Enhanced SERS aptasensor for sensitive detection of saxitoxin based on HAuCl ₄/H ₂O ₂reaction system and Pt/Au nanozyme

Saxitoxin (STX) is a marine biotoxin produced by cyanobacteria and methanobacteria, which is harmful to humans and aquatic organisms. Therefore, it is urgent to establish an efficient, sensitive and selective method for the screening of STX. In this paper, based on the HAuCl₄/H₂O₂ reaction system, gold nanoparticles (Au NPs) decorated Fe₃O₄magnetic beads (Fe₃O₄@Au NPs)and Pt/Au nanozymes (Pt/Au NZs), an enhanced SERS aptasensor was proposed for sensitive and selective detection of STX. Firstly, SERS tag (4-MBA) and aptamer modified Fe₃O₄@Au NPs were hybridized with complementary DNA modified Pt/Au NZs (Pt/Au-cDNA) to form the specific complexes. Wherein, aptamer acted as capture agent to specifically recognize STX, Pt/Au NZs catalyzed HAuCl₄/H₂O₂ reaction to enhance SERS signal, and Fe₃O₄ facilitated the magnetic separation and simple detection operations. The SERS aptasensor achieved sensitive detection of STX with a wide linear range from 0.02 μmol/L to 0.8 μmol/L and a low detection limit of 13 nmol/L (LOD, S/N=3). To evaluate the performance of this method, STX were detected in the spiked seafood samples with recoveries from 78.75% to 150% with relative errors below 6.52%. Besides, the SERS aptasensor behaved good stability and repeatability, revealing its promising potential in STX detection and food safety detection.