Design of a Solid-State Electrochemiluminescence Biosensor for Detection of PML/RARα Fusion Gene Using Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$-AuNPs Aggregations on Gold Electrode

Abstract A solid‐state electrochemiluminescence (ECL) biosensor based on special ferrocene‐labeled molecular beacon (Fc‐MB) for highly sensitive detection of promyelocytic leukemia/retinoic acid receptor alpha (PML/RARα) fusion gene was developed successfully using Ru(bpy) ${{{2+\hfill \atop 3\hfill}}}$ /2‐(dibutylamino)ethanol (DBAE) as detecting pattern. Such a special sensor involves two main parts, an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Ruthenium (II) tris‐(bipyridine) and Au nanoparticles (Ru(bpy) ${{{2+\hfill \atop 3\hfill}}}$ ‐AuNPs) onto the Au electrode (AuE) surface. The molecular beacon probe in which the ferrocene tag could effectively quench the ECL of the Ru(bpy) ${{{2+\hfill \atop 3\hfill}}}$ acted as ECL intensity switch. The molecular beacon probe was designed with special base sequence, which could hybridize with its complementary target DNA. In the absence of a target, the hairpin structure of the probe forced the ferrocene (Fc) into close proximity with the ECL substrate, thus reducing ECL intensity. Target binding allowed the Fc away from the ECL substrate and resulted in an obvious increment in ECL intensity due to the decreased Fc quenching effect. The effect of the amount of Ru(bpy) ${{{2+\hfill \atop 3\hfill}}}$ and the mixing procedure of Ru(bpy) ${{{2+\hfill \atop 3\hfill}}}$ and AuNPs solution on the fabrication of ECL film had been investigated. As a result, the change of ECL intensity had a direct relationship with the logarithm of PML/RARα fusion gene concentration in the range of 0.05–500 pM with a detection limit of 7 fM, and the developed biosensor possessed good molecular recognizability in human serum. Thus, the approach holds promise for the early diagnostics and prognosis monitoring of APL and other diseases.