Novel pore confinement enhanced europium functionalized porphyrin covalent organic framework electrochemiluminescence microreactor and its application to microRNA-21 detection

Here, an electrochemiluminescence (ECL) microreactor lanthanide europium functionalized porphyrin covalent organic framework (Eu@TAPP-COF) was developed through Schiff base condensation between 1,3,5-benzenetricarboxaldehyde (BTCA) and 5,10,15,20-tetrakis(4-aminophenyl)-porphyrin (TAPP) with the coordination reaction between the COF skeleton and Eu3+. Compared with O2/S2O82− and TAPP-COF/S2O82− systems, the ECL intensity of Eu@TAPP-COF/S2O82− is significantly enhanced by 5.1 and 1.3 times, respectively. It can be attributed to the positively charged micropore structure of the Eu@TAPP-COF, providing a relatively independent reaction environment for the electrochemical oxidation of S2O82− and the intermediate SO4•−, moreover shortening the distance among the ECL luminophore TAPP, the co-reaction accelerator Eu3+, and the co-reaction reagent S2O82−. Based on this novel emitter, an ECL biosensor was developed for microRNA-21 detection via the signal amplification strategy of catalytic hairpin assembly (CHA). The as-prepared biosensor displayed high sensitivity for target with a dynamic linear response range from 100 aM to 100 pM, and a lower detection limit of 21 aM (S/N = 3). This work provides an idea for the sensing application of weak luminophore and a simple, effective and accurate detection platform for tumor markers. •Eu@TAPP-COF was prepared and used as the ECL microreactor.•An efficient ECL ternary system was constructed in Eu@TAPP-COF microreactor.•ECL intensity of Eu@TAPP-COF/S2O82− is 5.1-fold higher than that of O2/S2O82−.•A simple, sensitive and efficient ECL sensor for miRNA-21 detection was developed.•This ECL sensor achieves sensitive detection of miRNA-21 in actual samples.