Sensitive detection of early growth of Skeletonema costatum using a gold-doped carbon sphere-gold nanoparticle electrochemical biosensor

Abstract

The red tide caused by Skeletonema costatum (S. costatum), which greatly harms the ecosystem, makes the accurate, sensitive, and quick detection of S. costatum a challenge within the field, despite early warning being conducive to intervening and managing its occurrence. This paper proposes an electrochemical biosensor composed of gold-doped carbon spheres (CBAu) and gold nanoparticles to detect its early growth. CBAu has excellent conductivity and provides an effective channel for the transmission of electrical signals in the biosensor. At the same time, the unique characteristics of gold nanoparticles can effectively enrich ferrocene-labeled DNA (FcDNA). Therefore, this biosensor displays excellent detection performance, including a low detection limit (LOD = 51.28 fg μL⁻¹), a low limit of quantitation (LOQ = 137.85 fg μL⁻¹), and a wide linear range (100 fg μL⁻¹–10 pg μL⁻¹). A linear relationship has been established between the algal density and current value, with the calculated LOD being 2672 cells per L and LOQ 4575 cells per L. Both of these values are far below the algal bloom threshold of 10⁷ cells per L. The reliability and accuracy of the biosensor are further verified by comparison with optical microscopy and droplet digital PCR (ddPCR). In addition, the applicability of the biosensor is re-verified in the field test in the Beibu Gulf.