A smartphone-integrated colorimetric and fluorescent sensor for monitoring salmon freshness

Background

Salmon is a tasty and nutritious fish that is widely welcomed by consumers worldwide. However, salmon is susceptible to spoilage and generates biogenic amines (BAs), which are detrimental to human health upon ingestion. Traditional testing methods are often cumbersome and time-consuming, and cannot achieve rapid and accurate evaluation of salmon quality, and only relying on visual observation will cause certain errors, so we need to develop portable smart labels with the help of the smartphone to facilitate ordinary consumers to judge the freshness of salmon.

Results

In this study, an “OFF-ON” fluorescent probe CDT with a donor (D)-π-acceptor (A) structure is synthesized through the Knoevenagel condensation reaction between 2,4-thiazolidinedione and dimethylaminocinnamaldehyde. CDT emits long-wavelength red fluorescence (607 nm) and exhibits distinct colorimetric and fluorescence rapid response (5 s) to 15 amines, with a detection limit for trimethylamine (TMA) as low as 5.47 μM. The CDT + H ⁺ -loaded indicator label, obtained by protonating CDT with hydrochloric acid, can effectively assess the freshness of salmon. At 4 °C, a smartphone sensing platform is constructed based on the red/blue (R/B) value of the label color and the total volatile basic nitrogen (TVB-N) content of salmon, allowing for accurate visual assessment of the salmon freshness. Furthermore, the accuracy of this smartphone sensing platform is validated at 25 °C.

Significance

In conclusion,CDT can rapidly detect amines via colorimetric and fluorescent dual channel. CDT serves as a portable tool that presents significant advantages in convenience, speed, cost-effectiveness and mobility. It provides an exceptionally effective solution for the rapid, non-destructive, and intuitive assessment of the freshness of aquatic products.