Sensors detect potentially risky oestrogenic compounds

Oestrogen occurs naturally in the body and a variety of plants, pharmaceuticals, microbial byproducts and industrial chemicals are also known to activate or block the activation of oestrogen receptors in human cells.

In a statement, Illinois University chemical and biomolecular engineering professor and project leader Huimin Zhao said: ‘There are so many oestrogenic compounds in our environment and some of them could be a danger to health.’

‘We are concerned about oestrogenic compounds because they interact with the oestrogen receptor, which plays an important role in many important biological processes, such as reproduction, bone growth, cell differentiation and metabolism.’

The oestrogen receptor is also implicated in a majority of breast cancers, he said, with compounds that activate it potentially spurring the growth of cancer cells.

The researchers used part of the oestrogen receptor itself in the design of their sensors. They took the region of the receptor that binds to oestrogenic compounds (called the ligand-binding domain) and added two halves of a fluorescent protein that glows only when the halves are reunited. The ligand-binding domain changes its conformation when it binds to an oestrogenic compound. This change, the researchers hoped, would draw the two parts of the fluorescent protein together to produce a signal.

In a series of trials, the researchers found that two of their sensors reliably signalled the presence of oestrogenic compounds. The first, ‘sensor 2’, differentiated between compounds that activate and those that block oestrogen receptors, glowing more brightly in the presence of one and dimming when bound to the other. A second bio-engineered molecule, ‘sensor 6’, fluoresced in the presence of both types of compounds, making it a reliable indicator of chemicals that bind to the receptor.

When incubated in human cells, the sensors responded to oestrogenic compounds within a few hours, Zhao said, with the fluorescent signals gradually increasing in strength up to 24 hours. ‘And also the sensitivity is pretty high,’ he added. ‘Of course it depends on the compound that you’re testing — different compounds will have different affinities. But for a truly oestrogenic compound, we can detect at the nanomolar level — a very low level.’

These are the first such sensors to work in human cells without costly additional chemical steps, he said.

The work appears in the journal Biotechnology and Bioengineering.