Microneedle Biosensor Brings Speed and Accuracy to Fish Freshness Testing

Assessing the freshness of seafood is essential for food safety and quality, but traditional checks, such as inspecting eyes and gills or relying on smell, often fall short. Spoilage can begin well before visible signs appear, making it difficult to catch early degradation. Electrochemical biosensors are becoming rapid, reliable, and affordable devices for real-time assessment of food quality, but their use can be limited by the need for sample preparation. Other approaches to freshness testing, such as optical devices and sensing films, have also been explored. These methods use fluorescence, spectroscopy, or bioimpedance to assess spoilage, but often face challenges with accuracy or practicality.

To address this, a team of researchers in Australia have developed a microneedle array-based electrochemical biosensor, designed for direct food safety and quality analysis without any sample preparation. Microneedles are ideal for biosensing, offering simple application and easy customization. The sensor can directly measure hypoxanthine (HX), a compound that forms early in the spoilage process and correlates with the breakdown of muscle tissue after death.

How the sensor works

Unlike standard laboratory techniques, which require extensive sample preparation and specialized equipment, this sensor works by simply pressing it onto the surface of the fish, eliminating the need for complex pretreatment. The device features a gold-coated polymeric microneedle array, functionalized with a chitosan-gold nanoparticle composite and immobilized xanthine oxidase. This configuration allows for selective detection of HX: the electrodes anchor into the fish tissue, where the enzyme breaks down HX and the sensor measures the resulting electrical changes.

Performance and validation

In tests, the researchers monitored salmon steaks stored at room temperature over 48 hours. The sensor was able to detect HX concentrations down to less than 500 parts per billion—levels consistent with “very fresh” fish—and delivered results in about 100 seconds. Its sensitivity and accuracy matched those of commercial laboratory kits, but with the added benefit of portability and speed.

Broader implications

This microneedle sensor represents a significant step toward real-time, on-site food safety monitoring. Its design overcomes the limitations of previous biosensors, which often required labor-intensive sample preparation and were confined to laboratory settings. By enabling direct analysis of whole fish tissue, the technology could help reduce food waste, improve quality grading, and reinforce consumer trust.

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