Protein-Induced\nElectrochemiluminescence Enhancement\nof Tetraphenylvinyl Derivatives for Ultrasensitive Bioanalysis

Herein,\nthe bovine serum albumin (BSA)-loaded tetrakis[4-(4′-cyanophenyl)phenyl]ethane\nnanoaggregates (NAs) (BSA@TBPE-(CN)<sub>4</sub> NAs) as a novel electrochemiluminescence\n(ECL) emitter were first prepared, which exhibited superior ECL performance\nvia the newly defined protein-induced ECL enhancement. Impressively,\nBSA not only restricted the intramolecular motions by its hydrophobic\ncavity to improve optical radiation for enhancing ECL efficiency but\nalso promoted the electrochemical excitation of BSA@TBPE-(CN)<sub>4</sub> NAs in which amino acid residues of BSA altered the surface\nstates and narrowed the energy gap of BSA@TBPE-(CN)<sub>4</sub> NAs\nfor further boosting the ECL efficiency. Furthermore, the BSA@TBPE-(CN)<sub>4</sub> NAs displayed a more dispersed state due to electrostatic\nrepulsion caused by its considerable negative charges, which was conducive\nto reacting more fully with coreactants for improving ECL emission.\nExcitingly, the BSA@TBPE-(CN)<sub>4</sub> NAs exhibited a threefold\nstronger ECL intensity and a 4.8-fold higher ECL efficiency compared\nto those of TBPE-(CN)<sub>4</sub> NAs. Thus, as an application, an\nECL biosensor was fabricated based on the BSA@TBPE-(CN)<sub>4</sub> NAs as an efficient emitter and the mismatch-fueled three-dimensional\n(3D) DNA walker as an effective signal amplifier for the rapid and\nultrasensitive detection of microRNA-21 with a detection limit (LOD)\nof 19.1 aM, and it was successfully applied to assess the microRNA-21\nexpression of human cancer cells MCF-7 and HeLa. This work developed\na novel avenue to reasonably synthesize highly efficient organic ECL\nemitters for motivating their potential application in ultrasensitive\nbiosensing and high-resolution ECL bioimaging.