Micro machines shine a light on ecstasy
Scientists in Denmark and Spain have designed a molecular machine that can detect MDMA – the active ingredient in ecstasy – in tiny quantities and with almost 100% certainty.
Molecular machines – extraordinarily tiny machines made from individual moving molecules – are a burgeoning area of research. Last year’s Nobel Prize in Chemistry went to three chemists for their ground-breaking efforts in this area.
Now Jan Jeppesen, from the University of Southern Denmark, and his team of researchers from universities in Denmark and Spain, have turned the concept to great effect, in a recent paper published in our journal Chemical Communications.
A commonly used molecular machine is a large ring-shaped molecule threaded onto a separate rod-like molecule. Under certain conditions the ring can unthread from the rod, and if we can work out what those conditions are and how to control them, we can control the ‘machine’. This type of structure is referred to as a pseudorotaxane.
Jan and his team have used this type of machine in their detector. They start with a porous silica nanoparticle, essentially a tiny hollow ball with holes in it, and fill it with smaller fluorescent molecules.
They then attach pseudorotaxanes to the surface of the ball in such a way that the rings, which are relatively large and bulky, block the pores and stop the fluorescent molecules from escaping.
Sensitive and highly selective
Enter MDMA. The particular type of ring that the authors are using – referred to by chemists as a ‘blue box’ – binds strongly to MDMA. This means that when MDMA is present the rings will detach from the pseudorotaxane and bind to the MDMA instead.
The porous ball is then left wide open and the fluorescent molecules are able to stream out. Once liberated from their cage, they are simply detected by a fluorescence sensor.
Crucially the blue box doesn’t bind to other molecules – just MDMA – in other words the sensor is highly selective. The authors tested their system with other drugs, such as morphine, methadone, heroin and cocaine, and did not observe the same effect.
And you only need a tiny amount of MDMA – the equivalent of 1 gram in 1000 litres of water – for the effect to occur.
It’s an elegant approach that dispenses with the need for expensive, specialist machines. What’s more, it is incredibly reliable, and could make for a cheap, easily transportable testing kit.
The paper has already garnered interest in the media, with articles appearing on Science News Line, Phys.org, MixMag and Laboratory Equipment.
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