Researchers Use an Electronic Tongue to Identify Antibiotics in Milk
Researchers from Brazil and the United States tested an electronic tongue that uses MXene nanomaterials to identify antibiotics in milk. The study, published in ACS Omega, examined samples containing more than one antibiotic in a complex liquid that also includes proteins, fats, sugars and salts.
MXene is a family of two-dimensional nanomaterials that has been studied for about 15 years. Its structures contain layers of transition metals, such as titanium, niobium, vanadium or molybdenum, combined with carbon, nitrogen or both. The materials have high electrical conductivity, a large surface area and surfaces that can be modified to interact with different substances.
For the milk device, the researchers used three MXene compositions, changing the ratio of carbon to nitrogen. Each coated fibre therefore responded differently to the chemical environment of a sample. Connected to an impedance meter, every fibre served both as a support and as a sensing element. The instrument applied a small electrical signal and recorded resistance, capacitance, and the real and imaginary components of impedance.
“When we change the composition of MXene, we also change its properties. That was exactly what we were looking for in the electronic tongue: sensors with different properties and performance combined in the same device,” said Facure, the researcher who worked on the system.
The approach differs from that of a conventional chemical sensor, which is designed to select one substance. No individual sensor in the electronic tongue has to recognise a specific antibiotic. The system instead analyses the combined pattern of responses produced by a sample. The researchers used multivariate statistical methods, including principal component analysis, to reduce the number of variables and identify the main differences between samples.
“The simultaneous presence of more than one antibiotic is especially relevant for demonstrating how the system works. Instead of looking for a single molecule in a simple solution, the electronic tongue has to extract information from a complex matrix such as milk, in which proteins, fats, sugars, salts and many other substances can also interact with the sensors,” said Daniel Corrêa of Embrapa Instrumentation. Corrêa supervised Facure during his doctorate at the Federal University of São Carlos, or UFSCar.
The project involved researchers from Embrapa Instrumentation, UFSCar, the Federal University of Bahia and Drexel University in the United States. Drexel professor Yury Gogotsi reported the first MXene material in 2011. Facure spent a year in Gogotsi’s group from 2022 to 2023 with support from FAPESP and continues to collaborate with the American institution. Luiza Mercante of the Federal University of Bahia is also part of the research line, which has previously applied a related principle to detect neurotransmitters including acetylcholine, dopamine, glycine, glutamate, histamine and tyrosine.
Facure said that the work remains laboratory research conducted under controlled conditions. No finished instrument is yet available for farms, dairies or inspection authorities. The researchers are also studying MXenes for energy-storage composites, including supercapacitors, as well as nanogenerators and pollution-remediation systems. FAPESP financed the milk study through a thematic project coordinated by Osvaldo Novais de Oliveira Junior of the University of São Paulo’s São Carlos Institute of Physics.
