Ultrasensitive electrochemical immunosensing of tumor suppressor protein p53 in unprocessed human plasma and cell lysates using a novel nanocomposite based on poly-cysteine/graphene quantum dots/gold nanoparticle.

An ultrasensitive electrochemical immunosensor for quantitation of tumor suppressor protein p53 based on ternary signal amplification strategy was fabricated. In this work, p53-antibody was immobilized onto a green and biocompatible nanocomposite containing poly l-cysteine (P-Cys) as conductive matrix and graphene quantum dots (GQDs)/gold nanoparticles (GNPs) as dual amplification elements. Therefore, a novel multilayer film based on P-Cys, GQDs, and GNPs was exploited to develop a highly sensitive immunosensor for detection of p53. Fully electrochemical methodology was used to prepare a new transducer on a gold surface which provided a high surface area to immobilize a high amount of the anti-p53. Under optimized condition the calibration curve for p53 concentration was linear up to 0.000197-0.016 pM (by SWV technique) and 0.195-50 pM (by DPV technique) with lower limit of quantification of 0.065 fM. Also, linear range and lower limit of quantification of p53 in unprocessed human plasma were 0.000592-1.296 pM and 0.065 fM, respectively. The method was applied to the assay of p53 in human plasma sample and normal and malignant cell line lysates such as normal cell Line from mouse C3H (L929), colon cancer cell-HCT, prostate cancer cell line PC-3, and human breast adenocarcinoma cell line-MCF7.