Analyst Blog

Can this technique answer the need for a method to acurately identify adultered food products?

This paper presents an electrochemical way of discriminating between the DNA of different bovine species. It targets the mitochondrial Cox-1 gene which is considered to be a standard ‘barcode sequence’, having low variation within species but high degrees of variation between taxa.  The benefit of targeting mitochondrial DNA is that each cell will have hundreds to thousands of copies, facilitating the use of very small samples.

Electrochemical impedance spectroscopy is central to the method and was used to probe for charge resistance transfer differences due to mismatched DNA. Zinc ions were added when DNA hybrids (matched or mismatched) formed on the gold electrode surface, expediting charge transfer to the solution phase redox probe. The zinc ions effectively adjust the charge transfer in situations where complementary sequences exist.  It is therefore possible to use charge resistance transfer differences to tell if the correct DNA had been captured. The authors also carried out a dehybridization study to show if the sensor could be reused.

Find out more by reading the article for free until 4th October.

Electrochemical identification of artificial oligonucleotides related to bovine species. Potential for identification of species based on mismatches in the mitochondrial cytochrome C1 oxidase gene
Mohtashim Hassan Shamsi and Heinz-Bernhard Kraatz
Analyst
DOI: 10.1039/C1AN15414A

Recap on some related papers below…

The effects of oligonucleotide overhangs on the surface hybridization in DNA films: an impedance study
Mohtashim Hassan Shamsi and Heinz-Bernhard Kraatz
Analyst, 2011, 136, 3107-3112
DOI: 10.1039/C1AN15253J

Probing nucleobase mismatch variations by electrochemical techniques: exploring the effects of position and nature of the single-nucleotide mismatch
Mohtashim H. Shamsi and Heinz-Bernhard Kraatz
Analyst, 2010, 135, 2280-2285
DOI: 10.1039/C0AN00184H

Enzymatically modified peptide surfaces: towards general electrochemical sensor platform for protein kinase catalyzed phosphorylations
Sanela Martic, Mahmoud Labib and Heinz-Bernhard Kraatz
Analyst, 2011, 136, 107-112
DOI: 10.1039/C0AN00438C

"Bringing optical histopathology into the clinic would have a huge impact for surgeons, pathologists and patients," says Dr Bevin Lin

Detecting early-stage nasopharyngeal carcinomas via a non-invasive technique which could improve the survival rates of patients has been reported by scientists from Singapore.  Diagnosing nasopharyngeal carcinomas before they have become life-threatening is very difficult, with five-year survival rates only around 34 per cent.

A team led by Bevin Lin, from the National University of Singapore, has developed a technique that uses a bifurcated fibre optic probe to collect nasopharyngeal tissue data. By combining ultraviolet auto fluorescence excitation-emission matrix (EEM) spectroscopy and parallel factor analysis calculations, they can then diagnose early-stage carcinomas.

To find out more, including comments from Dr Lin, read Jennifer Newton‘s article in Chemistry World, and access the paper for free using the link below.

Diagnosis of early stage nasopharyngeal carcinoma using ultraviolet autofluorescence excitation–emission matrix spectroscopy and parallel factor analysis
Bevin Lin, Mads Sylvest Bergholt, David P. Lau and Zhiwei Huang
Analyst, 2011
DOI: 10.1039/c1an15525c

Ricin, a toxin derived from the castor bean plany may be easily amendable as a deliberate food biocontaminate

This study describes the characterisation and selection of an aptamer against the toxin, ricin B.  The aptamer functioned well in liquid food matrices and was tested against a commercially available ELISA kit.

Read the paper for free until 30th August to learn more…

A single DNA aptamer functions as a biosensor for ricin
Elise A. Lamont, Lili He, Keith Warriner, Theodore P. Labuza and Srinand Sreevatsan
Analyst
DOI: 10.1039/C1AN15352H

You might also be interested in these papers:

Aptamer-based surface-enhanced Raman scattering detection of ricin in liquid foods
Lili He, Elise Lamont, Belamaranahally Veeregowda, Srinand Sreevatsan, Christy L. Haynes, Francisco Diez-Gonzalez and Theodore P. Labuza
Chem. Sci., 2011, 2, 1579-1582
DOI: 10.1039/C1SC00201E

Simultaneous quantification of five bacterial and plant toxins from complex matrices using a multiplexed fluorescent magnetic suspension assay
Diana Pauly, Sebastian Kirchner, Britta Stoermann, Tanja Schreiber, Stefan Kaulfuss, Rüdiger Schade, Reto Zbinden, Marc-André Avondet, Martin B. Dorner and Brigitte G. Dorner
Analyst, 2009, 134, 2028-2039
DOI: 10.1039/B911525K

DESI and PADI are useful when determining the siloxane contents of anti-aging creams.

Tara Salter and colleagues present a preliminary study for a non-invasive in vivo investigation of personal care products on fixed fibroblast cells. They carried our mass spectrometry analyses of 13 molecules commonly used in personal care products, including organosiloxanes, with both PADI and DESI to determine the different sensitivities of the techniques.

Read the paper for free until 16th August.

Analysis of personal care products on model skin surfaces using DESI and PADI ambient mass spectrometry
Tara L. Salter, Felicia M. Green, Nilofar Faruqui and Ian S. Gilmore
Analyst
DOI: 10.1039/C1AN15138J

On a similar note, why not check out the themed issue on ambient mass spectrometry that we published last year, in particular this paper from Graham Cooks and colleagues

Desorption electrospray ionization and other ambient ionization methods: current progress and preview
Demian R. Ifa, Chunping Wu, Zheng Ouyang and R. Graham Cooks
Analyst, 2010, 135, 669-681
DOI: 10.1039/B925257F