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

Abstract

Phosphorylated p53 at serine 15 (phospho-p53¹⁵) is a potential biomarker of gamma-radiation exposure. In this paper, we described a new magnetic particle (MP)-based electrochemical immunoassay of human phospho-p53¹⁵ using carbon nanospheres (NS) and protein cage nanoparticles (PCN) for signal amplification. Greatly enhanced sensitivity was achieved for three reasons: 1) PCN and the p53¹⁵ signal antibody (p53¹⁵ Ab₂) are linked to the carbon NS (PCN-p53¹⁵ Ab₂-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-p53¹⁵ 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-p53¹⁵. This method shows an acceptable stability and reproducibility and the assay results for phospho-p53¹⁵-spiked human serum presented good recovery rates.