Although electrochemical biosensors are often used for food quality assessment, their application is often limited by the requirement for intensive sample preparation, resulting in time delays and higher costs.

Azadeh Nilghaz, a research fellow at Monash University studying drug delivery disposition and dynamics, and Nicolas H. Voelcker, scientific director for the Melbourne Center for Nanofabrication and professor of pharmaceutical sciences at Monash University, directed the research team.

“Food freshness testing is still too dependent on lab methods and sample preparation,” Nilghaz said. “Our ‘aha’ moment came when we realized a microneedle interface could access the fish tissue chemistry directly—so we could measure freshness markers on-site without extraction or filtration. The goal became creating a microneedle array [MNA]-based electrochemical biosensor, designed for direct food safety and quality analysis, without the need for sample preparation.”

Physical signs of spoilage in meat products might take hours or even days to appear. In contrast, compounds such as HX start forming almost immediately after death because nucleic acids and other molecules begin to break down. Therefore, the researchers decided to build a sensor that measures the level of HX, indicating how fresh the fish is that is being tested.

To build the sensor, the team created a four-by-four microneedle array and coated it with specialized gold nanoparticles and an enzyme to break down HX. The sensor is pressed into the surface of a piece of fish and anchored by the microneedles. As the enzyme breaks down HX, the electric potential within the fish changes and the sensor measures and interprets these changes.