Portable Smartphone-based Colorimetric Analyzer with Enhanced Gold Nanoparticles for On-site Tests of Seafood Safety

Saxitoxin (STX) is one of the paralytic shellfish poisons (PSP) that endanger people's health. It is necessary to develop methods for the on-site rapid detection for STX in order to prevent safety accidents. An enzyme-linked immunosorbent assay (ELISA) is timesaving and effective, but it is not suitable for large-scale in-field tests due to the expensiveness of commercial ELISA kits and the bulkiness of a microtiter plate reader (MTPR). In this study, a portable smartphone-based colorimetric analyzer (SBCA) with a cost-effictive enhanced gold nanoparticle-based ELISA (EGNB-ELISA) was proposed for STX detection. In a bicinchoninic acid (BCA) protein assay (R² = 0.9939) and a glucose assay (R² = 0.9937), SBCA was shown to be in good agreement with MTPR. EGNB-ELISA had a 12.5-fold lower detection limit (0.4 ng/mL) and a lower detection range (1 - 50 ng/mL, Y = 0.4037X + 0.3564, R² = 0.9797) than the classical ELISA. The recovery rate ranged over 89.1 - 112.2%. The whole detection system, combining both homemade SBCA and ENGB-ELISA, is expected to satisfy the needs of on-site STX sample tests to guarantee seafood safety.