Scientists create a biological sensor that can detect and trap chemical pollutants in water ‘in the same way that a Venus flytrap catches insects’

  • Experts worked with chemicals called porphyrins — which are natural pigments 
  • Members of this class are responsible for making blood red and plants green
  • Researchers found that could invert metal-free porphyrins and add to their core
  • This creates little traps that can be tuned to close around certain pollutants

Insect-snaring Venus flytraps have inspired scientists to create a new kind of biological sensor that can detect and trap water pollutants, a study reports.

The pollutant-catching senors are based on porphyrins, pigments whose natural roles include making red blood cells red and light-harvesting chlorophyll green.

By turning metal-free versions of the pigment inside out and adding in special core, researchers have turned the molecules into little traps.

Thus the sensors can detect and grab target molecules — such as pollutants — a finding that could have various environmental, medical and security applications.

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Insect-snaring Venus flytraps, pictured, have inspired scientists to create a new kind of biological sensor that can detect and trap water pollutants, a study reports 

WHAT DO WE KNOW ABOUT PORPHYRINS?

Porphyrins are a class of unique chemicals that are deeply coloured.

In nature they often serve as pigments, for example giving colour to red blood cells and acting to make light-harvesting chlorophyll green. 

Porphyrins usually have metal cores that confer their special properties.

However, chemists from Trinity College Dublin have found that metal-free porphyrins can be turned inside out and given different active cores.

This turns the pigment into a molecular trap which can be tuned to ensnare particular pollutants as desired.

Although porphyrins in nature contain metal cores that generate their varied properties, chemists Mathias Senge and Karolis Norvaiša of Trinity College Dublin and colleagues instead began looking a metal-free porphyrins.

This has opened up an entirely new range of molecular receptors.

The team have found that they can force the porphyrin molecules to turn inside-out — as so that they loosely resemble a saddle — thereby allowing them to take advantage of the porphyrins’ previously inaccessible cores.

Into this core the team can place so-called functional groups designed to catch small target molecules — like pharmaceutical or agricultural pollutants — and store them in the porphyrins larger, trap-like structure.

‘If you bend the molecules out of shape, they resemble the opening leaves of a Venus flytrap and, if you look inside, there are short stiff hairs that act as triggers,’ said Dr Norvaiša.

‘When anything interacts with these hairs, the two lobes of the leaves snap shut.’

‘The peripheral groups of the porphyrin then selectively hold suitable target molecules in place within its core, creating a functional and selective binding pocket.’

This works, he added, ‘in exactly the same way as the finger-like projections of Venus flytraps keep unfortunate target insects inside.’

The pollutant-catching senors are based on porphyrins, pigments whose natural roles include making red blood cells red and light-harvesting chlorophyll green. Pictured, the research is highlighted on the cover of the journal Angewandte Chemie International Edition, showing the porphyrin molecules’ structure superimposed over the concept’s natural inspiration 

Furthermore, the pigment-based nature of porphyrin compounds mean that they change colour when they capture a target — thus making it easy to observe them working.

‘Gaining an understanding of the porphyrin core’s interactions is an important milestone for artificial porphyrin-based enzyme-like catalysts,’ added Professor Senge.

‘We will slowly but surely get to the point where we can realise and utilise the full potential of porphyrin-substrate interfaces to remove pollutants, monitor the state of the environment, process security threats and deliver medical diagnostics.’

‘A colleague has shown that he can use these molecules to detect lung cancer by analysing people’s breath,’ Professor Senge told the Times. 

The full findings of the study were published in the journal Angewandte Chemie International Edition. 

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