静电自组装碳纳米管/壳聚糖复合材料

采用化学氧化法制备了表面带负电荷的多壁碳纳米管水溶胶,通过静电作用力与带正电荷的壳聚糖自组装,制备出生物兼容性的碳纳米管/壳聚糖复合材料.通过调节pH值控制氧化碳纳米管和壳聚糖的Zeta势(表面电势),从而改变颗粒表面电荷类型和电势强弱,以及复合体系黏度发生的变化,使用NDJ-79旋转黏度计、红外光谱(FTIR)、高分辨透射电镜(HRTEM)和热重分析仪(TGA)对碳纳米管/壳聚糖复合材料进行表征,发现pH=5时碳纳米管/壳聚糖复合体系的黏度最低,表明碳纳米管与壳聚糖具有强的静电作用,得到性能稳定的碳纳米管/壳聚糖复合材料,厚度约4nm规整非晶薄层壳聚糖;热重分析表明复合材料中壳聚糖的质量分数达到40%.     

用于自组装小分子药物载体的合成与研究

以4-羟基扁桃酸为原料,2-(2-氨基乙氧基)乙醇为亲水基团,通过11步反应合成了以萘啶酮酸为药物分子,对青霉素酶敏感的苯乙酰基的有机小分子药物载体。目标化合物结构经1H NMR确证。     

层层自组装纤维素硫酸钠-壳聚糖复合膜

采用层层自组装技术,以具有良好生物相容性的多糖类物质——壳聚糖（chitosan）和纤维素硫酸钠（NaCS）为原料,制备了NaCS-chitosan复合膜。使用扫描电子显微镜观察复合膜形貌特征以表征自组装复合膜的形成,使用红外光谱分析了复合膜形成机理,使用紫外-可见光吸收研究了复合膜形成的动力学特征。同时还考察了各实验因素对NaCS-chitosan复合膜形成过程的影响。 结果表明,制备条件对复合膜形成过程有明显的影响,在现有的制备条件下,层层自组装复合膜的形成是一个一级反应过程。     

自组装肽基纳米材料运载药物和基因的研究进展

肽基分子自组装以其丰富的自组装驱动力、新颖的自组装体纳米结构、自组装体的特殊功能及良好的生物相容性等,在纳米生物材料、护肤和化妆产品、药物传输释放、组织工程支架材料等方面有着广泛的应用前景。由天然氨基酸组成的自组装短肽具有良好的低细胞毒性,可控的降解性能,高的运载效率及细胞摄取率,同时还具有降低药物的毒副作用等优点。因此,它在作为药物和基因的纳米载药材料方面有着巨大的发展前景。使用自组装肽基材料形成的纳米载体对疏水性抗癌药物、蛋白质药物及基因等进行传递释放已成为生物医药学领域的研究重点,因此,对近年来自组装肽基纳米材料作为药物和基因载体在生物医药学上的研究进展做了综述。     

靶向羧甲基壳聚糖-熊果酸纳米药物载体的制备及表征

将叶酸(FA)和氧-羧甲基壳聚糖(OCMCS)通过化学键连接制成叶酸-羧甲基壳聚糖聚合物,再偶联上熊果酸(UA)得到叶酸-羧甲基壳聚糖-熊果酸聚合物(FA-OCMCS-UA),并通过自组装包裹另一种抗癌药物10-羟基喜树碱(HCPT),形成叶酸-羧甲基壳聚糖-熊果酸/10-羟基喜树碱纳米药物粒子(FA-OCMCS-UA/HCPT)。采用1 HNMR和FT-IR对FA-OCMCS-UA进行结构表征;TEM观察FA-OCMCS-UA/HCPT NPs的形状。结果表明,1 HNMR和FT-IR证实了FA和UA成功偶联到OCMCS上。TEM显示FA-OCMCS-UA/HCPT纳米粒子呈球形,粒径为200～300nm。     

一种siRNA药物载体薄膜的稳定性与基因沉默效应评价

目的分析一种siRNA药物载体薄膜在溶液中的稳定性,并评价其基因沉默效应。方法利用层层自组装(layer-by-layer self-assembly,LBL)技术制备壳聚糖(chitosan,CHS)-透明质酸(hyaluronic acid,HA)-siRNA多层薄膜。通过UV-vis吸光度法对siRNA在薄膜上的生长过程以及在不同缓释液中的稳定性分别进行验证。结合荧光图像和流式细胞术,采用直接与细胞接触的方式检测该siRNA载体薄膜的HEK293T细胞转染效应。结果 CHS-HA-siRNA多层薄膜在260 nm处有很强的吸收峰,且随着含siRNA的组装层数的增加,在260 nm的吸光度值越大。该siRNA载体薄膜在1 mol/L NaCl溶液中释放效果最好,在pH 7.4的PBS缓冲液中次之,在纯水中稳定性最好。过低或过高的盐离子浓度对促进薄膜的崩解无优势。阳性对照组7-eGFP-siRNA和2-eGFP-siRNA具有较好的沉默绿色荧光蛋白基因的效应;在细胞培养2 d后的转染试验中,阳性对照组7-eGFP-siRNA较2-eGFP-siRNA组显示出更强的基因沉默效应。结论成功构建了一种非病毒siRNA递送载体系统,为未来实现siRNA局部给药开辟了一条可行的途径。     

作为基因载体的低分子量壳聚糖的制备及研究进展

低分子量壳聚糖作为非病毒性基因治疗载体有着广阔的前景,已成为研究的热点。综述了低分子量壳聚糖的制备方法以及载基因的研究进展,并讨论了影响转染的因素。     

O,O-双十二酰化壳聚糖自组装纳米药用泡囊

通过扫描电镜和原子力显微镜实验表明O,O–双十二酰化壳聚糖可形成一种新型的自组装纳米药用泡囊,其粒径主要分布在100～200nm。考察了3种不同酰化取代度的O,O–双十二酰化壳聚糖自组装泡囊的体外药物(维生素B12)释放行为。结果表明自组装泡囊的药物释放速率随酰化取代度的增大而降低。同时在自组装泡囊的制备过程中加入胆固醇,能引起自组装泡囊的药物释放速率增大。壳聚糖基材料的酰化取代度对自组装药用泡囊的载药量的影响较小,但对自组装药用泡囊的药物包封率有显著的影响。酰化取代度为1.3、1.4和1.7的三种O,O–双十二酰化壳聚糖自组装泡囊药物包封率分别为29.52%、31.55%和39.88%。     

壳聚糖/功能性自组装多肽复合支架的制备及神经再生研究

利用天然生物交联剂京尼平交联壳聚糖(CS)和功能性自组装多肽(F-SAP),经冷冻干燥制备了不同配比的CS/F-SAP复合支架;通过比较复合支架的微观形貌、孔隙率、力学性能和吸水率确定复合支架的最佳配比,并通过研究复合支架对神经干细胞分化的影响探究其对神经再生的作用。结果表明,CS/F-SAP复合支架具有多孔结构;20 mg·mL~(-1)的CS溶液与10 mg·mL~(-1)F-SAP溶液最佳体积比为1∶1,该条件下制备的CS/F-SAP复合支架能够促进神经干细胞向神经元方向分化,促进神经再生。     

叶酸偶联N-季铵化壳聚糖的制备及其基因载体性能

首先对壳聚糖进行季铵化改性合成N-季铵化壳聚糖（HTCC）,再接枝叶酸基团制备了叶酸偶联N-季铵化壳聚糖（FA-HTCC）,用FTIR和1H NMR等对产物进行表征,并对其作为基因载体进行研究。结果表明,合成产物具有较好的水溶性,N/P为4的FA-HTCC/DNA复合物粒径为188 nm、Zeta电位为15.4 mV。与PEI和阳离子脂质体相比,FA-HTCC具有更低的细胞毒性和更高的转染效率。     

壳聚糖复合纳米基因载体的制备

目的制备壳聚糖复合纳米基因载体,并探讨其理化性质、细胞毒性、稳定性及体外转染效率。方法采用复凝聚法制备包封聚乙烯亚胺(Polyethylenimine,PEI)/DNA复合物的壳聚糖复合纳米基因载体,用纳米粒度分析仪测定其粒径和Zeta电位;透射电镜观察其形态;MTT法检测其细胞毒性;在PBS溶液(pH 7.4)及含10%小牛血清的RPMI1640培养基中,于37℃条件下放置0、1、3、5 d,1%琼脂糖凝胶电泳检测其稳定性;体外转染CNE细胞,评价其转染活性。结果当N(PEI的氨基)/P(DNA的磷酸根)≥6时,能够形成稳定的壳聚糖复合纳米粒,平均粒径约为300 nm,表面电荷约为30 mV;壳聚糖复合纳米基因载体呈球形,圆整且分散性好;复合纳米基因载体的细胞毒性较低;1%琼脂糖凝胶电泳分析显示,DNA被完全包裹在复合纳米载体中,且5 d内无游离DNA释放;体外转染活性与壳聚糖/DNA复合物相比,提高了约1 000倍,且转染能力不受血清的干扰。结论制备的壳聚糖复合纳米基因载体是一种高效、低毒的非病毒载体,具有作为体内基因治疗载体的应用潜力。     

壳聚糖／水溶性高分子共混膜相容性的预测与表征

高分子（聚乙烯醇和聚乙二醇）间的相容性,壳聚糖与极性水溶性高分子在溶液状态时,分子间相互吸引,相容性好,向本体转化而成膜时,CS／PVA体系比CS／PEG体系有更好的本体相容性。原因可归结为PEG不能像PVA一样提供足够多的极性基团与壳聚糖分子形成强烈相互作用,CS与PEG间的氢键强度要弱于CS与PVA间的氢键;另一个方面,PEG结晶能力很强,在由溶液转化为本体而成膜过程中,PEG分子自身之间易于形成较规整的结晶而逐渐使体系发生分相。     

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.     

Self-assembly and Fractal Feature of Chitosan and Its Conjugate with Metal Ions: Cu (II)/Ag (I)

In this paper, we investigated the self-assembly and fractal feature of chitosan and Ag (I), Cu (II)-chitosan due to the theoretical and practical importance of chitosan in biomedical engineering, biomaterials and environmental sciences etc. The self-assembly and fractal structures of chitosan and Ag (I), Cu (II)-chitosan were observed using atomic force microscope (AFM), and the fractal dimensions of chitosan and Ag (I)-chitosan were calculated. The results indicate that their fractal dimension is approximate 2 and relates with the accumulation degree: the fractal dimension decreases with the accumulation degree increases. In addition, a new self-assembly strategy was presented to study the lyotropic liquid crystals (LLC) of chitosan and the formation mechanism of LLC was primarily analyzed and discussed. All of these results are valuable for the structure/function relationship study of chitosan and useful for application in biomedical materials.     

Construction of quantum-scale catalytic regions on anatase TiO2 nanoparticles by loading TiO2 quantum dots for the photocatalytic degradation of VOCs

We constructed quantum-scale catalytic regions on the surfaces of TiO₂ nanoparticles by loading TiO₂ quantum dots (QDs) with a two-step method. The removal rate and mineralization efficiency of toluene were measured and then used in evaluating the oxidation performance of the prepared samples. A home-built atmospheric surface photovoltage spectrometer and X-ray photoelectron spectrometer were used in analyzing band alignment across the interface between TiO₂ QD and TiO₂ particle and the transfer of charge carriers at the surface. Results showed that an upward band bending formed from the TiO₂ particle to the TiO₂ QD and promoted the accumulation of holes at the QD side. Moreover, the QD and surrounding substrate TiO₂ formed a quantum-scale catalytic region, improving the reaction probability of electron-hole pairs and corresponding intermediates. The mineralization efficiency of toluene in QD-loaded TiO₂ reached 95.8%. The synthetic method is green and simple, showing potential in scale production and industrial application.     

Interaction of water soluble chitosan with multiwalled carbon nanotubes

A water soluble chitosan derivative (p‐chitosan) was synthesized and used to functionalize multiwalled carbon nanotubes (MWCNTs) through the noncovalent interaction. The interaction of p‐chitosan with MWCNTs was investigated by analyzing the spectra of ultraviolet‐visible, Fourier transform infrared, Raman, and X‐ray photoelectron. Circular dichroism spectroscopy was used to study the interaction as well. The results of the circular dichroism spectra indicate that, the interaction of p‐chitosan with MWCNT makes p‐chitosan less regularly structured. It was found that the interaction of p‐chitosan with MWCNTs at a lower temperature is stronger than that at a higher temperature; pH conditions affect the interaction between p‐chitosan and MWCNTs. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

One-step colloidal synthesis of biocompatible water-soluble ZnS quantum dot/chitosan nanoconjugates

Quantum dots (QDs) are luminescent semiconductor nanocrystals with great prospective for use in biomedical and environmental applications. Nonetheless, eliminating the potential cytotoxicity of the QDs made with heavy metals is still a challenge facing the research community. Thus, the aim of this work was to develop a novel facile route for synthesising biocompatible QDs employing carbohydrate ligands in aqueous colloidal chemistry with optical properties tuned by pH. The synthesis of ZnS QDs capped by chitosan was performed using a single-step aqueous colloidal process at room temperature. The nanobioconjugates were extensively characterised by several techniques, and the results demonstrated that the average size of ZnS nanocrystals and their fluorescent properties were influenced by the pH during the synthesis. Hence, novel ''cadmium-free’ biofunctionalised systems based on ZnS QDs capped by chitosan were successfully developed exhibiting luminescent activity that may be used in a large number of possible applications, such as probes in biology, medicine and pharmacy.     

Immobilization of penicillin G acylase on a composite carrier with a biocompatible microenvironment of chitosan

BACKGROUND: Penicillin G acylase (PGA) has been used extensively in the β‐lactam antibiotics industry. As a biocatalyst, it is better to use immobilized enzymes than free enzymes, therefore, the immobilization of PGA on a composite carrier consisting of an adsorbent resin and biocompatible chitosan were investigated. RESULTS: First, FT‐IR, BET and SEM analysis confirmed the structure of the composite carrier. Then, the immobilization process was optimized. The activity of the immobilized PGA on the chitosan–resin (IP‐CsR) was about 1300 U (g dry carrier)^?1 with a protein loading of about 27 mg (g dry carrier)^?1. Compared with the immobilized PGA on unmodified resin (IP‐R), the specific activity of IP‐CsR was enhanced about 2‐fold. The operational, thermal and pH stability were investigated. IP‐CsR maintained more than 75% initial activity after 35 cycles, while IP‐R was active for only 10 cycles. The half‐life at 50 °C increased from 75 to 300 min and the most stable pH was changed from 8.0 to 5.5. CONCLUSION: A novel composite carrier containing a biocompatible chitosan was very effective for PGA immobilization. Copyright © 2008 Society of Chemical Industry     

In situ preparation of fluorescent CdTe quantum dots with small thiols and hyperbranched polymers as co-stabilizers

A new strategy for in situ preparation of highly fluorescent CdTe quantum dots (QDs) with 3-mercaptopropionic acid (MPA) and hyperbranched poly(amidoamine)s (HPAMAM) as co-stabilizers was proposed in this paper. MPA and HPAMAM were added in turn to coordinate Cd²⁺. After adding NaHTe and further microwave irradiation, fluorescent CdTe QDs stabilized by MPA and HPAMAM were obtained. Such a strategy avoids the aftertreatment of thiol-stabilized QDs in their bioapplication and provides an opportunity for direct biomedical use of QDs due to the existence of biocompatible HPAMAM. The resulting CdTe QDs combine the mechanical, biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs together.     

Subwavelength Fabry-Perot resonator: a pair of quantum dots incorporated with gold nanorod

The two apexes of an elongated gold nanorod (GNR) irradiated by a plane wave are shown to be the hotspots at the longitudinal plasmon modes. This phenomenon implies that a pair of quantum dots (QDs) located at these apexes might be excited simultaneously if the excitation band of QDs coincides with one of these modes. Consequently, a coherent emission of the two emitters could happen subsequently. In the following coherent emission, these two-level emitters are simulated as two oscillating dipoles (bi-dipole) with some possible phase differences. Our results show that the maximum radiative and nonradiative powers of the bi-dipole occur at the longitudinal plasmon dipole, quadrupole, sextupole, and octupole modes of GNR. Moreover, the strongest emissions are induced by the in-phase bi-dipole coupled to the odd modes and the 180° out-of-phase one to the even modes, respectively. The excitation and emission behaviors of a pair of QDs incorporated with GNR demonstrate the possibility of using this structure as a subwavelength resonator of Fabry-Perot type. In addition, the correlation between these modes of the GNR and the dispersion relation of gold nanowire is also discussed.