Biosensor detects one-billionth of a gram in minutes

Known as a biochemiresistor, the technology meets a long-standing challenge to create a sensor that is both sensitive to the presence of chemical compounds and responds quickly.

According to researchers at the University of New South Wales (UNSW), there are a range of potential uses in detecting drugs, toxins and pesticides for biomedical or environmental analysis.

“Our biochemiresistor was able to detect enrofloxacin in neat milk in 40 minutes, at level as low as one nanogram in a litre of milk. To put that number in perspective, a nanogram is a billionth of a gram and is the mass of a single cell.

“While that is impressive enough, the sensor is a general concept that can be widely applied across many different fields.”

The biochemiresistor uses gold-coated magnetic nanoparticles modified with antibodies that are selective for the chemical constituent – or analyte - of interest.

The nanoparticles are dispersed into the sample for analysis and if the analyte is present some of the antibodies detach from the nanoparticles.

Using a magnet, the nanoparticles are then assembled into a film between two electrodes and the electrical resistance is measured.

The more analyte is present, the more antibodies leave the nanoparticles and the lower the resistance in the nanoparticle film.

“This new type of biosensor is rapid in response because the magnetic nanoparticle biosensors go and get the analyte rather than the usual approach of waiting for the analyte to find the sensing surface,” says Gooding.

“The biochemiresistor is also more sensitive than the usual biosensor because, as the nanoparticles are dispersed throughout the sample, the entire sample is analysed, not just a small portion of the solution.”