A novel ultrasensitive aptasensor based on silver nanoparticles measured via enhanced voltammetric response of electrochemical reduction of riboflavin as redox probe for cocaine detection

•The aptasensor is constructed by covalent immobilization of aptamer-functionalized AgNPs on the MWCNTs/IL/Chit nanocomposite as the sensing interface.•Riboflavin (RF) has been used for the first time as the probe redox in the development of the electrochemical aptasensor for the diagnosis of cocaine.•AgNPs lead to the acceleration of the electron transfer kinetics related to the reduction of RF.•The aptasensor showed high sensitivity and selectivity.•Linear range from 2nM to 2500nM with LOD of 150pM for cocaine detection. A novel, simple and selective aptasensor for ultrasensitive detection of the addictive drug, cocaine, is developed using the electrochemical transduction method. The aptasensor is constructed by covalent immobilization of aptamer-functionalized AgNPs on the MWCNTs/IL/Chit nanocomposite as the sensing interface which improves the conductivity and performance characteristics of the aptasensor and enhances the loading amount of the aptamer DNA sequence. In this study, riboflavin (RF) has been used for the first time as the redox probe in the development of the electrochemical aptasensor for the diagnosis of cocaine. AgNPs lead to the acceleration of the electron transfer kinetics related to the reduction of RF. The differential pulse voltammetric (DPV) signal of the RF linearly decreases with increased concentration of cocaine from 2nM to 2.5μM with a detection limit (S/N=3) of 150pM. By using certain analgesic drugs as the interfering agents, the excellent specificity of this sensing system for cocaine measurement is also demonstrated. Finally, the proposed aptasensor has successfully been used to detect cocaine in human serum samples.