Cocaine detection: Concentrating on SERS

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  • Published: Nov 1, 2016
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Cocaine detection: Concentrating on SERS

Nanomolar

Structure of cocaine generated using JMol on ChemSpider by David Bradley

A cocaine detector based on surface enhanced Raman spectroscopy (SERS) could be much more efficient and effective alternative to existing technology, according to researchers from Valencia and the Basque Country. Their approach works at very low concentrations of cocaine.

Researchers at the Universitat Politècnica de València (UPV), CICbiomaGUNE and CIBER-BBN, of the Carlos III Health Institute, the study describe details of their approach in "Chemistry - A European Journal". Their method combines of gated mesoporous silica nanoparticles and SERS spectroscopy using signal amplification based on gold nanoparticles. They have demonstrated proof of principle in detecting nanomolar concentrations of cocaine; specifically down to 10 nanomolar. The same technology can also be used to detect the genomic DNA of bacteria, such as mycoplasma, at a level of just 30 copies of the per microlitre.

"Cocaine is an alkaloid obtained from the leaves of the coca plant, which is extensively used in developed countries as an illegal recreational drug." The team says. "Although cocaine production and distribution are restricted and illegal in most contexts, it is a powerful nervous system stimulant that causes strong addiction among consumers, frequently leading to serious health as well as social and legal problems." As such, there is a critical regulatory and forensic need for detection of this drug of abuse at very low levels, where criminal investigation and conviction might hinge on only trace quantities being present in evidence or at a crime scene.

Different spheres

In an entirely different sphere, mycoplasma, which refers to a genome of prokaryotic microorganisms that have been described as parasites of various animals and plants, characteristically lack a cell wall and are resistance to many of the common antibiotics used in medicine. They are almost ubiquitous in research laboratories as cell-culture contaminants, which can cause interference with results. There is thus a need to be able to detect them in the biomedical and life sciences and the same technology that can detect cocaine and other small molecules might be just as applicable despite the differences between small natural product molecules and biological macromolecules.

The team's detection system relies on release of a dye molecule (crystal violet) from within the silica nanoparticles. The dye is a SERS reporter and readily identifiable by SERS spectroscopy but only when the target substance is present because it is capped with either a suitable DNA sequence for the detection of mycoplasma genomic DNA or with an aptamer that selectively coordinates to cocaine. "In the presence of mycoplasma or cocaine, the pores of the nanoparticles unblock, letting in the dye that interacts with gold nanotriangle. It is this interaction that is detected by SERS spectroscopy," the team explains. "The concentration of the substance being detected is proportional to the signal detected", adds Ramón Martínez Máñez, director of the Inter-university Research Institute for Molecular Recognition and Technological Development and scientific director of CIBER-BBN.

New context

SERS spectroscopy has not been used in this context before wherein gated mesoporous silica nanoparticles are key to the method. The preliminary results obtained so far are positive, the team suggests, and point to the possibility of using this technique in the detection of other small molecules and other pathogens.

"We propose that a wide variety of SERS-active molecules can be used as cargo in different capped systems, which can be selectively opened in the presence of specific target analytes and combined with SERS efficient plasmonic nanoparticles, rendering this approach appealing and full of potential for the design of new sensing systems," the team concludes.

"We are currently trying to detect other molecules and biomolecules following the same principle in order to know if this can be applied to a wide range of situations," Martínez Máñez told SpectroscopyNOW.

Related Links

Chem Eur J 2016, 22, 13488–13495: "Surface Enhanced Raman Scattering and Gated Materials for Sensing Applications: The Ultrasensitive Detection of Mycoplasma and Cocaine"

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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