Analyst Blog

Analysis of intracellular enzyme activity by SERS

Enzymatic activity in cells has been revealed by surface enhanced Raman scattering (SERRS) spectroscopic studies, according to new research led by Duncan Graham at the University of Strathclyde.

X-Gal, a SERRS inactive precursor and a common marker for galactosidase enzymes, was introduced to macrophage cells along with metal nanoparticles. On incubation, enzymatic activity of galactosidase on X-Gal produces a SERRS active trans-alkene dimerised product. This product adsorbs onto the delivered citrate capped gold nanoparticles producing a distinctive SERRS signal. Using SERRS mapping to evaluate the formation of this product, enzyme activity was assessed, not only across a cell population, but also at sub-cellular levels. The authors note that the SERRS activity in this study may not reflect the only sites of galactosidase activity, but rather the sites where both galactosidase and the nanoparticles are co-located. Nevertheless, approaches towards sub-cellular analysis of enzyme activity are important.

Advances in targeted nanoparticle uptake combined with the multiplexing capability of SERRS make this an interesting approach to sub-cellular studies of biochemical activity.

To read the full article, please click on the link below. This paper will be free to read until October 18th.

Analysis of intracellular enzyme activity by surface enhanced Raman scattering
Ross Stevenson, Sarah McAughtrie, Laura Senior, Robert J. Stokes, Helen McGachy, Laurence Tetley, Paola Nativo, James M. Brewer, James Alexander, Karen Faulds and   Duncan Graham
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN00729D

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An investigation into the simultaneous enzymatic and SERRS properties of silver nanoparticles
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Electrochemical piezoelectric-excited millimeter-sized cantilever (ePEMC) for simultaneous dual transduction biosensing
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Ultrasensitive electrochemical detection of leukemia cells

Detecting cancerous cells, such as those of leukemia, in early stages can greatly affect patient treatment and survival. Current diagnostic tools such as immunohistochemistry require large concentrations of cells, which occur in advanced stages of the disease.

Jun-Jie Zhu and co-workers at Nanjing University , China, developed an assay for leukemia cells using aptamers in a unique, competition-based electrochemical sensor. This involves the use of magnetic (Fe3O4) and gold nanoparticles and the detection of electrochemical signals from deposited silver nanoparticles using square wave anodic stripping voltammetery. The gold nanoparticles bind to the much larger magnetic particles through an apatmer, but the apatmer has a higher specificity for the leukemia cells. Upon introduction of the cells, some of the gold nanoparticles are released from the magnetic surface affecting the amount of detectable signal from the silver. The researchers successfully detected as few as 10 cells and demonstrated a high specificity of the aptamers for only one type of leukemia cells. Although they chose leukemia cells, the only limitation is the specificity of aptamers available and ideally, any cancer could be tested for in this system.

To read the full article, please access the link below. This paper will be free to read for the next three weeks.

A novel aptamer-based competition strategy for ultrasensitive electrochemical detection of leukemia cells
Kui Zhang, Tingting Tan, Jia-Ju Fu, Tingting Zheng and   Jun-Jie Zhu
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01255G

Detection of E. coli in Ringer's solution

Sophisticated analytical tests producing a readout which can be interpreted by the naked eye, or by image editing software, are becoming increasingly popular.  They offer a low cost alternative to tests requiring expensive equipment and highly trained analysts. Jürgen Popp and colleagues from the Friedrich Schiller University and the Institute of Photonic Technology in Jena, Germany, have developed a new detection method for DNA which provides a distinctive colour change in the case of a positive result.

The bacterial contamination of intravenous fluids in hospitals is a significant concern in modern medicine, so Popp and his team chose the detection of E. Coli in Ringer’s solution as the first test for their assay. The technique uses surface-modified magnetic beads which can bind complementary target DNA by hybridisation. A silver deposition kit provides the visual colour change: for a positive result, silver nanoparticles are generated by enzymatic silver deposition, turning the sample black. As well as being an inexpensive and convenient qualitative test, a quantitative result can be found by analysing a digital photograph of the colour change in standard image editing software.

To read the full article, please cick on the link below. The paper will be free to read for the next three weeks.

Convenient detection of E. coli in Ringer’s solution
Martha Schwarz, Susanne Pahlow, Thomas Bocklitz, Carolin Steinbrücker, Dana Cialla, Karina Weber and Jürgen Popp
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01240A

BODIPY-Based Probe for HClO Imaging

Detection of suitable biomarkers of disease is critical for medical diagnosis. However, detection becomes a paradoxical challenge when the biomarker is naturally found in healthy individuals. This is the case for the biomarker hypochlorous acid (HClO), a reactive oxygen species that plays an essential role in maintaining a healthy immune system under normal conditions. Yet, when optimal levels of HClO cannot be maintained by the body, cellular functions become disrupted and this can result in diseases such as atherosclerosis, arthritis, and cancer. Consequently, HClO requires medical monitoring, particularly in the mitochondria where a high concentration tends to reside. To help distinguish between healthy and diseased states, the ideal biosensor must provide fast response, high selectivity, high sensitivity and mitochondrial permeability.

To address this challenge, Xiaojun Peng and colleagues from the Dalian University of Technology in China have created a fluorescent imaging probe to detect HClO by localizing to mitochondria in live cells. Their probe makes use of boron dipyrromethene (BODIPY) dye for its outstanding fluorescent properties. Incorporation of an oxime group onto the BODIPY scaffold allows the tuning of fluorescence to an on/off state depending on the presence/absence of HClO, respectively. Lastly, incorporation of a triphenylphosphine group onto BODIPY provides the localization signal to the mitochondria. Learn all the details of this exciting new discovery by accessing the link below:

A highly specific BODIPY-based probe localized in mitochondria for HClO imaging
Guanghui Cheng, Jiangli Fan, Wen Sun, Kun Sui, Xin Jin, Jingyun Wang and   Xiaojun Peng  
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01152F

This pap[er will be free to read for the next three weeks. Let us know what your thoughts are by leaving a comment!