Molecular Biology Videos: The Tryptophan Repressor.

Source: All About Molecular Biology

Plasma DNA Tissue Mapping for Cancer Diagnosis

Using blood plasma samples to detect cancer and pinpoint its anatomical location could be just a few years away from regular medical practice. Dubbed plasma DNA tissue mapping, the approach will allow doctors to ‘visualize’ which organs are affected by cancer, and at what stage, through a blood test.

Choh Ming-li Professor of Chemical Pathology and Assistant Dean (Research) at the Faculty of Medicine at The Chinese University of Hong Kong, Professor Rossa Chiu, says the latest developments in human plasma cancer DNA analysis are pushing new boundaries.

“We have developed a brand new technology which takes cancer DNA analysis in plasma, often referred to as ‘liquid biopsies’, to the next level. It can detect abnormal DNA caused by cancer, and also allow us to scan a blood sample in order to locate which organ it is coming from. In simple terms, it enables us to take a CT scan of the blood,” she explains.

“For instance, we might be able to identify that 10% of the DNA in the blood plasma is from the liver and so we know that person has a tumor located in the liver. In the past we have tried to find a marker for liver cancer, but every cancer is very different and no single marker is particularly useful for a specific type of cancer. That means previously we would have detected cancer in a blood sample, then we would do a radiological imaging examination to see if there are shadows in any parts of the body.”

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Plasma DNA Tissue Mapping for Cancer Diagnosis

Source: ePathWay

Ebola Virus - Amplification-free direct detection on a hybrid optofluidic platform

Low-complexity detection of infectious diseases with high sensitivity and specificity is urgently needed, especially in resource-limited settings. Optofluidic integration combines clinical sample preparation with optical sensing on a single chip-scale system, enabling the direct, amplification-free detection of single RNA from Ebola viruses. The optofluidic system fulfills all key requirements for chip-based clinical analysis, including a low limit of detection, wide dynamic range, and the ability to detect multiple pathogens simultaneously.

Illustration of a virus and blood cells (Shutterstock)

Introduction

The recent Ebola and Zika outbreaks [1, 2] have made it clear that viral infections continue to pose diverse and widespread threats to humanity. Resource-limited settings, in particular, call for diagnostic devices and technologies that are robust and feature relatively low complexity for easy handling by potentially unskilled personnel. At the same time, such instruments need to fulfill all the technical requirements for accurate and reliable diagnosis. These include a limit of detection and dynamic range that are compatible with clinically observed viral loads as well as the ability to carry out multiplexed differential detection by screening simultaneously for several pathogens with similar clinical symptoms.

Figure 1. (a) Cross-sectional view of liquid-core ARROW. (b) Schematic of Automaton integrated with ARROW chip. (c) A hybrid optofluidic ARROW system. (d) Digitized fluorescence signal counts above background. (e) Concentration-dependent RNA counts for off-chip (open squares) and using the automaton (solid circles) sample preparation. Negative controls (SUDV, MARV) did not create any counts. Dashed line indicates predicted particle count determined from initial concentration and experimental parameters. EBOV, Zaire Ebola virus; MARV, Marburg virus; SUDV, Sudan Ebola virus. (Adapted from Cai et al., 2015 [12])

The 'gold standard' test for hemorrhagic fevers as well as other infectious diseases is real-time polymerase chain reaction (RT-PCR) [3]. PCR fulfills the sensitivity and specificity requirement for clinical testing. However, it is not ideal for resource-limited environments and point-of-care applications because of to its complexity. An alternative economic and portable option is antigen-capture enzyme-linked immunosorbent assay (ELISA) testing. However, ELISA requires more highly concentrated samples and thus its clinical application, especially for early disease detection, is restricted.

For the last two decades, the lab-on-chip approach, which features a small footprint and sample volume, has been considered as a promising candidate for the next generation low-complexity medical diagnostics [4]. Among all the approaches, optofluidics, which integrates optics and microfluidics in the same platform, has received increased attention [5, 6]. Microfluidics is ideal for performing biological sample processing on a chip-scale level and leads to miniaturization and simplification of the current diagnostic system. If it can be integrated with an optical sensing/read-out platform that enables high detection sensitivity down to the single pathogen level, an analytic system for which nucleic acid amplification is no longer needed becomes possible.

Figure 2. (a) Schematic of multi-mode interferometer (MMI) waveguide intersecting with liquid-core ARROW. (b) Excitation spots, 9 (blue), 8 (green), and 7 (red), generated by the MMI at wavelength of 488nm, 553nm and 633nm, respectively. (c) Optical signal detected from various labelled single virus particles. (Adapted from Ozcelik et al., 2016 [14])

In order to detect single molecular biomarkers and bioparticles, an in-flow based detection scheme is preferred. In a typical in-flow detection scheme, bioparticles are transported to the sensing region in a stream of gas or liquid where they are detected in transient fashion as they pass an optical interrogation region [7, 8]. Therefore, fast read-out of the optical signal from single bioparticles in sequence can be achieved, and many concerns associated with traditional surface-based sensing schemes such as unwanted nonspecific binding, probe photobleaching, and diffusion-limited transportation are eliminated.

Read more: Ebola Virus - Amplification-free direct detection on a hybrid optofluidic platform

Source: cli-online.com