Spherical carrier amplification strategy for electrochemical immunosensor based on polystyrene-gold nanorods @L-cysteine/MoS2 for determination of tacrolimus

A novel sensitive electrochemical immunosensor has been designed for determination of tacrolimus (Tac) based on spherical carrier amplification strategy. In this work, a spherical signal carrier was prepared by conjugating gold nanorods (AuNRs) functionalized L-cysteine (AuNRs@L-Cys) onto polystyrene nanoparticles (PS) to form a nanostructure, greatly increasing the amount of loaded capture antibodies. The PS was a stable spherical functional polymer with large specific surface area and was labeled with AuNRs@L-Cys via coupling reagent to increase active groups, biocompatibility and conductivity. The capture antibodies could be attached on the PS-AuNRs@L-Cys via linkage reagent glutaraldehyde (GA). Furthermore, single-layer molybdenum disulfide (MoS2) fixed by chitosan were utilized to construct the base of this immunosensor, increasing the carrying capacity and stability of the electrode. After electrochemical reduction, the conductivity and electron transfer rate of MoS2 were obviously improved, which offered a platform for this immunosensor and further amplified the signal. Under the optimized conditions, the proposed immunosensor revealed a linear Tac-concentration behavior from 1.0 to 30 ng mL(-1) with a detection limit of 0.17 ng mL(-1) (S/N = 3). The immunoassay was successfully applied to the quantification of Tac in serum samples with acceptable precision. The results indicated that a potentially analytical platform may be used to recognize the concentration of other drugs.