Analyst Blog

Liquid chromatography using nanofluidic chip and DIC-TLM

The field of separation science has been continually evolving to enable the separation of smaller volumes. This interdisciplinary field has required developments in capillary electrophoresis, microfluidics and new detection technologies such as plasmonic sensing and thermal lensing. 

Researchers from the Department of Applied Chemistry, University of Tokyo lead by Prof. Kitamori have shown the ability to perform femtolitre (1 x 10^-15) separation and detection of nonfluorescent samples in a nanofluidic device. Using an extended nanofluidic device the researchers were able to separate and detect nonfluorescent molecules for the first time. Previous detection methodologies relied mainly on laser-induced fluorescence. 

The researchers showed the ability of nanofluidic separation science combined with differential interference contrast thermal lens microscopy (DIC-TLM) to enable detection of 370 molecules in a 2.3 μm wide by 350 nm deep nanochannel with a separation efficiency of 150,000 plates/m. DIC-TLM is thermal lens microscopy with an increased detection limit by realising background-free photodetection using differential interference contrast. 

Amazingly the injection volume and number of molecules were estimate to be 21 fL (1 x 10^-15) and 250 zmol at the limit of detection. This limit of detection provides separation of a sample 8 orders of magnitude smaller that that possible with high-performance liquid chromatography. This injection volume is much smaller than a single cell and detection limit is similar to the number of typical protein molecules in a single cells. Providing a promising tool for single cell research. 

To read more about this research download the HOT article which is free to access until April 5^th 

Femtoliter-Scale Separation and Sensitive Detection of Nonfluorescent Samples in an Extended-Nano Fluidic Device
Hisashi Shimizu, Kazuma Mawatari and Takehiko Kitamori 
Analyst, 2014, Accepted Manuscript

The authors work features on the front cover of Issue 5

This blog has been written by Adam Davis, a Guest Web-Writer for Analyst and Analytical Methods.

Enteric coatings are used to protect acid labile active pharmaceutical ingredients upon entry into the stomach, allowing for controlled and sustained release of active ingredients to the small intestine later. Enteric coated formulations typically consist of a sugar core, a layer of active ingredient followed by the enteric coating. Using current analysis methods determining the thickness of these layers can take up to 24hrs.

In this article, which appears in Issue 5 of Analyst, researchers from University College Cork, Ireland and Kinetox, Netherlands, have demonstrated how Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) can be used for rapid profiling of enteric coated spheres. The BARDS technique is a novel approach which utilises the acoustic signature of cores spheres and enteric coating as they dissolve, which arise as result of the changes in compressibility of the solvent as a compound dissolves in it. This alters the speed of sound through the solvent, which in turn changes the frequency in solution. The use of BARDS has important implications for manufacturing, quality assurance and stability testing for pharmaceuticals.

Rapid profiling of enteric coated drug delivery spheres via Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS)
D. Fitzpatrick, R. Evans-Hurson, Y. Fu, T. Burke, J. Krüse, B. Vos, S. G. McSweeney, P. Casaubieilh and J. J. Keating
Analyst, 2014, 139, 1000-1006
DOI: 10.1039/C3AN01809A

Early and accurate monitoring of pathogens such as Escherichia coli is critical for food and water safety, clinical diagnosis, and biosecurity. However there are a number of limitations to current detection methods such as cell culturing, and immunoassays. These drawbacks include non-specificity, insensitivity, as well as the requirement of long analysis time, intensive labor, and extensive sample purification. To address some of these limitations, Christopher Pöhlmann and his colleagues from the University of Bayreuth in Germany have developed a lateral flow device based on a sandwich assay design using gold nanoparticle-oligonucleotides to detect ribosomal RNA of E. coli. The new device is able to provide specific detection of E. coli within 25 minutes and requires no signal amplification step.

A Lateral Flow Assay for Detection of E. coli Ribosomal RNA

Find out more about this discovery by reading the full paper below, which is free to download until March 7th:

A lateral flow assay for identification of Escherichia coli by ribosomal RNA hybridization
Christopher Pöhlmann, Irina Dieser and Mathias Sprinzl
Analyst, 2014, 139, 1063-1071
DOI: 10.1039/C3AN02059B

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