Nanobody-Based Microfluidic Immunosensor Chip Using Tetraphenylethylene-Derived Covalent Organic Frameworks as Aggregation-Induced Electrochemiluminescence Emitters for the Detection of Thymic Stromal Lymphopoietin

Abstract

In this letter, a sensitive microfluidic immunosensor chip was developed using tetrakis(4-aminophenyl)ethene (TPE)-derived covalent organic frameworks (T-COF) as aggregation-induced electrochemiluminescence (AIECL) emitters and nanobodies as efficient immune recognition units for the detection of thymic stromal lymphopoietin (TSLP), a novel target of asthma. The internal rotation and vibration of TPE molecules were constrained within the framework structure, forcing nonradiative relaxation to convert into pronounced radiative transitions. A camel-derived nanobody exhibited superior specificity, higher residual activity and epitope recognition postcuring compared to monoclonal antibodies. Benefiting from the affinity between silver ions (Ag⁺) and cytosine (C), a double-stranded DNA (dsDNA) embedded with Ag⁺ was modified onto the surface of TSLP. A positive correlation was obtained between the TSLP concentration (1.00 pg/mL to 4.00 ng/mL) and ECL intensity, as Ag⁺ was confirmed to be an excellent accelerator of the generation of free radical species. We propose that utilizing COF to constrain luminescent molecules and trigger the AIECL phenomenon is another promising method for preparing signal tags to detect low-abundance disease-related markers.