Enzyme-catalyzed modification of PES surfaces: reduction in adsorption of BSA, dextrin and tannin

The effect of pH on the build-up of polyelectrolyte multilayers, PEMs, composed by poly-L-lysine and heparin onto two different substrates, silica and gold, has been studied by means of ellipsometry and quartz crystal microbalance with dissipation, QCM-D. Ellipsometry results indicate that the dry mass grows exponentially with the number of layers, and that this amount is larger as the pH values are raised. From QCM-D data the viscoelastic properties of the multilayered structure have been obtained. These data reflect that PEMs become more viscoelastic as the pH values are increased for silica substrates, while for gold the highest viscoelastic behavior is obtained at neutral pH and the elastic behavior becomes dominant as the pH is further increased or decreased. By combining these two surface techniques it has been also possible to determine the solvent content in the multilayers and reach a deeper understanding of the internal structure.     

硅基芯片表面化学性质对蛋白质固定化的影响

制备蛋白质芯片的关键在于将蛋白质固定到芯片表面并保持其生物学活性.本实验中,我们分别采用物理吸附、直接化学固定、加入间隔臂化学固定和生物亲和作用固定的方法将癌胚抗原(CEA)抗体固定到硅基芯片的二氧化硅表面.基于抗原-抗体的特异性相互作用,利用双抗体夹心酶联免疫法(ELISA)评价各种方法固定抗体的效果.实验结果表明,在修饰有氨基的表面采用戊二醛作为偶联试剂固定CEA抗体具有最高的偶联效率,引入多聚赖氨酸(poly-L-lysine)作为间隔臂可以显著增强固定效果,并可进一步降低非特异性吸附.而利用生物亲和作用固定CEA抗体也可获得较好的固定效果,但是非特异性吸附较严重.     

Electrochemical studies of chloroperoxidase on poly-L-lysine film modified GC electrode

<正>Poly-L-lysine(PLL) was first electrodeposited onto the surface of a glassy carbon(GC) electrode.The PLL modified electrode was used to immobilize chloroperoxidase(CPO) via 1-[(3-dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride(EDC).The electrochemical behaviors of immobilized CPO on PLL/GC electrode were investigated by cyclic voltammetry(CV).The CV results obtained showed that CPO was successfully immobilized on the PLL/GC electrode and a fast direct electron transfer between CPO and PLL-GC electrode was achieved with a formal redox potential of -0.23 V vs.SCE.The CPO-PLL/GC modified electrode showed a good catalytic activity for electrocatalytical reduction of O_2,promising for a broad range of CPO-catalyzed transformations.     

层-层自组装构建固相可降解基因传递体系的研究

近年来,随着人类对基因研究的深入,基因治疗作为一种新的手段,受到人们的广泛重视．在组织工程材料、介入医用材料和医用植入体的应用中,与传统的溶液给药方式不同,基因技术需要一种可直接作用于材料表面贴壁细胞的长效、高转染固相基因传递体系．目前,国内外研究者将蛋白质药     

一种基于二氧化硅微颗粒的基因载体的制备新方法

建立了一种基于二氧化硅微颗粒的基因载体的制备新方法. 首先将正硅酸乙酯在乙醇和氨水环境下水解， 合成得到二氧化硅微颗粒, 然后通过静电作用将多聚赖氨酸修饰到硅微颗粒上, 制备出可有效地结合DNA的基因载体. 所制备的基因载体可将绿色荧光蛋白表达载体pEGFP导入COS-7细胞中, 实现了绿色荧光蛋白的高效表达. 本方法简便、 快速, 在基因转染与基因治疗研究领域具有较好的潜在应用价值.     

Evaluation of Properties and Structural Transitions of Poly-L-lysine: Effects of pH and Temperature

Abstract

The structural response to temperature and pH changes of poly-l-lysine (PLL) has been studied by a variety of experimental methods including turbidimetry, dynamic light scattering, and Zeta potential analysis. The experimental results and the molecular dynamics simulations showed that the PLL structural transitions were a result of a competition between electrostatic repulsion, which promotes an extended state, and the hydrophobic effect, which favors a compact state. In fact, as the pH was decreased, the PLL conformation changed from α-helix to the random coil and the hydrophilic volume increases resulted in a transition to spherical micelles which then swelled due to charge-charge repulsions. Following a rise in temperature and/or at high pH, PLL undergoes the α-helix-to-β-sheet transition and reacted more rapidly to form hydrophobic aggregates.     

Mineralization and osteoblast behavior of multilayered films on TiO2 nanotube surfaces assembled by the layer-by-layer technique

In this paper, the multilayer films of poly-L-lysine (PLL) and DNA were created on TiO₂ nanotube surfaces using the layer-by-layer (LBL) self-assembly technique. Chemical compositions of the assembled multilayered films were investigated by X-ray photoelectron spectroscopy. Biological properties of the multilayered films were evaluated by the biomimetic mineralization and osteoblast cell culture experiments. The results indicated that PLL and DNA were successfully assembled onto TiO₂ nanotube surfaces by electrostatic attraction. Moreover, the samples of assembled PLL or/and DNA had better bioactivity in inducing HA formation and promoting osteoblast cells adhesion, proliferation and early differentiation.     

A facile route for shape-selective synthesis of silica nanostructures using poly-L-lysine as template

A facile method for the shape-selective synthesis of silica nanostructures using a reversemicroemulsion -mediated template(RMMT) technique is reported.In this method,positive poly-Llysine (PLL) is selected as template due to its configuration diversity.By adjusting pH and concentration, PLL demonstrates various secondary structures containing random coil,α-helix andβ-sheet,which result in the formation of silica nanorods,silica nanospheres and silica nanotubes in the reversemicroemulsion system,respectively.Thus,the shape-selective synthesis of silica nanostructures might be achieved by using PLL as structural template in the reverse-microemulsion system.     

POLY-L-LYSINE-GRAFT-PEG COMB-TYPE POLYCATION COPOLYMERS FOR GENE DELIVERY

ABSTRACT

Polycations have been used for gene delivery in vitro quite successfully, however, in vivo applications suffered from serum effects that lower the overall gene drug efficiency. PEG polymers have been used extensively to minimize serum effects and create “stealth liposomes”, biocompatible materials, and proteins with extended circulation. Here, we report our efforts towards creating “stealth polyplexes”. A comb-type polycation, poly-L-lysine-graft-PEG copolymers were successfully prepared by ring opening of PEG-epoxide with e-amino lysine groups of linear poly-L-lysine. The ratios of PEG-epoxide to poly-L-lysine, PEG-epoxide size (2K, 3K, and 5K), and poly-L-lysine size (10K, 26K, and 38K) were varied. Copolymers with as little as 2% grafted PEG chains sterically stabilized DNA/copolymer complexes (polyplexes) even at charge neutrality. These polyplexes, formed with copolymers with various size of PEG chains grafted on various lenghths of poly-L-lysine backbone, remained relatively small, approximately 100 nm in saline With higher degree of grafting, the binding was significantly diminished. In addition, the morphology of polyplexes changed from thoroidal to more elongated, worm-like forms. Some globular structures were detected in cases of a lower degree of grafting. Finally, DNA release form polyplexes when exposed to negatively charged macromolecules, poly-L-aspartic acid sodium salt, is very structure dependant. Enhanced levels of luciferase expression observed with PLL-PEG polyplexes versus either free DNA or PLL polyplexes are encouraging and warrant further optimization of the polymeric gene delivery system.     

光谱法研究聚赖氨酸与纤维蛋白原的相互作用

聚赖氨酸是一种重要的聚阳离子,在生物医药领域具有广泛的应用前景。但是,目前其血液相容性的相关报道较少,特别是通过光谱法研究其与血液中重要蛋白的相互作用。因此,通过多种光谱法研究聚赖氨酸与纤维蛋白原的相互作用,进一步评价其血液相容性具有一定的创新性。本实验通过荧光、紫外和圆二色谱研究聚赖氨酸对纤维蛋白原结构的影响。其中,聚赖氨酸的正电性随着浓度增大而增大;复合实验显示,0.01 mg·mL-1的聚赖氨酸对纤维蛋白原的功能影响较小,随着浓度增大,相互作用增强;荧光光谱显示,纤维蛋白原在λ_em=341 nm处出现浓度依赖性的荧光猝灭;紫外光谱显示,聚赖氨酸对纤维蛋白原吸收强度(200～240和278 nm处)的影响在0.025 mg·mL-1时较小,并出现浓度依赖性的减少;圆二色光谱显示,随着聚赖氨酸浓度增大,纤维蛋白原的α-螺旋含量减少,β-折叠、β-转角和无规卷曲含量增加。结果表明,聚赖氨酸会与纤维蛋白原发生静电相互作用,对其结构造成浓度依赖性的影响。当浓度为0.01和0.025 mg·mL-1时,聚赖氨酸对纤维蛋白原结构的影响较小;而浓度过大时,影响较大,势必破坏纤维蛋白原的生理功能。因此,研发和应用聚赖氨酸时必须充分考虑浓度因素。本实验提供了一种简便而系统的方法来研究材料与蛋白的作用,有利于充分评价材料的血液相容性。此外,上述研究结果对聚赖氨酸的生物医学应用具有重要的指导意义。