Ringing the changes: Environmental endocrine detection

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  • Published: Mar 1, 2013
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Ringing the changes: Environmental endocrine detection

Starchy response

Credit: Elsevier/Biosensors and Bioelectronics 42 (2013) 632–639 Cyclodextrin, the natural starch ring molecule, can be used to create a sensitive coating on gold for surface enhanced Raman spectroscopic (SERS) detection of endocrine disrupters present in environmental water samples, according to a new study.

Cyclodextrin, the natural starch ring molecule, can be used to create a sensitive coating on gold for surface enhanced Raman spectroscopic (SERS) detection of endocrine disrupters present in environmental water samples, according to a new study.

Cheng Fang, Narasimha Murthy Bandaru and Amanda Vera Ellis of the School of Chemical and Physical Sciences at Flinders University, in Bedford Park, South Australia and Nicolas Hans Voelcker of the Mawson Institute, University of South Australia, in Mawson Lakes, have used nanosphere lithography to create a monolayer of silica nanospheres (330 nanometres diameter) on a gold surface. The nanospheres then act as a template to allow them to modify the surface with mono-6-deoxy-6-((2-mercaptoethyl)amino)-beta-cyclodextrin.

Molecular mops

EDCs represent a group of both naturally occurring and synthetic compounds that can often interfere with the hormonal, or endocrine systems of animals including humans. There is widespread environmental concern that the presence of EDCs in ecosystems and the food chain might be detrimental to living things and also human health. As such, analytical technology that can quickly and easily detect various EDCs even at trace quantities in environmental and medical samples is essential for tracking their progress through waterways, the food chain in medical conditions that may arise from their assimilation by people. The Australian team has developed one such technology that shows great promise.

Cyclodextrins (also known as cycloamyloses) are a group of cyclic oligosaccharides well known to supramolecular chemists and others. They are usually produced from starch by enzymatic conversion and used in the food, pharmaceutical and chemical industries because they have the ability to "host" smaller "guest" molecules. The seven-sugared ring that is beta-cyclodextrin even finds uses in Procter and Gamble's deodorizing products. Now, the Australian team has found yet another use for beta-CD.

Modified metal detector

The researchers have now demonstrated that their beta-CD coated metal surface can mop up trace quantities of model compounds used to simulate endocrine-disrupting chemicals (EDCs) in environmental samples. The models used included 3-amino-2-naphthoic acid (NAPH), potassium hydrogen phthalate (PHTH) and the beta-estradiol (ESTR). With the EDC-type compounds trapped as guests in the cyclodextrin hosts on the metal surface, the team was then able to carry out SERS experiments to reveal the presence of the EDCs in the spectra obtained.

Indeed, the modified metal surface offers a limit of detection of 3.0 micromolar for NAPH, 10 micromolar for PHTH and 300 nanomolar for ESTR, the team reports in the journal Biosensors and Bioelectronics. These figures are between ten and one hundred times lower than the detection limits for the naked lithographed metal lacking the beta-CD. "The three selected compounds have previously been shown to exhibit weak Raman activity or low affinity to a Ag/Au surface," the team says. "Individual and simultaneous detection of NAPH and PHTH from their mixture was achieved as evidenced using the bianalyte Raman technique," the team adds.

The team concludes that the same approach, but perhaps with modified beta-CD or other host molecules might be used to detect a wider range of EDCs and other compounds of environmental and medical concern.

Related Links

Biosens Bioelectron 2013, 42, 632–639: "Beta-cyclodextrin decorated nanostructured SERS substrates facilitate selective detection of endocrine disruptor chemicals"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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