Simulation Mechanism within Co-reactant Electrogenerated Chemiluminescence System
Electrogenerated chemiluminescence (ECL) bioassay has witnessed remarkable growth in biosensing and diagnostics. The understanding of the reaction mechanism within ECL is important for improving and designing sensitive ECL methods. Herein we developed a sidelong ECL microscopy and finite element simulation for tomography imaging from single magnetic microbeads and deciphering reaction mechanism within bead-based co-reactant ECL system. Ruthenium derivative labelled magnetic beads (Ru1-Mag@MB) was used as bead-based ECL lumiphore while 2-(dibutylamino) ethanol (DBAE), Tri-n-propylamine (TPrA) and 2,2-Bis(hydroxymethyl)-2,2',2''-nitrilotriethanol (BIS-TRIS) were chosen as co-reactant. ECL emissions from Ru1-Mag@MB in different co-reactant were imaged via the sidelong ECL microscopy, which can allow the spatially resolved measurement of the ECL emitting layer from single microbeads in the vertical direction of the electrode surface. It was found that the lifetime of DBAE•+, TPrA•+ and BIS-TRIS•+ was estimated to be 99 μs, 231 μs and 347 μs, respectively. Importantly, the effect of pKa on the ECL behavior is simulated since it is a physicochemical parameter used to quantify the strength of an acid that indicates the tendency of an acid (HA) to donate a proton (H⁺) in an aqueous solution. Numerical simulation revealed that pKa influences both ECL intensity and the radical lifetime, and identified BIS-TRIS as exhibiting superior performance. The influence of pH was further studied using BIS-TRIS as a model system, with the results indicating that a pH of 6.8 is optimal. The sidelong ECL microscopy with the tomography of the ECL emitting layer can provide a promising way for insightful mechanistic information and screening co-reactants within bead-based ECL system.
