Analyst Blog

A new MTS Search Engine has been recently optimised to identify volatile compounds such as pesticides, pollutants and nitrosamines.
The mass to structure or MTS Search Engine is a database containing theoretical molecular mass information for about 20,000 compounds and it was initially developed for identification of compounds in atmospheric pressure ionization (API)-LC-MS. The database can be used for forensic studies and allows determination of street drugs, doping agents in urine samples and determination of pesticides in food. So far, it has been used exclusively for non-volatile analytes determined by LC-MS.

MTS Search Engine based on GC-MS spectra

Wenta Liao and William Draper from USA now extend the identification to volatile and semi-volatile compounds using chemical ionization GC-MS. According to the authors, this new MTS Search Engine has the advantage to identify a wide variety of pesticides, nitrosamines and other toxic substances, as well as halogenated and non-halogenated structures, which could not be identified before.

To read more about this research, take a look at the full article by clicking the link below. This paper will be free to read until January 24th.

Identification of volatile and semivolatile compounds in chemical ionization GC-MS using a Mass-To-Structure (MTS) Search Engine with integral isotope pattern ranking
Wenta Liao and William M. Draper
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36490E

Carbohydrate microarrays have become an important tool for studying glycan-cell interactions, carbohydrate-binding proteins, and in detecting dangerous pathogens. The current sensor methods require complex labeling or indirect analyte detection.

C–H insertion photocoupling reaction and copper “click” methods

Using surface plasmon resonance spectroscopy (SPR), Sabine Szunerits and coworkers at  Lille 1 University detected carbohydrate-binding protein complexes directly and without labels. In order to use SPR, they developed a unique substrate of Ti, Au, and silicon dioxide and tested two carbohydrate surface attachment chemistries. The azide-functionalized surfaces were linked to a glycan using a copper “click” chemistry or photocoupling. Both methods showed comparable binding efficiency and sensitivity of the carbohydrate binding protein.

To read the full article, click on the link below. It will be free to read until January 9th.

Comparison of photo- and Cu(I)-catalyzed “click” chemistries for the formation of carbohydrate SPR interfaces
Nazek Maalouli, Alexandre Barras, Aloysius Siriwardena, Mohamed Bouazaoui, Rabah Boukherroub and Sabine Szunerits
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36272D

Electrochemical Sensing Using Target-Induced Strand Release

The toxic, bioaccumulative, and non-biodegradable effects of heavy metals pose a severe environmental concern. Hence, monitoring toxic metals such as lead requires effective detection methods. Bo Tang and colleagues from the Shandong Normal University, China, have developed the latest electrochemical detection strategy, which is based on the target-induced strand release method. In their design, the lead-binding DNA aptamer forms a duplex with a complementary DNA sequence that is immobilized to an electrode surface. In this state, methylene blue redox indicators are able to intercalate along the duplex structure, and provide a readable electrochemical signal. However, in the presence of lead, the metal ions bind specifically to the aptamer, which allows release of the lead-aptamer complex into solution. The subsequent release of methylene blue molecules away from the electrode surface leads to a measurable decrease in signal to signify lead detection.

Find out more details by accessing the link below:

A selective amperometric sensing platform for lead based on target-induced strand release
Feng Li, Limin Yang, Mingqin Chen, Peng Li and Bo Tang
Analyst, 2013, 138, 461-466
DOI: 10.1039/C2AN36227A

Take a look at these new articles published in Analyst free for you to enjoy until January 9th.

Topics include aptamer based spectrofluorometry, the development of enzyme-free colorimetric bioassays based on gold nanoparticle catalyzed dye decolorization, new ways to identify DNA G-quadruplex structures, and a new set-up to monitor biphasic switchable solvent synthesis. We also have an interesting review on coupled isothachophoresis and capillary electrophoresis which describes the features, advantages and limitations of the methodologies currently in use.

To have a read now, click on the links below:

Coupling isotachophoresis and capillary electrophoresis: a review and comparison of methods
Supreet S. Bahga and Juan G. Santiago
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36150G

A novel signal-amplified strategy based on assembly reactivation for highly specific and sensitive detection of chair-like antiparallel G-quadruplex
Wei Gai ,  Qianfan Yang ,  Junfeng Xiang ,  Wei Jiang ,  Qian Li ,  Hongxia Sun ,  Lijia Yu ,  Qian Shang ,  Aijiao Guan ,  Hong Zhang and Yalin Tang
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36557J

Aptamer-based spectrofluorometry for cellular prion protein using N,N′-bis[3,3′-(dimethylamino)propylamine]-3,4,9,10-perylenetetracarboxylic diimide
Lei Zhan ,  Li Jiao Liang ,  Shu Jun Zhen ,  Chun Mei Li and Cheng Zhi Huang
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36322D

Comprehensive monitoring of a biphasic switchable solvent synthesis
Sonja Hardy ,  Irene M. de Wispelaere ,  Walter Leitner and Marcel A. Liauw
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36044F

Enzyme-free colorimetric bioassay based on gold nanoparticle-catalyzed dye decolorization
Wei Li ,  Jie Li ,  Weibing Qiang ,  Jingjuan Xu and Danke Xu
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36374G

The affordable and rapid testing of DNA hybridization and polymorphisms is crucial for the diagnosis of genetic and infectious diseases. DNA biosensors based on nucleic recognition represent one of the most recent technologies currently employed. Electrochemical transducers are commonly used for sensing of DNA hybridization because they are inexpensive, small and highly sensitive. However, this kind of device sees the attachment of a single DNA probe onto the electrode surface to act as recognition element for the complementary target, and an external electro-active label that recognises this complex structure is required. To avoid the use of an external electro-active label, researchers have started to use new materials.

Differential pulse voltammetry to examine the oxidation of guanine on target DNA

Adeline Huiling Loo and co-workers, from the Nanyang Technological University of Singapore, used graphene, a low cost substance made of a single layer of carbon atoms densely packed. Graphene has high electron conductivity, large specific surface area and fast electron transfer, and is considered a material with a great potential for biosening applications.

The authors analysed the properties of graphene oxide, electrochemically reduced graphene oxide and thermally reduced graphene oxide and investigated for the first time the mechanisms behind physically immobilized hairpin DNA hybridization. For the label free detection of DNA hybridization and polymorphism, they employed differential pulse voltammetry and examined the oxidation of guanine on target DNA molecules hybridized with an inosine-substituted hairpin DNA probe. According to the study, graphene oxides show the best performance in terms of recognition of complementary and non-complementary DNA sequences.

To know more about this research, click on the link below. This paper will be free to read until January 9th.

An insight into the hybridization mechanism of hairpin DNA physically immobilized on chemically modified graphenes
Adeline Huiling Loo ,  Alessandra Bonanni and Martin Pumera
Analyst, 2013, 138, 467-471
DOI: 10.1039/C2AN36199J

In 2004 the World Health Organisation estimated that over half a million women died from breast cancer.  A great deal of research is now conducted to improve the diagnostics and prognosis of cancers.  One avenue of research is to improve our understanding of cancers at a cellular level. Anhong Zhou and coworkers from Utah State University have recently used atomic force microscopy (AFM) and Raman spectroscopy to attempt just that.

Combined Raman spectroscopy and AFM to detect differences in cancer cells

Their preliminary study, in this new Analyst HOT paper, examines the use of atomic force microscopy (AFM) and Raman spectroscopy to study a breast cancer cell line and the effect of the presence or absence of a metastasis suppressor gene on cell behaviour.  They have also compared various cancer cell lines to examine the differences in behaviour at the cellular level between cancer types. The authors provide a comprehensive analysis of both the practical and data processing techniques required to differentiate the cell types.  The use of both AFM and Raman reveals information about the biochemical and biomechanical attributes of the cell lines and is an approach that could increase our understanding of cancer cell behaviour and tumour development.

Subcellular spectroscopic markers, topography and nanomechanics of human lung cancer and breast cancer cells examined by combined confocal Raman microspectroscopy and atomic force microscopy
Gerald D. McEwen, Yangzhe Wu, Mingjie Tang, Xiaojun Qi, Zhongmiao Xiao, Sherry M. Baker, Tian Yu, Timothy A. Gilbertson, Daryll B. DeWald and Anhong Zhou
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36359C

This article will be free to read for the next two weeks.

Pesticides are necessary for effective crop production but their toxicity can pass onto consumers and cause dangerous health effects. Mass spectrometry continues to be the gold standard for pesticide residue testing by providing highly sensitive and specific tests for food safety. Although many versions of mass spectrometry have been applied to this field, there are still problems such as loss of sample, requiring high voltages, complex ionization preparation, and difficulty in heterogeneous solutions. To overcome these limitations, researchers at East China Institute of Technology and Nanchang University have coupled thermal dissociation atmospheric chemical ionization (TDCI) to linear trap mass spectrometry (LTQ-MS), for a more environmentally friendly pesticide detection technique. TDCI uses ionic liquids to create ions, instead of an external source, and the resulting solution exchanges charge with the thermally evaporated analytes. In order to test the capabilities of TDCI, a common pesticide, dimethoate, was measured in highly viscous solutions, fruit juices. TDCI rapidly detected trace levels of dimethoate in a variety of fruit juices below the EU standardized levels for fruit and with high specificity.

Dissociation atmospheric chemical ionization (TDCI) source coupled with LTQ-MS

To know more about the study, click on the link below:

Thermal dissociation atmospheric chemical ionization ion trap mass spectrometry with a miniature source for selective trace detection of dimethoate in fruit juices
Yongzhong Ouyang,  Xinglei Zhang,  Jing Han,  Xiali Guo,  Zhiqiang Zhu,  Huanwen Chen and Liping Luo
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN36244A

Our health and well-being is deeply impacted by the air that we breathe. Maintaining good quality of air is highly dependent on the ability of chemical gas sensors to monitor toxic air pollutants in the environment. While many sensors are currently available, there is still a need for a detection system that is highly sensitive and selective, robust, accurate, fast, adaptable to mass production, and capable of monitoring many different chemical gases. Jong Kyu Kim and colleagues from the Republic of Korea have addressed some of these challenges by developing an “electronic nose” – a series of high performance gas sensors based on an array of TiO₂ nanohelices fabricated by the method of rotating oblique angle deposition (OAD).

Gas sensors based on an array of near single crystalline TiO2

Find out more by clicking on the link below:

A near single crystalline TiO2 nanohelix array: enhanced gas sensing performance and its application as a monolithically integrated electronic nose
Sunyong Hwang,  Hyunah Kwon,  Sameer Chhajed,  Ji Won Byon,  Jeong Min Baik,  Jiseong Im,  Sang Ho Oh,  Ho Won Jang,  Seok Jin Yoon and Jong Kyu Kim
Analyst, 2013, Advance Article
DOI: 10.1039/C2AN35932D

With the first issue of Analyst 2013, we also have a good number of HOT papers for you to have a read.

Articles cover a wide range of topics including improved biosensing methodologies, some interesting data on volatile biomarkers of tumour cells and this novel tattoo-based potentiometric sensor (see picture). According to Wang and co-workers, these new tattoos have a potential in measuring strenuous physical activity by monitoring the pH of the skin.

These papers will be free to read until December 12th.

Photograph of the tattoo ISE sensor. Bandodkar et al., Analyst, 2013, 138, 123-128

Electrogenerated chemiluminescence of nanomaterials for bioanalysis
Shengyuan Deng and Huangxian Ju
Analyst, 2013, 138, 43-61
DOI: 10.1039/C2AN36122A

Integration of rapid DNA hybridization and capillary zone electrophoresis using bidirectional isotachophoresis
Supreet S. Bahga ,  Crystal M. Han and Juan G. Santiago
Analyst, 2013, 138, 87-90
DOI: 10.1039/C2AN36249J

Quantification by SIFT-MS of acetaldehyde released by lung cells in a 3D model Abigail
V. Rutter ,  Thomas W. E. Chippendale ,  Ying Yang ,  Patrik Španěl ,  David Smith and Josep Sulé-Suso
Analyst, 2013,138, 91-95
DOI: 10.1039/C2AN36185J

Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring
Amay J. Bandodkar ,  Vinci W. S. Hung ,  Wenzhao Jia ,  Gabriela Valdés-Ramírez ,  Joshua R. Windmiller ,  Alexandra G. Martinez ,  Julian Ramírez ,  Garrett Chan ,  Kagan Kerman and Joseph Wang
Analyst, 2013, 138, 123-128
DOI: 10.1039/C2AN36422K

Integration of multiple components in polystyrene-based microfluidic devices part I: fabrication and characterization
Alicia S. Johnson ,  Kari B. Anderson ,  Stephen T. Halpin ,  Douglas C. Kirkpatrick ,  Dana M. Spence and R. Scott Martin
Analyst, 2013, 138, 129-136
DOI: 10.1039/C2AN36168J

Integration of multiple components in polystyrene-based microfluidic devices part II: cellular analysis
Kari B. Anderson ,  Stephen T. Halpin ,  Alicia S. Johnson ,  R. Scott Martin and Dana M. Spence
Analyst, 2013, 138, 137-143
DOI: 10.1039/C2AN36171J

Microfluidic integration of Western blotting is enabled by electrotransfer-assisted sodium dodecyl sulfate dilution
Chenlu Hou and Amy E. Herr
Analyst, 2013, 138, 158-163
DOI: 10.1039/C2AN36033K

Screening reactive metabolites bioactivated by multiple enzyme pathways using a multiplexed microfluidic system
Dhanuka P. Wasalathanthri ,  Ronaldo C. Faria ,  Spundana Malla ,  Amit A. Joshi ,  John B. Schenkman and James F. Rusling
Analyst, 2013, 138, 171-178
DOI: 10.1039/C2AN35993F

Biofuel cell-based self-powered biogenerators for online continuous monitoring of neurochemicals in rat brain
Hanjun Cheng ,  Ping Yu ,  Xulin Lu ,  Yuqing Lin ,  Takeo Ohsaka and Lanqun Mao
Analyst, 2013, 138, 179-185
DOI: 10.1039/C2AN36385B

Fast and continuous-flow separation of DNA-complexes and topological DNA variants in microfluidic chip format
Martina Viefhues ,  Jan Regtmeier and Dario Anselmetti
Analyst, 2013, 138, 186-196
DOI: 10.1039/C2AN36056J

Ultrasensitive detection of mRNA extracted from cancerous cells achieved by DNA rotaxane-based cross-rolling circle amplification
Sai Bi ,  Yangyang Cui and Li Li
Analyst, 2013,138, 197-203
DOI: 10.1039/C2AN36118C

A biosensor fabricated by incorporation of a redox mediator into a carbon nanotube/nafion composite for tyrosinase immobilization: detection of matairesinol, an endocrine disruptor
Jahangir Ahmad Rather ,  Sanaz Pilehvar and Karolien De Wael
Analyst, 2013, 138, 204-210
DOI: 10.1039/C2AN35959F