Colorimetric Aptasensor Based on Truncated Aptamer and Trivalent DNAzyme for Vibrio parahemolyticus Determination

In this work, after optimizing the original aptamer sequence by truncation and site-directed mutagenesis, a simple and sensitive colorimetric aptasensor was established for detecting the widespread food-borne pathogen Vibrio parahemolyticus ( V. parahemolyticus). The detection strategy was based on the competition for an V. parahemolyticus specific aptamer between its complementary DNA (cDNA) and V. parahemolyticus. The aptamer-conjugated magnetic nanoparticles (MNPs) were used as capture probes, and the G-quadruplex (G4) DNAzyme was employed as the signal amplifying element. Under optimal conditions, a wide linear detection range (from 10² to 10⁷ cfu/mL) was available, and the detection limit could be as low as 10 cfu/mL. This method was also used to detect V. parahemolyticus in contaminated salmon samples, and the results showed good consistency with those obtained from standard plate counting method. Therefore, this novel aptasensor could be a good candidate for sensitive and selective detection of V. parahemolyticus without complicated operations.