Surface functionalization for self-referencing surface plasmon resonance (SPR) biosensors by multi-step self-assembly

Recently, a novel SPR sensor with on-chip referencing has been realized. In this sensor, one-half of the gold sensing surface is covered with a high refractive index overlayer of tantalum pentoxide (Ta₂O₅). When polychromatic beam illuminates the sensing surface, surface plasmon resonance in the areas with and without the overlayer occur at different wavelengths. Therefore, the reflected light exhibits two dips associated with SPRs in those two areas. When functionalized properly, one of the areas can be used as a specific sensing channel for detection of specific bio-interactions and the other can act as a reference channel for compensation for background refractive index fluctuations. In this paper we present a new functionalization approach for these mixed architecture chips. The gold side of the chip is functionalized with a mixed self-assembled monolayer of polyethylene oxide (PEO) and biotin terminated (BAT) thiols whereas the Ta₂O₅ side is coated with PEO terminated silanes. The PEO terminated thiols and silanes serve as a protein resistant background, while the biotin terminated thiols are used to bind streptavidin, which in turn immobilizes biotinylated antibodies. Hence, the gold side of the chip is used for the binding and detection of target analytes and the Ta₂O₅ side functions as a reference channel that monitors bulk refractive index changes and temperature drift. We have studied human chorionic gonadotropin (hCG) as a model system, currently detecting down to 5 ng/ml. In addition, we demonstrate the power of the on-chip reference channel for compensating for refractive index changes and eliminating false alarms.     

Ultrasensitive immunosensing of tuberculosis CFP-10 based on SPR spectroscopy

An antigen (Ag), CFP-10, found in tissue fluids of tuberculosis (TB) patients may be an ultimate candidate for use as a sensitive TB marker with a sensing method for early simplified diagnosis of TB. In this study, chemical and optical optimizations were carried out using novel immuno-materials for establishment of a self-assembled surface plasmon resonance (SPR) optical immunosensor system for detection of CFP-10, which is valuable for pre-clinical work, prior to conduct of massive clinical observations. For creation of a simple sensing interface, a monoclonal antibody (anti-CFP-10) was immobilized directly on a gold surface, followed by blocking with cystamine. Orientation and accessibility of anti-CFP-10 were assessed by the selective binding of CFP-10. Recent results indicate that the reusability of the sensor chip adopting the cystamine method was found to be preferable to other immobilization methods. A linear relationship was well correlated between SPR angle shift and CFP concentrations in the range from 100 ng mL⁻¹ to 1 μg mL⁻¹. Modification of the SPR chip with antibody provides a simple experimental platform for investigation of isolated proteins under experimental conditions resembling those of their native environment.     

SPR生物传感器在食品安全领域的应用研究

使用集成化手持式SpreetaTM SPR传感器快速检测大肠杆菌E.Coli 0157∶H7,利用大肠杆菌抗体的免疫吸附反应,采用亲和素—生物素系统放大检测的响应信号,并引入复合抗体作为第二抗体,整个检测过程在1 h内完成,实现病原微生物的快速检测。     

SPR生物传感检测系统软件的设计与实现

介绍了一种基于VC++6.0的表面等离体激元共振(SPR)生物传感检测系统软件的设计与实现.软件利用VC++6.0的MSComm控件,通过串口输入采集数据,结合Access数据库对数据进行操作、保存.数据处理后可得到SPR信号中的共振角度,并可实时绘制出反应曲线.同时,可以选择不同的化学反应动力学模式与相应的公式进行化学反应动力学的模拟,以便实验过程的指导和实验结果的分析.该软件已用于本实验室自主研制的Kretschman结构SPR生物传感器.水和空气的传感检测实验证实了该软件在SPR生物传感信号采集与分析中的可行性.     

SPR生物传感器的应用现状与发展趋势

表面等离子体共振(SPR)生物传感器是一种基于物理光学原理的新型生化分析系统.与传统的超速离心、荧光法相比,具有实时检测、无需标记、耗样量少等特点.介绍了SPR生物传感器的基本原理,着重介绍了SPR生物传感器在生命科学,药物残留,疾病诊断以及食品检测中的应用,并对其发展趋势进行了展望.     

基于SPR的光纤传感器的研究与实验

基于表面等离子体共振（SPR）的光纤传感器不仅具有SPR高灵敏性的特点,还发挥了光纤本身的诸多优点,具有广泛地研究和应用价值。在分析了光纤SPR原理的基础上,设计并实现了光纤SPR传感器,给出了系统结构模型。通过对不同质量分数的甘油溶液进行测试,获得了SPR光谱共振波长等随待测环境介质折射率变化的有效信息,证实了使用这种传感器进行环境介质检测的可行性。     

金纳米棒对SPR生物传感器灵敏度的增强效应

研究不同长径比的金纳米棒对表面等离子体共振(SPR)生物传感器灵敏度的增强效应.利用晶种生长法合成不同长径比的金纳米棒,并对其形貌、光学性质进行表征.采用双抗体夹心法,以金纳米棒 与羊抗人IgG的偶联体作为第二抗体,利用实验室自行研制的波长调制SPR生物传感器对人IgG进行测 试.实验结果表明:不同长径比的金纳米棒...     

一种小型化SPR生物传感器的设计与实现

介绍了一种采用不规则四边形棱镜设计的小型化表面等离子体共振(SPR)生物传感器。棱镜结构与已有的TI Spreeta传感器类似,但是在尺寸、光学性能等方面做了较大优化。新研制的SPR传感器在光学检测精度和系统集成性等方面也有了很大提高。在光路设计中,采用波长为630 nm的宽光束红光LED作为光源,5 000像素点线阵CCD作为光电检测器,光学检测效果要大大优于TI Spreeta波长为830 nm的近红外光源和128像素点的线阵硅光二极管。在光路优化的同时,系统集成了流动控制模块、信号采集处理模块,形成了一个可实现生物大分子相互作用分析的集成小型化SPR检测装置。利用空气、水及乙醇等进行的SPR实验表明:该装置能够对单一样本进行精确检测,共振角的检测精度高达0.01°,且检测结果线性度高,稳定性好,单一样本的检测偏差小于0.5%。     

Detection of EGFR on living human gastric cancer BGC823 cells using surface plasmon resonance phase sensing

Label-free and real-time information acquisition of molecular phenotype and its function on living cells plays a significant role in disease diagnosis and drug development. In this paper, SPR phase sensing was applied to monitor the interactions between EGFR antibody, EGFR1, and membrane proteins EGFR on living human gastric cancer BGC823 cells. When 50 μg/mL EGFR1 was added onto the fixed cells chip and the living cells chip, a significant difference in the binding amount could be observed from the immunofluorescence images. Quantitative results were obtained by following SPR detection, which were 722 RU and 438 RU, respectively. On the same living cells chip, SPR detection also showed markedly different results of cellular responses when it was stimulated by EGFR1 at different concentrations, such as adhesion and/or morphology variation, revealing the EGFR1's cytotoxic effect on the BGC823 cells. The results demonstrate SPR phase sensing is capable of real-time detection of molecular interactions and cellular responses on living cells, and suggest that further studies on the mechanism and the technique may allow SPR sensing become a powerful tool not only for the basic research of cell biology, but also for medical diagnosis and drug development.     

Thermodynamic analysis of the interaction between 3-aminophenylboronic acid and monosaccharides for development of biosensor

The special interaction between 3-aminophenylboronic acid and monosaccharides, particularly glucose, fructose and galactose, has been investigated and used for the development of electrochemical and surface plasmon resonance (SPR) based saccharide sensors. The binding constants and thermodynamic parameters of interaction such as free energy of binding (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined for the first time using isothermal titration calorimetry revealed the enthalpic and entropic contributions to the free energies of binding. Effects of pH and buffer on the binding constants (k) between 3-aminophenylboronic acid and monosaccharides were also examined. The binding constant of fructose was found to be six times higher than glucose and four times higher than galactose at pH 11, leading the specific detection of fructose. SPR and potentiometric calibration for fructose were linear in the concentration range of 10–120 mM and 8–84 mM, respectively. Limit of detection of the SPR and potentiometric method were found to be as 8.9 mM and 1.4 mM, respectively.     

Automatic recognition of alertness level from EEG by using neural network and wavelet coefficients

Electrophysiological recordings are considered a reliable method of assessing a person's alertness. Sleep medicine is asked to offer objective methods to measure daytime alertness, tiredness and sleepiness. As EEG signals are non-stationary, the conventional method of frequency analysis is not highly successful in recognition of alertness level. This paper deals with a novel method of analysis of EEG signals using wavelet transform, and classification using ANN. EEG signals were decomposed into the frequency sub-bands using wavelet transform and a set of statistical features was extracted from the sub-bands to represent the distribution of wavelet coefficients. Then these statistical features were used as an input to an ANN with three discrete outputs: alert, drowsy and sleep. The error back-propagation neural network is selected as a classifier to discriminate the alertness level of a subject. EEG signals were obtained from 30 healthy subjects. The group consisted of 14 females and 16 males with ages ranging from 18 to 65 years and a mean age of 33.5 years, and a Body Mass Index (BMI) of 32.4±7.3 kg/m². Alertness level and classification properties of ANN were tested using the data recorded in 12 healthy subjects, whereby the EEG recordings were not used to train the ANN. The statistics were used as a measure of potential applicability of the ANN. The accuracy of the ANN was 95±3% alert, 93±4% drowsy and 92±5% sleep.