A Multi − Site initiation reversible Addition − Fragmentation Chain − Transfer electrochemical cocaine sensing

[Display omitted] •RAFT sensor for the amplified detection of cocaine was firstly reported.•Combining RAFT with host–guest interaction for the first time.•This biosensor was successfully achieved in biological samples. In this study, we reported a novel amplification method based on thermally mediated surface − initiated reversible addition − fragmentation chain transfer (SI–RAFT) and host–guest chemistry for electrochemical analysis of cocaine. Firstly, the NH2–DNA probes were fixed on the surface of the indium tin oxide (ITO) electrode by addition reaction with 1,4–phenylenediisothiocyanate (PDITC). Then the NH2–DNA could specifically recognize target cocaine, and the Ferrocene–DNA (Fc–DNA) probes was connected to the ITO electrode also by specifically binding with cocaine. Next, β–CD–Br15 was fixed on the surface of the ITO by host–guest interaction between Fc and β–cyclodextrin (β–CD). Finally, ferrocenylmethyl methacrylates (FcMMA) were grown on the surface of ITO via SI–RAFT to form polymer, and then the obtained electrode was measured by square wave voltammetry (SWV). The intensity of signal and the logarithm of cocaine concentration has a good linear relationship in the range of 0.01 ng/mL to 1 µg/mL (R2 = 0.9963), and the detection limit can go down to 0.003 ng/mL (S/N = 3). Moreover, this strategy is appropriate for illegal drugs detection and possess good anti–interference ability for the detection of cocaine in serum samples.