Sandwiched Electrochemiluminescent Peptide Biosensor for the Detection of Prognostic Indicator in Early‐Stage Cancer Based on Hollow, Magnetic, and Self‐Enhanced Nanosheets

Currently, peptide-based protein-recognition has been recognized as an effective and promising approach for protein assays. However, sandwiched peptide-based biosensor with high sensitivity and low background has not been proposed before. Herein, a sandwiched electrochemiluminescence (ECL) peptide-based biosensor is constructed for Cyclin A(2) (CA2), a prognostic indicator in early stage of multiple cancers, based on nanosheets with hollow, magnetic, and ECL self-enhanced properties. First, hollow and magnetic manganese oxide nanocrystals (H-Mn(3)O(4)) are synthesized using triblock copolymeric micelles with core-shell-corona architecture as templates. Then, polyethyleneimine (PEI) and the composite of platinum nanoparticles and tris (4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium (II) (PtNPs-Ru) are immobilized on H-Mn(3)O(4) to form H-Mn(3)O(4) -PEI-PtNPs-Ru nanocomposite, in which PEI as coreactant can effectively enhance the luminous efficiency and PtNPs as nanochannels can greatly accelerate the electron transfer. Finally, due to the coordination between Eu(3+) and carboxyl, the obtained H-Mn(3)O(4) -PEI-PtNPs-Ru aggregates locally to form sheet-like nanostructures ((H-Mn(3)O(4) -PEI-PtNPs-Ru)(n) -Eu(3+)), by which the luminous efficiency is further increased. Based on the nanosheets and two designed peptides, a sandwiched ECL biosensor, using palladium nanocages synthesized through galvanic replacement reaction as substrate, is proposed for CA2 with a linear range from 0.001 to 100 ng mL(-1) and a detection limit of 0.3 pg mL(-1).