Optical resonator biosensors: molecular diagnostic and nanoparticle detection on an integrated platform

Optical resonator biosensors are emerging as one of the most sensitive microsystem biodetection technology that does not require amplification or labeling of the analyte. This minireview provides a scholarly introduction to this research area and reviews current advances in molecular diagnostics and nanoparticle detection.     

扫描近场光学显微镜及其在单分子探测中的应用

扫描近场光学显微镜在光学显微镜中具有独特的性能,其突破衍射光限制,具有单分子探测灵敏度,且在研究时不损伤生物样品。文中简要介绍了扫描近场光学显微镜的原理,详述近年来扫描近场光学显微镜在单分子探测中的应用,介绍了扫描近场光学显微镜结合量子点对单分子探测的进展,并对单分子探测的前景做了展望。     

Progress in the development of techniques based on light scattering for single nanoparticle detection

Nanoparticles have recently attracted extensive attention in view of their great potential in biomedicine and bioanalytical ap- plications. Single particle detection via light scattering offers a simple and efficient approach for the size, size distribution, and concentration analysis of nanoparticles. In particular, intrinsic heterogeneity or rare events masked by ensemble averaging can be revealed. However, the sixth power dependence of Rayleigh scattering on particle size makes it very challenging to det...     

A simple detection system for gas chromatography based on molecular absorption spectrometry in the gas phase

Summary A simple and inexpensive detection system for gas chromatography, based on gas-phase, molecular absorption measurements, is presented in which the chromatographic column is directly joined to the spectrophotometer flow cell, without heated transfer lines. A mixture of eight benzene compounds (including methyl, halogen and nitrogen derivatives) were separated and analyzed. Parameters affecting separation (temperature program and carrier gas flow) and measurement quality (wavelength and integration time) were studied and a measurement program designed to modify the wavelength during chromatography. The analytical characteristics of each compound were calculated, obtaining detection limits ranging from 0.5 to 9 g mL^–1. Finally, the method was applied to several synthetic mixtures, with good results.     

金纳米粒子的合成、特性及其在生物医学检测中的应用研究进展

近年来,纳米技术越来越广泛的应用到各个领域,金纳米粒子因其具有许多优良的物理、化学及生物学性质而引起了人们特别的关注。本文综述了金纳米粒子几种经典的合成方法,以及基于金纳米粒子独特的理化性质在病原体、核酸蛋白质检测方面的最新研究进展。     

基于纳米粒子的光学细胞传感器在癌细胞研究中的应用

作为一种极为灵敏、快速的新型生物检测技术,光学细胞传感器在生物医学领域的研究应用备受关注,成为当今生物分析化学领域的研究前沿和热点.它是以细胞作为传感元件来研究信号识别、传导和指示的过程,在毒性物质、病原体等外界条件作用下,研究细胞中活性分子及其生理条件的变化,通过光学信号的变化定量分析细胞膜表面分子、胞内酶分子及微环...     

Visual scanometric detection of DNA through silver enhancement regulated by gold-nanoparticle aggregation with a molecular beacon as the trigger

A convenient and label-free scanometric approach for DNA assay was designed by integrating a metal-ion-mediated conformational molecular beacon (MB) and silver-signal amplification regulated by gold-nanoparticle (AuNP) aggregation. The strategy was based on displacing the interaction between the target DNA sequence and a competitor Hg(2+) ion with a link DNA sequence. In the absence of the target DNA sequence, a link DNA sequence interacted with the Hg(2+) ions, thus forming an inactive cyclic conformation of the MB. This result led to the poor aggregation of polyadenosine-functionalized AuNPs (A-AuNP). In the presence of a target DNA sequence with a stronger affinity than that of the competitor, hybridization between the link DNA and target DNA sequences turned on the trigger. The polythymidine end of the resulting linear duplex structure could react with A-AuNP, thus leading to a cross-linking aggregation. This aggregation weakened AuNP-catalyzed silver enhancement on a spot substrate. Further, by using scanometric detection, the concentration of the target DNA sequence could be conveniently read out within a linear range from 1.0 to 30 nM. Interestingly, in the same amount of Hg(2+) ions, one-base mismatched DNA showed only 22% of the relative gray-scale intensity for the target DNA sequence at the same concentration, thus indicating good specificity. The designed approach, with the help of the ion-mediated conformational MB, was simple, cost effective, adaptable, and convenient and provided significant potential applications in clinical analysis.     

Colorimetric detection of fluoride ion in an aqueous solution using a thioglucose-capped gold nanoparticle

The thioglucose-capped gold nanoparticles have been prepared by the chemical reduction of HAuCl₄ using thioglucose as the reducing and capping agent, which displays selective colorimetric detection of fluoride ion in 10 mM HEPES buffer at physiological pH.     

Electrosorptive detection in liquid chromatography of simple charged organic compounds

Summary The applicability of electrosorptive (ES) detection in liquid chromatography to charged organic species, specifically amines, alkanolamines, and alkylsulfonates is demonstrated. Separations can be carried out using ion-pair chromatography, and detection acieved by measuring changes in differential double-layer capacitance (DLC), C_d, brought about by analyte adsorption at potentials either well negative or positive of the potential of zero charge (pzc), depending on whether cationic or anionic forms, respectively, are being determined. The C_d-analyte concentration response curves are linear over a limited range. A welcome feature of the technique is that organic modifiers may be used in the mobile phase without deleterious consequence to the detection. Attempts were also made to detect these charged species as ion pairs by DLC at potentials close to the pzc. This approach, however, appears to have less practical utility.     

Advances in Optical Detection of Human-Associated Pathogenic Bacteria

Bacterial infection is a global burden that results in numerous hospital visits and deaths annually. The rise of multi-drug resistant bacteria has dramatically increased this burden. Therefore, there is a clinical need to detect and identify bacteria rapidly and accurately in their native state or a culture-free environment. Current diagnostic techniques lack speed and effectiveness in detecting bacteria that are culture-negative, as well as options for in vivo detection. The optical detection of bacteria offers the potential to overcome these obstacles by providing various platforms that can detect bacteria rapidly, with minimum sample preparation, and, in some cases, culture-free directly from patient fluids or even in vivo. These modalities include infrared, Raman, and fluorescence spectroscopy, along with optical coherence tomography, interference, polarization, and laser speckle. However, these techniques are not without their own set of limitations. This review summarizes the strengths and weaknesses of utilizing each of these optical tools for rapid bacteria detection and identification.     

A Collection of Molecular Fingerprints of Single Aerosol Particles in Air for Potential Identification and Detection Using Optical Trapping-Raman Spectroscopy

Characterization, identification, and detection of aerosol particles in their native atmospheric states remain a challenge. Recently, optical trapping-Raman spectroscopy (OT-RS) has been developed and demonstrated for characterization of single, airborne particles. Such particles in different chemical groups have been characterized by OT-RS in recent years and many more are being studied. In this work, we collected single-particle Raman spectra measured using the OT-RS technique and began construction of a library of OT-RS fingerprints that may be used as a reference for potential detection and identification of aerosol particles in the atmosphere. We collected OT-RS fingerprints of aerosol particles from eight different categories including carbons, bioaerosols (pollens, fungi, vitamins, spores), dusts, biological warfare agent surrogates, etc. Among the eight categories, spectral fingerprints of six groups of aerosol particles have been published previously and two other groups are new. We also discussed challenges, limitations, and advantages of using single-particle optical trapping-Raman spectroscopy for aerosol-particle characterization, identification, and detection.     

Detection of Optical Stability of chiral 2-Methylbutyric Acid in Gas Phase with Quadrupole-Quistor-Quadrupole Mass Spectrometer

Inourpreviouswork'.wehaveinvestigatedtheopticalstabilityoforganicacidenantiomerswhichpossessonea-hydrogenatthechiralcarbonofthemoleculeduringElectronImpactionizationMassSpectrometry(EI-MS)process,thestudyshowedthesecompoundsareopticallystableinthepro...     

Simultaneous quantification of catecholamines in rat brain by high‐performance liquid chromatography with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence detection

A new method based on high‐performance liquid chromatography (HPLC) coupled with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence (CL) detection was developed for the simultaneous quantitation of catecholamines in rat brain. In the present CL system, gold nanoparticles were produced by the on‐line reaction of H₂O₂, NaHCO₃?Na₂CO₃ (buffer solution of luminol) and HAuCl_4. Norepinephrine (NE), epinephrine (EP) and dopamine (DA) could strongly enhance the CL signal of the on‐line gold nanoparticle‐catalyzed luminol system. The UV?visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was proposed. Catecholamines promoted the on‐line formation of more gold nanoparticles, which better catalyzed the luminol–H₂O₂ CL reaction. The good separation of NE, EP and DA was achieved with isocratic elution using a mixture of methanol and 0.2% aqueous phosphoric acid (5:95, v/v) within 8.5 min. Under the optimized conditions, the detection limits, defined as a signal‐to‐noise ratio of 3, were in the range of 1.32–1.90 ng/mL, corresponding to 26.4?38.0 pg for 20 μL sample injection. The recoveries of catecholamines added to rat brain sample were >94.6%, with the precisions <5.5%. The validated HPLC?CL method was successfully applied to determine NE and DA in rat brain without prior sample purification. Copyright © 2014 John Wiley & Sons, Ltd.     

反向毛细管电泳高频电导法测定牛黄中的胆酸

建立了毛细管电泳高频电导法快速简便测定牛黄粉中胆酸的新方法.考察了电泳介质的种类、浓度、 pH值以及操作电压和进样时间对分离检测的影响.缓冲液为0.5 mmol/L Na3PO4 2 mmol/L Na2HPO4 0.2 mmol/L CTAB(pH 11.7), 分离电压为 -15 kV时可实现较好的分离和检测.胆酸的线性范围为75～200 μg/mL, 检出限为0.1 μg/mL.线性方程为y=0.6054ρ-4.14991, r=0.953.回收率为100.9%, RSD(n=5)=2.1%.     

Exponentially modified Gaussian relevance to the distributions of translocation events in nanopore-based single molecule detection

Nanopore technique plays an important role in single molecule detection, which illuminates the properties of an individual molecule by analyzing the blockage durations and currents. However, the traditional exponential function is lack of efficiency to describe the distributions of blockage durations in nanopore experiments. Herein, we introduced an exponentially modified Gaussian （EMG） function to fit the duration histograms of both simulated events and experimental events. In comparison with the traditional exponential function, our results demonstrated that the EMG provides a better fit while covers the entire range of the distributions. In particular, the fitted parameters of EMG could be directly used to discriminate the sequence length of the oligonucleotides at single molecule level.     

毛细管电泳荧光检测模式的研究进展

毛细管电泳技术由于具有分析速度快、分离效率高、样品用量少、操作简单、抗污染能力强等特点,广泛的应用于环境监测、临床检验、生物样品分析等领域.荧光检测技术的引入使毛细管电泳在保持强大的分离能力的同时具有了较高的检测灵敏度.本文介绍了影响毛细管电泳-荧光检测灵敏度的两个重要因素(光源和检测模式),对目前常用的两种光源(激光和发光二极管)以及三种检测模式的光路结构(正交型、共线型和嵌入式光纤传导-柱内直接激发型)的设计进行了相应地比较.     

Selective and sensitive electrochemical detection of glucose in neutral solution using platinum-lead alloy nanoparticle/carbon nanotube nanocomposites

Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resulted in a stable PtPbNP/MWCNT nanocomposite with high electrocatalytic activity to glucose oxidation in either neutral or alkaline medium. More importantly, the nanocomposite electrode with a slight modification exhibited high sensitivity, high selectivity, and low detection limit in amperometric glucose sensing at physiological neutral pH (poised at a negative potential). At +0.30 V in neutral solution, the nanocomposite electrode exhibited linearity up to 11 mM of glucose with a sensitivity of 17.8 μA cm⁻² mM⁻¹ and a detection limit of 1.8 μM (S/N = 3). Electroactive ascorbic acid (0.1 mM), uric acid (0.1 mM) and fructose (0.3 mM) invoked only 23%, 14% and 9%, respectively, of the current response obtained for 3 mM glucose. At −0.15 V in neutral solution, the electrode responded linearly to glucose up to 5 mM with a detection limit of 0.16 mM (S/N = 3) and detection sensitivity of ∼18 μA cm⁻² mM⁻¹. At this negative potential, ascorbic acid, uric acid, and fructose were not electroactive, therefore, not interfering with glucose sensing. Modification of the nanocomposite electrode with Nafion coating followed by electrodeposition of a second layer of PtPbNPs on the Nafion coated PtPbNP/MWCNT nanocomposite produced a glucose sensor (poised at −0.15 V) with a lower detection limit (7.0 μM at S/N = 3) and comparable sensitivity, selectivity and linearity compared to the PtPbNP/MWCNT nanocomposite. The Nafion coating lowered the detection limit by reducing the background noise, while the second layer of PtPbNPs restored the sensitivity to the level before Nafion coating.     

Recent Achievements in Electrochemical and Optical Nucleic Acids Based Detection of Metal Ions

Recently nucleic acids gained considerable attention as selective receptors of metal ions. This is because of the possibility of adjusting their sequences in new aptamers selection, as well as the convenience of elaborating new detection mechanisms. Such a flexibility allows for easy utilization of newly emerging nanomaterials for the development of detection devices. This, in turn, can significantly increase, e.g., analytical signal intensity, both optical and electrochemical, and the same can allow for obtaining exceptionally low detection limits and fast biosensor responses. All these properties, together with low power consumption, make nucleic acids biosensors perfect candidates as detection elements of fully automatic portable microfluidic devices. This review provides current progress in nucleic acids application in monitoring environmentally and clinically important metal ions in the electrochemical or optical manner. In addition, several examples of such biosensor applications in portable microfluidic devices are shown.