1,721,056 research outputs found
Sensors. Special issue: "Biomarkers and Nanosensors: New Approaches for Biology and Medicine"
No full textCirculating tumor DNA and liquid biopsy: opportunities, challenges, and recent advances in detection technologies.
No full textCell-free DNA (cfDNA) refers to short fragments of acellular nucleic acids detectable in almost all body fluids, including blood, and is involved in various physiological and pathological phenomena such as immunity, coagulation, aging, and cancer. In cancer patients, a fraction of hematogenous cfDNA originates from tumors, termed circulating tumor DNA (ctDNA), and may carry the same mutations and genetic alterations as those of a primary tumor. Thus, ctDNA potentially provides an opportunity for noninvasive assessment of cancer. Recent advances in ctDNA analysis methods will potentially lead to the development of a liquid biopsy tool for the diagnosis, prognosis, therapy response monitoring, and tracking the rise of new mutant sub-clones in cancer patients. Over the past few decades, cancer-specific mutations in ctDNA have been detected using a variety of untargeted methods such as digital karyotyping, personalized analysis of rearranged ends (PARE), whole-genome sequencing of ctDNA, and targeted approaches such as conventional and digital PCR-based methods and deep sequencing-based technologies. More recently, several chip-based electrochemical sensors have been developed for the analysis of ctDNA in patient samples. This paper aims to comprehensively review the diagnostic, prognostic, and predictive potential of ctDNA as a minimally invasive liquid biopsy for cancer patients. We also present an overview of current advances in the analytical sensitivity and accuracy of ctDNA analysis methods as well as biological and technical challenges, which need to be resolved for the integration of ctDNA analysis into routine clinical practice
Electrochemical properties and applications of ionic liquids
No full textThis book presents the latest research in electrochemical properties and applications of ionic liquids. While there is no universally agreed upon definition, an ionic liquid may be conveniently described as a compound composed entirely of ions that is a liquid at temperatures less than 100 °C. However, this is an arbitrary definition employed to distinguish ionic liquids from classically well-known molten salts. This book addresses a comprehensive overview of the area, because it is obvious that ionic liquids have the ability to offer many advantages, but also some disadvantages, over traditional molecular solvent (electrolyte) media in the field of electrochemistry. (Imprint: Nova
Quantum dot-based sensitive detection of disease specific exosome in serum
No full textTumor-derived exosomes have emerged as promising cancer biomarkers due to their unique composition and functions. Herein, we report a stripping voltammetric immunoassay for the electrochemical detection of disease-specific exosomes using quantum dots as signal amplifiers. The assay involves three subsequent steps where bulk exosome populations are initially magnetically captured on magnetic beads by a generic tetraspanin antibody (e.g., CD9 or CD63) followed by the identification of disease-specific exosomes using cancer-related. Here, we used CdSe quantum dot (CdSeQD) functionalised-biotinylated HER-2 and FAM134B antibodies as breast and colon cancer markers. After magnetic washing and purification steps, acid dissolution of CdSeQDs and subsequent anodic stripping voltammetric quantification of Cd2+ were carried out at the bare glassy carbon working electrode. This method enabled sensitive detection of 100 exosomes per μL with a relative standard deviation (%RSD) of <5.5% in cancer cell lines and a small cohort of serum samples (n = 9) collected from patients with colorectal adenocarcinoma. We believe that our approach could potentially represent an effective bioassay for the quantification of disease-specific exosomes in clinical samples.Griffith Sciences, School of Natural SciencesNo Full Tex
An amplification-free electrochemical detection of exosomal miRNA-21 in serum samples
No full textRecent evidence suggests that small non-coding RNAs or microRNA (miRNA)s encapsulated in exosomes represent an important mechanism of communication between the cells. Exosomal miRNAs play an important role in oncogenesis via stimulating cell to cell communication and facilitating metastasis in cancers. Despite progressive advances, current methods for exosomal miRNA detection most rely on labor intensive sequencing approaches which are often prone to amplification bias and require costly and bulky equipment. Herein, we report an electrochemical approach for detection of cancer-derived exosomal miRNAs in human serum samples by selectively isolating the target miRNA using magnetic beads pre-functionalized with capture probes and then directly absorbing the targets onto the gold electrode surface. The level of adsorbed miRNA is detected electrochemically in the presence of the [Fe(CN)6]4-/3- redox system. This method enabled an excellent detection sensitivity of 1.0 pM with a relative standard deviation (%RSD) of <5.5% in cancer cells and serum samples (n = 8) collected from patients with colorectal adenocarcinoma. We believe that our approach could be useful for the quantification of exosomal miRNA in clinical samples.Griffith Sciences, School of Natural SciencesNo Full Tex
Detecting DNA methylation for cancer diagnostics and prognostics
No full textDNA methylation is an epigenetic process that has roles in many normal cellular processes and dysregulation of which can result in diseases such as cancer. The most well studied form of mammalian DNA methylation is the addition of a methyl group to the number 5 carbon of cytosine in CpG dinucleotides. Gene regulatory elements, such as gene promoters and enhancers associated with dense CpGs, are sensitive to DNA methylation silencing. Multiple studies have shown that promoter methylation profiling of cancer genes may be useful as biomarkers of cancer. DNA methylation information has the potential to provide information on a patient's cancer subtype, treatment response and prognosis. Current DNA methylation detection techniques can be broadly grouped into sodium bisulfite, restriction enzyme and methylated DNA enrichment based techniques. However, techniques for detection DNA methylation have largely been tailored to research purposes and may not be well suited for routine clinical use. In this chapter, some of these common DNA methylation detection methods are reviewed for their suitability in diagnostics. Also discussed are ways how some of these techniques may be or have been adapted for clinical and point-of-care applications. Emerging techniques that have evolved from classical research methods are also introduced
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Abstract 1243: FAM134B mutation in esophageal squamous cell carcinoma: Its clinical significance and quantification by electrochemical methods
No full textAbstract
Aim: The aim of this research was to detect novel sites of FAM134B mutations, copy number variations and their clinicopathological significance in esophageal squamous cell carcinoma (ESCC) patients. Also, this study was intended to develop a simple and inexpensive electrochemical detection method for the analysis of FAM134B mutations using a single-use and disposable screen-printed electrode.
Method: Approximately 102 fresh tissue samples of ESCC and matched non-cancer adjacent tissues were recruited. The DNA copy numbers of FAM134B were initially studied by qRT-PCR. The FAM134B mutations were then quantified via high resolution melt curve (HRM) and Sanger sequencing analysis. In order to quantify the level of point mutation or SNPs in FAM134B gene, a new electrochemical method was also developed. The underlying working principle of the method is relied on the base dependent affinity interactions towards gold electrode. Since two DNA sequences with different DNA base compositions (i.e., amplified mutated sequences will be distinctly different than its wild type sequence) will have different adsorption affinity towards an unmodified gold electrode, accurate measurement of adsorbed DNA on the electrode surface will give the measure of point mutation or SNPs present in the DNA sequences. Target DNA sequences were first extracted from clinical samples and then PCR amplified and purified prior to adsorption on a single-use screen-printed gold electrode. The amount of mutation sites on a DNA sequence is quantified by monitoring the Faradaic current generated by the [Fe(CN)6]3-/4- system present in the electrolyte solution.
Result: Amplification of FAM134B DNA was noted in 37% of ESCC tissues whereas 35% cases showed loss of FAM134B copies compared to matched non-tumor tissues. Overall, thirty-seven FAM134B mutations were documented in exons 4, 5, 7, 9 as well as introns 2, 4-8 of FAM134B. Also, FAM134B mutations were detected in all the metastatic ESCC cases and in 14% (8/57) of the primary ESCC. Using the new electrochemical method, we were able to detect mutations in 50 ng of target PCR-amplified product within 1 h with high reproducibility (% RSD= &lt;2) and specificity.
Conclusion: DNA copy number variations and frequent mutations of FAM134B in metastatic lymph node tissues in ESCC patients indicate its critical role in the pathogenesis of ESCCs. Also the mutation detection via electrochemical methods was successful distinguishing single point mutation in DNA from oesophageal cancer implying its potential application in point mutation detection in clinical diagnostics.
Note: This abstract was not presented at the meeting.
Citation Format: Md. Hakimul Haque, Vinod Gopalan, Muhammad J. A. Shiddiky, Alfred K. Lam. FAM134B mutation in esophageal squamous cell carcinoma: Its clinical significance and quantification by electrochemical methods [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1243. doi:10.1158/1538-7445.AM2017-1243</jats:p
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