Micro flow cytometry utilizing a magnetic bead-based immunoassay for rapid virus detection

The current study presents a new miniature microfluidic flow cytometer integrated with several functional micro-devices capable of viral sample purification and detection by utilizing a magnetic bead-based immunoassay. The magnetic beads were conjugated with specific antibodies, which can recognize and capture target viruses. Another dye-labeled anti-virus antibody was then used to mark the bead-bound virus for the subsequent optical detection. Several essential components were integrated onto a single chip including a sample incubation module, a micro flow cytometry module and an optical detection module. The sample incubation module consisting of pneumatic micropumps and a membrane-type, active micromixer was used for purifying and enriching the target virus-bound magnetic beads with the aid of a permanent magnet. The micro flow cytometry module and the optical detection module were used to perform the functions of virus counting and collection. Experimental results showed that virus samples with a concentration of 10(3)PFU/ml can be automatically detected successfully by the developed system. In addition, the entire diagnosis procedure including sample incubation and virus detection took only about 40min. Consequently, the proposed micro flow cytometry may provide a powerful platform for rapid diagnosis and future biological applications.     

纯化探针降低基因芯片杂交结果的背景

研究探针的纯化对基因芯片杂交结果的影响。将乙醇沉淀的探针和用DNA纯化试剂盒纯化的探针分别与基因芯片交,在同等条件下进行杂交后清洗和芯片扫描检测。结果表明,纯化的探针与基因芯片杂交结果的背景低,而未纯化的探针背景强,阳性信号界限比较模糊。运用基因芯片进行基因表达谱研究,要求杂交检测的结果必须低背景。探针的纯化是影响芯片杂交结果的一个重要因素。     

DNA芯片技术在微生物学研究中的应用

DNA芯片技术作为一种高通量的核酸分析方法,已经成为“后基因组时代”中研究海量序列信息的重要分析工具之一。本简述了目前一些常用以及和新出现的DNA芯片的技术原理,并从微生物基因表达谱研究,微生物基因组学研究以及微生物检测鉴定研究等多个方面概述了DNA芯片技术在微生物学中的应用,同时在对DNA芯片技术的不足进行简要分析的基础上,展望了其进一步应用的前景。     

微流控芯片在水环境污染分析中的应用

近年来,一种新型技术——微流控芯片技术因其分析速度快、消耗低、体积小、操作简单等特点而备受世界各国的广泛重视.该技术以微通道网络为基本特征,以微机电系统(MEMS)工艺为技术依托,将整个实验室的功能集成在微小芯片上,即构成所谓“芯片实验室”.本文从该技术的基本情况出发,介绍了微流控芯片的发展,并从仪器小型化、系统集成化、不同的芯片材料以及多种检测技术等方面,着重讨论了其在水环境污染分析方面的实际应用和发展前景,指出了它当前所面临的一些问题.随着微流控芯片的不断发展,高速多通道检测装置、低成本设备以及集成了多种方法的高通用性微流控检测芯片,都将成为未来研究的热点.     

肺癌循环肿瘤细胞的单细胞EGFR基因突变检测

循环肿瘤细胞（Circulating tumor cells,CTCs）是从肿瘤原发病灶脱落并侵入外周血循环的肿瘤细胞。由于CTCs存在较大的异质性,其与癌症发展转移密切相关,但目前尚缺乏有效的CTCs单细胞异质性检测方法。鉴于此,本文发展了在单细胞层面对CTCs进行基因突变的检测方法并用于单个肺癌CTC的EGFR（Epidermal growth factor receptor）基因突变检测。首先用集成式微流控系统完成血液中稀有CTCs的捕获,接着将CTCs释放入含有多个微孔的微阵列芯片中,得到含有单个CTC的微孔,通过显微操作将单个CTC转入PCR管内完成单细胞基因组的放大,并进行单细胞的EGFR基因突变检测。以非小细胞肺癌细胞系A549、NCI-H1650和NCI-H1975为样本,通过芯片与毛细管修饰、引物扩增条件（复性温度、循环次数）的优化,结果显示在复性温度59℃、30个循环次数的条件下,引物扩增效果最优。利用该方法成功地对非小细胞肺癌（Non-small cell lung cancer, NSCLC）患者的血液样本进行了测试。从患者2 mL血液中获取5个CTCs,分别对其EGFR基因的第18、19、20、21外显子进行测序,发现该患者CTCs均为EGFR野生型。研究结果证明此检测方法可以灵敏地用于单个CTC基因突变的检测,在临床研究上具有重要的指导意义。     

A simple and reliable assay for detecting specific nucleotide sequences in plants using optical thin-film biosensor chips

Here we report the adaptation and optimization of an efficient, accurate and inexpensive assay that employs custom-designed silicon-based optical thin-film biosensor chips to detect unique transgenes in genetically modified (GM) crops and SNP markers in model plant genomes. Briefly, aldehyde-attached sequence-specific single-stranded oligonucleotide probes are arrayed and covalently attached to a hydrazine-derivatized biosensor chip surface. Unique DNA sequences (or genes) are detected by hybridizing biotinylated PCR amplicons of the DNA sequences to probes on the chip surface. In the SNP assay, target sequences (PCR amplicons) are hybridized in the presence of a mixture of biotinylated detector probes and a thermostable DNA ligase. Only perfect matches between the probe and target sequences, but not those with even a single nucleotide mismatch, can be covalently fixed on the chip surface. In both cases, the presence of specific target sequences is signified by a color change on the chip surface (gold to blue/purple) after brief incubation with an anti-biotin IgG horseradish peroxidase (HRP) to generate a precipitable product from an HRP substrate. Highly sensitive and accurate identification of PCR targets can be completed within 30 min. This assay is extremely robust, exhibits high sensitivity and specificity, and is flexible from low to high throughput and very economical. This technology can be customized for any nucleotide sequence-based identification assay and widely applied in crop breeding, trait mapping, and other work requiring positive detection of specific nucleotide sequences.     

Genotoxicity of three pesticides used in Costa Rican banana plantations

The in vitro genotoxicity of imazalil and thiabendazole fungicides and the insecticide chlorpyrifos, compounds used in Costa Rican banana plantations, was evaluated with the single-cell gel electrophoresis technique (comet assay). The comet assay is a simple, rapid and low cost technique for quantification of DNA damage. This assay detects DNA single-strand breaks and alkali-labile sites in individual cells. The effects were analyzed by using human lymphocytes exposed to doses of 0, 25, 50, 75 and 100 microg/ml of each pesticide for 30 min at 37 degrees C. The cells were embedded in agarose, lysed, subjected to alkaline electrophoresis (pH >13) for 20 min at 25V, neutralized and dehydrated to be stained with a fluorescent dye and later comets visualization with the epifluorescence microscope. Chlorpyrifos and imazalil induced significant DNA damage in a dose-dependent manner. Chlorpyrifos was the major inductor of DNA breaks. These results indicate that both are genotoxic compounds in vitro. Thiabendazole fungicide did not induced DNA damage using the comet assay for all concentrations tested.     

应用生物反应器建立人用冻干狂犬病疫苗(Vero细胞)生产工艺的研究

应用15L生物反应器,采用片状载体对Vero细胞进行高密度培养、制备高毒力滴度的狂犬病毒收获液,经纯化后生产人用冻干狂犬病疫苗。采用15L生物反应器对培养方法(批次培养和连续灌流培养)进行试验,收获高毒力滴度的狂犬病毒收获液并制备人用冻干狂犬病疫苗。结果表明:Vero细胞在接种狂犬病毒后可以连续收获病毒液达到25d以上,冻干狂犬病疫苗的效价可以达到5.54IU/剂。本工艺可以用于进行大规模的人用冻干狂犬疫苗的生产。     

基因芯片技术及应用研究进展

采用高速打印或光刻合成技术可在硅片、玻璃或尼龙膜上制造ＤＮＡ微阵列。样品ＤＮＡ／ＲＮＡ通过ＰＣＲ扩增、体外转录等技术掺入荧光标记分子,与微阵列杂交后通过荧光扫描仪器扫描及计算机分析即可获得样品中大量基因序列及表达的信息。该技术可应用于高通量基因表达平行分析、大规模基因发现及序列分析、基因多态性分析和基因组研究等 。     

Use of whole blood directly for single-cell gel electrophoresis (comet) assay in vivo and white blood cells for in vitro assay

The present study investigated the use of whole blood from humans and rats directly for single-cell gel electrophoresis (comet) assay. As little as 20 microl of whole blood was sufficient for comet assay, and the comet images obtained from whole blood were not different from those obtained from isolated lymphocytes. The DNA remained intact up to 4 h at 4 degrees C after isolation and had no observable strand breakage, when whole blood was cryopreserved (at -80 degrees C) in 10% pre-cooled DMSO up to 60 days. To demonstrate that the whole-blood technique could be applied to in vivo studies, we injected rats with a known carcinogen Fe/NTA and measured DNA strand breaks in whole blood in comparison with isolated lymphocytes. We showed that Fe/NTA injection resulted in similar extent of DNA strand breakage in both whole blood and lymphocytes, indicating that whole-blood method can be used for in vivo genotoxic studies. One disadvantage of the whole-blood technique is that whole blood cannot be used for in vitro studies because of the interferences from red blood cell (RBC) components. However, this problem can be overcome by prior hemolysis of RBCs and a brief centrifugation to obtain white blood cells (WBCs), which can then be used for in vitro incubation with genotoxic compounds before comet assay. Overall, this whole-blood technique for comet assay is expected to provide a simple, rapid, and cost-effective alternative for the existing comet assay using isolated lymphocytes in situations such as when time and cost are limiting factors.     

Micromachined polymerase chain reaction system for multiple DNA amplification of upper respiratory tract infectious diseases

This paper presents a micro polymerase chain reaction (PCR) chip for the DNA-based diagnosis of microorganism genes and the detection of their corresponding antibiotic-resistant genes. The micro PCR chip comprises cheap biocompatible soda-lime glass substrates with integrated thin-film platinum resistors as heating/sensing elements, and is fabricated using micro-electro-mechanical-system (MEMS) techniques in a reliable batch-fabrication process. The heating and temperature sensing elements are made of the same material and are located inside the reaction chamber in order to ensure a uniform temperature distribution. This study performs the detection of several genes associated with upper respiratory tract infection microorganisms, i.e. Streptococcus pneumoniae, Haemopilus influenze, Staphylococcu aureus, Streptococcus pyogenes, and Neisseria meningitides, together with their corresponding antibiotic-resistant genes. The lower thermal inertia of the proposed micro PCR chip relative to conventional bench-top PCR systems enables a more rapid detection operation with reduced sample and reagent consumption. The experimental data reveal that the high heating and cooling rates of the system (20 and 10 degrees C/s, respectively) permit successful DNA amplification within 15 min. The micro PCR chip is also capable of performing multiple DNA amplification, i.e. the simultaneous duplication of multiple genes under different conditions in separate reaction wells. Compared with the large-scale PCR system, it is greatly advantageous for fast diagnosis of multiple infectious diseases. Multiplex PCR amplification of two DNA segments in the same well is also feasible using the proposed micro device. The developed micro PCR chip provides a crucial tool for genetic analysis, molecular biology, infectious disease detection, and many other biomedical applications.     

Full flexibility genotyping of single nucleotide polymorphisms by the GOOD assay

Recently a facile method for genotyping single nucleotide polymorphisms (SNPs) using MALDI mass spectrometry, termed the GOOD assay, was developed. It does not require any purification and is performed with simple liquid handling, thermal incubation and cycling steps. Although this method is well suited to automation and high-throughput analysis of SNPs, it did not allow full flexibility due to lack of certain reagents. A complete set of β-cyanoethyl phosphoramidites is presented herein that give this SNP genotyping method full sequence and multiplex capabilities. Applications to SNP genotyping in the prion protein gene, the β-2-adrenergic receptor gene and the angiotensin converting enzyme gene using the GOOD assay are demonstrated. Because SNP genotyping technologies are generally very sensitive to varying DNA quality, the GOOD assay has been stabilised and optimised for low quality DNA. A template extraction method is introduced that allows genotyping from tissue that was taken while placing an ear tag on an animal. This dramatically facilitates the application of genotyping to animal agricultural applications, as it demonstrates that expensive and cumbersome DNA extraction procedures prior to genotyping can be avoided.     

用聚丙烯酰胺凝胶电泳和微流体芯片电泳鉴别6种液态奶

目的:研究6种液态奶制品蛋白电泳图谱的区别,建立奶制品的蛋白质学鉴别方法。方法:以5种纯牛奶、羊奶、水牛奶、骆驼奶、牦牛奶、黄豆浆为研究对象,通过SDS-PAGE和Agilent 2100微流体芯片电泳法进行分析比较。结果:骆驼奶、黄豆浆与其他研究对象的图谱有明显区别,而牛奶、羊奶、水牛奶、牦牛奶的差异却不是很大;采用微流体芯片电泳可有效地对豆奶、骆驼奶进行区分,还可在一定程度上鉴别牛奶、羊奶、水牛奶和牦牛奶。结论:Agilent2100系统作为一种新型半自动微流体芯片技术,可以快速、高效、准确地应用于液态奶制品的蛋白成分分析及鉴别。     

30个祖先信息位点的筛选及应用

摘要：目的 筛选一组祖先信息SNPs位点（AIMs,Ancestry Informative Markers）,构建复合检测体系,用于东亚、欧洲和非洲人群遗传成分描述及个体种族来源推断。方法 以HapMap数据库9个人群的658份样本的分型数据为基础,从30个表型相关基因总共282个SNPs位点中筛选出30个AIMs位点,基于微测序-通用芯片技术构建复合检测体系,并建立人群等位基因频率数据库。使用这组位点分析HapMap数据库中658份人群样本,初步验证位点的区分效能;然后,使用研究构建的体系检验收集的5个人群194份无关个体的DNA样本。最后,通过Structure软件分析获取人群的成分构成以及个体的遗传成分,对个体样本进行种族来源推断。 结果 筛选的30个AIMs位点符合哈迪温伯格平衡（p>0.01）,位点之间没有连锁（r2<0.1）, 658份HapMap数据库样本和194份实验样本的祖先成分分析结果与已知结果完全一致。 结论 本文筛选并建立的30个AIMs位点复合检测体系,能够有效实现东亚、欧洲、非洲人群及混合人群的成分构成和个体遗传成分的分析,有效控制遗传连锁分析中由于人群分层现象带来的误差,也可以用于法医DNA检验中个体祖先来源推断。     

Polymerase chain reaction/ligase detection reaction/hybridization assays using flow-through microfluidic devices for the detection of low-abundant DNA point mutations

We have microfabricated a flow-through biochip for the analysis of single base mutations in genomic DNA using two different materials: (1) a polycarbonate (PC) chip for performing a primary polymerase chain reaction (PCR) followed by an allele-specific ligation detection reaction (LDR) and (2) a poly(methyl methacrylate) (PMMA) chip for the detection of the LDR products using a universal array platform. The operation of the device was demonstrated by detecting low-abundant DNA mutations in gene fragments (K-ras) that carry point mutations with high diagnostic value for colorectal cancers. The PC microchip was used for sequential PCR/LDR in a continuous-flow format, in which the following three steps were carried out: (1) exponential amplification of gene fragments from genomic DNA; (2) mixing of the resultant PCR product with a LDR mixture via a Y-shaped passive micromixer and (3) ligation of two primers only when the particular mutation was present in the genomic DNA. A PMMA chip was employed as the microarray device, where zip code sequences (24-mer), which were complementary to sequences present on the discriminating primer, were micro-printed into fluidic channels embossed into the PMMA substrate. We successfully demonstrate the ability to detect one mutant DNA in 80 normal sequences with the integrated microfluidic device. The PCR/LDR/hybridization assay using the microchips performed the entire assay at a relatively fast processing speed: 18.7 min for PCR, 8.1 min for LDR, 5 min for hybridization, 10 min for washing and 2.6 min for fluorescence scanning (total processing time=ca. 50 min) with an order of magnitude reduction in reagents compared to bench-top formats.     

基因芯片技术及其应用

基因芯片是近年来产生的一项生物高技术。它是利用原位合成或合成后交联法,将大量的核酸片段有规则地固定在固相支持物如载玻片、金属片、尼龙膜上,制成芯片,然后将要检测的样品用荧光素或同位素标记,再与做成的芯片充分杂交,通过对杂交信号的检测来分析样品中的信息。基因芯片技术已在基因表达水平的检测、基因点突变及多态性检测、DNA序列测定、寻找可能的致病基因和疾病相关基因、蛋白质作图、基因组文库作图等方面显示出了广阔的应用前景。     

Extremely low-frequency electromagnetic fields do not affect DNA damage and gene expression profiles of yeast and human lymphocytes

We studied the effects of extremely low-frequency (50 Hz) electromagnetic fields (EMFs) on peripheral human blood lymphocytes and DBY747 Saccharomyces cerevisiae. Graded exposure to 50 Hz magnetic flux density was obtained with a Helmholtz coil system set at 1, 10 or 100 microT for 18 h. The effects of EMFs on DNA damage were studied with the single-cell gel electrophoresis assay (comet assay) in lymphocytes. Gene expression profiles of EMF-exposed human and yeast cells were evaluated with DNA microarrays containing 13,971 and 6,212 oligonucleotides, respectively. After exposure to the EMF, we did not observe an increase in the amount of strand breaks or oxidated DNA bases relative to controls or a variation in gene expression profiles. The results suggest that extremely low-frequency EMFs do not induce DNA damage or affect gene expression in these two different eukaryotic cell systems.     

Purification and preconcentration of genomic DNA from whole cell lysates using photoactivated polycarbonate (PPC) microfluidic chips

We discuss the use of a photoactivated polycarbonate (PPC) microfluidic chip for the solid-phase, reversible immobilization (SPRI) and purification of genomic DNA (gDNA) from whole cell lysates. The surface of polycarbonate was activated by UV radiation resulting in a photo-oxidation reaction, which produced a channel surface containing carboxylate groups. The gDNA was selectively captured on this photoactivated surface in an immobilization buffer, which consisted of 3% polyethylene glycol, 0.4 M NaCl and 70% ethanol. The methodology reported herein is similar to conventional SPRI in that surface-confined carboxylate groups are used for the selective immobilization of DNA; however, no magnetic beads or a magnetic field are required. As observed by UV spectroscopy, a load of ~7.6 ± 1.6 µg/ml of gDNA was immobilized onto the PPC bed. The recovery of DNA following purification was estimated to be 85 ± 5%. The immobilization and purification assay using this PPC microchip could be performed within ~25 min as follows: (i) DNA immobilization ~6 min, (ii) chip washout with ethanol 10 min, and (iii) drying and gDNA desorption ~6 min. The PPC microchip could also be used for subsequent assays with no substantial loss in recovery, no observable carryover and no need for ‘reactivation’ of the PC surface with UV light.     

Nanoscale fabrication of biomolecular layer and its application to biodevices

Biodevices composed of biomolecular layer have been developed in various fields such as medical diagnosis, pharmaceutical screening, electronic device, photonic device, environmental pollution detection device, and etc. The biomolecules such as protein, DNA and pigment, and cells have been used to construct the biodevices such as biomolecular diode, biostorage device, bioelectroluminescence device, protein chip, DNA chip, and cell chip. Substantial interest has focused upon thin film fabrication or the formation of biomaterials mono- or multi-layers on the solid surfaces to construct the biodevices. Based on the development of nanotechnology, nanoscale fabrication technology for biofilm has been emerged and applied to biodevices due to the various advantages such as high density immobilization and orientation control of immobilized biomolecules. This review described the nanoscale fabrication of biomolecular film and its application to bioelectronic devices and biochips.     

DNA芯片制作原理及其杂交信号检测方法

文章讨论了DNA芯片的制作原理和杂交信号的检测方法。依其结构,DNA芯片可分为两种形式,DNA阵列和寡核苷酸微芯片。DNA芯片的制作方法主要有光导原位合成法和自动化点样法。DNA芯片与标记的探针或DNA样品杂交,并通过探测杂交信号谱型来实现DNA序列或基因表达的分析。适应于DNA芯片的发展,同时出现了许多新型的杂交信号检测方法。主要有激光荧光扫描显微镜、激光扫描共焦显微镜、结合使用CCD相机的荧光显微镜、光纤生物传感器、化学发生法、光激发磷光物质存储屏法、光散射法等。