A novel electrochemical aptasensor for ultrasensitive detection of fluoroquinolones based on single-stranded DNA-binding protein

Determination of fluoroquinolones (FQs) in foodstuffs and environment is of great importance. In this study, a novel electrochemical sensing method was developed for rapid, highly sensitive and specific detection of FQs, based on aptamer (Apt) as molecular recognition probe, single-stranded DNA-binding protein (SSB) as a physical and negatively charged barrier for the access of redox probe ([Fe(CN)6]3−/4−) to the surface of gold electrode. The designed electrochemical aptasensor needs less than 1 h for detection of ciprofloxacin. In the absence of ciprofloxacin, SSB interacts with Apt and restricts the access of redox probe to the surface of electrode, leading to a weak current signal. In the presence of target, SSB could not bind to the Apt, resulting in more access of redox probe to the surface of electrode and a strong current signal. The designed electrochemical sensor exhibited high specificity toward FQs with a limit of detection (LOD) as low as 263 pM for ciprofloxacin. Moreover, the developed sensing method was successfully applied for determination of ciprofloxacin in serum, milk and water samples with LODs of 336, 351 and 261 pM, respectively.