Protein imprinting and recognition via forming nanofilms on microbeads surfaces in aqueous media

In this paler, we present a technique of forming nanofilms of poly-3-aminophenylboronic acid (pAPBA) on the surfaces of polystyrene (PS) microbeads for proteins (papain and trypsin) in aqueous. Papain was chosen as a model to study the feasibility of the technique and trypsin as an extension. Obtained core-shell microbeads were characterized using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and BET methods. The results show that pAPBA formed nanofilms (60-100 nm in thickness) on the surfaces of PS microbeads. The specific surface area of the papain-imprinted beads was about 180 m² g⁻¹ and its pore size was 31 nm. These imprinted microbeads exhibit high recognition specificity and fast mass transfer kinetics. The specificity of these imprinted beads mainly originates from the spatial effect of imprinted sites. Because the protein-imprinted sites were located at, or close to, the surface, the imprinted beads have good site accessibility toward the template molecules. The facility of the imprinting protocol and the high recognition properties of imprinted microbeads make the approach an attractive solution to problems in the field of biotechnology.     

Protein imprinted polymer using acryloyl-β-cyclodextrin and acrylamide as monomers

A novel protein imprinted polymer was prepared using acryloyl-β-cyclodextrin (β-CD) and acrylamide as monomers on the surface of silica gel. The bovine hemoglobin was used as template and β-CD was allowed to self-assemble with the template protein through hydrogen bonding and hydrophobic interaction. Polymerization was carried out in the presence of acrylamide as an assistant monomer, which resulted in a novel protein imprinted polymer. After removing the template, imprinted cavities with the shape and spatial distribution of functional groups were formed. Bovine serum albumin (BSA) cytochrome c (Cyt) and lysozyme (Lyz) were employed as non-template proteins to test the imprinting effect and the specific binding of bovine hemoglobin to the polymer. The results of the adsorption experiments indicated that such protein imprinted polymer, which was synthesized with β-CD and acrylamide as monomers, could selectively recognize the template protein.     

Molecular imprinting and adsorption of metallothionein on nanocrystalline titania membranes

Metallothionein (MT) imprinted TiO₂ membrane was synthesized via surface sol-gel process, using MT as template and TiO₂ sol as imprinted matrix. Appropriate template cavities in the TiO₂ sol-gel membrane were formed after the template molecules were removed on treatment with 1% NaOH solution. In situ technique of quartz crystal microbalance (QCM) was employed to study the molecular imprinting behavior of MT on nanocrystalline titania membranes. The imprinted membrane showed selectivity recognition for MT as compared to the other proteins. The amount of adsorption increased with the increasing of MT concentration both on imprinted membrane and non-imprinted membrane. The adsorption amount increased with the increasing of pH on imprinted membrane.     

Synthesis, characterization and evaluation of uniformly sized core–shell imprinted microspheres for the separation trans-resveratrol from giant knotweed

A novel core–shell molecularly imprinting microspheres (MIMs) with trans-resveratrol as the template molecule; acrylamide (AA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker, was prepared based on SiO₂ microspheres with surface imprinting technique. These core–shell trans-resveratrol imprinted microspheres were characterized by infrared spectra (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and high performance liquid chromatography (HPLC). The results showed that these core–shell imprinted microspheres, which take on perfect spherical shape with average shell thickness of 150 nm, exhibit especially selective recognition for trans-resveratrol. These imprinted microspheres were applied as solid-phase extraction materials for selective extraction of trans-resveratrol from giant knotweed extracting solution successfully.     

Development of New Molecular Imprinted Solid Phase Extraction Material for Dimethoate

In this study, we have proposed a novel organophosphate mimic surface molecular imprinted polymer for selective binding of the nerve agent by chitosan–Cd(II) as a new metal-chelating monomer via metal coordination–chelation interactions and dimethoate templates. We have improved a method for the selective binding behavior of dimethoate compounds on the surface of molecular imprinted polymer, which was prepared using ligand-exchange (chitosan–Cd(II)) monomers. The influence of ligand exchange imprinting on the creation of recognition sites toward dimethoate has determined application of adsorption isotherms. The effect of initial concentration of dimethoate, adsorption time, and imprinting efficiency on the adsorption selectivity for molecular imprinted polymer-ligand exchange has been investigated. The number of accessible sites (Qmax), relative selectivity coefficients (k′), and binding abilities have also been evaluated. Then, molecular imprinted polymer-ligand exchange was treated with formaldehyde to remove dimethoate templates.     

Synthesis and Adsorption Study of BSA Surface Imprinted Polymer on CdS Quantum Dots

开发了CdS量子点用于牛血清白蛋白(BSA)表面压印的方法,将CdS量子点掺杂进BSA的分子压印聚合物中. 实验过程中对制备条件和吸附条件进行了优化. 量子点(QDs)和量子点分子压印聚合物(QDs-MIP)的形貌用扫描电子显微镜进行了表征. 当该QDs-MIP重新结合模板分子BSA时,CdS量子点的荧光被淬灭. 荧光淬灭的原因可能是量子点与模板蛋白质分子之间的荧光共振能量转移. 该聚合物对压印分子的吸附为单分子层吸附,符合Langmuir等温吸附模型. 化学吸附为速率控制步骤. 该新型聚合物的最大吸附容量可达226.0 mg/g,比未掺杂量子点的BSA压印聚合物提高142.4 mg/g.     

Synthesis and characterization of ZnO-Ag core-shell nanocomposites with uniform thin silver layers

This paper presents an investigation on the synthesis and characterization of ZnO-Ag core-shell nanocomposites. ZnO nanorods were employed as core material for Ag seeds, and subsequent nucleation and growth of reduced Ag by formaldehyde formed the ZnO-Ag core-shell nanocomposites. The ZnO-Ag nanocomposites were annealed at different temperature to improve the crystallinity and binding strength of Ag nanoparticles. The morphology, microstructure and optical properties of the ZnO-Ag core-shell nanocomposites were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible (UV-vis) absorption and photoluminescence measurement. It was demonstrated that very small face-center-cubic Ag nanoparticles were coated on the surface of ZnO nanorods. The ultraviolet absorption and surface plasmon absorption band of ZnO-Ag core-shell nanocomposites exhibited some redshifts relative to pure ZnO nanorods and monometallic Ag nanoparticles. The coating of Ag nanocrystals onto the ZnO nanorods completely quenched the photoluminescence. These observations reflected the strong interfacial interaction between ZnO nanorods and Ag nanoparticles. The effect of Ag coating thickness on the morphology and optical properties of ZnO-Ag core-shell nanocomposites was also investigated. Moreover, the growth mechanism of ZnO-Ag core-shell nanocomposites was also proposed and discussed in detail.     

Fabrication of bovine serum albumin nanotubes through template-assisted layer by layer assembly

One-dimensional protein nanostructures have many potential applications in the biomedical field. In this article, protein nanotubes have been fabricated via sequential filtration of bovine serum albumin (BSA) solution at pH 3.8 and 7.0 through the nanochannels of anodic aluminum oxide templates. The morphology of the nanostructures has been examined using scanning electron microscopy and transmission electron microscopy. Circular dichroism and UV/Vis spectroscopy have been used to select experimental conditions such as the pH values and the etching solution to release the fabricated protein nanotubes to minimize potential damage to the bioactivity of BSA. These results indicate that much more study needs to be done to strengthen the mechanical stability of the protein nanotubes and to better control their morphology.     

Chemical nature of phytic acid conversion coating on AZ61 magnesium alloy

Phytic acid (PA) conversion coating on AZ61 magnesium alloy was prepared by the method of deposition. The influences of pH, time and PA concentration on the formation process, microstructure and properties of the conversion coating were investigated. Scanning electron microscopy (SEM) was used to observe the microstructure. The chemical nature of conversion coating was investigated by energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) techniques. The corrosion resistance was examined by means of potentiodynamic polarization method. The adhesive ability was tested by score experiments. The results showed that the growth and microstructure of the conversion coatings were all obviously affected by pH, time and PA concentration. In 0.5 mg/ml PA solution with a pH of 5, an optimization conversion coating formed after 20 min immersion time by deposition of PA on AZ61 magnesium alloy surface through chelating with Al³⁺. It made the corrosion potential E_corr of sample shifted positively about 171 mV than that of the untreated sample, and the adhesive ability reached to Grade 1 (in accordance with GB/T 9286).     

A facile method to prepare monodispersed ZnO–Ag core-shell microspheres

Monodispersed and core-shell structured ZnO–Ag microspheres were realized by coating the Ag nanoparticles onto the surface of ZnO microspheres via a novel solution method. The obtained materials were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption measurement. It was shown that face-center-cubic Ag nanoparticles with the mean size of 20 nm were successfully grown on the surface of ZnO microspheres. The absorption band of ZnO–Ag core-shell microspheres showed a large redshift comparing to pure Ag nanoparticles, indicating the strong interfacial interaction between ZnO and Ag. The effects of Ag coating thickness on the structure, morphology and optical absorption of ZnO–Ag core-shell microspheres were investigated. The discussion on the growth process of ZnO–Ag core-shell microspheres revealed the important role of Sn²⁺. This approach was simple, mild and readily scaled up, affording a simple method for the synthesis of size-tunable inorganic-metal core-shell nanostructures.     

Preparation, characterization and infrared emissivity study of helical polyurethane@SiO2 core-shell composite

Helical polyurethane@SiO₂ (HPU@SiO₂) core-shell composite was prepared after surface modification of SiO₂ nanoparticles. HPU@SiO₂ was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified SiO₂. HPU@SiO₂ composite exhibits clearly core-shell structure. The ultraviolet absorption and crystallizability of HPU@SiO₂ are changed due to the shell of helical polyurethane, which possesses regular single-handed conformation and inter-chain hydrogen bonds. The infrared emissivity of HPU@SiO₂ was also investigated. The result indicates that the interfacial interactions between organic shell and inorganic core induce the infrared emissivity value being reduced from 0.781 for SiO₂ to 0.503 for HPU@SiO₂.     

SiO_2/Ag核壳结构纳米粒子的制备及其表面荧光增强

以罗丹明B掺杂的SiO2球为核,通过化学还原的方法制备了二氧化硅/银核壳结构复合纳米粒子。采用透射电镜(TEM)、紫外-可见-近红外(UV-Vis-NIR)分光光度计和荧光分光光度计对二氧化硅/银核壳结构纳米粒子的表面形貌、表面等离子共振和表面荧光增强特性进行了研究和表征。结果表明,二氧化硅/银核壳结构纳米粒子的表面等离子共振峰具有明显的可调谐性,且其表面荧光增强强烈依赖于银壳层的表面等离子共振,随银壳层厚度的增大而增强。     

Response of hydrogen bonding to low-intensity 50 Hz electromagnetic field in typical proteins in bi-distilled water solution

Samples of hemoglobin and bovine serum albumin in different bi-distilled water solutions were exposed to a 50?Hz electromagnetic field at the intensity of 1?mT to investigate the response of hydrogen bonding to the applied field after exposure of 3?h by means of Fourier Transform Infrared spectroscopy. Spectral analysis evidenced a significant decrease in the absorbance signal of the Amide I vibration in exposed samples of hemoglobin and bovine serum albumin water solutions. In addition, Fourier self-deconvolution analysis and min-max normalization applied in the mid-infrared region to exposed and unexposed hemoglobin samples revealed a significant increase in the absorbance signal of the Amide II band and an up-shift toward the high energies of 1.5?cm^?1 after exposure. Similar findings were observed after exposure of bovine serum albumin. These results can be easily explained assuming that hydrogen bonding in the secondary structure of these proteins in bi-distilled water solutions was enhanced after exposure to 50?Hz electromagnetic field.     

Thin layers of bovine serum albumin by matrix assisted pulsed laser evaporation

Thin films of bovine serum albumin were prepared by cryogenic matrix assisted pulsed laser evaporation technique under various deposition conditions. Energy density of laser beam changed in the range 0.1-0.5 J cm⁻². Films were deposited in vacuum or in nitrogen ambient. Targets were prepared from bovine serum albumin solution in phosphate buffered physiological saline and with an addition of UV absorbers as dimethylsulphoxide, phthalic acid, or adenine. Polyethylene and silicon (1 1 1) were used as substrates. Film properties were studied with atomic force microscopy and Fourier transform infrared spectroscopy attenuated total reflection. The deposition changed native conformation of albumin, resulting in the formation of water-insoluble aggregates. Addition of laser light absorbers in target solutions did not prevent the damage of albumin structure.     

Hydrogenated diamond-like carbon film deposited on UHMWPE by RF-PECVD

In this work, investigations were conducted to analyze the properties of diamond-like carbon (DLC) film deposited on ultra-high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) at a low temperature of 50 °C. Composition and structure of the films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Hardness and wettability of the film were tested. Tribological characterizations were carried out on a universal micro-tribometer, and reciprocating friction against ZrO₂ ball was adopted with 25% bovine serum as lubrication. Results show that DLC film was successfully deposited on UHMWPE surface by RF-PECVD and the sp³ content was about 20% in the film. The film increased the macrohardness of the substrate by about 42% and the wettability was improved too. Tribology test showed a higher friction coefficient but a much smaller wear volume after the deposition due to the surface roughening and strengthening.     

Protein adsorption and biomimetic mineralization behaviors of PLL-DNA multilayered films assembled onto titanium

Titanium and its alloys are frequently used as surgical implants in load bearing situations, such as hip prostheses and dental implants, owing to their biocompatibility, mechanical and physical properties. In this paper, a layer-by-layer (LBL) self-assembly technique, based on the polyelectrolyte-mediated electrostatic adsorption of poly-l-lysine (PLL) and DNA, was used to the formation of multilayer on titanium surfaces. Then bovine serum albumin (BSA) adsorption and biomimetic mineralization of modified surfaces were studied. The chemical composition and wettability of assembled substrates were investigated by X-ray photoelectron spectroscopy (XPS), fluorescence microscopy and water contact angle measurement, respectively. The XPS analysis indicated that the layers were assembled successfully through electrostatic attractions. The measurement with ultraviolet (UV) spectrophotometer revealed that the LBL films enhanced ability of BSA adsorption onto titanium. The adsorption quantity of BSA on the surface terminated with PLL was higher than that of the surface terminated with DNA, and the samples of TiOH/P/D/P absorbed BSA most. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that samples of assembled PLL or/and DNA had better bioactivity in inducing HA formation. Thus the assembling of PLL and DNA onto the surface of titanium in turn via a layer-by-layer self-assembly technology can improve the bioactivity of titanium.     

胶体金核壳型沙丁胺醇分子印迹聚合物的光谱特征分析

为了解决饲料和动物产品中沙丁胺醇残留现场快速检测的难题,开发以分子印迹技术为基础的快速检测沙丁胺醇的新方法,使用沙丁胺醇做为模板分子,甲基丙烯酸(methacrylic acid, MA)作为功能单体,以本体聚合法为基础合成常规SAL分子印迹聚合物（molecularly imprinted polymer,MIPs）和非分子印迹聚合物（non imprinted polymer NIPs）。在此基础上,以胶体金粒子为引发核,制备出新型的核壳型沙丁胺醇MIPs。应用紫外吸收光谱(UV spectra)、傅里叶红外光谱(IR spectra)和拉曼光谱（Raman spectru）、扫描电镜（scanning electron microscopy,SEM）等技术手段获得两种印迹物及各种相关化合物的光谱图、电镜图等表征图像。由实验结果可知,SAL和MA上的羧基形成稳定又容易洗脱的1∶1型氢键配合物,化学结合常数K=-0.245×106 L2·mol-2。与MA的—COOH中氢原子形成氢键的可能结合位点是SALCO中的氧原子。MIPs与MA中—OH的吸收峰比较可知,前者明显红移; 证明SAL作为模板分子与MA之间发生特定结合。未洗脱MIPs的CO的伸缩振动产生的吸收峰红移; 即能量损失明显,可知MA中—COOH的氢原子如果要生成氢键,可能的结合位点就是SAL分子内CO中的氧原子。MIPs和NIPs中CC, CO, —OH等吸收明显的官能团峰型大致相同。将MIPs洗脱掉作为模板分子的SAL后,留下了含有特殊且确定结构官能团化学及空间构成均与SAL高度匹配的空穴, 可与待测液中的目标检测分子SAL发生特异性识别和专一结合作用。而胶体金核壳型MIPs与常规MIPs相比,除具有以上相同特点外,其表面更加松散,表面孔穴明显增多。由此增加了吸附目标分子的有效面积,具有更优良的吸附性能。这两种印迹物的合成及光谱特征分析为建立基于分子印迹技术的快速检测SAL新方法奠定了理论和实践基础。     

Study on the interaction of CdTe quantum dots with ferulic acid and protocatechuic aldehyde by optical spectroscopy

Luminescent CdTe quantum dots (QDs) were synthesized using thioglycolic acid (TGA) as a stabilizing agent in aqueous medium and were characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In weak basic media the fluorescence of TGA-CdTe QDs was quenched notably by ferulic acid (FA) and protocatechuic aldehyde (PA), and the quenching values were proportional to the concentration of the quenchers in a certain range. The addition of bovine serum albumin (BSA) to TGA-CdTe QDs-FA and TGA-CdTe QDs-PA systems rendered a large recovery of the fluorescence of TGA-CdTe QDs.     

HREELS study of the adsorption and evolution of diethylamine (DEA) on Si(1 0 0) surfaces

The adsorption of diethylamine (DEA) on Si(1 0 0) at 100 K was investigated using high-resolution electron energy loss spectroscopy (HREELS) and electron stimulated desorption (ESD). The thermal evolution of DEA on Si(1 0 0) was studied using temperature programmed desorption (TPD). Our results demonstrate DEA bonds datively to the Si(1 0 0) surface with no dissociation at 100 K. Thermal desorption of DEA takes place via a β-hydride elimination process leaving virtually no carbon behind. Electronic processing of DEA/Si(1 0 0) at 100 K results in desorption of ethyl groups; however, carbon and nitrogen are deposited on the surface as a result of electron irradiation. Thermal removal of carbon and nitrogen was not possible, indicating the formation of silicon carbide and silicon nitride.     

Surface modification of gold nanorods using layer-by-layer technique for cellular uptake

Gold nanorods (NRs), rod-shaped gold nanoparticles, were modified with bovine serum albumin (BSA) and polyethylenimine (PEI) using layer-by-layer technique. From absorption spectroscopy and zeta potential measurements, it was obvious that NRs were wrapped with these polymers without aggregation of NRs. Following BSA modification, the surface-modified NRs (BSA-NRs) were well-dispersed without aggregation in biochemical conditions, verified from absorption spectroscopy. Further modification with PEI provided positively charged NRs (PEI-NRs). A transmission electron microscopy image of PEI-NRs revealed that the surface modification did not affect changing the shape of the initial NRs. In addition, the PEI-NRs retained the colloidal stability of BSA-NRs in biochemical conditions. We have evaluated that transfection activity of PEI-NRs with HeLa cells. From results of gene expression experiments, it was obvious that the stabilization of NRs by BSA and further modification with PEI realized transfection using NRs into cultured cells. Moreover, the cellular uptake of NRs enabled cellular imaging using light scattering from the NRs.