Rapid detection of Phaeocystis globosa by aptamer-gold nanoparticles based colorimetric assay

Phaeocystis globosa is a commonly occurring harmful algal blooms (HABs)-forming species that produces toxic substances in the waters of the South China Sea. HABs formed by P. globosa not only jeopardize the mariculture industry but also impact the safe operation of nuclear power plants. Therefore, the development of a rapid detection method for P. globosa is of significant importance for the prevention and control of hazards posed by this alga. Based on a pre-screened P. globosa-targeting aptamer (Pg-Apt2), a newly optimized aptamer, Pg-TA1, was first obtained through truncation, exhibiting a significantly higher affinity (K_D = 129.24 ± 29.28) and specificity compared to Pg-Apt2 (K_D = 243.16 ± 65.00). Subsequently, using Pg-TA1 as a cell-targeting probe in combination with gold nanoparticles (GNPs), a simple and rapid method, referred to as the aptamer-GNPs based colorimetric assay (AGBCA), was developed. The AGBCA, which relies on the determination of the A₆₇₀/A₅₂₀ values of the GNPs solution, exhibited a detection range of 1 × 10¹ cells mL⁻¹ ~ 1 × 10⁸ cells mL⁻¹, with a detection limit of 5 cells mL⁻¹. The AGBCA was further confirmed to be specific and unaffected by the nutritional conditions or growth stages of the target cells. Furthermore, no significant difference (P > 0.05) was observed between the quantitative results determined by AGBCA and those obtained through traditional microscopic examination. In conclusion, the developed AGBCA offers the advantages of simple operation, high specificity, sensitivity, and stability, and is therefore promising for future applications in monitoring P. globosa.