A long-standing challenge of biosensors is how to efficiently and economically detect traces of chemicals or pathogens in large volumes of sample. Researchers at the University of New South Wales (UNSW) in Sydney, Australia have developed a new class of biosensor that changes the detection paradigm to help overcome such obstacles.
The detector utilizes a technique which is most easily described as a sort of ‘reverse immunoassay.’ The detector distributes gold-coated magnetic nanoparticles labeled with selective antibodies into the sample. If the target analyte is present, some of the antibodies detach from the nanoparticles.
Then 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,” said Professor Justin Gooding.
The device, called a biochemresistor, can detect exceptionally small traces of contaminants in liquids in just 40 minutes. “The entire idea of the work was to develop a method that could allow us to detect rare species in large volumes in a reasonable amount of time,” said Gooding. “This new idea has potential for defense, food safety and water quality applications.”
The team recently published a paper in the prestigious chemistry journal Angewandte Chemie describing how they successfully tested the new sensor by detecting small traces of the veterinary antibiotic enrofloxacin in milk samples.
“Our biochemresistor was able to detect enrofloxacin in neat milk in 40 minutes, at levels 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.”
The research team included partners from the Australian Centre for NanoMedicine and the former ARC Centre of Excellence for Functional Nanomaterials at UNSW.