共查询到20条相似文献，搜索用时 93 毫秒
1.
Heidi Stoll Heiko Kiessling Martin Stelzle Hans Peter Wendel Julia Schütte Britta Hagmeyer Meltem Avci-Adali 《Biomicrofluidics》2015,9(3)
Aptamers are promising cell targeting ligands for several applications such as for the diagnosis, therapy, and drug delivery. Especially, in the field of regenerative medicine, stem cell specific aptamers have an enormous potential. Using the combinatorial chemistry process SELEX (Systematic Evolution of Ligands by Exponential enrichment), aptamers are selected from a huge oligonucleotide library consisting of approximately 1015 different oligonucleotides. Here, we developed a microfluidic chip system that can be used for the selection of cell specific aptamers. The major drawbacks of common cell-SELEX methods are the inefficient elimination of the unspecifically bound oligonucleotides from the cell surface and the unspecific binding/uptake of oligonucleotides by dead cells. To overcome these obstacles, a microfluidic device, which enables the simultaneous performance of dielectrophoresis and electrophoresis in the same device, was designed. Using this system, viable cells can be selectively assembled by dielectrophoresis between the electrodes and then incubated with the oligonucleotides. To reduce the rate of unspecifically bound sequences, electrophoretic fields can be applied in order to draw loosely bound oligonucleotides away from the cells. Furthermore, by increasing the flow rate in the chip during the iterative rounds of SELEX, the selection pressure can be improved and aptamers with higher affinities and specificities can be obtained. This new microfluidic device has a tremendous capability to improve the cell-SELEX procedure and to select highly specific aptamers. 相似文献
2.
Long Li Shujuan Xu Xueyu Peng Yuzhuo Ji He Yan Cheng Cui Xiaowei Li Xiaoshu Pan Lu Yang Liping Qiu Jianhui Jiang Weihong Tan 《国家科学评论(英文版)》2021,8(4):102-108
The use of aptamers in bioanalytical and biomedical applications exploits their ability to recognize cell surface protein receptors. Targeted therapeutics and theranostics come to mind in this regard. However, protein receptors occur on both cancer and normal cells; as such, aptamers are now taxed with identifying high vs. low levels of protein expression. Inspired by the flexible template mechanism and elegant control of natural nucleic acid-based structures, we report an allosteric regulation strategy for constructing a structure-switching aptamer for enhanced target cell recognition by engineering aptamers with DNA intercalated motifs (i-motifs) responsive to the microenvironment, such as pH. Structure-switching sensitivity can be readily tuned by manipulating i-motif sequences. However, structure-switching sensitivity is difficult to estimate, making it equally difficult to effectively screen modified aptamers with the desired sensitivity. To address this problem, we selected a fluorescent probe capable of detecting G-quadruplex in complicated biological media. 相似文献
3.
Hui Lin Weiting Zhang Shasha Jia Zhichao Guan Chaoyong James Yang Zhi Zhu 《Biomicrofluidics》2014,8(4)
With their advantages as molecular recognition elements, aptamers have been extensively studied and used for bioanalytical and biomedical applications. However, the process of enrichment and screening of aptamers remains a bottleneck for aptamer development. Recently, microfluidic methods have been increasingly used for rapid and efficient aptamer selection, showing their remarkable advantages over conventional methods. This review briefly introduces aptamers and their advantages. The conventional process of generating aptamers is discussed, followed by the analysis of the key obstacles to efficient aptamer selection. Microfluidic methods for highly efficient enrichment and screening of aptamers are reviewed in detail. 相似文献
4.
Yasemin U Budak Ka?an Huysal Hakan Demirci 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2015,25(1):97-102
Background
In heart failure patients, mean platelet volume (MPV) may reflect increased platelet activation or increased numbers of large, hyper-aggregable platelets. B-type natriuretic peptide (BNP) concentration in blood is a sensitive and specific marker of heart failure, correlating with the severity and prognosis of illness, in patients presenting with acute dyspnea to the emergency department. This study evaluated the correlation between BNP concentration and MPV.Material and methods
Data were collected from 319 patients admitted to the emergency department of a cardiology hospital from January–July 2014. EDTA blood samples drawn at admission were analyzed using automated hematology system, and BNP concentration was measured using a fluorescence immunoassay.Results
The study included 190 patients with and 129 without acute heart failure (AHF). These groups had BNP concentration of 200-5000 ng/L and 5-98 ng/L, respectively. MPV levels were significantly higher in the AHF group (P < 0.001). BNP concentrations were positively correlated with MPV (r = 0.41, P < 0.001) and neutrophil / lymphocyte ratio (r = 0.38, P < 0.001).Conclusion
Increased MPV values correlate with BNP concentration, an indicator of HF severity and clinical status, in patients with AHF admitted to the emergency department.Key words: natriuretic peptide, brain; heart failure; platelet; mean platelet volume 相似文献5.
One of the main obstacles for systematic evolution of ligands by exponential enrichment (SELEX) failure is the generation of a non-specific product, as selection-inherent amplification procedures tend to form by-products, which prevents the enrichment of target-binding aptamers. Herein, we reported a dual-microfluidic amplified system (dual-MAS) based on the real-time polymerase chain reaction (PCR) detection chip and the large volume PCR chip for one-step specific PCR and for evaluating the SELEX process. First, it is a simple method to accomplish analytical PCR and amplification PCR in one step, and the optimal number of cycles for generating the specific PCR product is the cycles when the slope of the linear amplification period of the real-time PCR curve begins to decrease. Second, the time used by the dual-MAS for generating a specific PCR product is reduced to 30 min, and the multi-functional dual-MAS can simultaneously evaluate the SELEX process by providing important information on the amounts of enriched sequences and the library diversity in every round of SELEX. In addition, pollution contamination and fragment loss can be significantly avoided in the closed chip. Last, the specific PCR product, the amounts of enriched sequences, and the library diversity can be obtained for every single SELEX in just 30 min. Compared with current methods, this system can reduce the time for generating a specific PCR product and SELEX, and it is easier to choose the optimal number of cycles for a specific PCR product. In a word, it is a sensitive, simple, and rapid strategy to improve the specificity of the PCR product and make the process of SELEX in a controlled way. 相似文献
6.
脑钠肽(BNP)是利尿钠肽家族里的一员，在人体内主要由心室肌细胞合成．它具有排钠、利尿和扩血管作用．其前体片段N端多肽(NT-proBNP)生物半衰期比BNP长，没有生物活性．BNP及NT-proBNP对于心功能不全病人的临床状态评估、治疗策略拟定和预后估计有一定的作用．BNP及NT-proBNP的检测可能会成为对有或者被怀疑有心脏舒张和＼或收缩功能不全的病人的常规性随访项目之一． 相似文献
7.
Brain type natriuretic peptide (BNP)—A marker of new millennium in diagnosis of congestive heart failure 总被引：1，自引：0，他引：1
Arun Raizada Suman Bhandari Muzaiyan Ahmed Khan Harsh Vardhan Singh Sherin Thomas Vikram Sarabhai Neelima Singh Naresh Trehan 《Indian journal of clinical biochemistry : IJCB》2007,22(1):4-9
The burden of disease in patients with congestive heart failure is high. The future of BNP looks promising as it may be a
better diagnostic tool for the diagnosis of CHF in developing countries in new millennium. Natriuretic peptide hormones, a
family of vasoactive peptides with many favourable physiological properties, have emerged as important contenders for development
of diagnostic tools and therapeutic agents in cardiovascular disease. Measurement of B-type natriuretic peptide has become
as an easy-to-perform bedside test. The clinical and diagnostic significance of the measurement of plasma Nt-proBNP in the
diseases of the cardiovascular system with particular emphasis on the assessment of patients with heart failure and their
effects on predicting survival rate. The plasma levels of Nt-proBrain Natriuretic peptide responds more vigorously after myocardial
infarction than those of other natriuretic peptides. This article is an attempt to give a short overview on the utility of
BNP-blood levels for the diagnosis and treatment of heart failure 相似文献
8.
9.
《Information processing & management》2023,60(4):103377
The recent boom in online courses has necessitated personalized online course recommendation. Modelling the learning sequences of users is key for course recommendation because the sequences contain the dynamic learning interests of the users. However, current course recommendation methods ignore heterogeneous course information and collective sequential dependency between courses when modelling the learning sequences. We thus propose a novel online course recommendation method based on knowledge graph and deep learning which models course information via a course knowledge graph and represents courses using TransD. It then develops a bidirectional long short-term memory network, convolutional neural network, and multi-layer perceptron for learning sequence modelling and course recommendation. A public dataset called MOOCCube was used to evaluate the proposed method. Experimental results show that: (1) employing the course knowledge graph in learning sequence modelling improves averagely the performance of our method by 13.658%, 16.42%, and 15.39% in terms of HR@K, MRR@K, and NDCG@K; (2) modelling the collective sequential dependency improves averagely the performance by 4.11%, 6.37%, and 5.47% in terms of the above metrics; and (3) our method outperforms popular methods with the course knowledge graph in most cases. 相似文献
10.
The vector space model (VSM) is a textual representation method that is widely used in documents classification. However, it remains to be a space-challenging problem. One attempt to alleviate the space problem is by using dimensionality reduction techniques, however, such techniques have deficiencies such as losing some important information. In this paper, we propose a novel text classification method that neither uses VSM nor dimensionality reduction techniques. The proposed method is a space efficient method that utilizes the first order Markov model for hierarchical Arabic text classification. For each category and sub-category, a Markov chain model is prepared based on the neighboring characters sequences. The prepared models are then used for scoring documents for classification purposes. For evaluation, we used a hierarchical Arabic text data collection that contains 11,191 documents that belong to eight topics distributed into 3-levels. The experimental results show that the Markov chains based method significantly outperforms the baseline system that employs the latent semantic indexing (LSI) method. That is, the proposed method enhances the F1-measure by 3.47%. The novelty of this work lies on the idea of decomposing words into sequences of characters, which found to be a promising approach in terms of space and accuracy. Based on our best knowledge, this is the first attempt to conduct research for hierarchical Arabic text classification with such relatively large data collection. 相似文献
11.
Weigang Chen Mingzhe Han Jianting Zhou Qi Ge Panpan Wang Xinchen Zhang Siyu Zhu Lifu Song Yingjin Yuan 《国家科学评论(英文版)》2021,8(5):62-70
DNA digital storage provides an alternative for information storage with high density and long-term stability. Here, we report the de novo design and synthesis of an artificial chromosome that encodes two pictures and a video clip. The encoding paradigm utilizing the superposition of sparsified error correction codewords and pseudo-random sequences tolerates base insertions/deletions and is well suited to error-prone nanopore sequencing for data retrieval. The entire 254 kb sequence was 95.27% occupied by encoded data. The Transformation-Associated Recombination method was used in the construction of this chromosome from DNA fragments and necessary autonomous replication sequences. The stability was demonstrated by transmitting the data-carrying chromosome to the 100th generation. This study demonstrates a data storage method using encoded artificial chromosomes via in vivo assembly for write-once and stable replication for multiple retrievals, similar to a compact disc, with potential in economically massive data distribution. 相似文献
12.
13.
随着时代不断地发展,计算机技术迅速地更新,为了人们的信息安全,验证码技术已经成为保护网络安全的重要手段。验证码技术属于人机区对于大小固定的、质心位置居中的验证码,可以得到百分之百的识别率。由于扭曲字符干扰较大,所以识别率达不到理想效果。文章采用的方法有助于提高验证码的安全性。 相似文献
14.
Seitaro Kumamoto Kenshiro Nakatake Souichiro Fukuyama Keiichiro Yasuda Yusuke Kitamura Masaaki Iwatsuki Hideo Baba Toshihiro Ihara Yoshitaka Nakanishi Yuta Nakashima 《Biomicrofluidics》2020,14(6)
To study an environmental or biological solution, it is essential to separate its constituents. In this study, a 3D-deformable dynamic microfilter was developed to selectively separate the target substance from a solution. This microfilter is a fine metallic nickel structure fabricated using photolithography and electroplating techniques. It is gold-coated across its entire surface with multiple slits of 10–20 μm in width. Its two-dimensional shape is deformed into a three-dimensional shape when used for fluid separation due to hydrodynamic forces. By adjusting the pressure applied to the microfilter, the size of the gap created by deformation can be changed. To effectively isolate the target substance, the relationship between the solution flow rate and the extent of microfilter deformation was investigated. The filtration experiments demonstrated the microfilter’s ability to isolate the target substance with elastic deformation without undergoing plastic deformation. Additionally, modification of the microfilter surface with nucleic acid aptamers resulted in the selective isolation of the target cell, which further demonstrates the potential application of microfilters in the isolation of specific components of heterogeneous solutions. 相似文献
15.
《Information processing & management》2023,60(4):103412
Recently, phishing scams have become one of the most serious types of crime involved in Ethereum, the second-largest blockchain-based cryptocurrency platform. The existing phishing scams detection techniques for Ethereum mostly use traditional machine learning or network representation learning to mine the key information from the transaction network and identify phishing addresses. However, these methods typically crop the temporal transaction graph into snapshot sequences or construct temporal random wanderings to model the dynamic evolution of the topology of the transaction graph. In this paper, we propose PDTGA, a method that applies graph representation learning based on temporal graphs attention to improve the effectiveness of phishing scams detection in Ethereum. Specifically, we learn the functional representation of time directly and model the time signal through the interactions between the time encoding function and node features, edge features, and the topology of the graph. We collected a real-world Ethereum phishing scam dataset, containing over 250,000 transaction records between more than 100,000 account addresses, and divided them into three datasets of different sizes. Through data analysis, we first summarized the periodic pattern of Ethereum phishing scam activities. Then we constructed 14 kinds of account node features and 3 kinds of transaction edge features. Experimental evaluations based on the above three datasets demonstrate that PDTGA with 94.78% AUC score and 88.76% recall score outperforms the state-of-the-art methods. 相似文献
16.
m序列是一种典型的伪随机序列,它在扩频通信、流密码、信道编码等领域有着十分广泛的应用。本文介绍了m序列构造方法及基本性能,并利用Matlab中的Simulink仿真系统及M语言编程实现它们的产生和分析。仿真结果验证了该方法的正确性和可行性. 相似文献
17.
利用脂肪酸组成分析鉴定海洋细菌的初步研究 总被引：3，自引：0，他引：3
报道了利用脂肪酸组成分析鉴定海洋细菌的初步研究结果。以16S rRNA鉴定的9株具生物活性的海洋细菌为研究对象,标准条件培养后测定其脂肪酸组成和含量,同时参照Ivanova和Venkateswaran等研究的5株Pseudoalteromonas属海洋细菌的脂肪酸测定结果(培养条件与本实验一致),通过SPSS软件对这些细菌进行脂肪酸聚类分析,并与它们的16S rRNA序列聚类分析(运用ClustalX软件)进行比较。结果表明脂肪酸组成可以作为海洋细菌鉴定到属的依据之一,但仅依靠脂肪酸将海洋细菌不能鉴定到种。 相似文献
18.
In this paper, we propose a novel approach for multilingual story link detection. Our approach utilized the distributional features of terms in timelines and multilingual spaces, together with selected types of named entities in order to get distinctive weights for terms that constitute linguistic representation of events. On timelines term significance is calculated by comparing term distribution of the documents on a day with that of the total document collection. Since two languages can provide more information than one language, term significance is measured on each language space, which is then used as a bridge between two languages on multilingual spaces. Evaluating the method on Korean and Japanese news articles, our method achieved 14.3% improvement for monolingual story pairs, and 16.7% improvement for multilingual story pairs. By measuring the space density, the proposed weighting components are verified with a high density of the intra-event stories and a low density of the inter-events stories. This result indicates that the proposed method is helpful for multilingual story link detection. 相似文献
19.
《Information processing & management》2023,60(5):103450
Despite growing efforts to halt distasteful content on social media, multilingualism has added a new dimension to this problem. The scarcity of resources makes the challenge even greater when it comes to low-resource languages. This work focuses on providing a novel method for abusive content detection in multiple low-resource Indic languages. Our observation indicates that a post’s tendency to attract abusive comments, as well as features such as user history and social context, significantly aid in the detection of abusive content. The proposed method first learns social and text context features in two separate modules. The integrated representation from these modules is learned and used for the final prediction. To evaluate the performance of our method against different classical and state-of-the-art methods, we have performed extensive experiments on SCIDN and MACI datasets consisting of 1.5M and 665K multilingual comments, respectively. Our proposed method outperforms state-of-the-art baseline methods with an average increase of 4.08% and 9.52% in the F1-score on SCIDN and MACI datasets, respectively. 相似文献
20.
本文测定了山羊草属Aegilops 3个组中异源多倍体物种的核rDNA ITS区序列,并用邻接法进行了聚类分析。结果表明,多倍体物种的ITS区序列长度为559∽606bp,其中ITS1、ITS2分别有变异位点51、42个,且存在多态位点。多倍体种均与各自的某一祖先种构成稳定分支,说明在杂交-多倍化后,这些多倍体的ITS区在同步进化的作用下已向着其某一祖先种的ITS区进化。对于sect．Vertebrata的异源多倍体物种来说,其ITS区主要向其祖先种Ae．umbellulata(UU)的ITS区进化,这与山羊草属的细胞遗传学研究结果基本一致。在sect．Cylindropyrum和sect．Polyeides中,Ae．cylindrica(CCDD)朝着Ae．caudata (CC)进化;Ae．ventricosa(DDMvMv)朝着Ae．comosa(MM)进化;Ae．vavilovii(DDMMSS)朝着Ae．crassa (DDMM)进化。 相似文献