Fabrication of an Impedimetric Immunosensor for Screening and Determination of Vincristine in Biological Samples

Terpenoids of medicinal plants are one of the most important sources of therapeutic drugs. Among them, Vincristine (VCR) is prescribed for a wide variety of cancer types. Therefore, development of sensitive methods for VCR determination is urgently required. Here, a label-free and highly sensitive impedimetric biosensor was fabricated for electrochemical detection of VCR. First, multi-wall carbon nano tubes (MWCNTs) were dropped on the surface of a glassy carbon electrode. Then, the VCR monoclonal antibody (Ab) was covalently immobilized on the MWCNTs via carbodiimide coupling reaction using N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide and N-hydroxy succinimide. The step-by-step modification process was characterized by electrochemical impedance spectroscopy and cyclic voltammetry in presence of a redox probe [Fe(CN)(6)](3-/4-). The VCR concentration was measured through increasing impedance values in the corresponding specific binding of VCR to the Ab. The increased electron-transfer resistance (R-et) values were proportional to the concentration of VCR and the biosensor detected concentrations varied in the range of 0.2-50 nM with a detection limit of 8 x 10(-2)nM (S/N = 3). Practical analytical utility of the proposed method was demonstrated by VCR determination in medicinal plant extracts and human serum samples with satisfactory recoveries. The proposed biosensor may be a promising alternative for screening of medicinal plants to produce VCR and for the determination of drug concentration in cancerous potions.