Rapid ultrasensitive bacteria detection using microelectrode sensors

Bacterial contamination can be a problem in medical settings and in the food industry. In both cases, rapid and accurate testing for the presence of harmful bacteria is essential, but existing methods generally only fulfil one of those two conditions. Culturing suspected bacteria samples is highly accurate but can take hours to produce results. Electrochemical sensors are fast alternatives but require large bacterial concentrations.

Lai et al. developed an electrochemical sensor using a silver microelectrode that exploits the effects of applying a strong electric field to a sample. Their sensor can detect bacteria rapidly and at extremely low concentrations.

“We designed an intracellular-extracellular combined detection method, which shows high sensitivity and is less time-consuming,” said author Zhengchun Liu. “The bacterial concentration in the solution can be quickly obtained within five minutes, and the minimum detection concentration can reach as low as one colony-forming unit per milliliter.”

Their sensor takes advantage of the extreme sensitivity afforded by microelectrodes bolstered with nanostructures. A multistep process sees aptamers on the electrodes capture the target bacteria, followed by a local high electric field generated by the electrodes triggering a leakage of intracellular ions. This combined process gives the sensor its ability to detect bacteria at such low concentrations.

The researchers hope to expand their method to detect other biological molecules at low concentrations, and to improve their device to make it more portable.

“Based on the construction and experimental basis of this work, we plan to develop microelectrode sensing systems integrated in microfluidic devices for portable and fast detection,” said Liu.

Source: “An ultrasensitive bacteria biosensor using “Multilayer cake” silver microelectrode based on local high electric field effect,” by Qingteng Lai, Qibin Niu, Wei Chen, Yanke Zhang, Mengqiu Long, Bo Liang, Fuliang Wang, and Zhengchun Liu, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0090107 .