An ultrasensitive sandwich type electrochemiluminescence immunosensor for triiodothyronine detection using silver nanoparticle-decorated graphene oxide as a nanocarrier

An ultrasensitive electrochemiluminescence (ECL) immunosensor was constructed to detect 3,3′,5-triiodothyronine (T3). The system employed T3-conjugated, silver nanoparticle-decorated carboxylic graphene oxide (Ag@fGO-T3) as a carrier and anti-T3 antibody-tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+) as a probe. The Ag@fGO-T3 and Ru(bpy)32+ complex could be mobilized rapidly to the anode in the reaction chamber through electrophoresis. The fGO is reduced electrochemically at the electrode, and the electrons could transfer from an anode to the Ru(bpy)32+. The complex is excited at the electrode and an ECL signal is produced upon reacting with tripropylamine (TPrA). Because of its large surface area and excellent conductivity, Ag@fGO could enhance ECL signal significantly in the system. Quantitative measurement of T3 could be achieved in the range from 0.1 pg/mL to 0.8 ng/mLwith a detection limit of 0.05 pg/mL. In addition, the novel immunosensor showed good specificity in the presence of serum, indicating its high potential in clinical use.