Ultrasensitive electrochemiluminescence aptasensor for Tau protein based on gold nanoparticle-modified perovskite nanocrystals.

Early diagnosis for Alzheimer's disease (AD) is vital for effective therapeutic intervention and improved patient prognosis. In this work, we developed a highly sensitive electrochemiluminescence (ECL) aptasensor for detecting a key AD biomarker, Tau protein. An all-inorganic perovskite CsPbBr3 nanocrystals (NCs) were used as ECL emitters and were encapsulated with polyvinylpyrrolidone (PVP) to improve the stability of CsPbBr3 NCs in aqueous solution. Moreover, -PVP encapsulation significantly enhanced the ECL response via coordination between the lone-pair electrons of oxygen atoms and Pb2+. The obtained CsPbBr3@PVP composite was further functionalized with gold nanoparticles, which served as anchoring sites for the immobilization of a Tau-specific aptamer. The sensing mechanism relies on the specific recognition between the surface-bound aptamer and the Tau protein. The formation of the aptamer-target complex impeded the ECL reaction efficiency of the system, resulting in an "off" ECL sensing response. This strategy enables ultrasensitive detection of Tau protein with a wide linear range from 10 fg/mL to 108 fg/mL and a detection limit as low as 0.80 fg/mL. The aptasensor also demonstrated satisfactory recoveries of 97.2% to 108.6% in mouse cerebrospinal fluid with relative standard deviations below 6.5%, indicating its promising potential for early diagnosis of AD.