A novel split aptamer–gold nanoparticle colorimetric assay for the rapid detection of Phaeocystis globosa

Phaeocystis globosa-forming blooms pose serious ecological and economic risks by releasing hemolytic toxins, inducing hypoxia, threatening fisheries, and even obstructing seawater intake in nuclear power plants. Rapid and reliable detection of this alga is therefore critical. Here, a rapid, sensitive, and quantitative visual detection method that is referred to as split aptamer–gold nanoparticle colorimetric assay (SAGCA) was established for P. globosa. For this purpose, a parent aptamer (PAP) (Pg-TA1) against P. globosa was first split into two segments (Pg-SP1 and Pg-SP2) followed by analyzing their synergistic binding efficiency. The results demonstrated that neither Pg-SP1 nor Pg-SP2 alone could recognize target cells. By contrast, Pg-SP1 and Pg-SP2 restored the binding ability comparable to the PAP when they were combined. Subsequently, the binding conditions of the split aptamers were optimized, and a SAGCA detection system based on the split aptamers was established. The detection limit of SAGCA was 2 cells mL⁻¹, with a linear range of 1 × 10¹ cells mL⁻¹–1 × 10⁸ cells mL⁻¹ (R² = 0.965). SAGCA demonstrated good specificity and strong anti-interference effectiveness. The quantification results of SAGCA were substantially consistent with those from microscopic examination. SAGCA may be used as a good alternative to the microscopy-based detection method for P. globosa, and thus offers an efficient, low-cost way for monitoring other hazardous microalgae.