A sensitive electrochemical DNA biosensor for Microcystis spp. sequence detection based on an Ag@Au NP composite film

Abstract

An electrochemical DNA biosensor was developed for detecting a gene sequence related to blooming genera of Cyanobacteria, Microcystis spp. In this sensor, gold nanoparticles (Au NPs) were electrodeposited on a gold electrode (GE) surface to enhance the amount of DNA immobilization. Silver was anchored on Au NPs to increase the electrochemical signal of hybridization because metallic films deposited as a continuous layer on a solid electrode can greatly enhance the rate of electron transfer. In the differential peak voltammograms, the peak current of the methylene blue (MB) hybridization indicator was about 10 times that of direct detection. Therefore, lower detection limits and a wider linear range for the biosensor were obtained. Based on silver enhancement, the change in the reduction peak current before and after hybridization (Δi_p) of MB was linearly related to the concentration of the target DNA sequence in the range of 3.0 × 10⁻¹² to 1.2 × 10⁻¹⁰ mol L⁻¹ with a detection limit of 1.6 × 10⁻¹² mol L⁻¹. In addition, the biosensor had good selectivity, and the base mismatch sequences from specific species could be distinguished.