Analyst Blog

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