Comparison of Surface Tension Components and Hansen Solubility Parameters Theories. Part I: Explanation of Protein Adsorption on Polymers

Surface tension components and Hansen solubility parameters are two different theories used to explain and predict the compatibility and miscibility for polymer blends, composite polymer materials, and additives in polymer matrix. In this paper, the adsorption mechanism of bovine serum albumin (BSA) on eight polymers (PC, POM, PBT, PPO, PSF, PVDF, PEI, and PES) was researched through surface tension components and Hansen solubility parameters theories. The adsorption amounts of BSA on the polymers were measured through static adsorption experiments. It was found that the BSA adsorption amount cannot be directly correlated with the Hansen solubility parameters. However, there is high correlation between the Lifshitz-van der Waals component of surface tension of the polymers and BSA adsorption amount. With the increase in van der Waals value, the BSA adsorption amount on the polymers increases, but there still exists a complicated behavior. The protein adsorption mechanism is complex.     

Understanding the Interaction of Glutamate Salts with Serum Albumin Protected Prism‐Shaped Silver Nanoparticles toward Glutamate Sensing

Surface plasmon spectroscopy of serum albumin protected prism‐shaped silver nanoparticles is used as simple and effective sensing tool to detect glutamate salts. The approach does not require any electrochemical setup to detect glutamates, in contrast to common techniques to detect glutamates in general. Experiments reveal that upon presence of high concentrations of glutamate salts, the prism‐shaped nanoparticles are transformed to smaller‐sized nanoclusters, while the remaining nanoparticles are assembled to form aggregates. Control experiments confirm that the interaction is specific to the serum albumin coating, the prism shape of the nanoparticles, and to silver.     

氮吸附法测定纳米粒子的比表面积实验

在纳米粒子的性能表征中,比表面积是一个非常重要的参数。本文研究了用氮吸附法测定纳米粒子比表面积的实验方法。     

蛋白溶液浓度对动态光散射测量结果的影响

蛋白质在生命活动中起着重要作用,一直是人们研究的热点,动态光散射技术由于其快速、准确、对样品无损坏等优点,而成为研究蛋白质的重要手段之一。本文采用美国布鲁克海文公司提供的BI-200SM激光散射仪对浓度分别为0.1mg/mL、0.5mg/mL、1mg/mL、5mg/mL、10mg/mL的牛血清白蛋白溶液进行动态光散射测量,讨论了光强自相关曲线和粒径测量的相对误差随浓度的变化关系,研究了蛋白浓度对测量结果的影响。实验结果表明,在一定浓度范围内,光强自相关函数曲线的稳定性随浓度增加而增加,而自相关曲线的迟豫时间随着溶液浓度的增加而减小,粒径测量的相对误差也随着浓度的增加而逐渐减小。     

Complexation of bovine serum albumin and gold nanorods revealed by plasmon-enhanced light scattering spectroscopy

Complexation of bovine serum albumin (BSA) and gold nanorods has been investigated by plasmon-enhanced light scattering spectroscopy under external stimuli such as the changes in hydrogen ion concentration value and ionic strength, with addition of ethanol. The results indicated that the BSA chains tend to adopt a coil conformation by decreasing hydrogen ion concentration value. Scattering intensity of the gold nanorods–BSA system gradually decreases because BSA chains tend to adopt a coil conformation with addition of sodium chloride. This work will further extend the application range of this method due to its simplicity, rapidity, and sensitivity.     

The Competitive Dynamic Binding of Some Blood Proteins Adsorbed on Gold Nanoparticles

Nanoparticle (NP) surfaces are modified immediately by the adsorption of proteins when injected into human blood, leading to the formation of a protein corona. The protein‐coated NPs may be recognized by living cells. Furthermore, the adsorption of serum proteins is a continuous competitive dynamic process that is the key to exploring the bioapplication and biosafety of NPs. In this study, the competitive dynamic adsorption of some serum proteins on gold nanoparticles (AuNPs) is investigated by fluorescence emission, dynamic light scattering, and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Serum proteins with different AuNPs binding affinities are used to address the competitive dynamic process of protein‐AuNP interactions in vitro. The results show that more abundant serum proteins, such as human serum albumin, adsorb on AuNPs first, and then the higher binding affinity and lower concentration serum proteins, such as fibrinogen (FIB), replace the abundant and lower binding affinity serum proteins. However, the lower binding affinity serum proteins, such as hemoglobin, do not replace the higher binding affinity proteins from the protein‐AuNP conjugates. During the dynamic exchange process, the larger the binding affinities difference between two proteins, the faster the exchange rate. This dynamic exchange process usually takes longer in inner protein‐AuNP conjugates (hard corona) than the external surface of protein‐AuNP conjugates (soft corona).     

Determination of Conjugation Efficiency of Antibodies and Proteins to the Superparamagnetic Iron Oxide Nanoparticles by Capillary Electrophoresis with Laser-Induced Fluorescence Detection

The method based on capillary electrophoresis with laser-induced fluorescence detection (CE/LIF) was developed for determination of magnetic iron oxide nanoparticles (hydrodynamic diameters of 100 nm) functionalized with molecules containing primary amino groups. The magnetic nanoparticles with carboxylic or aminopropyl-trimethoxysilane groups at their surface were conjugated to the model proteins (bovine serum albumin, BSA; streptavidin or goat anti-rabbit immunoglobulin G, IgG) using carbodiimide as a zero-length cross-linker.The nanoparticle–protein conjugates (hydrodynamic diameter 163–194 nm) were derivatized with naphthalene-2,3-dicarboxaldehyde reagent and separated by CE/LIF with a helium–cadmium laser (excitation at 442 nm, emission at 488 nm). The separations were carried out by using a fused-silica capillary (effective length 48 cm, inner diameter 75 um) and 100 mM sodium borate buffer (pH 9.2), the potential was 30 kV. The detection limit for BSA-conjugate was 1.3 pg/10 nl, i.e. about 20 amol. The present method provides an efficient and fast tool for sensitive determination of the efficacy of biomolecular functionalization of magnetic nanoparticles. The CE/LIF technique requires only negligible sample volumes for analysis, which is especially suitable for controlling the process of preparation of functionalized nanoparticles with unique properties aimed to be used for diagnostic or therapeutic purposes.     

L-半胱氨酸修饰的金纳米粒子与牛血清白蛋白相互作用的荧光光谱研究

采用荧光猝灭光谱和同步荧光光谱研究了L-半胱氨酸修饰的金纳米粒子(Cys-GNPs)与牛血清白蛋白(BSA)间的相互作用。根据荧光猝灭相关方程计算了Cys-GNPs与BSA相互作用的结合常数和结合位点数,探讨了其荧光猝灭机制为静态猝灭,并且根据热力学参数确定了二者间的作用力类型,推断出Cys-GNPs和BSA间主要靠疏水作用力结合。同步荧光光谱表明,二者的相互作用没有导致牛血清白蛋白的构象及色氨酸残基的微环境发生明显变化。     

探针5-氨基水杨酸锌测定蛋白质的应用研究

在模拟人体生理条件下,基于5-氨基水杨酸锌(5-ASZ)与血清白蛋白相互作用生成复合物,导致血清白蛋白的内源荧光产生特异性变化,从而建立了以5-ASZ为荧光探针,用固定波长同步荧光光谱分析测定蛋白质(HSA)的新方法。同步荧光光谱特征及强度与Δλ值、反应介质、反应温度等因素有关。在最佳实验条件下,体系的同步荧光强度(I_SF)与人血清白蛋白在1.66～496.8 μg·mL-1 范围内呈良好的线性关系,检测限为0.88 μg·mL-1(n=11)。在此基础上对血清、尿样和唾液中的蛋白质进行了测定,加标回收率在98.0 %～103.8%之间。实验结果表明：该方法具有简单、快速、灵敏度较高、线性范围宽、精密度和回收率较好等优点。该法直接用于样品中蛋白质总量的测定,获得了令人满意的结果,有望用于生化分析和临床分析领域。     

Absorption of Iodine on the Surface of Silica Modified by Polyvinylpyrrolidone and Albumin

The influence of modification of a fumed silica by polyvinylpyrrolidone (PVP) and bovine serum albumin (BSA) on its ability to adsorb iodine has been investigated by UV spectroscopy. It has been established that the adsorption of iodine molecules on the silica surface is increased several times after its modification by high-molecular compounds. The role of structural factors in complexing of iodine with macromolecules has been estimated. Using PVP and BSA as an example, it is shown that the structure of a modifying layer on the silica surface depends on the nature and structure of the polymer.     

The impact of adsorption of bovine pancreatic trypsin inhibitor on CTAB‐protected gold nanoparticle arrays: a Raman spectroscopic comparison with solution denaturation

The influence of an array of cetyltrimethylammonium bromide (CTAB)‐protected gold nanoparticles on the structure of a model protein, bovine pancreatic trypsin inhibitor (BPTI) at pH 7.4, was studied by Raman spectroscopy. The structural consequences of array adsorption were compared with the effects of deposition of the protein directly onto a roughened gold substrate and with thermal and reductive treatment of BPTI in solution. Both thermal and reductive denaturation in solution result in loss of α‐helix structure, with an increase in random conformations of the protein in the case of reductive denaturation and β‐sheet conformation and random coil on thermal denaturation. For reductive denaturation in particular, extensive loss of secondary structure is evident. Deposition of the protein onto the array resulted in increased β‐sheet conformation similar to that observed on thermal treatment of the protein. However, unlike denaturation, which for both thermal and reductive process resulted in changes in the disulfide stretching wavenumber, this remains largely unchanged on application of the protein to the array. Furthermore, deposition of the protein onto bare gold results in significant heterogeneity in the S S stretching signal with appearance of ggt and nonequilibrium geometry of the CCSSCC dihedral angles. Thermal denaturation results in a red shift of the SS mode, whereas dithiothreitol (DTT) treatment, as expected, induces significant loss of the S S stretching signal, although a signal at 517 cm⁻¹ remains suggesting that the unreduced disulfide has changed to the ggt geometry. In addition, an SH mode is observed at 2570 cm⁻¹ in solution. The response of BPTI to thermal and DTT treatment while on the array is very different to its solution behavior, and suggests that adhesion to the array increases the stability of the protein. Copyright © 2009 John Wiley & Sons, Ltd.     

Structure and Stability of PEG‐ and Mixed PEG‐Layer‐Coated Nanoparticles at High Particle Concentrations Studied In Situ by Small‐Angle X‐Ray Scattering

Ligand‐layer structure and stability of gold nanoparticles (AuNP) coated with α‐methoxypoly(ethylene glycol)‐ω‐(11‐mercaptoundecanoate) (PEGMUA) layers and mixed layers of PEGMUA and 11‐mercaptoundecanoic acid (MUA) at high AuNP concentrations are studied in situ by small‐angle X‐ray scattering (SAXS). The thickness of the ligand layer is modified by the molecular weight of the PEG‐ligands (2 and 5 kDa), and the PEG‐grafting density is decreased by coadsorption of MUA. The response of the conjugates to a pressure of up to 4 kbar is probed. The results indicate strongly hydrated PEG layers at high grafting densities. The stability of the mixed ligand‐layer conjugates is lower. This is most probably due to enhanced interparticle PEG–PEG interactions at lower grafting densities. The presented study demonstrates that a detailed structural characterization of polymer ligand layers in situ and in response to external stimuli is possible with SAXS.