基于微流控芯片的细菌趋化性检测研究进展

细菌趋化性是指有运动能力的细菌对环境化学物质梯度产生响应,趋向某些化学诱导剂或避开某些化学驱避剂的移动行为,是微生物适应环境变化而生存的一种基本属性.研究细菌趋化性对于利用细菌治理环境、控制病原菌侵染机体以及开发微生物工业项目等方面都具有重要意义.微流控芯片可以实现对细菌趋化性的定性与定量检测,与传统的检测方法相比,可以更好地对细菌的微环境进行控制,有较高的灵敏度.近年来,基于微流控技术检测细菌趋化性研究得到了飞速发展.本文从微流控芯片的结构、工作方式及主要应用3个方面对近年出现的微流控趋化性检测装置进行了介绍和评述.     

微流控芯片上的颗粒被动聚焦技术

微流控芯片上的颗粒聚焦技术已广泛用于生物、化学、工程和医疗等领域.精确的聚焦过程是计数、检测或分选等应用的关键预处理步骤.颗粒聚焦技术根据是否引入外部能场和鞘流,分为主动聚焦、被动聚焦和鞘流辅助聚焦.被动聚焦利用流体的惯性、黏弹性等特性操控颗粒在流体中的平衡位置,拥有结构简单、高通量、生物兼容、低成本和无标记等多重优点...     

微流控芯片上细胞培养与分析方法研究进展

微流控芯片以其强大的微流体和微小物质控制能力成为研究单细胞、细胞群落乃至生物组织的重要手段。在本篇综述中,我们将以微流控芯片上细胞体外培养模型的建立为主,对近几年来重要的研究工作加以评述,全面地介绍微流控技术在细胞生命科学研究中应用的优势和未来发展方向,具体包括微流控芯片的细胞操控能力、细胞培养微环境的构建以及芯片联用检测手段,希望为从事这一领域研究工作的读者提供一些新的思路。     

DNA片段分选微流控芯片发展现状

新一代测序速度越来越快,费用不断降低,但整个流程中还有不少瓶颈.最耗时且影响测序准确度和重复性的环节之一,就是在文库制备过程中,对打断的大量基因组DNA片段进行基于传统凝胶电泳的手工操作筛选.近几年市场上出现了几种目标片段自动分选仪器,并迅速被多家国际知名测序中心引入测试,从而引起了广泛关注.本文评述了DNA片段分选发展经历,包括凝胶电泳、毛细管电泳、特别是微流控芯片在分选精度和通量上的不断提升,并简要论述了DNA分选目前尚存在的问题.     

流动聚焦型微流控体系中的液滴的图案化排列和转变模式

流体在微流通道中形成剪切流场（低雷诺数）．不同于宏观体系,由于剪切力和表面张力的竞争作用,产生的液滴在微尺度下的微流通道中形成特殊的排列现象---周期性类似“晶格”排列现象．设计了新型流动聚焦型微流控芯片,分析研究在微流体系中液滴周期性图案化排列和转变机理性,液滴排列模式受两方面因素影响：水油两相的流速比值和微通道尺寸．当微通道宽度为250或300 μm时,液滴形成单层分散,双层和单层挤压排列．当微通道宽度为350 μm 时,液滴会形成单层分散到三层排列到双层挤压最后到单层挤压排列．当出口通道宽度增加到400 μm时,甚至出现了液滴四层排列的现象．同时研究了各个液滴排列模式的“转变点”.     

Recent Electrokinetic and Microfluidic Strategies for Detection of Amyloid Beta Peptide Biomarkers: Towards Molecular Diagnosis of Alzheimer's Disease

Among all neurodegenerative diseases, Alzheimer's Disease (AD) is the most prevalent worldwide, with a huge burden to the society and no efficient AD treatment so far. Continued efforts have been being made towards early and powerful diagnosis of AD, in the hope for a successful set of clinical trials and subsequently AD curative treatment. Towards this aim, detection and quantification of amyloid beta (Aβ) peptides in cerebrospinal fluid (CSF) and other biofluids, which are established and validated biomarkers for AD, have drawn attention of the scientific community and industry over almost two decades. In this work, an overview on our major contributions over 15 years to develop different electrokinetic and microfluidic strategies for Aβ peptides detection and quantification is reported. Accordingly, discussions and viewpoints on instrumental and methodological developments for microscale electrophoresis, microfluidic designs and immuno‐enrichment / assays on magnetic beads in microchannels for tracing Aβ peptides in CSF are given in this review.     

基于等离子体技术制作微流控纸芯片及其在血糖检测中的应用研究

滤纸经十八烷基三氯硅烷(OTS)疏水化处理以后,用等离子体区域降解滤纸纤维表面的OTS疏水单分子层,使滤纸的局部区域恢复亲水性,得到具有亲疏水图案化的微流控纸芯片. 考察了等离子体处理时间对滤纸表面亲水性、亲水深度(水溶液由滤纸表层下渗至内部的纵向深度)的影响. 优化模具的设计,依据对滤纸亲水深度的不同需求,设计了两种PMMA-PDMS复合片的组合模具. 初步探讨了该亲疏水性变化过程的化学机理. 将制得的纸芯片用于人体全血中血糖含量的测定,线性范围为1.7～17.7 mmol·L^-1,可满足血液样品中血糖的测定.     

Mixing of non-Newtonian fluids in wavy serpentine microchannel using electrokinetically driven flow

A numerical investigation is performed into the mixing performance of electrokinetically driven non-Newtonian fluids in a wavy serpentine microchannel. The flow behavior of the non-Newtonian fluids is described using a power-law model. The simulations examine the effects of the flow behavior index, the wave amplitude, the wavy-wall section length, and the applied electric field strength on the mixing performance. The results show that the volumetric flow rate of shear-thinning fluids is higher than that of shear-thickening fluids, and therefore results in a poorer mixing performance. It is shown that for both types of fluid, the mixing performance can be enhanced by increasing the wave amplitude, extending the length of the wavy-wall section, and reducing the strength of the electric field. Thus, although the mixing efficiency of shear-thinning fluids is lower than that of shear-thickening fluids, the mixing performance can be improved through an appropriate specification of the flow and geometry parameters. For example, given a shear-thinning fluid with a flow behavior index of 0.8, a mixing efficiency of 87% can be obtained by specifying the wave amplitude as 0.7, the wavy-wall section length as five times the characteristic length, the nondimensional Debye-Huckel parameter as 100, and the applied electric field strength as 43.5 V/cm.     

微流控芯片测定单细胞内化学组分的进展

细胞是生命的基本单元。由于细胞的个体差异,传统分析群体细胞的方法难以得到单细胞的重要信息。准确可靠地测定单细胞内化学组分的含量能大大提高从正常细胞中辨别不正常细胞的能力,为进一步研究和发展生物化学、医学和临床检验等领域奠定基础。近年来,用微流控芯片进行单细胞分析已引起广泛的兴趣。微流控芯片可以集成单细胞进样、溶膜、电泳分离胞内化学组分和高灵敏度测定等一系列操作步骤,为分析单细胞内的化学组分提供了新的技术平台。本文主要综述了近年来微流控芯片测定单细胞内化学组分的进展。重点在于利用电渗流、压力结合电渗流和激光镊子等技术操控单细胞在微流控芯片上完成单细胞进样、溶膜、细胞内化学组分的电泳分离和高灵敏度测定等一系列操作步骤。对在微流控芯片上的衍生技术也做了较为详细的阐述。     

离心式微流控固相萃取光盘的研制及其在铬价态分析中的应用

本实验设计了由5层结构组成的离心式微流控光盘,研究了在光盘上制备固相萃取柱的方法,并将其应用于Cr与Cr的分离,ICP-MS法检测总Cr与未被固相萃取柱吸附的Cr含量,从而计算溶液中Cr含量.该光盘可同时处理8个样品,样品预处理快速、分离效果好,样品用量只需要100 μL;Cr的检出限达到2 μg/L.     

Development and application of high‐performance affinity beads: Toward chemical biology and drug discovery

In drug development research, the elucidation and understanding of the interactions between physiologically active substances and proteins that numerous genes produce is important. Currently, most commercially available drugs and physiologically active substances have been brought to market without knowledge of factors interacting with the drugs and the substances. Affinity purification is a useful and powerful technique employed to understand factors that are targeted by drugs and physiologically active substances. However, use of conventional matrices for affinity chromatography often causes a decrease in efficiency of affinity purification and, as a result, more practical matrices for affinity purification have been developed for application in drug discovery research. In this paper, we describe the development of high‐performance affinity beads (SG beads and FG beads) that enable one‐step affinity purification of drug targets and the elucidation of the mechanism of the action of the drugs. We also describe a chemical screening system using our affinity beads. We hope that utilization of the affinity beads will contribute to the progress of research in chemical biology. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 66–85; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20170     

Microfluidic bead-based multienzyme-nanoparticle amplification for detection of circulating tumor cells in the blood using quantum dots labels

This study reports the development of a microfluidic bead-based nucleic acid sensor for sensitive detection of circulating tumor cells in blood samples using multienzyme-nanoparticle amplification and quantum dot labels. In this method, the microbeads functionalized with the capture probes and modified electron rich proteins were arrayed within a microfluidic channel as sensing elements, and the gold nanoparticles (AuNPs) functionalized with the horseradish peroxidases (HRP) and DNA probes were used as labels. Hence, two signal amplification approaches are integrated for enhancing the detection sensitivity of circulating tumor cells. First, the large surface area of Au nanoparticle carrier allows several binding events of HRP on each nanosphere. Second, enhanced mass transport capability inherent from microfluidics leads to higher capture efficiency of targets because continuous flow within micro-channel delivers fresh analyte solution to the reaction site which maintains a high concentration gradient differential to enhance mass transport. Based on the dual signal amplification strategy, the developed microfluidic bead-based nucleic acid sensor could discriminate as low as 5 fM (signal-to-noise (S/N) 3) of synthesized carcinoembryonic antigen (CEA) gene fragments and showed a 1000-fold increase in detection limit compared to the off-chip test. In addition, using spiked colorectal cancer cell lines (HT29) in the blood as a model system, the detection limit of this chip-based approach was found to be as low as 1 HT29 in 1 mL blood sample. This microfluidic bead-based nucleic acid sensor is a promising platform for disease-related nucleic acid molecules at the lowest level at their earliest incidence.     

基于石蜡庚烷溶液的低成本纸基微流控分析装置的制备及其应用

介绍了一种新型的使用石蜡庚烷溶液制备纸基微流控分析装置的工艺,操作更加简单迅速,成本更加低廉。使用混合样品溶液进行测试,证明该装置可以完成对蛋白质、葡萄糖和pH值的同时检测,并可以用于定量分析。纸基微流控分析装置对样品检测的精度范围分别为:牛血清蛋白2.0×10-5~1.00×10-4mol/L,葡萄糖0.02~0.1 mol/L。并对加热处理过程中微流控通道壁的扩散现象进行了初步研究,发现加热前后通道壁厚度的变化呈线性规律。     

Electrochemical Detection of Droplets in Microfluidic Devices: Simultaneous Determination of Velocity,Size and Content

Microfluidic devices were designed to electrochemically detect in a two‐phase flow the velocity, size and content of aqueous droplets containing redox species. The principle of these determinations is based on the analysis of a unique chronoamperometric response recorded during the passage of a droplet over channel microelectrodes. Two configurations of electrochemical cell with different geometries were investigated both theoretically and experimentally. Velocity and size of droplets, as well as internal recirculating convection within droplets, were evaluated from chronoamperometric curves by specific transition times depending on the cell configuration. In addition, the droplet content was probed from the Faradaic current controlled by mass transport and by internal hydrodynamic regime. For droplet velocity and size, experimental data were systematically compared to optical measurements. All the results demonstrated the high performance of the electrochemical detection reached under these conditions. They successfully validate the concept of self‐consistent electrochemical detections of aqueous droplets within microchannels for the simultaneous determination of their velocity, size and content.     

Monodispersed Magnetic Polystyrene Beads with Excellent Colloidal Stability and Strong Magnetic Response

Monodispersed polystyrene beads incorporated with Fe₃O₄ nanoparticles are prepared via dispersion polymerization. The resultant magnetic beads present well‐defined composite structures, excellent colloidal stability, and strong magnetic response. The formation mechanism for the monodispersed composite beads, incorporated with preformed Fe₃O₄ nanocrystals, was investigated. The potential applications of the monodispersed magnetic beads in bacteria capturing were demonstrated. After being coated with anti‐Salmonella CSA‐1 antibody, the magnetic beads show capturing efficiencies of >99.4% in isolating Salmonella sp.

     

Catalytic Coatings for Active and Passive Diesel Particulate Filter Regeneration

Summary. This paper will give an overview how catalytic coatings are applied in diesel particulate filter systems to support filter regeneration by soot oxidation with nitrogen dioxide or oxygen. Catalytic coatings can be placed on a catalyst substrate in front of a diesel particulate filter, on a filter, or in a combined system on both. Strategies and conditions for successful filter regeneration of those systems will be discussed.This revised version was published online in February 2005. In the previous version the issue was not marked as a special issue, and the issue title and the editor was missing     

Diamond Quantum Devices in Biology

The currently available techniques for molecular imaging capable of reaching atomic resolution are limited to low temperatures, vacuum conditions, or large amounts of sample. Quantum sensors based on the spin‐dependent photoluminescence of nitrogen‐vacancy (NV) centers in diamond offer great potential to achieve single‐molecule detection with atomic resolution under ambient conditions. Diamond nanoparticles could also be prepared with implanted NV centers, thereby generating unique nanosensors that are able to traffic into living biological systems. Therefore, this technique might provide unprecedented access and insight into the structure and function of individual biomolecules under physiological conditions as well as observation of biological processes down to the quantum level with atomic resolution. The theory of diamond quantum sensors and the current developments from their preparation to sensing techniques have been critically discussed in this Minireview.     

Combination of Passive and Active Solar Heating with Thermal Energy Storage

This study investigated the impact of individual and combination of different sources of heating (passive solar heating, electric oil-heater, and solar air heater) in a pilot-scale building containing phase change material (PCM) for a potential reduction in energy consumption while maintaining thermal comfort. Unlike most of the recent simulations and modelling studies, this impact was tested experimentally using two identical control and test huts located at the University of Auckland. The control hut was equipped with standard gypsum boards while the test hut had gypsum boards containing PCM (PureTemp 20, PT20). The study found that combining both active and passive solar heating with a temperature-controlled electric oil heater demonstrated the ability to provide significant energy savings and maintain thermal comfort in the test hut, most notably overnight. The suggested combination was tested over different weather conditions and with different temperature constraints to maintain thermal comfort and achieve energy savings ranging from 33% to 87.5%.     

Determination of Total PSA Using Magnetic Beads and a Re‐usable Screen Printed Carbon Electrode Array

A total PSA (tPSA) assay using magnetic beads (1 µm) and a re‐usable 8‐channel screen printed electrochemical array is here reported. The reaction scheme is based on a one step sandwich assay. The linear range obtained is comprised between 5 and 100 ng/mL of tPSA and have a limit of detection of 1.86 ng/mL. This methodology was validated, performing determination of tPSA in serum and the results were compared with a commercial ELISA kit.