Analyst Blog

Heat given off by the reaction between the substance of interest and an enzyme is used to determine the amount of that substance present.

Srinivas Tadigadapa and colleagues at Pennsylvania State University have designed a calorimetric sensor as a point-of-care diagnostic instrument that can detect low levels of glucose.

Calorimetric sensors can detect minute heat changes released during biological reactions so could be used to measure trace amounts of clinically relevant biochemicals, such as glucose and urea. But, until now, designing these sensors has been complex and unreliable and the sensors produced have not been robust enough for practical use.

To find out how this recent work overcomes some of these limitations, read Harriet Brewerton’s news article in Chemistry World, and access the paper using the link below:

Monitoring biochemical reactions using Y-cut quartz thermal sensors
Kailiang Ren, Ping Kao, Marcelo B. Pisani and Srinivas Tadigadapa
Analyst, 2011, Advance Article
DOI: 10.1039/C1AN15153C

A recent collection of Noteworthy Chemistry from the ACS featured an Analyst article from Ben Zhong Tang and co-workers at Zhejiang University, Hangzhou, China.

They prepared BSA–tetraphenylethylene derivative conjugates with aggregation-induced emission (AIE) properties that act as effective fluorescent reporters for simple, sensitive, rapid, low-cost, label-free homogeneous detection of proteases such as trypsin and the protease inhibitor α1-antitrypsin.

Anomalous or elevated physiological levels of proteases and altered α1-antitrypsin function are both implicated in several diseases.  As stated in the ACS article, “the simplicity, high sensitivity and rapidity of the BSA–tetraphenylethylene bioconjugate assay make it a prime candidate for AIE probes for biological process monitoring and cancer diagnostics.”

Read the paper by following the link below:

BSA–tetraphenylethene derivative conjugates with aggregation-induced emission properties: Fluorescent probes for label-free and homogeneous detection of protease and α1-antitrypsin
Jian-Ping Xu, Yuan Fang, Zhe-Gang Song, Ju Mei, Lan Jia, An Jun Qin, Jing Zhi Sun, Jian Ji and Ben Zhong Tang
Analyst, 2011, 136, 2315-2321
DOI: 10.1039/C0AN00813C

(a) Capacitor array biochip immobilized with viable E. coli and (b) response of E. coli and surface charge distribution under the applied AC electrical frequency.

Javed H. Niazi and colleagues from Sabanci University, Turkey, have developed a new capactitive biochip capable of detecting cellular stress caused by chemicals thanks to immobilised bacteria.

The biosensor works by using non-Faradaic electrochemical impedance spectroscopy to monitor changes in surface capacitance which occur when chemicals, such as acetic acid and hydrogen peroxide, disrupt the membrane function of the immobilised E. coli cells.

One referee described it as a “canary in a coal mine chip”.

The team still have some challenges to overcome but once properly developed, it could potentially be used as a cytotoxicity indicator.

It’s a must-read for anyone involved in drug, food and water safety research and will be free to access until 1st July.

Probing chemical induced cellular stress by non-Faradaic electrochemical impedance spectroscopy using an Escherichia coli capacitive biochip
Anjum Qureshi, Yasar Gurbuz and Javed H. Niazi
Analyst
DOI: 10.1039/C1AN15202E

Because of their use in food producing animals, the risk of occurrence of unwanted residues in edible products exists.

Read this critical review from our sister journal, Analytical Methods,  on sample preparation methods for the determination of veterinary residues in food matrices by porous monolith microextraction-based techniques. Several porous monolith microextraction formats, including in-tube solid-phase extraction, stir bar sorptive extraction and stir rod sorptive extraction modes, are described.  One referee commented that the review will be ‘a very useful guide for future study and application of correlative techniques.’

This is an important area of research as veterinary drugs are regularly administered via drinking water and feed with the aim of hindering the spread of disease amongst animals.  However, even low levels of these drugs, including antibiotics and pesticides, can cause health issues in humans.

You can access the critical review for free until 28th June.

Methods of sample preparation for determination of veterinary residues in food matrices by porous monolith microextraction-based techniques
Fang Wei and Yu-Qi Feng
Anal. Methods, 2011
DOI: 10.1039/C1AY05079F

Why not take a look at some of the papers we’ve published this year on veterinary drug residue analysis

Semi-targeted residue screening in complex matrices with liquid chromatography coupled to high resolution mass spectrometry: current possibilities and limitations
Anton Kaufmann, Patrick Butcher, Kathryn Maden, Stephan Walker and Miryam Widmer
Analyst, 2011, 136, 1898-1909
DOI: 10.1039/C0AN00902D

Assessment of terahertz spectroscopy to detect antibiotic residues in food and feed matrices
Albert Redo-Sanchez, Gerard Salvatella, Regina Galceran, Eva Roldós, José-Antonio García-Reguero, Massimo Castellari and Javier Tejada
Analyst, 2011, 136, 1733-1738
DOI: 10.1039/C0AN01016B

High-throughput chemical residue analysis by fast extraction and dilution flow injection mass spectrometry
Sergio C. Nanita
Analyst, 2011, 136, 285-287
DOI: 10.1039/C0AN00720J

And one more from Analytical Methods:

Development and validation (according to the 2002/657/EC regulation) of a method to quantify sulfonamides in porcine liver by fast partition at very low temperature and LC-MS/MS
Renata Pereira Lopes, Daniella Vasconcellos Augusti, Leonardo Francisco de Souza, Flávio Alves Santos, Josefa Abucater Lima, Eugênia Azevedo Vargas and Rodinei Augusti
Anal. Methods, 2011, 3, 606-613
DOI: 10.1039/C0AY00587H

Read this critical review for the theoretical background of dielectric barrier discharges (DBD) and an introduction to the application of DBD in analytical chemistry.  DBD refers to a kind of gas discharge in which plasma is separated from one or two electrodes by a dielectric barrier.

In contrast to usual discharges with direct current, the plasma is separated from one or two electrodes by a dielectric barrier. This gives rise to two main features of the dielectric barrier discharges: it can serve as a dissociation and excitation device and as an ionization mechanism, respectively.

One referee commented that ‘as a discharge method at ambient pressure and using low power, the DBD is becoming increasingly attractive in various areas of analytical chemistry.’

Dielectric barrier discharges in analytical chemistry

The paper will be free to access to until 1st June.

Dielectric barrier discharges in analytical chemistry
C. Meyer, S. Müller, E. L. Gurevich and J. Franzke
Analyst
DOI: 10.1039/C0AN00994F