A portable biosensor based on exonuclease III-assisted amplification strategy for on-site monitoring and early warning of Phaeocystis globosa bloom.

In recent years, the frequent outbreaks of Phaeocystis globosa (P. globosa) bloom have seriously threatened the safety of coastal nuclear power. However, existing detection technologies cannot meet the demand for the early warning of P. globose blooms. In this study, a DNA electrochemical biosensor for the specific detection of P. globosa was developed based on gold-loaded carbon cube (Au-CC) electrode modification materials and an exonuclease III (Exo III)-assisted amplification strategy. The biosensor was then successfully applied to the early warning and dynamic monitoring of P. globosa blooms. The limit of detection (LOD) and limit of quantitation (LOQ) of the biosensor were 32.25 fg/μL (926 cells/L) and 97.36 fg/μL (2456 cells/L), respectively, which were significantly lower than the outbreak threshold of P. globosa (1.0 × 10 cells/L). The excellent detection performance of the biosensor was due to the sensitive response of Au-CC to electrode interface disturbance and the indirect amplification of P. globosa DNA by the Exo III-assisted target cycling process. In addition, compared to ddPCR and traditional microscopy methods, the biosensor exhibited good accuracy and reliability (P > 0.05). In analyzing actual samples, this biosensor achieved consistent results with the standard survey method and successfully predicted the low outbreak risk of P. globosa in the sampling area. Therefore, this biosensor offers great potential in the dynamic detection and early warning of P. globosa bloom and may serve as a powerful tool for ensuring coastal nuclear power safety and protecting marine ecology.