Design and Biosensing of a Ratiometric Electrochemiluminescence Resonance Energy Transfer Aptasensor between a g-C3N4 Nanosheet and Ru@MOF for Amyloid-β Protein.

A dual-wavelength ratiometric electrochemiluminescence resonance energy transfer (ECL-RET) aptasensor based on the carbon nitride nanosheet (g-C3N4 NS) and metal-organic frameworks (Ru@MOFs) as energy donor-receptor pairs is first designed for the detection of the amyloid-β (Aβ) protein. The cathode ECL of g-C3N4 NS gradually decreased, whereas the anode ECL from Ru@MOF pyramidally enhanced along with the increasing concentration of Aβ in a 0.1 M phosphate-buffered saline solution containing 0.1 M S2O82-. Additionally, it is worth noting that 2-amino terephthalic acid from MOF not only can load abundant amounts of luminophor Ru(bpy)32+ but also promote the conversion of more amounts of S2O82- that served as a coreactant accelerator into SO4•-, further enhancing the ECL signal of Ru@MOF. Besides, the ECL intensity from the g-C3N4 NS had a tremendous spectrum overlap with the UV-vis spectrum of Ru@MOF, demonstrating the high-efficiency ECL-RET from g-C3N4 NS to Ru@MOF. According to the ratio of ECL460nm/ECL620nm, the constructed aptasensor for the detection of Aβ showed a wide linear range from 10-5 to 500 ng/mL and a low detection limit of 3.9 fg/mL (S/N = 3) with a correction coefficient of 0.9965. The obtained results certified that the dual-wavelength ratiometric ECL sensor could provide a reliable direction and have the potential for application in biosensing and clinical diagnosis fields.