Magnetic particle-based immunoassay of phosphorylated p53 using protein cage templated lead phosphate and carbon nanospheres for signal amplification

Phosphorylated p53 at serine 15 (phospho-p53(15)) is a potential biomarker of gamma-radiation exposure. In this paper, we described a new magnetic particle (MP)-based electrochemical immunoassay of human phospho-p53(15) using carbon nanospheres (NS) and protein cage nanoparticles (PCN) for signal amplification. Greatly enhanced sensitivity was achieved for three reasons: 1) PCN and the p53(15) signal antibody (p53(15) Ab(2)) are linked to the carbon NS (PCN-p53(15) Ab(2)-NS) as a label; 2) PCN increases the amount of metal ions in the cavity of each apoferritin; 3) MPs capture a large amount of primary antibodies. Protein cage templated metallic phosphates, instead of enzymes, as multi-labels have the advantage of eliminating the addition of mediator or immunoreagents and, thus, makes the immunoassay system simpler. Subsequent stripping voltametric analysis, detected olead ions on a disposable screen-printed electrode. The response current was proportional to the phospho-p53(15) concentration in the range of 0.02 to 20 ng mL(-1) with a detection limit of 0.01 ng mL(-1), which was 30-fold lower than that of the ELISA measurement of phospho-p53(15). This method shows an acceptable stability and reproducibility and the assay results for phospho-p53(15)-spiked human serum presented good recovery rates.