Highly Efficient Signal On/Off Electrochemiluminescence Gel Aptasensor Based on a Controlled Release Strategy for the Sensitive Detection of Prostate Specific Antigen

The controlled release strategy can make the constructed sensor have the function of self-on/off, which has an obvious effect on improving the sensitivity in immunoassays. Metal organic gels (MOGs) are the most noteworthy. They are materials with ultrahigh surface area, highly dispersed atomical metal sites, and well-defined porosity and can be used as an efficient luminophore to cause the developed sensor to have good hydrophilicity and adjustability, thus further improving the detection sensitivity. In this work, a novel on/off electrochemiluminescence (ECL) gel aptasensor was constructed using the Cys-[Ru(dcbpy)3]2+ gel as a luminophore, ZnS quantum dots (QDs) as quenchers, and aminated mesoporous silica nanocontainers (SiO2-NH2) as carriers of controlled release for prostate specific antigen (PSA) detection. Specifically, the ssDNA and PSA aptamer made up clamp-like molecules to block holes of the SiO2-NH2 after encapsulating the quencher ZnS QDs. Because of the specific binding between the PSA antigen and aptamer, the clamp-like molecules of ssDNA and the PSA aptamer were disassembled. Finally, the release of ZnS QDs was triggered, thereby realizing a self-off mode of the ECL signals under a co-reactant-free environment by ECL resonance energy transfer (ECL-RET) between the Cys-[Ru(dcbpy)3]2+ and ZnS QDs. In addition, the quenching mechanism was confirmed by molecular orbitals from the theoretical calculation level. The detection limit of the gel aptasensor for PSA was as low as 1.01 fg/mL, showing excellent sensitivity and accuracy. These strategies provided a feasible idea for PSA and even other tumor marker immunoassays.