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.