of acrylamide onto a chitosan backbone was carried out at three acrylamide concentrations (polymer/monomer ratio = 1:1, 1:2, and 1:3). The synthesis of the grafted polymer was achieved by K₂S₂O₈‐induced free‐radical polymerization. Microspheres of polyacrylamide‐g‐chitosan crosslinked with glutaraldehyde were prepared to encapsulate nifedipine (NFD), a calcium channel blocker and an antihypertensive drug. The microspheres of polyacrylamide‐g‐chitosan were produced by a water‐in‐oil emulsion technique with three different concentrations of glutaraldehyde as the crosslinking agent. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were used to characterize the grafted copolymers, and the microspheres were prepared from them. FTIR and DSC were also used to analyze the extent of crosslinking. The microspheres were characterized by the particle size; the water transport into these microspheres, as well as the equilibrium water uptake, were studied. Scanning electron microscopy confirmed the spherical nature of the particles, which had a mean particle size of 450 μm. Individual particle dynamic swelling experiments suggested that with an increase in crosslinking, the transport became case II. The release of NFD depended on the crosslinking of the network and on the amount of drug loading. Calculating the drug diffusion coefficients with the initial time and later time approximation method further supported this. The drug release in all 27 formulations followed case II transport, and this suggested that the time dependence of the NFD release followed zero‐order kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2940–2949, 2003     

Preparation and characterization of superparamagnetic chitosan microspheres: Application as a support for the immobilization of tyrosinase

Superparamagnetic chitosan microspheres were prepared by a water‐in‐oil suspension‐crosslinking technique. To this end, magnetite particles were dispersed in a chitosan solution in acetic acid. The dispersion was added to toluene containing Span 20 as a surfactant with stirring. Chitosan solution droplets were hardened with glutaraldehyde. The magnetic chitosan microspheres obtained were characterized with scanning electron microscopy, differential thermal analysis, and vibrational magnetometry. The microspheres had a wide size distribution, ranging from 43 ± 25 to 255 ± 55 μm, that depended on the reaction conditions. The mean particle size decreased with an increase in the concentration of Span 20 or the amount of glutaraldehyde and with the addition of NaCl. However, a major size reduction was achieved by an increase in the stirring rate. Tyrosinase was immobilized on the microspheres. The immobilized enzyme retained 70% of its activity, as determined by the capacity to degrade phenolic compounds. The immobilized tyrosinase resulted in greater stability than the free enzyme. In addition, the enzyme maintained 65% of its phenol oxidation activity after 10 cycles of reuse. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 651–657, 2005     

Cu(Ⅱ)螯合壳聚糖磁性微球的制备、表征及性能研究

以(NH4)2Fe(SO4)2.6H2O、NH4Fe(SO4)2.12H2O和壳聚糖为原料,经羟丙基化、Cu(Ⅱ)螯合,采用一步包埋法制备了一种Cu(Ⅱ)螯合壳聚糖磁性微球。通过正交实验法确定了磁性微球的最佳制备条件,即搅拌速度1 200 r/min,壳聚糖用量3.0 g,环氧氯丙烷用量1.0 mL,CuCl2.2H2O为0.010 mol。并用IR、TG、XRD和SEM对其结构及形貌进行了表征,结果表明,Fe3O4磁性粒子已包埋了一层Cu(Ⅱ)螯合壳聚糖,呈较规则的球形,平均粒径为240 nm,且具有顺磁性。     

水溶性壳聚糖及磁性壳聚糖微球的制备

以废弃蟹壳为原料制备出了高脱乙酰度壳聚糖和脱乙酰度50%的水溶性壳聚糖,通过电位滴定、红外光谱等对产物的脱乙酰度、功能基团作了表征,测定了产物的黏度,结果表明制备的水溶性壳聚糖的动力黏度为82.9 mPa.s。以0.01 mol/L硝酸钴和0.02 mol/L硝酸铁的混合溶液,采用微乳液法制备了纳米铁酸钴,以水溶性壳聚糖为原料制备了壳聚糖/纳米铁酸钴复合微球,TEM结果显示该磁性壳聚糖微球为规则球形,粒径13μm左右,分散性好。     

Synthesis and characterization of composite magnetic microspheres of artemisia seed gum and chitosan

In this study, composite magnetic microspheres of artemisia seed gum and chitosan were prepared in a well‐shaped spherical form with a size range of 230–460 μm by the suspension crosslinking technique for use in the application of magnetic carrier technology. The magnetic material used in the preparation of the composite microspheres was prepared by precipitation from FeCl₃ and FeSO₄ solution in basic medium. The morphological, magnetic properties, and the functional groups of the microspheres were characterized by different techniques (i.e., SEM, magnetometry, and FTIR). The results demonstrated that the stirring rate of the suspension and the Fe₃O₄/chitosan ratio are the most effective parameters for the average of the size distributions and the magnetic quality of the microspheres, while the amount of artemisia seed gum and Tween‐80 have no significant effect on these properties. The best magnetic quality of the composite magnetic microspheres is around 4.08 emu/g microspheres at 10 KG magnetic field intensity. The thermal stability of the composite magnetic microspheres was measured by using DSC methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3045–3049, 2007     

石蜡聚苯乙烯微球的制备Ⅲ.壁膜的选择及包覆研究

通过悬浮聚合技术合成了以聚苯乙烯为壁材、以石蜡为芯材的储能微球,研究了壁膜的选择及包覆程度。结果表明:聚苯乙烯很适合作为石蜡储能微球的壁膜,合成的石蜡聚苯乙烯微球包覆完整。     

石蜡聚苯乙烯微球的制备Ⅱ.分散剂及复合介质的影响

通过悬浮聚合法合成了石蜡聚苯乙烯微球,研究了合成过程中复合介质的配比和用量以及分散剂种类和用量对微球粒径及其分布的影响。结果表明:采用聚乙烯醇作分散剂,更有利于合成小粒径高产率的石蜡聚苯乙烯微球,悬浮聚合体系中水-乙醇复合介质的最佳体积配比和用量分别为1:2.5和150mL。     

亲水性高分子磁性微球的合成和应用研究

对近年来国内外有关亲水性高分子磁性微球的研究成果和发展现状进行了综述,具体讨论了包埋法、单体聚合法及原位法等常用的合成制备方法及其优缺点,指出反相(微)乳液聚合是制备亲水性聚合物微球的有效方法。分析了亲水性高分子磁性微球在酶固定化和实现靶向给药等方面的应用及存在的问题,对磁性微球的发展前景进行了展望。     

磁性壳聚糖微球的研究进展

磁性氧化铁纳米粒子（Fe3O4,γ-Fe2O3等）因具有尺寸小、超顺磁性和低毒性等特点,已经引起了生物化工、医药工业研究领域的广泛关注。磁性壳聚糖微球具有表面非常光滑的球形结构。近年来,已经制备出了平均粒径在10～2.5×105 nm之间的磁性壳聚糖微球,并在生物医药、食品工程和污水处理等许多领域已经取得了初步的应用,特别是在污水处理和酶固定化领域。本文综述了近年来磁性氧化铁纳米粒子和磁性壳聚糖微球的制备方法、磁性壳聚糖微球的改性方法及应用的最新研究成果。     

Magnetic polymer microspheres with azidocarbonyl groups: Synthesis,characterization and application in protein immobilization

A novel magnetic polymer microsphere with amide groups and carboxyl groups was synthesized and reported here. The azidocarbonyl groups were derived from amide groups and linked to the proteins to investigate their immobilization capacity. The morphology, size, functional groups and magnetic properties of magnetic microspheres were characterized by optical microscopy, particle size analyzer, atom force microscopy, magnetic force microscopy, fourier transform infrared spectrometer, vibrating‐sample magnetometer and thermal gravimetric analysis. The results indicated that the magnetic polymer microspheres had a well spherical shape with the size ranging from 1 to 10 μm, highly reactive functional groups, superparamagnetism and strong magnetic responsibility with saturation magnetization of 18.443 emu/g and Fe₃O₄ content around 21%. The immobilization capacity (η) was over 70%. The novel azidocarbonyl magnetic polymer microspheres showed potentials to be a good magnetic support and promising applications in bioseparation and biomedical fields. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009