Zn2+-Modified Nonmetal Porphyrin-Based Metal–Organic Frameworks with Improved Electrochemiluminescence for Nanoscale Exosome Detection

Exploring effective and robust strategies for enhancing electrochemiluminescence (ECL) emissions of porphyrin-based metal–organic frameworks (MOFs) is of great importance for expanding their applications in bioassays. Herein, a simple, convenient, and effective endogenous strategy of post-synthesis-modified Zn2+ was proposed to enhance ECL of nonmetal porphyrin-based MOFs. The ECL emissions of porphyrin-cobuilt UiO-66-NH2 (TCPP/UiO-66-NH2), PCN-224, PCN-222, and Ce–TCPP–LMOF could be enhanced 31.9, 47.1, 49.9, and 19.2 times, respectively. By studying TCPP/UiO-66-NH2 nanoluminophores as a model, Zn2+ was incorporated into TCPP/UiO-66-NH2 through the coordination of Zn and pyrrolic N of TCPP. The ECL enhancement was attributed to the conversion of TCPP to ZnTCPP with high emission efficiency and MOFs could enrich co-reactants, shorten the ion/electron-transfer distance, and render electrochemical activation of porphyrin luminophores. On this basis, a simple ECL biosensor for detecting nanoscale exosomes was developed based on the boosted ECL signal of Zn–TCPP/UiO-66-NH2 nanoluminophores without additional recognition and amplification elements. The ECL biosensor exhibited good sensitivity with a detection range from 1.00 × 104 to 3.16 × 106 particles/μL and a detection limit of 9.08 × 103 particles/μL (S/N = 3). The linear range and detection limit of the proposed label-free ECL biosensor are better than most of the existing label-free methods for detecting exosomes, indicating its good performance as a powerful tool for accurate and sensitive detection of HepG2-derived exosomes. As a result, this work provides inspiration for exploring strategies to enhance ECL efficiencies of porphyrin-based MOFs, which has important application prospects in sensitive bioassays.