Magnetic gold nanocomposite and aptamer assisted triple recognition electrochemical immunoassay for determination of brain natriuretic peptide

A triple recognition voltammetric method for the determination of brain natriuretic peptide (BNP) is described. Gold nanoparticles (AuNPs) and magnetic nanoparticles (MagNPs), sized 26 and 310 nm, respectively, were synthesized and characterized by transmission electron microscopy (TEM), FT-IR, dynamic light scattering (DLS), and Z-potential measurements. Antibody-modified MagNPs and methylene blue-labeled aptamer (Apt-MB)-modified AuNPs were used as an identifier, a signal reporter, and an amplifier, respectively. In the presence of BNP, the magnetic gold nanocomposite is formed through cascade conjugation via specific interaction. It then hybridized with complementary DNA (cDNA) on the interface, thereby amplifying the current signal of Apt-MB and increasing the selectivity of the immunoassay. Results obtained demonstrate the development of a highly selective method with a detection limit of 0.56 pg mL(-1) and a linear response over the concentration range 1-10,000 pg mL(-1). The standard deviation of the method is < 6% while the recovery ranged from 92.2 to 104.2%. Schematic representation of triple recognition electrochemical immunosensor based on two functionalized nanoparticles (antibody-modified magnetic nanoparticle (MNP-Ab) and aptamer-modified gold nanoparticle (AuNPs-Apt)) for determination of brain natriuretic peptide (BNP).