A sensitive electrochemical biosensor based on Exo III cyclic amplification strategy for Phaeocystis globosa detection

Phaeocystis globosa (P. globosa), a main culprit of harmful algal blooms (HABs), is highly prone to blocking the inlet filter screens of nuclear power cold sources, thus posing a significant threat to nuclear power safety. However, existing methods for P. globosa detection fail to achieve rapid and on-site monitoring of single-cell densities prior to bloom outbreaks, limiting timely defensive measures. In this study, we developed a novel biosensor platform for efficient P. globosa detection, leveraging an Exo III-assisted signal amplification strategy to significantly enhance sensitivity and selectivity. The biosensor achieved an ultra-low limit of detection (LOD) of 268.91 fg µL⁻¹ (3119 cells L⁻¹), far below the benchmark concentration for P. globosa blooms (10⁷ cells L⁻¹), and demonstrated a wide linear detection range from 500 fg µL⁻¹ to 10 ng µL⁻¹. Furthermore, the biosensor’s accuracy and reliability were validated through comparative analysis with droplet digital PCR (ddPCR) using actual samples from the Beibu Gulf of China, revealing a low risk of P. globosa blooms in the region at the sampling time. This study represents a significant advancement in HAB monitoring by providing a highly sensitive, rapid, and field-deployable tool for early warning of P. globosa blooms. The biosensor’s innovative design and performance address critical gaps in current detection methods, offering practical implications for safeguarding coastal nuclear power facilities and protecting marine ecosystems.