Self-enhanced electrochemiluminescence immunosensor based on nanowires obtained by a green approach

Co-reactant electrochemiluminescence (ECL) is a simple and effective method for sensitive detection with amplified ECL signals. However, the intermolecular interaction between the luminescent reagents and their corresponding co-reactants, which is widely applied, has disadvantages in poor stability, low efficiency of electron transfer and relatively high loss of energy. In this work, an intramolecular self-enhanced ECL is proposed to settle this problem. Firstly, palladium nanowires (PdNWs) are synthesized with a green procedure in which Lentinan (LNT), one of β-glucans with a triple helical conformation (t-LNT) in aqueous solution and single chains (s-LNT) at a temperature higher than 130 °C, is used as stabilizer and reducing agent. The abtined PdNWs are applied to immobilize polyamidoamine (PAMAM) dendrimer which further reacts with tris (4, 4′-dicarboxylicacid-2, 2′-bipyridyl) ruthenium (II) dichloride to form a new electrochemiluminescent derivative (PdNWs-PAMAM-Ru). In this way, the Ru (II) luminophore and its co-reactive groups (amine groups in PAMAM) exist in the same complex, by which the electronic transmission distance is shortened and the luminous properties including stability and efficiency are enhanced. Moreover, due to the high specific surface areas and good electro-catalytic ability of PdNWs, the obtained PdNWs-PAMAM-Ru can be also applied to immobilize detection antibody (Ab2). Then, a sandwiched and sensitive ECL immunosensor is fabricated for the detection of carcinoembryonic antigen (CEA) with a wide linear ranged from 0.001 ng mL−1 to 80 ng mL−1 and a low detection limit of 0.3 pg mL−1.